CHAPTER 3
EXPERIMENTAL
Experimental Electron Beam Curable Nanocoatings Chapter 3: Experimental
3.0 Experimental
In the present work effect of type of polyol, diisocyanate, diacrylate and acrylate on
properties of EB curable urethane acrylate coatings were studied. The EB coating
system properties were also studied using nanoalumina and nanosilica.
3.1 Materials
The polyols used for present study are pentaerythritol, glycerol, 1,4-butanediol, 1,6hexanediol, NPG were supplied by s.d.fine-chem limited, Mumbai and of laboratory
reagent (LR) grade. Pentaerythritol, procured from Asian PPG, Mumbai. Adipic acid
supplied by s.d.fine-chem was also of LR grade. IPDI, TDI and MDI were supplied
by Merck, India and were of LR grade. HEA, TMPTA and EGDMA were supplied by
ChemFine Int.Co.,Ltd (China).
Nanosilica and nanoalumina dispersion were provided by BYK, Mumbai. Catalyst
Dibutyl tindilaurate (DBTDL) was obtained by Maharashtra organic chemicals.
Xylene, toluene and DMSO were of LR grade from s.d.fine-chem Ltd, Mumbai.
3.2 Experimental
3.2.1 Raw material analysis
The raw materials used for present work were assessed for their purity (%). The
polyols were analyzed on the basis of hydroxyl value, diisocyanates were analyzed by
determination of NCO (%) and adipic acid was analyzed by determination of acid
value.
3.2.2 Determination of percentage purity of Pentaerythritol
Weigh 2 gm of the sample into a 100 ml flask. Dissolve in minimum quantity of water
and diluted to 100 ml. Mix 10 ml of this solution with 1 ml of p-nitrobenzaldehyde
distilled (prepared by dissolving 1gm p-nitrobenzaldehyde in 5 ml of methanol and 2
ml of concentrated HCl) heat to boil under reflux condition in water bath for 1hr 30
min in a 250 ml flask. Cool and neutralize the contents with NaOH solution. Add
sufficient quantity of methanol. Boil the contents for a short time. Cool and filter
under vacuum. Wash the residue and weigh.
69 Experimental Electron Beam Curable Nanocoatings Percentage purity of Pentaerythritol =
.
Where, M= Weight in g of residue obtained
M1= Weight in g of material taken.
M = Weight of the residue = 6.0 g
M1 = Weight of the material taken = 2.06 g
.
Purity of monopenta =
.
100 = 98.55 %
.
Purity of pentaerythritol = 98.55 %
3.2.3 Determination of Glycerol content
Weigh the sample in a conical flask and add 100 ml of water and 3 drops of phenol
red and acidify with 0.1 N aqueous H2SO4 solution till solution turns to yellow colour.
Heat the contents to boiling and cool to room temperature. Adjust pH to 8-9 by 0.1 N
aqueous NaOH solution till contents become just pink. 50 ml of sodium metaper
iodate solution was added to the solution. Swirl and keep it in dark for 30 minutes.
Wash the sides with distilled water and add 5 ml of ethylene glycol. Shake well and
keep it in dark for 20 min. Titrate liberated formic acid with 0.1N standardized
aqueous NaOH solution. End point is yellow to pink. Carry out blank under identical
conditions.
Percentage purity of glycerol content by weight =
S = Volume in ml of standard NaOH solution for sample
B = Volume in ml of standard NaOH for blank
N = Normality of standard NaOH solution
W = Weight of sample in g
Sample reading (S) = 30.5 ml
Blank reading (B) = 17.6 ml
S – B = 30.5 – 17.6 = 12.9 ml
=
.
.
.
.
= 98.43 %
Purity of glycerol = 98.43 %
70 .
Experimental Electron Beam Curable Nanocoatings 3.2.4 Percentage purity of 1, 6-hexanediol, NPG, 1, 4-butanediol
The percentage purity of all the three diols is determined by OH value. (ISO 46291978 (E))
Weigh 1 gm of sample in Erlenmeyer flask, to this add 5 ml of pyridine-acetic
anhydride reagent in the ratio of 3:1 by volume. The contents are thoroughly mixed
by gentle swirling. Keep flask on a steam bath using reflux condensers and heat it for
1 hour. (Add a few porcelain pieces to prevent bumping). Add 10 ml of distilled water
through the condenser into the flask and heated on the steam bath for 10 minutes with
reflux condenser. Allow the flask to cool to room temperature. Add about 10 ml of
neutralized butanol, through the condenser to the flask. Remove the condenser and
add 20 ml butanol to wash down the sides of the flasks. Add 1 ml of phenolphthalein
indicator solution and titrate the contents 0.5 N alcoholic solution till contents
becomes just pink. The blank readings were conducted under identical conditions.
Calculations:
The hydroxyl value is calculated as follows
Hydroxyl value =
.
Where, B = ml of KOH solution required for the reagent blank.
S = ml of KOH solution required for the titration of the acetylated
sample
NKOH = Normality of alcoholic KOH solution
W = Weight of the sample used for acetylation
Theoretical OH value =
3.2.4.1 Purity of 1,6-hexanediol
Molecular weight of 1,6-hexanediol = 118 g/mol
Theoretically hydroxyl value was calculated using following empirical
formula
OH-value of 1, 6-hexanediol =
= 950.847 %
Theoretical OH-value = 950.847 mg of KOH/ g of resin
71 Experimental Electron Beam Curable Nanocoatings Average OH-value =
.
.
.
.
= 938.29
.
Average hydroxyl value of 1,6-heaxanediol = 938.29 mg of KOH/ g of resin
Purity of 16-hexanediol =
Purity = 938.29/ 950.847 = 0.9868 x 100 = 98.68 %
3.2.4.2 Purity of 1,4-butanediol
Molecular weight of 1, 4-butanediol = 90 g/mol
Theoretically hydroxyl value was calculated using following empirical
formula
OH- value of 1, 4-butanediol =
Actual OH-value =
.
.
= 1246.67 mg of KOH/g of resin
.
.
1225.51
.
Average hydroxyl value of 1,4-butanediol = 1225.51 mg of KOH/g of resin
Purity = 1223.51/1246.67 = 0.9830 x 100 = 98.30 %
3.2.4.3 Purity of Neopentylglycol
Molecular weight of NPG = 104 g/mol
Theoretically hydroxyl value was calculated using following empirical
formula
OH value of Neopentylglycol =
Actual OH-value =
.
.
= 1078.85 mg of KOH/g of resin
.
.
.
= 1016.34
Average hydroxyl value of NPG = 1016.34 mg of KOH/g of resin
Purity = 1078.85/1016.34 = 0.94.21 x 100 = 94.21 %
72 Experimental Electron Beam Curable Nanocoatings 3.2.5 Percentage purity of adipic acid
The percentage purity of adipic acid is found by the determination of acid value as per
the ASTM D 1639-70.
Weigh about 1.5 g +/- 0.1 of the sample accurately into conical flasks and dissolved it
in neutral alcohol-toluene mixture. 3-4 drops of the phenolphthalein indicator was
added. The contents were titrated against 0.5 N aqueous KOH solution till pink colour
persist.
Practical acid value was calculated using following formula
.
Acid value =
Average acid value of adipic acid = 762.35 mg KOH/g of resin
Molecular weight of adipic acid = 146 g/mol
Theoretically acid value was calculated using following empirical formula
Acid value of adipic acid =
Average acid value =
.
2
.
.
.
768.49 %
762.70
.
99.20 %
Purity =
3.2.6 Percentage purity of monomers (hydroxy ethyl acrylate and hydroxy
methacrylate)
The percentage purity of the monomers was found by determination of hydroxyl value
as per the ISO 4629-1978 (E).
3.2.6.1 Hydroxy ethyl acrylate
Molecular weight of Hydroxy ethyl acrylate = 116 g/mol
Theoretically hydroxyl value was calculated using following empirical
formula
Theoretical hydroxyl value =
483.62
.
.
Actual value hydroxyl value =
.
.
.
.
= 478.09
Average hydroxyl value = 478.09 mg of KOH/g of resin
Purity =
.
98.86 %
.
73 Experimental Electron Beam Curable Nanocoatings 3.2.6.2 Hydroxy ethyl methacrylate
Molecular weight of Hydroxy ethyl methacrylate = 130 g/mol
Theoretically hydroxyl value was calculated using following empirical
formula
Theoretical hydroxyl value =
Practical hydroxyl value =
431.54
.
.
.
.
.
.
422.43
Average hydroxyl value = 422.43 mg of KOH/ g of resin
.
Purity =
97.89 %
.
