
Text|Mate Polymer Winlong
Plastic products made of PP polypropylene, PE polyethylene, HIPS, ABS and other polymer alloys and filled polymers are often subjected to external stresses such as stretching, bending and impact during use. Whitening may occur. If heat treatment (such as heating above glass transition temperature, etc.) or high-pressure stretching is performed on a portion where stress whitening already exists, portion of whitening may partially or completely disappear.
There are approximately two definitions of stress bleaching: first definition refers to local bleaching of polymer materials under stress. Irregularities, etc. The latter definition assumes that polymer material forms a large number of crazes under stress, and refractive index in region of crazes decreases and becomes silvery white. The latter definition equates phenomenon of stress whitening with phenomenon of crazing, or that cracking causes stress whitening. To best of current research, first definition is more general. For this, we can refer to first definition to improve stress bleaching of polymers.
Why are TPVs with high hardness susceptible to stress bleaching? The main reason is that content of polypropylene in high hardness TPV is relatively high. For example, in TPV 90A, content of PP reaches about 35% of total. As content of polypropylene increases further, phenomenon of stress whitening becomes more evident.
So, how to improve high hardness TPV stress whitening? First, it is unrealistic to reduce hardness and reduce amount of PP, because such a high hardness is really required. According to research of some scientists and precursors of modified plastics, stress bleaching of high hardness TPV can usually be improved by following methods:
1. The use of homopolymer polypropylene is better than bleaching under influence of copolymerization and high-impact polypropylene, whitening of high-impact polypropylene under stress is especially obvious;
2. Add certain polyolefin elastomers such as POE, POP, etc.;
3. If it is a black product, consider increasing use of black masterbatch (carbon black);
4. The addition of some nucleating agents may improve stress whitening.
5. Add low crystallinity polypropylene homopolymer.

The use of Asahi Kasei low crystalline polypropylene can significantly improve stress whitening (SW)
However, methods 1, 3, and 4 cannot significantly improve stress whitening; Methods 2 and 5 can greatly improve, but result in a significant reduction in TPV, which must also be carefully considered.
Meteor Polymer has specially released TPV 1060DB-UWE folding tape in white, which is mainly used for sealing edges of car shelves and does not leave white pinhole marks when sewing on edge seals. If you are interested, please leave a message or private message!
Recommended Reading: Key Features and Influencing Factors of TPV(1)
Related
December 04 2023
Why is high hardness TPV susceptible to stress bleaching? And a few ideas to improve anti-stress whitening.
November 17 2023
Why is TPV low hardness thermoplastic rubber agglomerated easily?
November 04 2023
Preparation, Structure and Properties of Low Hardness and 3D Printable BIIR/PP-TPV
November 12 2023
The port cover of automotive high voltage line junction box is made of flame retardant TPV, and injection molding turns out to be defective when mixed with black masterbatch.
May 25 2023
Why are anti-epidemic medical garbage bags and household garbage bags different in color?
September 27 2023
Wave flow traces and solutions to eliminate defects in TPV injection molding products
September 28 2023
Crude oil halved, why did price of oil fall only a few cents? Break down various processes from crude oil to gasoline
June 04 2023
PVC Hardness Comparison Chart
December 01 2023
American high-performance resin IMPERA manufactured by Eastman to improve tire slip resistance on wet roads.
November 06 2023
Analysis and discussion of defects and problems of TPV material extrusion