| With the rapid development of PVC plastics industry,coloured PVC films is becoming more and more popular.However,it is susceptible to aging and degradation after using for a long time.In order to prepare coloured PVC films,colorants might be added to the formula.Among many factors affecting aging of the material,colorant is important.At present,titanium dioxide is widely used in all kinds of plastic products.However,titanium dioxide is often mixed with other pigments in order to obtain a bright appearance.Therefore,it is necessary to study the performance of different pigment in the presence of titanium dioxide,and to analyze the influence of pigments during the process of aging.Mechanical properties and color properties are important properties,which are primary standards to evaluate the performance of materials.Aging process is also accompanied by the change of many properties,which we should focus on in aging research.Most scholars believe that dehydrochlorination reaction is an important feature of PVC aging.The change of carbonyl index in the infrared spectrum is usually accompanied by the change of material mechanics,and the change of the number of conjugated double bonds is the main cause of the yellowing of PVC film.The multiplicity of the properties of the pigment determines that it is likely to affect the strength of the material and the change of color during aging process.To study the effect of coloured pigments on the properties of PVC film,the formula of PVC film was designed based on the basic formula of PVC membrane used in factories,common pigments were selected and then PVC film with good surface properties was prepared on a double roller mixer,which can well meet the test and experiment requirements.The effect of pigments on the initial properties of the material was studied,and the artificial accelerated oxygen aging test was carried out to study the effect of pigments on the aging process of the material.Based on this goal,the research is carried out from following aspects:(1)Influence of the pigment on the mechanical properties and chemical composition of the finished product of the colored PVC filmSeveral common pigments were selected and added into the basic formula of PVC film,then the PVC film was prepared.The tensile strength,infrared spectrum and ultraviolet spectrum of the original samples were tested to study the influence of pigments on the mechanical properties and micro groups of products.The results showed that there was no distinct rule in the effect of pigment addition on the mechanical properties of the original materials,and tensile properties of the materials were not always increased.Moreover,pigment had no great influence on the carbonyl content of the original material,and the carbonyl absorbance value of each sample was very close.In addition,the ultraviolet spectrum of each sample containing different pigments also had certain regularity,which can reflect the composition and color information of some materials.(2)Influence of pigment on the breaking strength of PVC film during artificial accelerated agingArtificial accelerated light oxygen aging test was carried out,two samples were selected and tensile mechanics and related properties were tested.The results showed that the changes of mechanical properties of the two samples were different after aging.There were more white spots on the surface of the sample containing pigments.The change of the groups during aging was similar,which shows that the aging mechanism of the two samples is basically the same.(3)Effect of pigment on the color change of PVC film during artificial accelerated aging processBy artificial accelerated ageing test,color change of samples with different colored pigments after aging was compared,differences in the process of color change of the two kinds of samples were compared.The results showed that chromatic aberrations of samples containing different pigments were not the same after a certain period of aging.Appropriate pigments may have a good covering effect,thus the appearance chromatic aberration of materials after aging can be reduced effectively.In addition,most of the inorganic pigments have better performance in the color retention of the materials.After aging,the change of ?E* mostly came from the change of ?b* and UV spectrum can reflect the change of color of the samples to a certain extent.Based on the above research and results,in order to study the effect of the pigments on the properties of original samples and samples during aging,PVC films were prepared,its original properties were tested,artificial accelerated aging was carried out and related properties were tested.The results showed that the selected pigments have little effect on the samples' original properties.After adding coloured pigment,the aging degradation rate of the sample was different,and the change of micro-structure was also different.In addition,the color difference of samples containing inorganic pigments after aging was generally smaller than that of the samples containing organic pigments.Discoloration of the material was also reflected in the changes of the UV spectrum. |
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