3.2.7 Isocyanate Content (Isocyanate value) for determination of percentage of
purity of isocyanate monomer
3 g of TDI (Toluene diisocyanate) was weighed accurately into a 250 ml Erlenmeyer.
20 ml of dry toluene was added, followed by 25 ml of Dibutyl amine solution (diluted
260 g of dry Dibutyl amine to one liter with dry toluene). Flask was shaked during the
addition of the Dibutyl amine solution. Side’s of the flask was washed with 5 ml of
dry toluene. The flask was closed and allows it to stand at room temperature for 15
minutes. 110 ml of isopropanol was added from a graduated cylinder. 0.4 ml of
bromocrysol green indicator was added. The solution was titrated against 1 N aqueous
hydrochloric acid solution while shaking the flask contents to effect a rapid mixing till
a yellow color which persists for atleast 15 seconds. Blank sample was also prepared
under identical condition omitting the sample. The percentage purity of isocyanate is
calculated using the following formula
% purity =
Where, B = ml of acid for blank
S = ml of acid for sample
N = Normality of acid used
E = Equivalent weight of isocyanate
W = weight in gms of sample used
74 Experimental Electron Beam Curable Nanocoatings 3.2.7.1 Percentage purity of methylene diisocyanate (MDI)
Theoretically isocyanate value was calculated using following empirical
formula
Molecular weight = 250 g/mol
125
Equivalent weight of MDI =
Actual value
Weight of MDI = 1.31 g
Blank = 41.2
Burette reading = 31.9 ml
NCO content =
.
.
.
40.73 %
.
Equivalent weight of MDI =
103.12
.
103.12
Purity =
82.50 %
.
3.2.7.2 Percentage purity of Toluene diisocyanate (TDI)
Theoretically isocyanate value was calculated using following empirical
formula
Molecular weight =174 g/mol
87.0
Equivalent weight of TDI =
Actual value
Weight of TDI = 1.26 g
Blank = 41.2
Burette reading = 30.2 ml
NCO content =
.
.
Equivalent weight of TDI =
Purity =
.
50.08 %
.
83.86
.
100
.
.
75 96.39%
Experimental Electron Beam Curable Nanocoatings 3.2.7.3 Percentage purity of isophorone diisocyanate (IPDI)
Theoretically isocyanate value was calculated using following empirical
formula
Molecular weight = 221
110.5
Equivalent weight of IPDI =
Weight of IPDI = 1.51 g
Blank = 22.2
Burette reading = 10.8 ml
NCO content =
.
.
.
Equivalent weight of IPDI =
Purity =
43.31 %
.
100
96.98
.
.
.
76 87.76 %
Experimental Electron Beam Curable Nanocoatings 3.3.0 Synthesis of Polyester polyol with varying type of polyol
In polymer chemistry, polyols are compounds with multiple hydroxyl functional
groups available for organic reactions. A molecule with two hydroxyl groups is a diol
one with three is a triol, one with four is a tetrol and so on. Polymeric polyols are
generally used to produce other polymers. They are reacted with isocyanates to make
polymers. Polyesters formed by condensation or step-growth polymerization of diols
and dicarboxylic acids (Alper et al 2009; Kaszynki et al 2009).
The polyester polyols were synthesized using adipic acid, 1, 6-hexanediol and varying
polyol viz., PENTA, glycerol, 1, 4-butanediol and NPG. The polyester polyols were
synthesized with hydroxyl number 160-170 mg of KOH/gm of resin.
3.3.1 Synthesis of Polyester polyol from PENTA, adipic acid and 1, 6-hexanediol
The schematic representation of polyester polyol formation are depicted in Fig. 3.1
+ 4 H2O
Polyester polyol
77 Experimental Electron Beam Curable Nanocoatings The above structure is represented as
Figure 3.1: Two-Dimensional theoretical representation of the synthesis of
PENTA co-polyester polyol.
The polyester polyols were synthesized with adipic acid, 1, 6-hexanediol and
PENTA. In polyester reaction the synthesis was done with different solvents, with
varying ratio of PENTA, 1,6-hexanediol, with varying concentration of DBTDL as
a catalyst, varying ratio of carboxylic acid : hydroxyls. The reaction was melt
condensation type.
The reactions were carried out in nitrogen atmosphere using xylene as azeotropic
solvent for removal of water from reaction mixture. The progress of reaction was
monitored by amount of water of reaction as well as acid value. The reactions were
terminated when required water of reaction is collected azetropically and acid value
reached to 10 mg of KOH/gm of resin. The typical formulations for synthesis of
polyester polyols with varying concentration of DBTDL and varying type of
solvents are presented in Table 3.1. The typical formulations with varying
concentration of 1, 6-hexanediol, PENTA and acid: hydroxyl ratios are presented in
Table 3.2.
Typical reaction conditions
Catalyst: DBTDL
Reaction time: 10 hrs
Atmospheric condition: Nitrogen purging
78 Experimental Electron Beam Curable Nanocoatings Table 3.1: Effect of type of solvent and catalyst concentration on properties of
polyester polyol
Batch
PENTA
Adipic
1,6-
Solvent Catalyst Temp
acid
Hexanediol
Pgel
(%)
(°C)
(%)
moles
g
moles
g
moles
g
PP1
0.5
68
1.0
146
0.5
59
xylene
0.1
140
100
PP2
0.5
68
1.0
146
0.5
59
DMSO
0.1
153
100
PP3
0.5
68
1.0
146
0.5
59
DMF
0.1
189
100
PP4
0.5
68
1.0
146
0.5
59
-
0.1
189
100
PP5
0.5
68
1.0
146
0.5
59
-
0.05
190
100
PP6
0.5
68
1.0
146
0.5
59
-
0.05
160
100
Typical reaction conditions
Catalyst: DBTDL
Conc. of catalyst: 0.05%
Reaction temperature: 160°C
Reaction time: 7 hrs 30 min Atmospheric condition: Nitrogen purging
Table 3.2: Typical formulation for polyester polyols with varying acid to
hydroxyl ratio as well as varying ratio of diol to tetrol
Batch
PENTA
Adipic
1,6-
acid :
diol :
Pgel
acid
Hexanediol
polyol
tetrol
(%)
1.0:2.0
87.34
moles
g
moles
g
moles
PP7
0.50
68
1.0
146
0.25
PP8
0.40
54.4
1.0
146
0.50
59
1.0:0.9
1.25:1.0
PP9
0.20
27.2
1.0
146
1.0
118
1.0:1.2
5.0:1.0
109
PP10
0.16
21.8
1.0
146
1.0
118
1.0:1.16 6.25:1.0
108
79 g
29.5 1.0:0.75
Experimental Electron Beam Curable Nanocoatings 3.3.2 Synthesis of Polyester polyol from Glycerol, adipic acid and 1, 6-hexanediol
The polyester polyols were synthesized with adipic acid, 1, 6-hexanediol and glycerol.
The schematic representation of polyester polyol formation are depicted in Figure 3.2
+ 3H2O
Polyester polyol
The above polyol is represented as
HO
O
OH
O
OH O
Figure 3.2: Two-Dimensional theoretical representation of the synthesis of
glycerol co-polyester polyol.
The reactions were carried out in nitrogen atmosphere using xylene as azeotropic
solvent for removal of water from reaction mixture. The progress of reaction was
monitored by amount of water of reaction as well as acid value. The reactions were
terminated when required water of reaction is collected azetropically and acid value
reached to 10 mg of KOH/gm of resin. The mole ratio was decided for the hydroxyl to
80 Experimental Electron Beam Curable Nanocoatings be approximately around 160-170 mg of KOH/gm of resin. The typical formulations
with varying concentration of 1, 6-hexanediol, glycerol and acid: hydroxyl ratios are
presented in Table 3.3.
Typical reaction conditions
Catalyst: DBTDL
Conc. of catalyst: 0.05%
Reaction temperature: 180°C
Reaction time: 7 hrs
Atmospheric condition: Nitrogen purging
Table 3.3: Typical formulation for polyester polyols with varying acid to
hydroxyl ratio as well as varying ratio of diol to triol
Batch
Glycerol
Adipic
1,6-
acid :
diol :
Pgel
acid
Hexanediol
polyol
triol
(%)
moles
g
moles
g
moles
g
GP1
0.2
18.6
1.0
146
0.9
94.4
1.0:1.1
4.5:1.0
105
GP2
0.3
27.9
1.0
146
0.9
94.4
1.0:1.2
3.0:1.0
110
GP3
0.4
37.2
1.0
146
0.9
94.4
1.0:1.3
2.25:1.0
115
3.3.3 Synthesis of Polyester polyol from 1, 4-butanediol, adipic acid and 1, 6hexanediol The polyester polyols were synthesized with adipic acid, 1, 6-hexanediol and 1,4butanediol.
