PVC plastic is a commonly used plastic, and many products are currently obtained by processing PVC plastic.
However, many people worry that PVC plastic will be toxic and affect health, so PVC plastic is toxic in that case? Why does PVC plastic turn yellow? Today, we will introduce in detail the "PVC plastic in which case is toxic, why does it turn yellow?"
1. Under what circumstances is PVC plastic toxic?
1). Due to the lack of characteristics of PVC material itself, people have to add A large number of additives in it to stabilize PVC plastic, in fact, pure PVC plastic is not toxic, but after people add a large number of additives to transform, PVC plastic under the comprehensive action of a variety of additives chemical reaction out of toxic substances, That is to say, these additives can make PVC plastic into a more soft chemical additive phthalein, after the use of a large amount of PVC plastic, the impact on the human body's inner kidney, liver and so on is very large.
2). PVC plastic includes urea aldehyde and melamine formaldehyde. If we process and manufacture PVC plastic, their reaction is not complete, which will lead to the existence of a large amount of free formaldehyde in PVC plastic, and this formaldehyde is a protoplasmic toxin of cells. If a bowl made of PVC material is used to hold hot food, After human consumption, it is easy to cause the deterioration of some cells, which is harmful to human health, and PVC plastic contains chlorine, when we burn it, it will produce a toxic substance and pollute the environment.
2. Why does PVC material turn yellow?
1). Production process problems
PVC in the extrusion process, by heating and screw and barrel shear action, if the process is not properly set, will cause PVC decomposition yellow to a certain extent. The solution is as follows:
(1) Properly reducing the temperature of the barrel can improve the yellowing phenomenon.
(2) Reduce the speed of the main engine within the appropriate range, improve the feed ratio, can reduce the shear, and can make the material in the spiral groove more evenly mixed, the stabilizer fully play a role, thereby reducing yellowing.
(3) Improper boot method will also cause yellowing of the product, and restarting may solve this problem.
2) Formulation problem
This situation generally occurs after the replacement of a certain batch or manufacturer of additives PVC yellow. The solution is as follows:
(1) Increase the content of stabilizer.
(2) Adjust the internal and external lubricant balance.
(3) yellowing is solved by pigment complement or increasing the proportion of PVC special fluorescent whitening agent.
(4) By adding ultraviolet absorbent to increase the anti-aging effect, durable protection against fading and yellowing!