the role and use of pigments, nir absorbers and additives
TRANSCRIPT
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Sibylle Glaser
Treffert GmbH & Co.KG
The role and use of pigments, NIR absorbers and additives
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Topics
• What is colour?- colour- colorants
• Laser welding of polymers- material- colorants – additives
• Conclusions
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What is colour?
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Wavelengths
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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 wavelengthsspectrum of a light source which is detected by the eye andidentified as colour.
• Colour is an individual perception which is stimulated by lightreceived by the eye.
• The observed colour is influenced by the light source.
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What affects colour?
adjacent colours
light source
surface structure
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Colorants
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Classification of colorants
ColorantsDyes
soluble in plastics
Pigmentsinsoluble in plastics
organic inorganicorganic
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Properties of colorants
difficult / solubleusually goodDispersion
in function to the recipenoPlate-out
Moderate to excellent /low to moderateexcellentMigration
low to excellentexcellentWeather fastness
low to excellentmoderate to excellentLight fastness
low to highhighHeat resistance
generally transparentgenerally opaqueTransparency
highlow - moderateColour strength
0.01 – 0.1 mm / dissolve0.5 – 1.0 mmParticle size
Organic Pigments / DyesInorganic PigmentsProperties
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Interaction pigment - light
absorptionpigments
metallicpigments
pearl lusterpigments
Specific colour, gloss and colour shift due to light interference (reflection and scattering)
Metallic gloss due to reflection
Specific colour due to light absorption
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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.
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Laser welding of polymers
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Laser welding of polymers
material
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Polymer type
Partially cross linkedpolymer chains
elastomers
Highly cross linkedpolymer chains duromers
amorphous(transparent) thermoplastics
crystalline(translucent/opaque)
laser-weldable
(thermoplastic elastomers (TPE))
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Transmission spectra
Transmission depending on wall thickness ofvisually transparent polymers
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wavelength in nm
tran
smis
sion
in %
polycarbonate 1mm
polycarbonate 2mm
polycarbonate 3mm
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Transmission spectra
Transmission depending on wall thicknessof opaque polymers
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wavelength in nm
tran
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in %
ABS 1 mmABS 2 mmABS 3 mm
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Transmission of styrene based polymers
Transmission spectra
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wavelength in nm
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in %
ABSPC/ABSM-ABS
wall thickness: 2 mm
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Transmission of glass filled polyamides
Transmission spectra
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wavelength in nm
tran
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sion
in %
PPA GF 30PA 6.6 GF 30PA 6 GF 15PA 6.6 GF 50
wall thickness: 1 mm
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Transmission of several engineering plastics
Transmission spectra
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wavelength in nm
tran
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sion
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PBT type APBT type BPOM
wall thickness: 1 mm
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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
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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.
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Laser welding of polymers
Colorants - Additives
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Joint partner LST/LSA - Colorants
Absorption range of polymers
LST
LSA
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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.
Requirements for the colouring of thetransparent joint partner
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Colorants respectively additives absorb the NIR-light 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.
Requirements for the colouring of theabsorbing joint partner
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Degree of complexity
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Black – NIR absorbing
• Carbon blackBroadband absorber for all wavelengths.
• Only for dark, grey and black applications
Source: Paragon AG
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Black – NIR transparent
• Formulation is a mixture of different dyes:Absorption between400 – 700 nm (black)transparent in the NIR
• NIR-transparent black already available for many polymers as a standard product.
• Many variations of black available!
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Wavelength in nm
Tra
nsm
issi
on in
%
Carrier material
D.Y.54
S.R.179
S.G.3
in the visible in the NIR
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Black – NIR transparent
� Temperature stabileup to 350°C
� Neutral black
� Stabile to migration
� Excellent light andweather fastness
� Insoluble in organic solvents and water
� Inert against physicaland chemical influences
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type A 0,2% in PC 2mm
type B 0,2% in PC 2mm
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Degree of complexity
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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
Colour – NIR absorbing
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Colour – NIR absorbing
Example:
Inorganic NIR-absorber for opaque colours
1% in atransparent polymer,1mm wall thickness
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Wellenlänge in nm
Abs
orpt
ion
in %
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• In general:The darker the colour the better the transmission.The exception proves the rule.
• Choice of colorant is depending on thetransmission 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
Colour – NIR transparent
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Transmission spectra of selected dyes
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D.Y. 54S.R. 179S.G. 3
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Transmission spectra of four types of P.R. 101
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Wavelength in nm
Tran
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in %
Type 1Type 2Type 3Type 4
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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 )
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Degree of complexity
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Transparent NIR-absorber
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wavelength in nm
abso
rptio
n in
%
Typ ATyp BTyp CTyp D
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White / White
white laser absorbing
white laser transparent
Laser absorbing part:
By use of colour neutral NIR-absorbera RAL 9003 is possible.
Laser transparent part:
Challenge
⇒ transmissive scattering
⇒ adjustment milky translucent
White surface => total reflection of the visible light
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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.
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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