GB2060180A - Method of measuring the photoactivity of pigments - Google Patents
Method of measuring the photoactivity of pigments Download PDFInfo
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- GB2060180A GB2060180A GB8032041A GB8032041A GB2060180A GB 2060180 A GB2060180 A GB 2060180A GB 8032041 A GB8032041 A GB 8032041A GB 8032041 A GB8032041 A GB 8032041A GB 2060180 A GB2060180 A GB 2060180A
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- pigment
- radiation
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- photoactivity
- absorption
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- 239000000049 pigment Substances 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims description 26
- 230000005855 radiation Effects 0.000 claims abstract description 53
- 239000000463 material Substances 0.000 claims abstract description 47
- 238000010521 absorption reaction Methods 0.000 claims abstract description 43
- 239000004033 plastic Substances 0.000 claims abstract description 29
- 229920003023 plastic Polymers 0.000 claims abstract description 29
- 238000012360 testing method Methods 0.000 claims abstract description 21
- 239000011159 matrix material Substances 0.000 claims abstract description 14
- 239000011248 coating agent Substances 0.000 claims abstract description 12
- 238000000576 coating method Methods 0.000 claims abstract description 12
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 34
- 230000003595 spectral effect Effects 0.000 claims description 22
- 238000005259 measurement Methods 0.000 claims description 11
- 239000012860 organic pigment Substances 0.000 claims description 10
- 239000001023 inorganic pigment Substances 0.000 claims description 9
- 239000004408 titanium dioxide Substances 0.000 claims description 8
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 5
- 229910052753 mercury Inorganic materials 0.000 claims description 5
- 238000001228 spectrum Methods 0.000 claims description 5
- 238000006731 degradation reaction Methods 0.000 description 23
- 230000015556 catabolic process Effects 0.000 description 22
- 238000000354 decomposition reaction Methods 0.000 description 13
- 229920000642 polymer Polymers 0.000 description 9
- 239000001034 iron oxide pigment Substances 0.000 description 8
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 8
- 238000000862 absorption spectrum Methods 0.000 description 7
- 239000004417 polycarbonate Substances 0.000 description 6
- 229920000515 polycarbonate Polymers 0.000 description 6
- 229920000180 alkyd Polymers 0.000 description 5
- 238000000295 emission spectrum Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 239000007767 bonding agent Substances 0.000 description 4
- 229920002292 Nylon 6 Polymers 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 210000003298 dental enamel Anatomy 0.000 description 3
- 235000014113 dietary fatty acids Nutrition 0.000 description 3
- 229930195729 fatty acid Natural products 0.000 description 3
- 239000000194 fatty acid Substances 0.000 description 3
- 150000004665 fatty acids Chemical class 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000012463 white pigment Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 238000007605 air drying Methods 0.000 description 2
- VQLYBLABXAHUDN-UHFFFAOYSA-N bis(4-fluorophenyl)-methyl-(1,2,4-triazol-1-ylmethyl)silane;methyl n-(1h-benzimidazol-2-yl)carbamate Chemical compound C1=CC=C2NC(NC(=O)OC)=NC2=C1.C=1C=C(F)C=CC=1[Si](C=1C=CC(F)=CC=1)(C)CN1C=NC=N1 VQLYBLABXAHUDN-UHFFFAOYSA-N 0.000 description 2
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 2
- 239000001030 cadmium pigment Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000012447 hatching Effects 0.000 description 2
- 239000004922 lacquer Substances 0.000 description 2
- NYGZLYXAPMMJTE-UHFFFAOYSA-M metanil yellow Chemical group [Na+].[O-]S(=O)(=O)C1=CC=CC(N=NC=2C=CC(NC=3C=CC=CC=3)=CC=2)=C1 NYGZLYXAPMMJTE-UHFFFAOYSA-M 0.000 description 2
- 238000001782 photodegradation Methods 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- 229910052724 xenon Inorganic materials 0.000 description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 2
- JFGQHAHJWJBOPD-UHFFFAOYSA-N 3-hydroxy-n-phenylnaphthalene-2-carboxamide Chemical class OC1=CC2=CC=CC=C2C=C1C(=O)NC1=CC=CC=C1 JFGQHAHJWJBOPD-UHFFFAOYSA-N 0.000 description 1
- RZVAJINKPMORJF-UHFFFAOYSA-N Acetaminophen Chemical compound CC(=O)NC1=CC=C(O)C=C1 RZVAJINKPMORJF-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 229920000571 Nylon 11 Polymers 0.000 description 1
- 229920002302 Nylon 6,6 Polymers 0.000 description 1
- 241000227425 Pieris rapae crucivora Species 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 239000004904 UV filter Substances 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000001055 blue pigment Substances 0.000 description 1