The schematic representation of polyester polyol formation are depicted in Figure 3.3
81 Experimental Electron Beam Curable Nanocoatings The above polyol is represented as
Figure 3.3: Two-Dimensional theoretical representation of the synthesis of 1,4butanediol co-polyester polyol.
The reactions were carried out in nitrogen atmosphere using xylene as azeotropic
solvent for removal of water from reaction mixture. The progress of reaction was
monitored by amount of water of reaction as well as acid value. The reactions were
terminated when required water of reaction is collected azetropically and acid value
reached to 10 mg of KOH/gm of resin. The mole ratio was decided for the hydroxyl to
be approximately around 160-170 mg of KOH/gm of resin. The typical formulations
with varying concentration of 1, 6-hexanediol, glycerol and acid: hydroxyl ratios are
presented in Table 3.4.
Typical reaction conditions
Catalyst: DBTDL
Conc. of catalyst: 0.05%
Reaction temperature: 210°C
Reaction time: 7 hrs
Atmospheric condition: Nitrogen purging
82 Experimental Electron Beam Curable Nanocoatings Table 3.4: Typical formulation for polyester polyols with varying acid to
hydroxyl ratio as well as varying type of diol
Batch
1,4-
Adipic
1,6-
acid :
Pgel
butanediol
acid
Hexanediol
polyol
(%)
moles
g
moles
g
moles
g
BP1
0.6
54
1.0
146
0.7
82.6
1.0:1.3
115
BP2
0.7
63
1.0
146
0.7
82.6
1.0:1.4
119
BP3
0.8
72
1.0
146
0.7
82.6
1.0:1.5
125
3.3.4 Synthesis of Polyester polyol from NPG, adipic acid and 1, 6-hexanediol
The polyester polyols were synthesized with adipic acid, 1, 6-hexanediol and NPG.
The schematic representation of polyester polyol formation are depicted in Figure 3.4
The reactions were carried out in nitrogen atmosphere using xylene as azeotropic
solvent for removal of water from reaction mixture. The progress of reaction was
monitored by amount of water of reaction as well as acid value. The reactions were
terminated when required water of reaction is collected azetropically and acid value
reached to 10 mg of KOH/gm of resin. The mole ratio was decided for the hydroxyl to
be approximately around 160-170 mg of KOH/gm of resin. The typical formulations
with varying concentration of 1, 6-hexanediol, NPG and acid: hydroxyl ratios are
presented in Table 3.5.
83 Experimental Electron Beam Curable Nanocoatings The above polyol is represented as
Figure 3.4: Two-Dimensional theoretical representation of the synthesis of NPG
co-polyester polyol.
Typical reaction conditions
Catalyst: DBTDL
Conc. of catalyst: 0.05%
Reaction temperature: 210°C
Reaction time: 7 hrs
Atmospheric condition: Nitrogen purging
Table 3.5: Typical formulation for polyester polyols with varying acid to
hydroxyl ratio as well as varying ratio of diol
Batch
Neopentyl
Adipic
1,6-
acid :
Pgel
glycol
acid
Hexanediol
polyol
(%)
moles
g
moles
g
moles
g
NP1
0.6
62.4
1.0
146
0.7
82.6
1.0:1.3
115
NP2
0.7
72.8
1.0
146
0.7
82.6
1.0:1.4
119
NP3
0.8
83.2
1.0
146
0.7
82.6
1.0:1.5
125
84 Experimental Electron Beam Curable Nanocoatings 3.4.0 Synthesis of urethane acrylate oligomer
Urethane acrylates are simple addition products of multifunctional isocyanates, like
toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone
diisocyanate (IPDI) with polyols and hydroxyalkyl acrylates, for instance
hydroxyethyl acrylate (HEA), hydroxy butyl acrylate or pentaerythritol acrylate.
Urethane acrylates with low functionality exhibit a high flexibility and are often based
on flexible polyester or polyether diols, which are reacted with bifunctional
isocyanates and endcapped with hydroxyalkyl acrylates (Jianwen et al 2006; Srba et
al 2004). The higher functional urethane acrylates are often used to obtain hard,
scratch and chemical resistant coatings (Enis et al 2012). Besides the good
mechanical properties, these aliphatic type urethane acrylate resins exhibit good
weatherability and do not yellow upon exposure to exterior conditions (Byoung and
Hyun 2006; Seubert et al 2003; Valet et al 1999; Yang et al 2001).
The majority of commercial urethane oligomers are based on polyisocyanates, such as
TDI or MDI. Polyester oligomers based on IPDI are often used for weatherable
coating applications. Aliphatic isocyanates such as IPDI are less susceptible to
yellowing and UV-induced photo degradation than their aromatic counterparts and
polyesters are also more resistant to UV degradation (Wang and Pourreau 2004).
Treating branched polyester polyols with diisocyanates usually causes rapid
crosslinking of the polymer chains and produces highly viscous or gelled products
which are not suitable for high-solids coatings. However, by using IPDI, polyester
based polyols with all secondary OH functionality and carefully controlling the
reaction conditions, low viscosity aliphatic urethane oligomer were obtained in
quantitative yield (Guo et al 2002).
The urethane acrylate oligomer was synthesized using three different isocyanates
MDI, TDI and IPDI further reacted with two different acrylates viz., HEMA and
HEA. Varying molar ratio of polyol: isocyanate: acrylate was used to synthesize the
oligomer. The progress of reaction was monitored by determining isocyanate content
(%) isocyanate as well as acrylation reaction.
85 Experimental Electron Beam Curable Nanocoatings The typical formulations and mode of reaction of urethane acrylate are described as
follows.
3.4.1 Synthesis of urethane acrylate using PENTA polyol, diisocyanate and
hydroxyl acrylate
A three neck flask equipped with nitrogen inlet, condenser and addition funnel is
placed in a water bath. Diisocyanate is charged in the reactor, and dropwise addition
of hydroxyl acrylate.
After the addition of diisocyanate, isocyanate content is
determined. Further the dropwise addition of polyester polyol. The reaction is carried
out in an inert atmosphere. The reaction was performed till the resultant had an
isocyanate value ≤ 0.5%. The reaction mode is as shown in Figure 3.5 and Figure
3.6.
O
NCO
NCO
+
HO
CH2
O
HEA
IPDI
O
O
NCO
NH
O
O
CH2
Isocyanate terminated prepolymer
Figure 3.5: Two-Dimensional Theoretical Representation of the Synthesis of
Isocyanate terminated prepolymer
Figure 3.6: Synthesis of Urethane Acrylate Oligomer from PP9
86 Experimental Electron Beam Curable Nanocoatings Table 3.6: Typical formulations of urethane acrylate using varying isocyanate
and acrylate monomer from PENTA polyol
Polyol
Isocyanate
Batch
PUA1
Hydroxyl
Solvent
Catalyst
Temp
acrylate
(wt %)
(wt %)
(°C)
-
0.01
30
Xylene-
0.01
20
-
0.0097
30
Xylene-
0.0097
30
0.342
30
0.342
20
0.342
20
0.343
20
0.366
20
moles
g
moles
g
moles
g
0.015
5.19
MDI-0.03
3.09
HEMA-
1.99
0.015
PUA2
0.01
3.46
MDI-0.02
2.06
HEMA-
1.33
0.01
PUA3
0.015
5.19
TDI-0.03
2.52
HEMA-
1.37(20)
1.99
0.015
PUA4
0.015
5.19
TDI-0.03
2.52
HEMA-
1.99
0.015
PUA5
0.5
172.92
TDI-1.2
100.06
HEMA-
0.097(10)
69.06
0.6
PUA6
0.5
172.92
TDI-1.2
100.06
HEMA-
69.06
0.6
PUA7
0.6
207.50
TDI-1.2
100.06
HEA-0.6
Xylene68.40(20)
Xylene68.40(20)
70.40
Xylene75.59(20)
PUA8
0.5
172.92
TDI-1.2
100.06
HEA-0.6
70.40
Xylene68.68(20)
PUA9
0.6
207.50
TDI-1.2
100.06
HEA-0.5
58.67
Acetone36.62(10)
PUA10
0.6
207.50
IPDI-1.2
116.38
HEMA-
79.68
-
0.404
55
0.6
PUA11
0.6
207.50
IPDI-1.2
116.38
HEA-0.6
70.40
-
0.394
55
PUA12
0.7
207.50
IPDI-1.4
135.77
HEA-0.7
82.14
-
0.425
55
PUA13
0.9
311.25
IPDI-1.6
155.17
HEA-0.7
82.14
-
0.549
55
Not e: MDI (Methylene biphenyl diisocyanate), TDI(Toluene diisocyanate), IPDI (Isophorone diisocyanate), HEA
(hydroxy ethyl acrylate), HEMA (hydroxy ethyl methacrylate)
87 Experimental Electron Beam Curable Nanocoatings Typical reaction conditions
Catalyst: DBTDL
Conc. of catalyst: 0.01 wt % (catalyst is added on the basis of total weight of polyol,
isocyanate, and hydroxy acrylate)
Reaction time: 1 hr 15min (in case of MDI)
4 hr (in case of TDI)
6 hr (in case of IPDI)
Atmospheric condition: Nitrogen blanket
3.4.2 Synthesis of urethane acrylate using glycerol polyol, diisocyanate and
hydroxyl acrylate
A three neck flask equipped with nitrogen inlet, condenser and addition funnel is
placed in a water bath. Diisocyanate is charged in the reactor, and dropwise addition
of hydroxyl acrylate.
