The role and use of pigments,
NIR absorbers and additives
Sibylle Glaser
Treffert GmbH & Co.KG
page 1
Topics
• What is colour?
- colour
- colorants
• Laser welding of polymers
- material
- colorants – additives
• Conclusions
page 2
1
What is colour?
page 3
Wavelengths
page 4
2
What is colour?
• In the range of 400 to 700 nm the electromagnetic waves are
visible for the human eye.
• Illuminated objects reflect a fraction of the wavelengths
spectrum of a light source which is detected by the eye and
identified as colour.
• Colour is an individual perception which is stimulated by light
received by the eye.
• The observed colour is influenced by the light source.
page 5
What affects colour?
light source
surface structure
adjacent colours
page 6
3
Colorants
page 7
Classification of colorants
Colorants
Dyes
soluble in plastics
organic
Pigments
insoluble in plastics
organic
inorganic
page 8
4
Properties of colorants
Properties
Inorganic Pigments
Organic Pigments / Dyes
Particle size
0.5 – 1.0 mm
0.01 – 0.1 mm / dissolve
low - moderate
high
generally opaque
generally transparent
high
low to high
moderate to excellent
low to excellent
Weather fastness
excellent
low to excellent
Migration
excellent
Moderate to excellent /
low to moderate
Plate-out
no
in function to the recipe
usually good
difficult / soluble
Colour strength
Transparency
Heat resistance
Light fastness
Dispersion
page 9
Interaction pigment - light
pearl luster
pigments
Specific colour, gloss and
colour shift due to light
interference (reflection and
scattering)
metallic
pigments
Metallic gloss due to
reflection
absorption
pigments
Specific colour due to light
absorption
page 10
5
Influence on laser welding
• Absorption pigments
- Used in laser transparent and laser absorbing colour
•
•
application
Pearl luster pigments
- Due to platelets structure nearly no use in laser transparent
colour formulations
- Use in laser absorbing formulations possible
(e.g. as NIR absorber)
Metallic pigments
- Due to the brilliant surface of the platelet structured
pigments and therefore, mirror effect, the use in colour
formulations for laser welding is not recommended.
page 11
Laser welding of polymers
page 12
6
Laser welding of polymers
material
page 13
Polymer type
crystalline
(translucent/opaque)



amorphous
(transparent)
thermoplastics
laserweldable
(thermoplastic
elastomers (TPE))
Partially cross linked
polymer chains
elastomers
Highly cross linked
polymer chains
duromers
page 14
7
Transmission spectra
Transmission depending on wall thickness of
visually transparent polymers
100
transmission in %
95
90
85
polycarbonate 1mm
polycarbonate 2mm
polycarbonate 3mm
80
400
500
600
700
800
900
1000
1100
wavelength in nm
page 15
Transmission spectra
Transmission depending on wall thickness
of opaque polymers
70
60
transmission in %
50
40
30
20
ABS 1 mm
ABS 2 mm
ABS 3 mm
10
0
400
500
600
700
800
900
1000
1100
wavelength in nm
page 16
8
Transmission spectra
Transmission of styrene based polymers
100
90
transmission in %
80
70
60
50
40
30
ABS
PC/ABS
M-ABS
20
10
0
400
500
wall thickness: 2 mm
600
700
800
900
1000
1100
wavelength in nm
page 17
Transmission spectra
Transmission of glass filled polyamides
100
90
transmission in %
80
70
60
50
40
30
PPA GF 30
PA 6.6 GF 30
PA 6 GF 15
PA 6.6 GF 50
20
10
0
400
500
wall thickness: 1 mm
600
700
800
900
1000
1100
wavelength in nm
page 18
9
Transmission spectra
Transmission of several engineering plastics
70
60
transmission in %
50
40
30
20
PBT type A
PBT type B
POM
10
0
400
500
wall thickness: 1 mm
600
700
800
900
1000
1100
wavelength in nm
page 19
Optical properties of thermoplastics
Behaviour of thermoplastics in regard to light in
the visible and the NIR range:
• transmission
• scattering
• reflection
• absorption (very low)
• depending on wavelength and wall thickness
page 20
10
Influence of fillers on the transmission
„Macroscale“ fillers have a negative influence
on the function of the NIR-transparent joint
partner.
For example, glass fibres, glass balls, chalk,
talcum powder, flame retardants etc. decrease
the transmission values by scattering,
reflection and absorption.
page 21
Laser welding of polymers
Colorants - Additives
page 22
11
Joint partner LST/LSA - Colorants
LST
LSA
Absorption range of polymers
page 23
Requirements for the colouring of the
transparent joint partner
Colorants should influence the NIR-light as little as
possible.