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 206010016256 fatigue Diseases 0.000 description 1
- RBTKNAXYKSUFRK-UHFFFAOYSA-N heliogen blue Chemical compound [Cu].[N-]1C2=C(C=CC=C3)C3=C1N=C([N-]1)C3=CC=CC=C3C1=NC([N-]1)=C(C=CC=C3)C3=C1N=C([N-]1)C3=CC=CC=C3C1=N2 RBTKNAXYKSUFRK-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- RLSSMJSEOOYNOY-UHFFFAOYSA-N m-cresol Chemical compound CC1=CC=CC(O)=C1 RLSSMJSEOOYNOY-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 229940100630 metacresol Drugs 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 230000019612 pigmentation Effects 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 229920005749 polyurethane resin Polymers 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 239000005297 pyrex Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- 229920006337 unsaturated polyester resin Polymers 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
- G01N17/004—Investigating resistance of materials to the weather, to corrosion, or to light to light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/26—Oils; Viscous liquids; Paints; Inks
- G01N33/32—Paints; Inks
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Pathology (AREA)
- Immunology (AREA)
- Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Food Science & Technology (AREA)
- Engineering & Computer Science (AREA)
- Biodiversity & Conservation Biology (AREA)
- Ecology (AREA)
- Environmental & Geological Engineering (AREA)
- Environmental Sciences (AREA)
- Paints Or Removers (AREA)
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Spectrometry And Color Measurement (AREA)
Abstract
The photoactivity of pigments present in plastics materials and surface coating materials is determined by irradiation of samples of materials containing the pigments with light of predetermined wavelengths utilising an irradiation band in which the short wave limit is arranged to fall beyond the absorption limit of the pigment under test but such that the intensity is low in the region of the absorption limit of the matrix material but as great as possible in the region of the absorption limit of the pigment and in the adjoining short wave region whilst intensity in the adjoining long wave region is as low as possible. The amount of incident radiation is measured throughout the test period in the region of the absorption limit of the pigment and in the adjoining short wave region so that testing is carried out with a known amount of radiation.
Description
SPECIFICATION
Method of measuring the photoactivity of pigments
This invention relates to a method of measuring the photoactivity of organic and inorganic pigments present in a plastics material or in a surface coating material, by irradiation of samples with light having a predetermined spectral range in test chambers under specified climatic conditions with constant recording of the total amount of incident radiation and assessment of the decomposition of the material caused by the photoactivity by means of known methods.
Pigmented plastics materials and pigmented surface coating materials (e.g. painting materials, lacquers) are of considerable importance as technical materials entering into daily life (e.g. car varnishes, house paints, coloured plastics material components used in the building industry). Most of these materials are exposed to atmospheric agents such as sunlight and humidity. Damage is incurred after longer or shorter periods of time due to the action of these atmospheric agents. Initially this manifests itself by a loss of surface lustre, and later on by a measurable decomposition of the material. This decomposition is referred to as "chalking" in the case of systems containing titanium dioxide or other inorganic white pigments.
The term "pigmented systems" is used hereinafter as a generic term to denote both pigmented plastics materials and pigmented surface coating materials.
It is desirable that pigmented systems having high resistance to weathering should be developed. This pre-supposes that the weatherstability of pigmented systems must be measured.
Apart from so-called exposure to open-air weathering, accelerated weathering apparatus is used preponderantly to reduce the time factor in testing. The photoactivity of the pigments is of interest on the one hand in the case of accelerated weathering experiments, and on the other hand, in connection with the degradation of the matrices or more especially plastics materials by the shorterwave lengths of the incident radiation (so-called
UV degradation). Pigment photoactivity is commonly understood to denote photochemical processes proceeding at the pigment surface which lead to a degradation or decomposition of the polymer matrix surrounding the pigment particles with the production of secondary radical products.