After the addition of diisocyanate, isocyanate content is
determined. Further the dropwise addition of polyester polyol. The reaction is carried
out in an inert atmosphere. The reaction was performed till the resultant had an
isocyanate value ≤ 0.5%.
Figure 3.7: Synthesis of Urethane Acrylate Oligomer from GP2
88 Experimental Electron Beam Curable Nanocoatings Typical reaction condition
Catalyst: DBTDL
Conc. of catalyst: 0.01 wt % (catalyst is added on the basis of total weight of polyol,
isocyanate, and hydroxy acrylate)
Reaction time: 4 hr (in case of TDI)
6 hr (in case of IPDI)
Atmospheric condition: Nitrogen blanket
Table 3.7: Typical formulation for Urethane Acrylate synthesized from polyester
polyol
Polyol
Isocyanate
Batch
GUA1
Hydroxyl
Solvent
Catalyst
Temp
acrylate
(wt %)
(wt %)
(°C)
Acetone-
0.032
20
0.032
20
moles
g
moles
g
moles
G
0.5
173.26
TDI-1.0
83.86
HEA-0.5
58.67
31.58
GUA2
0.5
173.26
TDI-1.0
83.86
HEMA-
66.4
0.5
GUA3
0.5
173.26
IPDI-1.0
96.98
HEMA-
Acetone32.35
66.4
-
0.034
55
58.67
-
0.033
55
0.5
GUA4
0.5
173.26
IPDI-1.0
96.98
HEA-0.5
3.4.3 Synthesis of urethane acrylate using 1,4-butanediol polyol, isophorone
diisocyanate and hydroxyl ethyl acrylate
A three neck flask equipped with nitrogen inlet, condenser and addition funnel is
placed in a water bath. IPDI is charged in the reactor, and dropwise addition of
hydroxyl ethyl acrylate. After the addition of diisocyanate, isocyanate content is
determined. Further the dropwise addition of polyester polyol. The reaction is carried
out in an inert atmosphere. The reaction was performed till the resultant had an
isocyanate value ≤ 0.5%.
89 Experimental Electron Beam Curable Nanocoatings Typical reaction condition
Catalyst: DBTDL
Conc. of catalyst: 0.01 wt % (catalyst is added on the basis of total weight of polyol,
isocyanate, and hydroxy acrylate)
Reaction time: 8 hr
Reaction temperature: 55°C
Atmospheric condition: Nitrogen blanket
Table 3.8: Typical formulation for Urethane Acrylate synthesized from 1,4butanediol polyester polyol
Batch
IPDI
moles
g
Polyol
moles
g
HEA
moles
g
Catalyst
(wt %)
BUA1
1.0
96.98
0.5
169.53
0.5
58.67
0.033
BUA2
2.0
193.96
1.0
339.05
1.0
117.34
0.065
Figure 3.8: Synthesis of Urethane Acrylate Oligomer from 1,4-butanediol
polyester polyol
90 Experimental Electron Beam Curable Nanocoatings 3.4.4 Synthesis of urethane acrylate using Neopentyl glycol polyol, isophorone
diisocyanate and hydroxyl ethyl acrylate
A three neck flask equipped with nitrogen inlet, condenser and addition funnel is
placed in a water bath. IPDI is charged in the reactor, and dropwise addition of
hydroxyl ethyl acrylate. After the addition of diisocyanate, isocyanate content is
determined. Further the dropwise addition of polyester polyol. The reaction is carried
out in an inert atmosphere. The reaction was performed till the resultant had an
isocyanate value ≤ 0.5%.
Table 3.9: Typical formulation for Urethane Acrylate synthesized from NPG
polyester polyol
Batch
IPDI
moles
g
Polyol
moles
g
HEA
moles
G
Catalyst
(wt %)
NUA1
1.0
96.98
0.5
170.71
0.5
58.67
0.33
NUA2
2.0
193.96
1.0
341.43
1.0
117.34
0.65
Typical reaction condition
Catalyst: DBTDL
Conc. of catalyst: 0.01 wt % (catalyst is added on the basis of total weight of polyol,
isocyanate, and hydroxy acrylate)
Reaction time: 8 hr
Reaction temperature: 55°C
Atmospheric condition: Nitrogen blanket
Figure 3.9: Synthesis of Urethane Acrylate Oligomer synthesized from Neopentyl
glycol polyester polyol
91 Experimental Electron Beam Curable Nanocoatings 3.5 Characterization and analysis
3.5.1. Characterization and analysis of polyester polyols
The polyester polyol obtained were analyzed by determination of acid value, hydroxyl
value,
and
viscosity.
Characterization
was
done
by
FTIR,
NMR,
UV
spectrophotometer, GPC.
3.5.1.1 Acid Value
It is defined as milligrams of KOH required to neutralize the free carboxylic acid
present in one gram of resin. Acid value of the obtained polyester polyol was
measured according to ASTM D 1639-70 during the reaction.
3.5.1.2 Hydroxyl Value
The hydroxyl value is defined as the number of milligrams of KOH required to
esterifies the hydroxyl (-OH) groups. The hydroxyl value of polyester polyols was
determined as per ISO 4629-1978(E).
3.5.1.3 Viscosity by Brookfield (ASTM D 1638 -74)
Viscosities were measured using a Brookfield viscometer. The viscosity in centipoise
was found by multiplying the reading by the factor (f) that goes with the spindle and
speed used.
Viscosity = Reading x f.
3.5.1.4 FTIR analysis
The FTIR spectra were recorded using a NaCl cell on a Perkin-Elmer spectrum BX
FT-IR (USA) spectrophotometer taking 256 scans. The transmission mode was used
and the wave number range was set from 400-4000 cm-1. Fourier transform infrared
(FTIR) method was employed to study the formation of polyester polyol, urethane
acrylate and the electron beam curing of the samples.
3.5.1.5 1H NMR and 13C NMR analysis
1
H NMR and 13C NMR was recorded on a Bruker Avnace (Germany) with 5 mm BBI
probe (500 MHz) in CDCl3 with tetramethylsilane as an internal standard.
92 Experimental Electron Beam Curable Nanocoatings 3.5.1.6 Gel permeation chromatography (GPC)
Molecular weight and molecular weight distribution were estimated by Gel
permeation chromatography (GPC) on a Shimadzu LC-10 GPC System (Japan)
calibrated with polystyrene as a standard and chloroform as an eluent at a flow rate of
1.0 ml/min at 30°C.
3.5.2. Characterization and analysis of polyester urethane acrylate oligomer
The polyester urethane acrylate obtained was analyzed by determination of hydroxyl
value, isocyanate content, unsaturation and viscosity. Characterization was done by
FTIR, NMR, UV spectrophotometer, GPC.
3.5.2.1 NCO content
This method is used to determine the amount of the isocyanate groups present in the
sample. The sample is taken and then dissolved with Dibutyl amine solution and
isopropanol is added. The indicator bromo-cresol green is used. Then titrated against
0.1 N HCl. End point of the titration is blue to yellow.
3.5.2.2 Unsaturation by wij’s method
This method is used to determine the unsaturation present in the resin. Weigh the
sample in a dry flask, add CCl4, pipette 25 ml Wijs solution into flask and swirl to
insure an intimate mixture. Store the flasks in a dark place for 30 minutes. Prepare
and conduct blank determinations with samples simultaneously and similar manner in
all respect. Remove the flasks from storage and add 20 ml of KI solution, followed by
100 ml of distilled water. Titrate with 0.1 N Na2S2O3 solution, adding it gradually and
with constant and vigorous shaking. Continue the titration until the brown color is
yellow. Add 1 to 2 ml of starch indicator solution and continue the titration until the
blue color has just disappeared.
