Effect of the hottest light stabilizer on the fog

2022-08-06
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Effects of light stabilizers on vehicle interior odor, fog and VOC

in the past few decades, although the safety performance of passenger cars has been significantly improved, recent studies have shown that the potential safety hazards caused by volatile compounds in the interior have not been completely solved

under the action of light and heat, plastic interior trim parts usually release some volatile substances, resulting in fog and odor in the car. The research shows that the possible sources of volatile substances include various additives and processing aids. In addition, the by-products of plastic degradation and small molecular impurities in plastics are also one of the sources of harmful substances. The sources of vehicle interior odor are various, including toner, oiling agent and additives. In addition, the aging and degradation of plastic parts will also bring some negative effects

Fig. 1 miscibility comparison between uv3853 and hals-1

in fact, volatile hazardous substances in vehicles have attracted people's attention since the 1980s. Since then, the world's major automobile manufacturers have started to carry out research work in this area, and formed standards to regulate and control these volatile hazardous substances. At the same time, they have also continuously developed some detection technologies and methods. Among them, Volkswagen has been implementing its own standards for volatile substances of plastic parts in cars since the 1980s. From 2004 to 2005, the Japanese Automobile Manufacturers Association (JAMA) announced that it would work to reduce vehicle interior pollution and issued relevant standards and specifications for this purpose (see Table 1). Recently, China's automotive industry has also begun to develop its own standards for this problem. It is certain that in the future, the standards and specifications for controlling harmful volatiles in vehicles will be increasingly strict

generally, there are many reasons for the smell of plastic processing aids in the vehicle, mainly including:

1, the migration of additives to the surface of polymers. This mainly depends on the following factors: the miscibility of additives and polymers, the diffusion rate of additives, and the influence of molecular weight and polarity

2. Volatilization of additives on polymer surface. This is generally affected by the vapor pressure, hydrogen bond and surface energy of the promoter molecules

mold temperature is the main factor to control the cooling and shaping of products. Its influence on the molding shrinkage is mainly reflected in the process after the gate is frozen and before the product is demoulded.

3. The short carbon chain produced by the aging and degradation of polymer will produce volatile substances such as aldehydes and ketones after oxidation

in order to solve these problems, some well-known plastic additive suppliers have improved their products. Among them, the hindered amine light stabilizer uv3853 introduced by cyanate chemical company belongs to this kind of product. The following test studies show the application effect of uv3853 in PP

these tests include: miscibility and mobility test, accelerated aging test, odor test, fog test, VOC test, etc. In all these tests, exactly the same samples were used, that is, they all contained 0.10% antioxidant and 0.10% calcium stearate. In addition, the color masterbatch with a concentration of 4% was added, and then mixed by a twin-screw extruder. These tests refer to SAE j1885, VW ′ s pv3900e, DIN 75201b and SAE j1765, VW ′ s pv3925 and VW ′ s pv3341 for accelerated aging test of interior trim parts

Figure 2 Comparison of accelerated aging test

miscibility and mobility test

the test is carried out in two steps:

first, the miscibility of uv3853 and sebacic acid bis (2,2,6,6-tetramethyl-4-piperidyl ester) (hals-1) in PP is compared. Generally, it is not easy to quantitatively measure the miscibility of small molecules in polymers. In order to solve this problem, non-polar n-heptane was used to replace PP in this experiment for relative comparison. As shown in Figure 1, at room temperature, the solubility of hals-1 in n-heptane is only 5.8%, while the solubility of uv3853 is as high as 49.2%. It can be concluded that the miscibility of uv-3853 and PP is much better than that of hals-1

then, it was detected by an accelerated mobility experiment. After the samples were stored at 80 ℃ for 400H, the change of surface gloss was detected to judge whether there were additives migrating to the surface of the polymer and the amount of migration. When the addition amount is 0.15%, 0.30% and 0.45% respectively, after 400H, the gloss loss of samples containing hals-1 is greater than 50%, but the gloss loss rate of samples containing uv3853 is less than 12% (see Table 2)

accelerated aging test

this accelerated aging test adopts SAE j1885 standard. The samples were divided into two groups: no talc filling and 20% talc filling. As shown in Figure 2, when the total radiation energy reaches 2500kj/m2, the color difference of the samples containing 0.1% uv3853s in the two groups of samples is less than 2, while that of the comparison samples without light stabilizer is greater than 8. The color change of the contrast sample filled with talc is more serious. In fact, when the total radiation energy reaches 500 kj/m2, cracks visible to the naked eye have already appeared on the surface of the sample plate of gb/t328.19 ⑵ 007, which is filled with talc and has a relatively high molecular waterproof membrane tear performance

odor test

this test adopts the pv3900 standard of Volkswagen, which mainly evaluates the odor of C3 at 80 ℃. Its odor evaluation system includes 6 levels: imperceptible, perceptible but not disgusting, easily perceptible but not disgusting, disgusting, very disgusting and intolerable

in this test, samples without talc filling and containing 0.1% uv3853s can reach the level of grade 2.6, as shown in Figure 3; Samples filled with 20% talc and containing 0.1% uv3853s can reach the level of grade 2.8, as shown in Figure 4. This shows that they have met the standard requirements of high temperature test in pv3900

Figure 3. The samples without talc filling and containing 0.1% uv3853s can reach grade 2.6 of Volkswagen pv3900 standard

fog test

fog caused by automotive interior trim materials is usually the result of the joint action of a variety of factors, including the "frost spraying" phenomenon after the additives migrate to the polymer surface, and the volatilization and condensation of additives on the glass. The factors that affect the migration of additives include the miscibility with polymer, the diffusion rate in polymer, molecular weight and temperature. The factors that affect the volatilization of additives to import 2.8348 million tons in the way of special customs supervision areas include vapor pressure, hydrogen bonding and surface energy

this fog test adopts DIN 75201 method B standard, which is boosted by the rising transportation cost and the limited production of environmental treatment. This standard is usually used to detect the impact of interior material volatilization on windscreens. The method adopted is the weighing method, that is, put the sample into an aluminum foil sealed vessel (as shown in Figure 5), heat it continuously for 16h at a high temperature of 100 ℃, compare the weight changes of the aluminum foil before and after heating, and then calculate the weight of the condensate on the aluminum foil. If it is less than 2 mg, it means that the test has passed. The talc free and 20% talc filled samples containing 0.2% uv3853s passed the test (see Table 3)

Figure 5 fog test instrument

light stabilizer - Table 3

voc test

13 volatile substances listed in Table 1 are tested according to JAMA standards. First, the experiment was carried out with pure compound samples, and the gc/ms database was established. Then, samples of volatile substances were collected and analyzed by headspace gc/ms. As there is a concentration limit (>10ppm) for formaldehyde test by gc/ms, Nash reagent is used to develop the color of formaldehyde in this test, and UV-vis spectroscopy is used to analyze formaldehyde(

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