Commercial accelerated weathering devices comprise either high-pressure Xenon radiators or carbon arc radiators as sources of radiation. These sources of radiation emit a spectrum analogous to that of sunlight which however has a greater amount of radiation in the UV range as well as one shifted towards the shorter wavelengths when compared to normal total radiation. If special UV filters are interposed, the spectrum of these radiators may be approximated to the spectrum of sunlight (so-called solar or integral radiation) (standard light type D65). The samples are exposed to artificial rain or dew, respectively, in accordance with a particular chronological program, during the irradiation. In many devices, the irradiation is also performed whilst interposing cyclic periods of darkness.By means of a high air throughput, it is assured that the temperature of the sample (black panel temperature) does not exceed a specific value.
A precise measurement of the photoactivity of pigments such as required for a programmed development of improved products, could not hitherto be accomplished with the known accelerated weathering devices. Two actions occur side-by-side during weathering tests on pigmented systems: because of the reciprocal action between pigment and bonding agent or rather pigment and plastics material, a degradation occurs in proximity to the pigment (photoactivity of the pigments), and at the same time, a degradation of the actual polymer matrix occurs due to the shortwave part of the incident radiation (so-called UV degradation). For quantitative determination of the course of degradation, use is made of lustre measurement, of the so-called Kempf-punch test according to
DIN 53159 or of the adhesive tape method according to DIN 53223.This determines the total degradation of the sample, but not the degradation due solely to the photoactivity of the pigments. The proportion of the UV degradation may exceed the proportion attributable to reciprocal action by a multiple; a direct reliable determination of the photoactivity of the pigment in the absence of the usually greater decomposition brought about by UV degradation is not possible in this manner.
To reduce the testing period, the samples are irradiated with an enhanced proportion of UV radiation as compared with solar radiation, by incorporation of special filters. Thus it is specified in numerous publications that, in order to shorten the weathering period, a part of the conventional
Corex-D filters or Pyrex filters are to be replaced by quartz plates. This has the result that the samples are acted upon by radiation fractions which are of shorter wavelength than those present in solar radiation. This involves a decisive intervention in the course of the natural degradation reactions, and the degradation in accelerated weathering devices may thus differ substantially from natural degradation.It is known that numerous pigments which, based upon the results of open air weathering and of accelerated weathering (irradiation with standard light type
D65) display less degradation than other pigments when present in the same polymers, have frequently been assessed as being inferior to the pigments of the group used for comparison, when irradiated with an increased UV fraction.
To shorten the weathering periods, radiation sources having an exceptionally high density of irradiation are partially utilised. The high radiation performance is linked with correspondingly high thermal stresses on the sample; this leads to undesirable effects upon the sample (embrittlement, fissuring) and thus to a different evolution than that occurring during open-air weathering.
In the case of commercial accelerated weathering devices, the samples are assessed after a preset weathering period. Because of this testing technique -- provided that measurements are not limited to purely comparative measurement within a test series - an excess divergence of the test results occurs since a timedependent variation of their spectral distribution and intensity can occur in the case of all sources of radiation.
The invention is based upon the task of developing a method of measuring the photoactivity of organic and inorganic pigments when incorporated in plastics materials or surface coating materials which is free from the disadvantages noted above. For this purpose it should be possible to determine the total effective quantity of incident radiation and to resort to the same for evaluation purposes. It should be assured that only those methods which relate to the photoactivity of pigments are recommended.
The present invention provides a method of determining the photoactivity of organic and inorganic pigments incorporated in plastics materials or in surface coating material by irradiation of samples using light having a limited spectral range in test chambers under predetermined climatic conditions and measurement of the quantity of radiation, characterised in that the test of the photoactivity of the pigments is performed in a plastics material or surface coating material the absorption limit of which is sufficiently shifted towards the shortwave end of the spectrum as compared to the absorption limit of the pigment, that the sample is irradiated with light the spectral range of which is so limited in the short wavelengths that the intensity is very low in the region of the absorption limit of the matrix, that it is as great as possible in the region of the absorption limit of the pigment and in the shortwave section immediately adjacent to the former, and that the long-wave section is as low as possible, and that the amount of incident radiation is measured throughout the irradiation period in the region of the absorption limit of the pigment and in the short wave section immediately adjacent to the former and that the weathering treatment is performed with a predetermined amount of radiation.