The iodine value = (B-S) x N x 12.69/ Weight of sample
B = Titration of blank
S = Titration of sample
N = Normality of Na2S2O3
93 Experimental Electron Beam Curable Nanocoatings 3.5.2.3 UV visible spectrophotometer
UV visible spectra was determined using double beam spectrophotometer 6.84,
chemito spectra scan 2700.
Other procedure and instruments were same as given in section 3.5.1.
3.6 Formulation of UV and EB curable coating
3.6.1. Effect of concentration of reactive diluent
The coating systems cured by UV and EB were formulated using crosslinked
monomers viz., TMPTA, EGDMA and HEA.
UV curable formulations with varying concentration of IRGACURE-184 as a
photoiniator were prepared. The photoinitiator 1-5% of wt/wt of total oligomer and
reactive diluent were used. In case of EB curable coating formulation photoiniator
was not used. The effect of exposure time in UV-curable system was studied whereas
effect of EB dose variation in EB curable system was studied. For UV-curable
systems UV-curing assemble and for EB curing system the EB accelerator (model
ILU-6). The typical UV curing formulations with varying ratio of photoinitiator,
oligomer, reactive diluent and irradiation time are presented below.
3.6.1.1 UV curing of UA oligomer (PUA13)
The urethane acrylate oligomer with desired properties PUA13 was optimized for
further study. The UV formulations with different types of reactive diluent viz.,
Trimethylol propane triacrylate (TMPTA), Ethylene glycol diacrylate (EGDMA) and
Hydroxy ethyl acrylate (HEA) with varying ratio to oligomer are presented in
Table.3.10. Oligomer and reactive diluent were mixed in different proportions with
continuous stirring at 40°C to get homogeneous mixture to be used for coating. These
formulations were applied onto glass plates and pretreated MS-panels using bar
applicator.
The UV curing was performed by passing the sample under a medium pressure
mercury vapor lamp (200 watts/inch). The typical curing behaviour is presented in
Table 3.11. For UV curing only basic coating properties like flexibility and impact
was checked. The thickness of the cured coating was found to be approx. 100 µm.
94 Experimental Electron Beam Curable Nanocoatings Films for FTIR, gel fraction were cured on glass plates, were peeled off to conduct
these studies.
Table3.10 Typical UV curing formulations with photoinitiator, oligomer and
reactive diluent
Batch
Oligomer
Reactive diluent
Photoinitiator
(wt %)
(HEA) wt %
(wt %)
90
10
5%
PUA2
PUA6
PUA7
PUA8
PUA9
PUA10
PUA11
PUA12
Table 3.11 Typical UV curing with varying irradiation time
HEA
Batch↓
No. of Passes
Conveyor speed (m/min)
PUA2
2
7
PUA6
2
7
PUA7
2
7
PUA8
2
7
PUA9
2
7
PUA10
2
7
PUA11
2
7
PUA12
2
7
95 Experimental Electron Beam Curable Nanocoatings Table 3.12 Typical UV curing formulations with varying ratio of photoinitiator,
oligomer (PUA13) and reactive diluent
Reactive Diluents (%)
Urethane acrylate
Adhesion
oligomer (%)
Promoter (wt %)
95
0.5
05
05
05
90
0.5
10
10
10
85
0.5
15
15
15
80
0.5
20
20
20
75
0.5
25
25
25
TMPTA
EGDMA
HEA
Table 3.13 Typical UV curing with varying irradiation time and reactive diluents
TMPTA
%
EGDMA
PI
No. of
Conveyor
(%)
Passes
speed
5
2
2
4.2
10
2
2
15
2
20
25
%
HEA
PI
No. of
Conveyor
(%)
Passes
speed
5
3
2
5.0
4.2
10
3
2
1
6.1
15
3
2
1
6.1
20
2
1
6.1
25
%
PI
No. of
Conveyor
(%)
Passes
speed
5
3
2
4.2
5.0
10
3
2
4.2
1
6.1
15
3
2
4.2
3
1
6.1
20
3
1
5.1
3
1
6.1
25
3
1
5.1
3.6.1.2 UV curing of UA oligomer (GUA4)
The UV formulations with reactive diluent viz., Trimethylol propane triacrylate
(TMPTA) with varying ratio to oligomer are presented in Table 3.14. Oligomer and
reactive diluent were mixed in different proportions with continuous stirring at 40°C
to get homogeneous mixture to be used for coating. These formulations were applied
onto glass plates, and pretreated MS-panels using bar applicator.
The UV curing was performed by passing the sample under a medium pressure
mercury vapor lamp (200 watts/inch). The typical curing behaviour is presented in
96 Experimental Electron Beam Curable Nanocoatings Table 3.15. For UV curing only basic coating properties like flexibility and impact
was checked. The thickness of the cured coating was found to be approx. 100 µm.
Table 3.14: Typical UV curing formulations with varying ratio of photoinitiator,
oligomer (GUA4) and reactive diluent
Urethane acrylate
TMPTA (%)
oligomer (%)
Adhesion
PI (wt %)
promoter
100
00
0.5
5
95
05
0.5
3
90
10
0.5
3
85
15
0.5
3
80
20
0.5
2
75
25
0.5
2
Table 3.15: Typical UV curing with varying irradiation time (GUA4)
TMPTA (%) No. of Passes Conveyor speed (m/min)
0
2
6.0
5
2
6.0
10
2
6.0
15
2
5.0
20
1
5.0
25
1
5.0
97 Experimental Electron Beam Curable Nanocoatings 3.6.1.3 UV curing of UA oligomer (BUA2)
The UV formulations with different types of reactive diluent viz., TMPTA with
varying ratio to oligomer are presented in Table 3.16. Oligomer and reactive diluent
were mixed in different proportions with continuous stirring at 40°C to get
homogeneous mixture to be used for coating. These formulations were applied onto
glass plates, and pretreated MS-panels using bar applicator. The UV curing was
performed by passing the sample under a medium pressure mercury vapor lamp (200
watts/inch). The typical curing behaviour is presented in Table 3.17. For UV curing
only basic coating properties like flexibility and impact was checked. The thickness
of the cured coating was found to be approx. 100 µm.
Table 3.16: Typical UV curing formulations with varying ratio of photoinitiator,
oligomer (BUA2) and reactive diluent
Urethane acrylate
TMPTA (%)
oligomer (%)
Adhesion
PI
promoter (wt %)
(wt %)
100
00
0.5
5
90
10
0.5
3
80
20
0.5
3
75
25
0.5
3
Table 3.17: Typical UV curing with varying irradiation time (BUA2)
TMPTA (%) No. of Passes Conveyor speed (m/min)
00
2
5.0
10
2
5.0
20
1
5.0
25
1
5.0
98 Experimental Electron Beam Curable Nanocoatings 3.6.1.4 UV curing of UA oligomer (NUA2)
The UV formulations with different types of reactive diluent viz., TMPTA with
varying ratio to oligomer are presented in Table 3.18. Oligomer and reactive diluent
were mixed in different proportions with continuous stirring at 40°C to get
homogeneous mixture to be used for coating. These formulations were applied onto
glass plates, wood panels and pretreated MS-panels using bar applicator. The UV
curing was performed by passing the sample under a medium pressure mercury vapor
lamp (200 watts/inch). The typical curing behaviour is presented in Table 3.19. For
UV curing only basic coating properties like flexibility and impact was checked. The
thickness of the cured coating was found to be approx. 100 µm.
Table 3.18: Typical UV curing formulations with varying ratio of photoinitiator,
oligomer (NUA2) and reactive diluent
Urethane acrylate
TMPTA (%)
oligomer (%)
Adhesion
PI (wt %)
promoter
100
00
0.5
5
90
10
0.5
3
80
20
0.5
3
75
25
0.5
3
Table 3.19: Typical UV curing with varying irradiation time (NUA2)
TMPTA (%) No. of Passes Conveyor speed (m/min)
00
2
5.0
10
2
5.0
20
1
5.0
25
1
5.0
99 Experimental Electron Beam Curable Nanocoatings 3.6.1.5 EB curing of UA oligomer (PUA13)
The EB formulations with different types of reactive diluent viz., Trimethylol propane
triacrylate (TMPTA), Ethylene glycol diacrylate (EGDMA) and Hydroxy ethyl
acrylate (HEA) with varying ratio to oligomer are presented in Table 3.20. Oligomer
and reactive diluent were mixed in different proportions with continuous stirring at
40°C to get homogeneous mixture to be used for coating. These formulations were
applied onto glass plates, wood panels and pretreated MS-panels using bar applicator.
