10urna l of Sc ientific & Industria l Research
Vol. 59, March 2000, pp 225 -228
Blends of Polyvinyl Acetate and Low Density Poly Ethylene
Nirm al K Pate l, Pras hant D Pand ya and Vij ay Kum ar Sinh a*
De par tme nt of Indu stri al C hemi stry,
V P and RPTP Sc ie nce Co ll ege,Vall ab h V idyan aga r 388 120, Ana nd , Gujarat, Ind ia
Received: 1 1 August 1999; acce pted: 17 December 1999
The feas ibi lity of synthesing a seri es of po lyv in ylacetate( PV Ac): low densit y polyeth ylene (LOPE) blends of different
weight ratio 0.25: 1,0.5: 1,0.75: I, I: I, I :0.75 , I :0.5 and I :0.25 respecti vely is stud ied by using so lution mi xi ng process. An
improvement in phys ical properties of blends is observed in compariso n with those of blends of LOPE wi th Nit ril e Bu tad iene
Ru bber(NBR) and Styrene Butadiene Rubbe r(S BR). It is fo un d th at these bl end s have superior mec hani cal properties as
compared to those of ru bber blends Confi rmati on of blendi ng is done with the help of IR . Thermal stabb il ity of PV Ac: LOPE
blends is determined by thermogravimetric analys is(TGA). Practica ll y no weight loss is observed up to 275 (lC and a high
value of MFI provides ease of process ing within varyi ng temperatures.
Introduction
Syntheti c polymers have gained importance du e
to the ir versatile nature and the ir products of tail or
made properti es at reduced cost. The deve lopment in
thi s fie ld has lowered the consumpti on of conventi onal
and natura l products.
Lo w density pol yeth ylene(LOPE) , one of the
synthetic polyme rs, is be ing ex tensively used presentl y
and di sposa l of its waste is causing a seri ous
environment a l probl em due to its nonbi odegradability.
It has been reported th at polysacc harides (starch,
cellul ose, and its deri vatives) can be used in bl end
I 6
compos iti on to improve bi odegradability of LOPE. But natural polysaccharides being hydrophili c in nature
hampe r the e lectrica l and mechani ca l properti es of
blends 7.
Blending of polyethyle ne w ith other syntheti c
polymers,
such
as
po lypro pylene,
po lyeste r,
polystyrene, polyamide and modi fied polya mide,
polyeth yle ne
terph athl ate(PET ),
polycarbonate,
modifi ed EPOM and BR, polymeth ylmeth acrylate
(PMM A), bl ock propylene-ethyle ne copo lymer,and
LLOPE graft ma le ic anh ydri de copolymers,has been
· So?,
reporte d ear I ter -. .
*Au th or for correspo ndence
T o incorporate the bi odegrad ability al ong with
improved mechani cal and e lectrical pro perties we
blended PY Ac w ith LOPE . Blending of po lyethy lene
with PY Ac was fo und to be difficult due to certa in
limitati ons. M ec hanica l mi xin g was not poss ible at low
te mperature and mi xin g at hi g h te mpe rature enh anced
the poss ibility of ox idative degradati on. Thu s, so luti on
mixin g was carri ed out for homogeneous ble nding of
LOPE w ith PY Ac . Since, both PY Ac,and L OPE are
so lubl e in xy lene, the ir bl ends we re prepared by
so luti on mi xin g process and tested fo r me lt flow
index(M FI), fl ex ura l strength , tensile strength, heat
di storti on temperature(HOT),and duro me ter hard ness .
IR spectroscopy confirmed the fo rmati on of polymeri c
bl end . T herma l stability of blends was also stud ied by
means of thermogravimetri c ana lys is(TGA) .
Improveme nt of ph ys ical prope lti es is attributed
to the reducti on of interfac ia l tension at the interface of
the compone nt s as well as penetrati on of surface
24
molecul es int o the polymeri c phase .
Material and Methods
PY Ac from Nati onal C he mi ca l, Baroda, LOPE
from Indi an Petroche mi cals Corporati on Lim ited
(lPCL), Baroda, and laboratory grade xy le ne and
meth anol were used.
J SCI INO RES VOL 59 MARCH 2000
226
Blending
Flexural Strength. (FS)
A threenecked flask equipped with water
condenser ,stirrer and, thermometer was charged with
calculated amounts of PV Ac, LDPE, and xylene. The
mixture was heated at 100 DC with co nstant stirring for
2 h. The blend cooled to room temperature and
prec ipitated in methanol , It was filtered and dried in
vacuum to constant mass 25 . 27 .
The measurement of FS was done as per the
procedure described in ASTM D790. A three poi nt
loading system utili zing central load ing on a single
supported beam was used for measurement. A
crosshead speed of 2.5 cm/min was used for all
specimens. Results given in Table I indicate that
flexural strength increases with increasing amolln t of
PV Ac in the blend compos ition. For example, fl exura l
<;trength of 1:0.25 (PV Ac : LDPE) compos iti on is
nearl y three times compared with th at of polyeth ylene.
Preparation o./,polymer Sheet
Sheets of specific thi ck ness were prepared by
sand witching th e blend between mould plates of
compress ion mac hine at ISOne fo r 10 min . The sheet
was held under 60 kg/cm2 pressure at 150 °C for 5 min
and then taken out of the mould for cooling at room
?8
temperature- .
Results and Discussions
Melt Flow Index (MFI
The measurement of MFI was carried out as per
the procedure described in ASTM D 1238-S3T. The
weight of polymeric blend flowed in 10 min under a
2.1 6 kg load at 190°C was measured by a Melt Indexer.