The method of the present invention involves the concept that not every pigmented system is suitable for measuring the photoactivity of organic and inorganic pigments when incorporated in plastics materials or in surface coating materials.
It is also essential to understand how the spectral range of the incident light affects the optical properties of the pigment and of the polymer, and that the quantity of incident radiation measured within the optimum range is suited as the dosage for the weathering action.
The need to measure the quantity of incident radiation and not merely the period of irradiation during weathering, is known per se. Since it has been impossible however to operate known radiation quantity meters or counters without servicing during long periods, this measurement has failed to gain acceptance in practice. An appropriate instrument for measuring the quantity of radiation in weathering devices has been disclosed in the German application no.
P29 40 325.6. All changes in the emission of the sources of irradiation are taken into consideration in this manner, and it is no longer necessary to rely upon values discovered by experience in order to judge the average period after which an impairment of the emission should be expected, and when to replace the source of radiation as a precaution before it has really become unusable.
The invention will now be described with reference to the accompanying drawings in which:
Figure 1 shows typical absorption spectra of a pigment, of a cut-off filter, and of a plastics material, as well as the emission spectrum of solar radiation;
Figures 2-5 show electron microscope screen photographs of samples which have been exposed to brief weathering.
When mention is made of the limit of absorption of the pigment or matrix or the cut-off filter, this should be understood as referring to a characteristic typical of each substance. In the case of the inorganic pigments from the photosemiconductor group (e.g. TiO2, ZnO, ZnS, CdS,
CdSe among others) this value corresponds to the ratio of the valence to conduction band difference.
In the case of many inorganic pigments (e.g.
manganese blue pigment), as well as of many organic pigments, the absorption spectrum does not however display any limiting value but a more or less pronounced bell-shaped curve (so-called absorption band(s)). In these cases, the spectral absorption range and, as a typical characteristic, the wavelength of the point of inversion Awp at the short wave end of the absorption band should approach. The value Awp may also be utilised to characterise the position of the absorption limit; Awp then corresponds to the wavelength at which the absorption has fallen to one half. Hereinafter, the value Awp is preferentially specified for this reason as a typical value for characterising the spectral absorption behaviour of pigments, plastics materials, matrices and cut-off filters.
Since the limiting value falls off very sharply in the case of many pigments, the numerical value varies but little if the wavelength Awp of the point of inversion is specified in this case instead of the wavelength of the limiting value. The limiting value falls off less sharply in the case of plastics materials; this is why a plastics material is preferred in the method of the invention in which the Awp value is shifted towards the shorter wavelengths by at least 20 nm and most preferably by 40 to 80 nm, as compared to the Awp value of the pigment which is to be tested.By interposing a cut-off filter the Awp value of which preferably lies halfway between the Awp values of the pigment and of the polymer, it is ensured that sufficient intensity is still available within the optimum range around the limiting value for the pigment and somewhat towards the short wave side thereof, this range being an optimum for photoactivity testing, on the one hand, but that the
UV fraction of the radiation is removed to such an extent that UV degradation of the plastics material is largely prevented, even if this value cuts-off less sharply.The absorption of the pigments which is a maximum as compared to solar radiation is calculated from the curvature of the wavelengthdependent absorption curve A(A) of the pigments having the radiation distribution E(A) known in this wavelength range, e.g. of the solar radiation (standard light type D 65 according to DIN 53231; the spectral distribution of the so-called daylight phase D65 corresponds to that of solar radiation).
The spectral graph of the absorption in the case of a pigment, of a cut-off filter and of a plastics material, as well as the emission spectrum of solar radiation (D65), are plotted on Fig. 1. The absorption and emission spectra are plotted in each case in relative units, as ordinates. For the most common white pigment titanium dioxide rutile, the value Awp lies at 405 nm (a value of 3.05 eV is calculated from the valency to conduction band difference for the absorption limit, corresponding to a wavelength of 41 5 nm).
The absorption graph is marked (1) on Figure 1. It is apparent from the graph (2) of the absorption spectrum of polycarbonate (thickness 2 mm, free from additives) the Awp value of which lies at 310 nm, that this plastics material is suitable for testing the photoactivity of rutile because this value differs sufficiently (approximately 95 nm).