The EB curing was performed by passing the sample under the EB accelerator,
BARC, Vashi-complex, at the energy= 1.0 MeV, frequency = 25 Hz, Average beam
current = 2.0 mA, conveyor speed = 3 cm/sec, dose/pass = 10 KGy. The EB curing
and evaluation of film characteristics of 100% oligomer at varying dose rate are
described in Table 3.21.EB curing and evaluation of film characteristics at varying
dose rate and reactive diluents are described in Table 3.22. The thickness of the cured
coating was found to be approx. 100 µm. Films for FTIR, DSC, gel fraction, and
swelling ratio were cured on glass plates, were peeled off to conduct these studies.
Table 3.20: Typical formulations of EB curing coating systems with varying ratio
of oligomer (PUA13)
Reactive Diluents (%)
Urethane acrylate
Adhesion
oligomer (%)
Promoter (wt %)
95
TMPTA
EGDMA
HEA
0.5
05
05
05
90
0.5
10
10
10
85
0.5
15
15
15
80
0.5
20
20
20
75
0.5
25
25
25
100 Experimental Electron Beam Curable Nanocoatings Table 3.21: EB curing and evaluation of film characteristics of 100% UA
oligomer (PUA13)
Oligomer
EB dose
Results after irradiation to EB
(KGy)
100 %
10
Tacky
30
Tacky
40
Slightly Tacky
60
Slightly Tacky
70
Non Tacky
80
Non Tacky film with shrinkage
Table 3.22: EB curing and evaluation of film characteristics at varying dose rate
and reactive diluents (PUA13)
Results after irradiation to EB doses (KGy)
TMPTA
EGDMA
HEA
%
10 20 30 50 70
%
30 40 50 70
%
50 60 70 80
5
1
2
3
4
-
5
1
2
3
4
5
1
2
3
4
10
1
2
3
4
-
10
1
2
3
4
10
1
2
3
4
15
1
3
3
4
-
15
1
2
3
4
15
1
2
3
4
20
1
3
3
4
-
20
1
2
3
4
20
1
2
3
4
25
1
3
3
4
-
25
1
2
3
4
25
1
2
3
4
Ratings: 1, tacky; 2, slightly tacky; 3, non-tacky, 4, non-tacky film was brittle
101 Experimental Electron Beam Curable Nanocoatings 3.6.1.6 EB curing of UA oligomer (GUA4)
The EB formulations with different types of reactive diluent TMPTA with varying
ratio to oligomer are presented in Table 3.23. Oligomer and reactive diluent were
mixed in different proportions with continuous stirring at 40°C to get homogeneous
mixture to be used for coating. These formulations were applied onto glass plates,
wood panels and pretreated MS-panels using bar applicator.
The EB curing was performed by passing the sample under the EB accelerator,
BARC, Vashi-complex, at the energy= 1.0 MeV, frequency = 25 Hz, Average beam
current = 2.0 mA, conveyor speed = 3 cm/sec, dose/pass = 10 KGy. The typical EB
curing coating of 100% oligomer and with varying ratio of oligomer and varying dose
rate are described in Table 3.24 and Table 3.25 respectively. The thickness of the
cured coating was found to be approx. 100 µm. Films for FTIR, DSC, gel fraction,
and swelling ratio were cured on glass plates, were peeled off to conduct these
studies.
Table 3.23: Typical formulations of EB curing coating systems with varying ratio
of oligomer (GUA4) to reactive diluent (TMPTA)
Urethane acrylate
TMPTA (%)
oligomer (%)
promoter (wt %)
100
00
0.5
95
05
0.5
90
10
0.5
85
15
0.5
80
20
0.5
75
25
0.5
102 Adhesion
Experimental Electron Beam Curable Nanocoatings Table 3.24: EB curing and evaluation of film characteristics of 100% UA
oligomer (GUA4)
Oligomer
EB dose
Results after irradiation to EB
(KGy)
100 %
10
Tacky
30
Tacky
40
Slightly Tacky
60
Slightly Tacky
70
Non Tacky
80
Non Tacky film with shrinkage
Table 3.25: EB curing and evaluation of film characteristics at varying dose rate
and reactive diluents (GUA4)
TMPTA
(%)
Results after irradiation to EB doses (KGy)
30
40
50
60
70
05
1
1
2
3
4
10
1
1
2
3
4
15
1
2
2
3
4
20
2
3
4
3
4
25
2
3
4
4
4
Ratings: 1, tacky; 2, slightly tacky; 3, non-tacky, 4, non-tacky film was brittle
103 Experimental Electron Beam Curable Nanocoatings 3.6.1.7 EB curing of UA oligomer (BUA2)
The EB formulations with different types of reactive diluent TMPTA with varying
ratio to oligomer are presented in Table 3.26. Oligomer and reactive diluent were
mixed in different proportions with continuous stirring at 40°C to get homogeneous
mixture to be used for coating. These formulations were applied onto glass plates,
wood panels and pretreated MS-panels using bar applicator.
The EB curing was performed by passing the sample under the EB accelerator,
BARC, Vashi-complex, at the energy= 1.0 MeV, frequency = 25 Hz, Average beam
current = 2.0 mA, conveyor speed = 3 cm/sec, dose/pass = 10 KGy. EB curing and
evaluation of film characteristics at varying dose rate are described in Table 3.27. The
thickness of the cured coating was found to be approx. 100 µm. Films for FTIR, DSC,
gel fraction, and swelling ratio were cured on glass plates, were peeled off to conduct
these studies.
Table 3.26: Typical formulations of EB curing coating systems with varying ratio
of oligomer (BUA2)
Urethane acrylate
TMPTA (%)
oligomer (%)
promoter (wt %)
100
00
0.5
90
10
0.5
80
20
0.5
75
25
0.5
104 Adhesion
Experimental Electron Beam Curable Nanocoatings Table 3.27: EB curing and evaluation of film characteristics at varying dose rate
(BUA2)
TMPTA
(%)
Results after irradiation to EB doses (KGy)
110
120
130
140
150
00
1
1
2
3
4
10
1
1
2
3
4
20
1
1
2
3
4
25
1
2
2
3
4
Ratings: 1, tacky; 2, slightly tacky; 3, non-tacky, 4, non-tacky film was brittle
3.6.1.8 EB curing of UA oligomer (NUA2)
The EB formulations with different types of reactive diluent viz., Trimethylol
propane triacrylate (TMPTA) with varying ratio to oligomer are presented in Table
3.28. Oligomer and reactive diluent were mixed in different proportions with
continuous stirring at 40°C to get homogeneous mixture to be used for coating. These
formulations were applied onto glass plates, wood panels and pretreated MS-panels
using bar applicator.
The EB curing was performed by passing the sample under the EB accelerator,
BARC, Vashi-complex, at the energy= 1.0 MeV, frequency = 25 Hz, Average beam
current = 2.0 mA, conveyor speed = 3 cm/sec, dose/pass = 10 KGy. EB curing and
evaluation of film characteristics at varying dose rate and reactive diluent are
described in Table 3.29. The thickness of the cured coating was found to be approx.
100 µm. Films for FTIR, DSC, gel fraction, and swelling ratio were cured on glass
plates, were peeled off to conduct these studies.
105 Experimental Electron Beam Curable Nanocoatings Table 3.28: Typical formulations of EB curing coating systems with varying
ratio of oligomer (NUA2)
Urethane acrylate
TMPTA (%)
oligomer (%)
Adhesion
promoter (wt %)
100
00
0.5
90
10
0.5
80
20
0.5
75
25
0.5
Table 3.29: EB curing and evaluation of film characteristics at varying dose rate
(NUA2)
TMPTA
(%)
Results after irradiation to EB doses (KGy)
70
80
90
110
120
00
1
1
2
3
4
10
1
1
2
3
4
20
1
1
2
3
4
25
1
2
2
3
4
Ratings: 1, tacky; 2, slightly tacky; 3, non-tacky, 4, non-tacky film was brittle
106 Experimental Electron Beam Curable Nanocoatings 3.6.2 Effect of addition of nanoparticles on properties of EB curable coating
systems
The coating formulations with varying concentration (wt/wt) of nanosilica and
nanoalumina were prepared in the optimized ratio of reactive diluents. The
nanoparticles used in these formulations were provided by nanoBYK. The particles
size of nanosilica and nanoalumina were almost 20 nm dispersed in TMPTA and
TPGDA respectively. The dispersion contained 50 % of nanoparticles. The addition
of nanoparticles to oligomer was sonicated 40°C to ensure proper mixing. These
formulations were applied onto glass plates, wood panels and MS-panels using bar
applicator. The coated panels were cured by electron beam at optimized dose for
particular reactive diluent. The thickness of the cured coating was found to be approx.
