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Common problems and solutions in the processing of thermoplastic elastomer TPV

In the development process of materials that emphasize environmental adaptability, thermoplastic elastomers that do not require vulcanization and mixing processes have the characteristics of energy saving, resource saving, and high production efficiency. Their annual growth rate is as high as 6%. In this context, the use of new thermoplastic elastomer materials in processing and manufacturing plants is gradually expanding, but the problems that follow (roughened surface of the molded product, deformation, etc.) have also increased. 1.1 Albino Bleaching means that stabilizers and other compounding agents migrate to the surface of the molded product, and the surface shows a white phenomenon like spraying powder. The reason is mainly due to excessive blending of the stabilizer or incompatibility with the polymer. Therefore, stabilizers with good compatibility with polymers should be selected or the amount of stabilizers should be controlled in the best range. Secondly, it is also very effective to replace it with a relatively high molecular weight stabilizer. In addition, there are stabilizers that exert their functions by migrating to the surface of the molded product. For example, antistatic agents, lubricants, etc. For this kind of stabilizer, it is very necessary to select a stabilizer that hardly causes whitening even if it migrates. Thermoplastic elastomers rarely bleach when used in general environments, but in high temperature, humidity and outdoor long-term use, heat resistance stabilizers (anti-aging agents) and weather stabilizers are added to improve durability Is very necessary. Especially at high temperatures, because it is very easy to cause migration, the choice of stabilizer is also very important. 1.2 Sticky Compared with resin, the surface of soft thermoplastic elastomer is more prone to stickiness. The reason is mainly due to the migration of low molecular weight polymers and plasticizers and stabilizers to the surface due to aging. But no matter what the situation is, using infrared spectroscopy (IR) and other analytical methods, by analyzing the sticky components, it can be relatively easy to determine the relevant substances. Tackiness is mainly due to the excessively high molding temperature and the formation of low molecular weight substances due to thermal decomposition of the polymer. Although the set temperature of the molding machine itself does not reach the thermal decomposition temperature, the shear heat generation in the molding process sometimes makes it temporarily reach a high temperature. As a countermeasure, reducing the molding temperature and reducing the shear, and purging the inside of the hydraulic cylinder of the molding machine with nitrogen are very effective. In addition, when the molding machine is suspended, the rubber is left in the molten state of the molding machine for a long time in the molten state, and may sometimes become sticky due to thermal aging. In addition, products used at high temperatures are prone to stickiness. Therefore, the selection of stabilizers and softeners and the determination of dosage are very important. 1.3 Aging Compared with inorganic materials and metal materials, polymer materials have poor heat resistance and ultraviolet resistance (relatively easy to aging). The mechanical properties of most products are significantly reduced due to aging, and the appearance quality is deteriorated. By blending stabilizers such as heat resistance and weather resistance, the occurrence of aging can be suppressed to a certain extent.

2020-04-13

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