The spectral energy distribution of solar radiation (standard light type D65 according to CIE, E 1.3.1) is plotted moreover to an arbitrary co-ordinate scale, as graph (3) on Figure 1. The effective spectral range of rutile/D65 is determined from the graphs of the emission spectrum (3) and of the absorption spectrum (1) of rutile. This range is shown by hatching and marked (4) on Figure 1. In accordance with the invention, a cut-off filter causes the intensity to become very small in the region of the absorption limit of the matrix, without excessively attenuating the intensity in the region of the absorption limit of the pigment and in the directly adjacent short wave section. In this instance, a cut-off filter is selected for which the Awp lies at 335 nm; for example, the filter
WG 335 of Schott s Gen., Mainz, is suitable.
Graph (5) shows the standardised absorption spectrum of this filter. Within the spectral range (6) from 410 to approximately 350 nm, which is the optimum for this pigmented system, the photoactivity of rutile is excited in the spectral range (6) shown by the double hatching in
Figure 1 and may be accurately measured without being impeded by decomposition of the plastics material caused by UV degradation.
The use of appropriate cut-off filters is logical in the conventional commercial accelerated weathering devices which are preponderantly equipped with high-pressure Xenon radiators or with carbon arc radiators. The additional interposition of thermal protection filters may lead to a reduction in the thermal stress on the samples. Filters which simultaneously act as UV cut-off filters and as thermal protection filters (infrared filters), are especially useful. As an example reference may be made to a filter which is distributed by Messrs. Schott & Gen., Mainz, and which largely reflects thermal radiation of wavelength greater than 700 nm and which has an absorption band in the UV at AWp approximately 350 nm.It is also especially advisable to use high-pressure mercury radiators since these have a relatively small emission in the long-wave range (thermal radiation) together with high radiation energy in the UV-A + B spectral range. The possibility is thus made available to make use of particularly powerful mercury radiators and thus obtain substantially shortened weathering periods as compared with conventional weathering devices, without deleterious thermal effect upon the samples.
If use is made of photoactinic radiators (socalled black light lamps having an appropriate spectral emission), the use of cut-off filters may be omitted; an appropriate spectral emission is present if the absorption limit of the pigment which is to be tested lies within the range of the radiation emitted and if, at the same time, the absorption limit of the polymer matrix (plastics material or bonding agent) no longer lies within the emission spectrum of the photoactinic radiator. This ensures that no radiant energy or only very little radiant energy is absorbed by the polymer matrix, the direct decomposition of the polymer matrix (UV degradation) thus being almost wholly prevented.
If, for example, the photoactivity of titanium dioxide rutile (absorption limit 41 5 nm) is to be measured in a short-oil fatty acid alkyd resin (Awp = 312 nm) or in a polycarbonate (Awp = 310 nm) by means of a photoactinic radiator of type TL W/09 marketed by Messrs.
Osram GmbH, the spectral emission of which lies within the range 320 to 41 5 nm.
Plastics materials and bonding agents having an absorption limit at sufficiently long wavelengths are particularly suitable polymers.
Examples of suitable plastics materials: polycarbonates, polyethylene, polypropylene, polyvinyl chloride, polyamide -6,-66,-11 and polymethylmethacrylate. Examples of suitable bonding agents: lacquers based upon acrylic resins, alkyd resins, saturated and unsaturated polyester resins, polyurethane and epoxide resins, silicone resins, urea, melamine and phenolic resins. The most frequently used inorganic pigment is titanium dioxide in its anatase and rutile forms; it is also possible in accordance with the method of the invention and in the same manner to make use of other inorganic pigments such as red iron oxide pigments, yellow iron oxide pigments, chromium oxide pigments, yellow cadmium pigments and red cadmium pigments as well as organic pigments, for example copper phthalocyanine pigments and azo pigments, for testing.
The method of the invention is illustrated by the following examples.
EXAMPLE 1
Measurement of the photoactivity of inorganic white pigment (titanium dioxide anatase):
The absorption limit of titanium dioxide anatase is calculated as 385 nm from the band difference of 3.15 eV. As compared to solar radiation (D 65), the spectral range which is an optimum for the photoactivity of titanium dioxide anatase is approximately 330 to 385 nm. The plastics material selected is a polycarbonate of 2,2-bis (4hydroxyphenyl)-propane having an MW of 28000 (thickness 2 mm, without additives); it shows 50% of its absorption at AWP = 310 nm. The pigmentation level with an untreated TiO2 pigment in anatase form amounts to 1.5% by weight.