100 µm. FTIR, DSC, gel fraction, swelling ratio, SEM, XRD, TGA and all coating
properties were studied according to ASTM standards.
3.6.2.1 EB curing of formulation with varying percentage of nanosilica and
nanoalumina in urethane acrylate oligomer with PENTA
Coating formulations with nanosilica and nanoalumina in different reactive diluents
viz., TMPTA, EGDMA and HEA are presented in Table 3.30 – Table 3.35. The
optimized ratio of oligomer: TMPTA, oligomer: EGDMA and oligomer: HEA were
85: 15, 85: 15 and 80: 20 respectively. The optimized dose for the same was 30 KGy,
50 KGy and 70 KGy respectively.
107 Experimental Electron Beam Curable Nanocoatings Table 3.30: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of TMPTA
UA
TMPTA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
30 kGy
Table 3.31: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of EGDMA
UA
EGDMA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
108 50 kGy
Experimental Electron Beam Curable Nanocoatings Table 3.32: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of HEA
UA
HEA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
70 kGy
Table 3.33: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of TMPTA
UA
TMPTA
TPGDA
NanoAl
NanoAl
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
109 30 kGy
Experimental Electron Beam Curable Nanocoatings Table 3.34: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of EGDMA
UA
EGDMA
TPGDA
NanoAl
NanoAl
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
50 kGy
Table 3.35: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of HEA
UA
HEA
TPGDA
NanoAl
NanoAl
EB
(%)
(RD)
content (%)
dispersion (%)
content (%)
Cured
15.00
00
0
0
14.50
0.5
1.0
0.5
14.00
1.0
2.0
1.0
13.50
1.5
3.0
1.5
13.00
2.0
4.0
2.0
12.50
2.5
5.0
2.5
85
110 70 kGy
Experimental Electron Beam Curable Nanocoatings 3.6.2.2 EB curing of formulation with varying percentage of nanosilica and
nanoalumina in urethane acrylate oligomer with Glycerol
Coating formulations with nanosilica and nanoalumina in reactive diluents viz.,
TMPTA, are presented in Table.3.36 and Table 3.37 respectively. The optimized
ratio of oligomer: TMPTA was 80: 20. The optimized dose for the same was 60 KGy.
Table 3.36: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of TMPTA
UA
TMPTA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
(%)
dispersion (%)
content (%)
Cured
20.00
00
0
0
19.50
0.5
1.0
0.5
19.00
1.0
2.0
1.0
18.50
1.5
3.0
1.5
80
60
kGy
18.00
2.0
4.0
2.0
17.50
2.5
5.0
2.5
17.00
3.0
6.0
3.0
16.50
3.5
7.0
3.5
111 Experimental Electron Beam Curable Nanocoatings Table 3.37: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of TMPTA
UA
TMPTA
TPGDA
NanoAl
NanoAl
EB
(%)
(RD)
(%)
dispersion (%)
content (%)
Cured
20.00
00
0
0
19.50
0.5
1.0
0.5
19.00
1.0
2.0
1.0
18.50
1.5
3.0
1.5
80
60
KGy
18.00
2.0
4.0
2.0
17.50
2.5
5.0
2.5
17.00
3.0
6.0
3.0
3.6.2.3 EB curing of formulation with varying percentage of nanosilica and
nanoalumina in urethane acrylate oligomer with 1,4-butanediol
Coating formulations with nanosilica and nanoalumina in reactive diluents viz.,
TMPTA, are presented in Table 3.38 and Table 3.39 respectively. The optimized
ratio of oligomer: TMPTA was 80: 20. The optimized dose for the same was 140
KGy.
112 Experimental Electron Beam Curable Nanocoatings Table 3.38: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of TMPTA
UA
TMPTA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
(%)
dispersion (%)
content (%)
Cured
20.00
00
0
0
19.0
1.0
2.0
1.0
18.0
2.0
4.0
2.0
17.0
3.0
6.0
3.0
16.0
4.0
8.0
4.0
15.0
5.0
10.0
5.0
14.0
6.0
12.0
6.0
13.0
7.0
14.0
7.0
80
140kGy
Table 3.39: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of TMPTA
UA
TMPTA
TPGDA
NanoAl
(%)
(RD)
(%)
dispersion (%)
20.0
00
0
0
19.0
1.0
2.0
1.0
18.0
2.0
4.0
2.0
17.0
3.0
6.0
3.0
16.0
4.0
8.0
4.0
15.0
5.0
10.0
5.0
80
EB
content (%) Cured
140
KGy
113 NanoAl
Experimental Electron Beam Curable Nanocoatings 3.6.2.4 EB curing of formulation with varying percentage of nanosilica and
nanoalumina in urethane acrylate oligomer with NPG
Coating formulations with nanosilica and nanoalumina in reactive diluent TMPTA,
are presented in Table 3.40 and Table 3.41 respectively. The optimized ratio of
oligomer: TMPTA was 80: 20. The optimized dose for the same was 110 KGy.
Table 3.40: EB curing and typical formulations with varying concentration of
nanosilica at optimized concentration of TMPTA
UA
TMPTA
TMPTA
NanoSi
NanoSi
EB
(%)
(RD)
(%)
dispersion (%)
content (%)
Cured
20.0
00
0
0
19.0
1.0
2.0
1.0
18.0
2.0
4.0
2.0
17.0
3.0
6.0
3.0
80
110
KGy
16.0
4.0
15.0
5.0
14.0
6.0
8.0
10.0
12.0
114 4.0
5.0
6.0
Experimental Electron Beam Curable Nanocoatings Table 3.41: EB curing and typical formulations with varying concentration of
nanoalumina at optimized concentration of TMPTA
UA
TMPTA
TPGDA
NanoAl
NanoAl
EB
(%)
(RD)
(%)
dispersion (%)
content (%)
Cured
20.0
00
0
0
19.0
1.0
2.0
1.0
18.0
2.0
4.0
2.0
110
KGy
80
17.0
3.0
6.0
3.0
16.0
4.0
8.0
4.0
15.0
5.0
10.0
5.0
3.7 Electrochemical Impedance Spectroscopy (EIS)
Corrosion is defined as the deterioration of the material, usually a metal, because of
reaction with its environment and which requires the presence of an anode, a cathode,
an electrolyte and an electric circuit (Rosliza and Wan 2010; Rosliza et al 2010). One
of the most popular uses of EIS is the characterization of the protective properties of
coatings on corrodible metals (Gordon et al 2003; Yasuda et al 2001). Many EIS
studies have been developed to study the changes in the impedance of coated metals
as they undergo either natural or artificial exposure to conditions that cause corrosive
failure of such systems. EIS has many advantages in comparison with other
electrochemical techniques. It is a non-destructive method for the evaluation of a wide
range of materials, including coatings, anodized films and corrosion inhibitors (Abdel
et al 2006; Patel et al 2012).
3.7.1 Experimental
The DC polarization study was performed during immersion in 3.5% NaCl solution
open to air and at room temperature. A Pyrex glass cell with a capacity of 300 ml was
used for the electrochemical corrosion tests. A three-electrode set-up was used with
impedance spectra being recorded at the corrosion potential Ecorr. The system was
115 Experimental Electron Beam Curable Nanocoatings composed of a working electrode, counter electrode, and reference electrode. A
saturated calomel electrode (SCE) was used as the reference electrode. It was coupled
capacitively to a counter electrode made of platinum wire to reduce the phase shift at
high frequencies. The probe tip was easily adjusted to bring it at a distance of about 2
mm from the working electrode schematic diagram of electrochemical cell used in
EIS is as shown in Figure 3.10.
A potentiostat (Versa STAT 3, by Princeton Applied Research) was used for the
electrochemical measurements. VersaStudio corrosion analysis software was used to
analyze the data and calculate the Tafel constants. DC polarization tests of specimens
were made at a scan rate of 1.66 mV/sec in the applied potential range from -1.5 V to
0.2 V with respect to Ecorr. The exposed surface area was 7 cm2. The corrosion rates
of hybrid coatings were reported as millimeter per year (mmpy).
Figure 3.10: Schematic diagram of electrochemical cell used in EIS
The EIS was performed for the optimized coating samples of different urethane
acrylates with TMPTA as reactive diluents with nanosilica and nanoalumina viz.,
PUA (85%): TMPTA (15%) with 2.5% nanosilica and 2.0% nanoalumina.
GUA (80%): TMPTA (20%) with 3.0% nanosilica and 2.5% nanoalumina.
BUA (80%): TMPTA (20%) with 6.0% nanosilica and 4.0% nanoalumina.
NUA (80%): TMPTA (20%) with 5.0% nanosilica and 4.0% nanoalumina.