Colorants create whished colour.
Linking of the colour in the visible and the function
in the NIR-range.
page 24
12
Requirements for the colouring of the
absorbing joint partner
Colorants respectively additives absorb the NIRlight and change it effectively into heat energy.
Colorants create whished colour.
Linking of the colour in the visible and the function
in the NIR-range.
page 25
Degree of complexity
page 26
13
Black – NIR absorbing
•
•
Carbon black
Broadband absorber for all wavelengths.
Only for dark, grey and black applications
Source: Paragon AG
page 27
Black – NIR transparent
100
•
•
Formulation is a mixture of
different dyes:
Absorption between
400 – 700 nm (black)
transparent in the NIR
NIR-transparent black
already available for many
polymers as a standard
product.
Many variations of black
available!
90
80
Transmission in %
•
70
60
50
Carrier material
40
D.Y.54
30
S.R.179
S.G.3
20
10
0
400
500
600
700
800
900
1000
1100
1200
Wavelength in nm
in the visible
in the NIR
page 28
14
Black – NIR transparent
100
90
transmission in %
80
Temperature stabile
up to 350°C
Neutral black
Stabile to migration
Excellent light and
weather fastness
Insoluble in organic
solvents and water
Inert against physical
and chemical influences
type A 0,2% in PC 2mm
type B 0,2% in PC 2mm
70
60
50
40
30
20
10
0
400
500
600
700
800
wavelength in nm
900
1000
1100
page 29
Degree of complexity
page 30
15
Colour – NIR absorbing
NIR-Absorber properties:
• Not based on carbon black
• Possibly neutral in colour
•
•
•
•
•
•
(bright, without own colour influence)
Wavelengths area 800 up to 1100 nm (1500nm)
Mostly pigments in use
Particle size in the µm range only for opaque colours
Nanoparticles as additives for transparent formulations
Polymer type
Regulatory requirements
page 31
Colour – NIR absorbing
100
Example:
90
Absorption in %
80
Inorganic NIRabsorber for
opaque
colours
70
60
50
40
30
1% in a
transparent polymer,
1mm wall thickness
20
10
0
400
600
800
1000
1200
1400
Wellenlänge in nm
page 32
16
Colour – NIR transparent
• In general:
•
•
The darker the colour the better the transmission.
The exception proves the rule.
Choice of colorant is depending on the
transmission of the polymer (type, wall thickness, filler, etc.)
Colour can also have an influence on the process
parameters (welding time, laser power,...)
- Opaque or translucent colours
- Bright or dark colours
- Wall thickness
- Polymer
page 33
Transmission spectra of selected dyes
100
90
transmission in %
80
70
60
50
40
D.Y. 54
S.R. 179
S.G. 3
30
20
10
0
400
500
600
700
800
900
1000
1100
wavelength in nm
page 34
17
Transmission spectra of four types of P.R. 101
90
Type 1
Type 2
Type 3
Type 4
80
Transmission in %
70
60
50
40
30
20
10
0
400
500
600
700
800
900
1000
1100
1200
Wavelength in nm
page 35
Colour/Colour
•
•
•
Laser transparent and laser
absorbing parts require different
colour solutions.
Challenge: metamerism,
i.e. both samples need to look
identical at different illuminations
Marquardt IP
(EP 0 751 865 B2 )
page 36
18
Degree of complexity
page 37
Transparent NIR-absorber
80
70
Typ A
Typ B
Typ C
Typ D
absorption in %
60
50
40
30
20
10
0
400
500
600
700
800
900
1000
1100
wavelength in nm
page 38
19
White / White
White surface => total
reflection of the visible light
Laser absorbing part:
By use of colour neutral NIR-absorber
a RAL 9003 is possible.
white laser absorbing
Laser transparent part:
Challenge
⇒ transmissive scattering
⇒ adjustment milky translucent
white laser transparent
page 39
Conclusion
• Knowledge about spectral data
of colorants and absorber
additives are essential for the
formulation of NIR-transparent
and absorbing colours.
• Broad range of colours, from
transparent to opaque and from
bright to dark are possible.
page 40
20
Thank you for your
attention!
Treffert GmbH & Co. KG
In der Weide 17
D-55411 Bingen
www.treffert.org
Sibylle Glaser
+49 (0) 6721 403 0
[email protected]
page 41
21