After subjecting to weathering action by exposure to an amount of incident radiation of approximately 90 kJ cam~2 in an accelerated weathering device comprising high-pressure mercury radiators, the weathered samples
(a) preponderantly undergo decomposition of the matrix (UV degradation) if conventional filters (thickness 2 mm, A- = =300 nm) are interposed; it is apparent from the electron microscope screen photograph (Figure 2a), that the pigment particles lie on the surface of the decomposed polycarbonate;
(b) undergo practically exclusive decomposition by photodegradation of the pigments if a cut-off filter for which the A- wP value of absorption lies at 335 nm (type WG 335 of Schott 8 Gen., Mainz, thickness 2 mm) is interposed in accordance with the method of the invention; the nearly washedout pigment particles lie within deep holes in the largely intact polycarbonate matrix (Figure 2b).
An almost identical result is obtained if a cut-off filter is interposed, for which the A- wP value lies at 375 nm (type WG 375), as apparent from
Figure 2c; because of the lesser incident quantity of radiation, the degradation caused by photoactivity of the pigments has progressed a little less when compared to Figure 2b.
EXAMPLE 2
Measurement of the photoactivity of an inorganic white pigment (titanium dioxide anatase):
A polyamide-6 having a relative viscosity of 2.8 to 3 measured in meta-cresol at a concentration of 10 g/l, is pigmented with 1.5--19/0 by weight of titanium dioxide anatase. The A- wP value of absorption of the polyamide-6 (without UV absorber, sample thickness 2 mm) lies around 350 nm.
After weathering with an amount of incident radiation of approximately 90 kJ cam~2 in an accelerated weathering device comprising highpressure mercury radiators -s, the samples
(a) exhibit an almost total destruction of the surface by UV degradation of the plastics material when conventional filters are interposed (thickness 2 mm, wp = 300 nm) (Figure 3a shows an overall view, Figure 3b shows a detail photographed with an electron microscope screen);;
(b) exhibit only decomposition by photodegradation, recognisable by the holes produced by the photoactivity of the pigment in the practically intact polyamide matrix, when interposing in accordance with the invention a cut-off filter having a thickness of 2 mm, and having wp at 375 nm (type WG 375 of Schott s Gen., Mainz) (figure 3c shows an overall electron
microscope screen photograph, Figure 3d shows a section of the same).
-EXAMPLE 3
Measurement of the photoactivity of an
inorganic coloured pigment (red iron oxide
pigment):
A long-oil air-drying fatty acid alkyd resin used for the production of painters enamels is
pigmented with 5% by volume of red iron oxide
pigment. Red iron oxide pigments (a-Fe203)
completely absorb radiation at wavelengths
> 540 nm; the spectral range which is particularly
effective for eventual photoactivity lies between
approximately 400 and 540 nm. The Awp value of
the alkyd resin used lies at 346 nm.
After weathering with an amount of incident
radiation of approximately 90 kJ cam~2 in an
accelerated weathering device, the samples
(a) display considerable matrix decomposition
(UV degradation) when conventional filters ( wp = 300 nm, thickness 2 mm) are interposed;
the electron microscope screen photograph in
Figure 4a shows pigment particles which lie upon
the considerably decomposed enamel surface;
(b) do not display any decomposition in case of
the interposition of cut-off filters having wp values > 350 nm (for example WG 375 or GG 395
or GG 435 of Schott h Gen., Mainz, thickness
2 mm); the electron microscope screen
photograph (Figure 4b) demonstrates that red iron
oxide pigments are practically photoinactive (the
particles appearing in isolated manner in Figure 4b
on thsenamel surface originate from impurities).
This example shows particularly clearly that
when testing in accordance with conventional
accelerated weathering methods, e.g. as
standardised in accordance with DIN 53 231, an
incorrect or at least unusable indication is
obtained regarding the photoactivity of red iron
oxide pigments. Only the method of the invention
allows of an aunequivocal indication.