116 Experimental Electron Beam Curable Nanocoatings 3.8.0 Characterization of EB cured coatings
3.8.1 Curing characteristics of EB curing
3.8.1.1 Gel fraction
The cured films of known weight were extracted for 12h in acetone and xylene using
soxhlet extraction were dried in vacuum and weighed to estimate gel fraction using
relation
3.8.1.2 Swelling ratio
Cured films of known weight were dipped in acetone and xylene for 50 h and
weighed after blotting the excess solvent from the surface to estimate the swelling
ratio of the cured film using relation:
Swelling ratio = swelled weight / initial weight
3.8.1.3 FTIR
IR spectrum was recorded using a cell NaCl cell on a Perkin-Elmer spectrum BX FTIR spectrophotometer taking 16 scans. The range of spectrophotometer is 400-4000
cm-1.
3.8.2 Performance characteristics of EB for mechanical properties
3.8.2.1Pendulum Hardness Tester (ASTM D4366)
This method evaluates hardness by measuring the damping time of an oscillating
pendulum (TQC SP0500 Pendulum Hardness Tester). The pendulum rests with 2
stainless steel balls on the coating surface. A physical relationship exists between
oscillation time, amplitude and the geometric dimensions of the pendulum. The
viscoelastic behavior of the coating determines its hardness. When the pendulum is
set into motion, the balls roll on the surface and put pressure on the coating.
117 Experimental Electron Beam Curable Nanocoatings 3.8.2.2 Pencil Hardness Test (ASTM D3363)
Pencil hardness measurement are used to determine the hardness of a coating, relative
to a standard set of pencil leads (3B to 8H), is determined by scratching the leads
across the coating at a controlled angle of 45º for a distance of approximately ¼ inch
(Komal scientific LTD. India).
3.8.2.3 Scratch resistance (ASTM D2027)
This test method describes a laboratory procedure using an instrumented scratch
machine to produce and quantify surface damage under controlled conditions (Sakova
Instruments, India). This test method is able to characterize the mar and scratch
resistance of polymers by progressively increasing scratch load which eventually
induces a critical point of damage such as coating delamination, coating cracking or
whitening in a single lot.
3.8.2.4 Impact resistance (ASTM 2794)
This method is to predict the ability of the coating resist cracking caused by rapid
deformation. Tubular impact resistance test was carried out using an indenter with
hemispherical head of diameter 0.625 inch and 2lb load (Precision Engineers, India).
3.8.2.5 Flexibility Testing (ASTM D522)
ASTM D522 is a method of determining the resistance to cracking on elongation of
organic coatings on metal panels. This method describes the use of both conical and
cylindrical mandrels. Here in our study flexibility was checked with conical mandrel
(HENRY ZUHR, Newyork).
3.8.2.6 Cross-hatch adhesion (ASTM D3359-83)
This test carried out as per ASTM D3359-83. Crosscut adhesion tape test was used to assess
the adhesion of coating films to metallic substrates. Cuts were made on the coating in one
steady motion with sufficient pressure on the cutting tool having a cutting edge angle between
15⁰ and 30°. After making two such cuts at 90° the grid area was brushed and a 2.5 cm wide
semi-transparent pressure-sensitive tape was placed over the grid (Khushboo Scientific India).
After 30 seconds of application, the tape was removed rapidly and the grid inspected
118 Experimental Electron Beam Curable Nanocoatings according to the ASTM standards. The amount of coated area retained under the tape
corresponds to the adhesion efficiency of the coating. The more coated material removed by
the tape, the poorer the adhesion of the coating to the substrate.
3.8.2.7 Tensile strength properties of thin films (ASTM D882)
In this test method the material is pulled until it breaks in order to measure elongation, tensile
modulus, tensile yield strength and elongation at break (Universal Testing Instrument,
LLOYD INSTRUMENTS, LR 50K, UK). However, it is designed specifically for thin film
less than 1mm (0.04 inch) thick. In this the specimens are rectangular strips of film and are
not “dumbbell” or “dogbone” shaped. The average of at least five measurements for each
sample was reported, the experimental error is +/- 10%.
3.8.2.8 Taber abrasion (ASTM 4060-01)
The wear resistance of the coatings was determined by Taber abrasion test [ASTM
4060-01]. CS-10 abrasive wheels were used with a 500 g weight in each wheel. The
regeneration of the wheel was done with an abrasive paper of S-11 (Khushboo
Scientific Pvt. Ltd, India). Before abrasion process the weight of the sample was
determined with an accuracy of 1mg. Every hundred cycles the weight of the
specimen was determined again and the weight loss calculated. Successive abrasion
cycles were performed till 500 cycles, showing the wear evolution on a graph of
weight loss versus the number of abrasive cycles.
3.8.2.9 Gloss (ASTM D523-99)
Gloss is a measure of ability of coated surface to reflect light at a particular angle without
scattering. Gloss was determined according to ASTM D523-99. Gloss of the cured sample
was measured at 45º and 60 º of reflectance using a digital mini gloss meter calibrated against
internal standard i.e. refractive index (Komal Scientific Co. Mumbai, India).
3.8.3 Characterization of EB curable systems for performance properties
3.8.3.1 Xenon Arc Weatherometer (ASTM G115)
The ability of a paint or coating to resist deterioration of its physical and optical
properties caused by exposure to light, heat and water can be significant for many
applications. Xenon arc testers are considered the best simulation of full spectrum
119 Experimental Electron Beam Curable Nanocoatings sunlight because they produce energy in the UV, visible and infrared regions
(Solarbox 1500e). The results are reported in terms of % gloss retention. The results
were noted in terms of % gloss retention after every 100 hrs upto 500 hrs.
3.8.3.2 QUV accelerated weathering testing (ASTM D4329)
Accelerated weathering simulates damaging effects of long term outdoor exposure of
materials and coatings by exposing test samples to varying conditions of the most
aggressive components of weathering- ultraviolet radiation, moisture and heat. A
QUV test chamber uses fluorescent lamps to provide a radiation spectrum centered in
the ultraviolet wavelengths. Moisture is provided by forced condensations and
temperature is controlled by heaters (Q-Panel Lab products, Europe). The results were
noted in terms of % gloss retention after every 100 hrs up to 500 hrs.
3.8.3.3 Salt spray testing (ASTM B117)
Corrosion resistance effect on long term exposure especially in a automotive
applications is studied in ASTM B117. In this 5% NaCl solution is prepared and
sprayed in the corrosion Box from UK.
3.8.3.4 Chemical resistance
Resistance to acid and alkali was determined by using ASTM D-4274-88 standard
while for detergent resistance standard ASTM D-2248a was followed. For this test,
the coated panels were immersed in 5% solution of HCL (acid), 5% solution of NaOH
(alkali) and 5% solution of detergent. The immersed panels were maintained at
constant temperature. The panels were removed for examination after 6, 12, 18 and 24
hours from the start of the test and observed loss of adhesion, blistering, popping or
any other deterioration of the film.
3.8.3.5 Solvent resistance
The resistance of the coating towards the solvents like methyl ethyl ketone (MEK)
and xylene was determined as per the procedure given in ASTM D-5402-93. The
coated panels were rubbed with the cotton moist with the respective solvent and
observed for any softness of the film, peeling of the film and loss of gloss etc
120 Experimental Electron Beam Curable Nanocoatings 3.8.4 Surface characteristics of coatings
3.8.4.1 Scanning electron microscope (SEM)
Scanning electron microscopical (SEM) images of the coating-free films were
obtained by the aid of FEI Quanta 200 SEM (Netherland). The SEM conditions for all
measurements were working distance of 9.1 mm, acceleration voltage of 15 kV, and
probe current 100 pA. The pictures were taken using a BSE detector.
3.8.4.2 Contact angle
Contact angle of water on the coating was determined by GBX, France model
Digidrop.
3.8.4.3 XRD analysis
To analyze the crystalinity of urethane-acrylate with dispersed nanosilica, X-Ray
analysis of films exposed to inside air was carried out on RIGAKU MINIFLEX.
3.8.5 Thermal properties
3.8.5.1 Thermogravimetric analysis (TGA)
Thermal properties of the EB cured polymer films were studied by thermal
gravimetric analysis (TGA) and differential scanning analysis (DSC). TGA was
carried out by using a DTG-6514 Shimadzu (Japan), with film samples weighing 4.5
mg. The temperature ranged from 20 to 500° C and the heating rate was 10° C/min in
a nitrogen flow rate of 75 ml/min.
3.8.5.2 Differential scanning calorimeter
DSC was studied by using a Q 100 TA (USA) instruments. The glass transition
temperatures (Tg) of various networks at a heating rate of 10° C/min.
121