Results of MFI measurements are given in Table I.
The MFI of blends increased with increase in the
amount of PV Ac.
Tensile Strength (TS)
Tensi Ie strength measurements were co nducted
by using a tensile tester at room temperature, foll ow ing
the process described in ASTM D 638. A cross head
speed of 10 em/min was use in all measurements. It is
observed th at TS- of I: I PVAc: LDPE is optimum
compared to other blends. On the other hand, per cent
elongation (fl ex ibility) continued to increase with
increasing contents of PVAc in blends (Tab le I).
Heat Distortioll Temperature (HDT)
HDT measurement was carried out following
procedure described in ASTM D 648. HDT of the
blends increased on increasing the amount of PV Ac in
blend . For example, HDT of LDPE is 42De and that of
I :0.25(PV Ac : LDPE) is 70° e (Tabl e I).
Durometer Hardn ess
Tabl e I Ratio
Physical properti es of PV Ac: LOPE blcnd s
MFI
Fl ex ural
Per ccnt
strength elongati on
PVAe: LOPE g/ IO min
(mean )
kg/em 2
per ccnt
Tcnsile
HOT
strength
kg/e m"
flC
(mean)
0: 1
0.5
69.63
100
31
42
0.25: I
0.9 1
70.25
133
35
47
0.5: 1
1.3
73.87
166
38
50
0.75 : I
1. 67
78.50
200
40
52
2.01
86.92
266
55
55
I: 0.75
4.26
97. 17
300
54
5~
1: 0.5
5.08
11 2.82
DJ
50
67
400
47
70
1: 0.25
6.67
197.43
Durometer hardness meas urements were done as
per the procedure described in ASTM D 22407S .Hardness is measured in terms of shore A and shore
D. They represent the hardness of a materi al when it is
subj ected to a certain force through a penetrating
object of well defined dimensions. The hardness of
blends decreases gradually with the increas ing
content of PV Ac because of its relatively fl exible
nature (Table 2).
Comparison of Mechanical Properties of
Different Polymeric Blends
The mechani ca l properties of blends synthesi zed
in our laboratory are compared with th at of LDPE29
Rubber hlends reported by Mohamad et al.
It is
observed that tensile properties (tensile strength and
per cent elongati on) of PV Ac: LDPE blends are bet ter
thall those or NBR: LDPE and SBR: LDPE blends .
PATEL el al.: BLENDS OF POLYVINYL ACETATE & POLY ETHYLENE
Table 2 - Dlirometer hardness
Tabl e 3 -
227
Compar ison of PV Ac:LDPE blends with ru bber -
Rati o
Dli rometer
hard ness
PVAc:LDPE
Shore A
Shore 0
Type of blend
LOPE
Tensi le
0: 1
90
40
Content
strength
elongati on
0.25:1
88
38
PVAe:LDPE
25
47
400
0.5:1
87
35
50
55
266
0.75: I
85
33
75
54
.100
1:1
84
29
25
21
:1 55
1:0.75
75
27
50
32
:140
1:0.5
72
23
75
35
2:1 0
:0.25
68
21
25
18
200
50
29
160
75
34
I HO
LOPE blends
NBR :LDPE
SBR :LDPE
Per cen t
Infarred Spectroscopy
T he IR spectra l analysis of blend s prepared by
so lution mix ing process was carried out on DuPont 951
IR spectrometer. In IR spectra the sharp peak around
1752 cm' l confirms the presence of ester linkage
present in PV Ac in a blend . A sharp absorpt ion band at
103 1cm' l i attri-buted to the aliphatic olefins(CH=CH)n- present in the bl end based on LOPE. C-O
stretching band is observed at 1254 cm' l. Sharp band
around 2925cm' l determines the vibrational stretchin g
of -(C-H)- and -(CH2)- present in LDPE.The presence
of above key peaks IR spectroscopy confirms the
successful synthesis of LDPE:PV Ac blends.
A series of compatib le blends of PV Ac and
LOPE were success full y synthes ized by using solu ti on
mixin g process. B lending of LOPE with PV Ac
e nhances its phys ica l and the rmal stability. The
cOtnparison indicates that PY Ac: LOPE blend s have
better mechanical prope rti es than th ose of NBR :
LOPE and SBR : LDPE blends.
Th ermogravimatric Analysis ofLDPE:PVAc
blend
The authors are thankfu l to Dr H K Patel,
Principal , Y P and RPTP Science Co ll ege and Mr K M
Patel, Head of Industrial Chemi stry De partment for
providin g necessa ry laboratory facilities.
M easure ments were conducted UStng a DuPont
2000 the rmograv imetric ana lyzer unde r nitrogen
atmosphe re at a heating rate of 20°Cimin up to 950 °C.
From the percentage wei ght loss, thennal stability o f
the ble nd was estimated . The bl e nd of LOPE with
PV Ac showed two decompos ition stages, (Figure B).
The first decompos ition occurs at 285 °C to 425 °c
which is attributed to PV Ac deco mposition . The
structure of PV Ac is branc hed, brownain move ment
within the molecule occurs more rapidl y compared to
the strai ght chain LOPE polymer. The second stage,
appearing at about 5 10 DC was due to LOP E
decomposition . The re was no weight loss up to 275 DC.
Integral Procedure Decompos ition Temperature (IPDT)
of the blend was found at 540 °C. Thus, blend offers
wide ran ge of process in g temperatures .
Conclusion
Acknowledgment
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