EXAMPLE 4
Measurement of the photoactivity of a coloured
organic pigment:
A long-oil, air-drying fatty acid alkyd resin used
for the production of painters enamels is
pigmented with 5% by volume of a red organic
pigment (mono-azo pigment of the Naphthol AS series of Messrs. Bayer AG). This organic pigment displays an absorption spectrum analogous to that of the inorganic red iron oxide pigment. In this case also, a false result is obtained when weathering in commercial accelerated weathering devices (amount of incident radiation approximately 90 kJ cam~2) in accordance with the known method; the electron microscope screen photograph in Figure 5 shows considerable decomposition which is however preponderantly brought about by the UV degradation of the bonder; on the contrary, the organic mono-azo pigment has extremely little photoactivity as demonstrated by accelerated weathering experiments using the cut-off filters used in example 3.
Claims (8)
1. A method of measuring the photoactivity of organic and inorganic pigments incorporated in plastics materials or in surface coating materials by irradiation of samples using light having a limited spectral range in test chambers under predetermined climatic conditions and measurement of the quantity of radiation, characterised in that the test of the photoactivity of the pigments is performed in a plastics material or surface coating material the absorption limit of which is sufficiently shifted towards the shortwave end of the spectrum as compared to the absorption limit of the pigment, that the sample is irradiated with light the spectral range of which is so limited in the short wavelengths that the intensity is very low in the region of the absorption limit of the matrix, that it is as great as possible in the region of the absorption limit of the pigment and in the short wave section immediately adjacent to the former, and that the long wave section is as low as possible, and that the amount of incident radiation is measured throughout the irradiation period in the region of the absorption limit of the pigment and in the short wave section immediately adjacent to the former and that the weathering treatment is performed with a predetermined amount of radiation.
2. A method according to claim 1, characterised in that the samples are irradiated with light which is passed through a cut-off filter, the absorption limit of the cut-off filter lying between the absorption limit of the pigment under test and that of the selected plastics material or surface coating material.
3. A method according to either of claims 1 and 2, characterised in that the absorption limit of the plastics material or of the surface coating material extends by at least 20 nm towards the shorter wavelengths than that of the pigment which is to be tested.
4. A method according to any of claims 1 to 3, characterised in that the samples are irradiated with light which has a maximum intensity in a spectral range which contains the absorption limit of the pigment and extends by approximately 20 nm further towards the short wavelengths.
5. A method according to any of claims 1 to 4, characterised in that the radiation is generated in a high-pressure mercury radiator.
6. A method according to any of claims 1 to 4, characterised in that the radiation is generated in a photoactinic lamp.
7. A method according to any of claims 1 to 6, characterised in that the radiation is passed through an infrared filter.
8. A method of measuring the photoactivity of a titanium dioxide pigment according to any of claims 1 to 7, characterised in that the testing of the pigment is performed within a plastics material the absorption limit of which is substantially 320 nm or lies within a range of even shorter wavelengths, that a cut-off filter is interposed between the sample and the light source, the absorption limit of which lies within the range from 330 to 375 nm, that the amount of radiation between 330 and 410 nm is measured throughout the irradiation period and that the weathering treatment is performed with a predetermined amount of radiation.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792940331 DE2940331B1 (en) | 1979-10-04 | 1979-10-04 | Method for determining the photoactivity of pigments |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2060180A true GB2060180A (en) | 1981-04-29 |
Family
ID=6082733
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8032041A Withdrawn GB2060180A (en) | 1979-10-04 | 1980-10-03 | Method of measuring the photoactivity of pigments |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS56107134A (en) |
| DE (1) | DE2940331B1 (en) |
| FR (1) | FR2466769A1 (en) |
| GB (1) | GB2060180A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004109259A2 (en) * | 2003-06-04 | 2004-12-16 | 3M Innovative Properties Company | Optical filters comprising opacified portion |
| EP1780288A1 (en) * | 2005-10-25 | 2007-05-02 | F.Hoffmann-La Roche Ag | Fluorescence spectroscopy in absorbing media |
| WO2015112143A1 (en) * | 2014-01-23 | 2015-07-30 | Sabic Global Technologies B.V. | Method for accelerated degradation of thermoplastics |
| US9557218B2 (en) | 2013-01-23 | 2017-01-31 | Sabic Global Technologies B.V. | Method for determining degradation of thermoplastics |
| US9897551B2 (en) | 2013-01-23 | 2018-02-20 | Sabic Global Technologies B.V. | Method for accelerated degradation of thermoplastics |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB429792A (en) * | 1934-02-09 | 1935-06-06 | William Pollard Digby | Improvements in apparatus for comparing the permanence of colour in pigments, dyes and the like |
| FR1077429A (en) * | 1952-05-20 | 1954-11-08 | Basf Ag | Process for examining the lightfastness of stains, paints, etc. |
| US3366789A (en) * | 1964-02-12 | 1968-01-30 | American Cyanamid Co | Calibration of ultraviolet radiation sources |
| US3426590A (en) * | 1964-11-10 | 1969-02-11 | Nagaichi Suga | Apparatus for exposing samples to light |
| US3501942A (en) * | 1967-02-01 | 1970-03-24 | Du Pont | Method for accelerating natural weathering of paint and other polymeric materials |
| DE1598468B2 (en) * | 1967-08-07 | 1976-08-19 | Bayer Ag, 5090 Leverkusen | METHOD AND DEVICE FOR SHORT-TERM EXPOSURE OF PIGMENTED BINDING SYSTEMS |
| US3847024A (en) * | 1969-07-23 | 1974-11-12 | Rockwell International Corp | Simulation and measurement apparatus |
| US3675477A (en) * | 1970-10-29 | 1972-07-11 | Avco Corp | Testing method and device using filtered ultra violet radiation |
-
1979
- 1979-10-04 DE DE19792940331 patent/DE2940331B1/en not_active Ceased
-
1980
- 1980-10-03 GB GB8032041A patent/GB2060180A/en not_active Withdrawn
- 1980-10-03 FR FR8021234A patent/FR2466769A1/en not_active Withdrawn
- 1980-10-04 JP JP13922880A patent/JPS56107134A/en active Pending
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004109259A2 (en) * | 2003-06-04 | 2004-12-16 | 3M Innovative Properties Company | Optical filters comprising opacified portion |
| WO2004109259A3 (en) * | 2003-06-04 | 2005-09-01 | 3M Innovative Properties Co | Optical filters comprising opacified portion |
| US6984058B2 (en) | 2003-06-04 | 2006-01-10 | 3M Innovative Properties Company | Optical filters comprising opacified portion |
| EP1780288A1 (en) * | 2005-10-25 | 2007-05-02 | F.Hoffmann-La Roche Ag | Fluorescence spectroscopy in absorbing media |
| US8338118B2 (en) | 2005-10-25 | 2012-12-25 | Roche Diagnostics Operations, Inc. | Fluorescence spectropscopy in absorbing media |
| US8501113B2 (en) | 2005-10-25 | 2013-08-06 | Roche Diagnostics Operations, Inc. | Fluorescence spectroscopy in absorbing media |
| US9557218B2 (en) | 2013-01-23 | 2017-01-31 | Sabic Global Technologies B.V. | Method for determining degradation of thermoplastics |
| US9897551B2 (en) | 2013-01-23 | 2018-02-20 | Sabic Global Technologies B.V. | Method for accelerated degradation of thermoplastics |
| US9921145B2 (en) | 2013-01-23 | 2018-03-20 | Sabic Global Technologies B.V. | Method for determining degradation of thermoplastics |
| KR20160098331A (en) * | 2014-01-23 | 2016-08-18 | 사빅 글로벌 테크놀러지스 비.브이. | Method for accelerated degradation of thermoplastics |
| CN105899942A (en) * | 2014-01-23 | 2016-08-24 | 沙特基础工业全球技术公司 | Method for accelerated degradation of thermoplastics |
| WO2015112143A1 (en) * | 2014-01-23 | 2015-07-30 | Sabic Global Technologies B.V. | Method for accelerated degradation of thermoplastics |
| KR101944855B1 (en) | 2014-01-23 | 2019-02-01 | 사빅 글로벌 테크놀러지스 비.브이. | Method for accelerated degradation of thermoplastics |
| CN105899942B (en) * | 2014-01-23 | 2019-12-17 | 沙特基础工业全球技术公司 | Method for accelerating the ageing of thermoplastics |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2940331B1 (en) | 1980-12-18 |
| JPS56107134A (en) | 1981-08-25 |
| FR2466769A1 (en) | 1981-04-10 |
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