Why is TPV low hardness thermoplastic rubber agglomerated easily?

Why is TPV low hardness thermoplastic rubber agglomerated easily?

Text|Meite Polymer Tough Brother

Why is TPV low hardness thermoplastic rubber agglomerated easily?

TPV particles

As a general rule, we rarely see agglomeration of plastic particles, but thermoplastic elastomers are more prone to agglomeration, especially in low hardness specifications. The reasons for agglomeration are as follows:

①The hardness is too low, for example, for materials close to 0 degrees, it is usually necessary to add a release agent to avoid agglomeration;

②Before filling, thermoplastic elastomer particles were not sufficiently cooled, which caused particles to stick together;

③Thermoplastic elastomer has oil deposits, and oil causes particles to stick to each other.

1. What is main reason for agglomeration of TPV particles?

If it is TPV thermoplastic vulcanizate, and degree of TPV vulcanization is relatively high, such as RENPRENE N1000, 4000 series, usually cause of agglomeration does not belong to above three situations, but due to shrinkage of TPV particles, resulting in cohesive force A, than greater shrinkage rate of material, greater cohesive force, so low hardness TPV is relatively easy to agglomerate, but this kind of agglomeration, adhesion between particles is very small, it can be used It can be separated with a light touch of hand. Watch video below:

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    If hardness of TPV particles is heavy enough to resist deformation caused by bonding, agglomeration will not occur.

    Reminder: As a general rule, lower TPV hardness, faster shrinkage rate, and higher TPV cure rate, faster shrinkage rate. Generally, TPV above 75A will not agglomerate.

    Of course, if you bake your TPV at temperatures above 130°C and package it right away, it will indeed cause TPV particles to stick together. The reason for this sticking is that surface of TPV has softened. particle and particle is very strong and requires a crusher to separate it. But usually filling temperature of our TPV particles is usually below 50°C, so TPV particles will not stick to each other due to insufficient cooling.

    2. Why is TPV agglomeration caused by cohesion and only occurs in winter?

    TPV agglomeration phenomenon mainly occurs only in winter, usually in December, January and February, and there is no such phenomenon at other times. Theoretically, agglomeration is more likely to occur in summer because temperatures are high. summer, and TPV particles may not be sufficiently cooled, resulting in a sticky surface and agglomeration, but we have never experienced agglomeration and agglomeration between TPV particles in summer, and have not encountered customer feedback. Thus, this twenty years of experience leads us to conclusion that TFE agglomeration is caused by adhesion between TFE particles.

    And how muchy rallying in summer does not lead to agglomeration? Because in summer lubricant migrates to surface of TPV particles faster, which plays a role in isolation and reduces attraction between particles due to shrinkage.

    3. What is difference between TPV particles and TPE-S particle agglomeration?

    There is an obvious phenomenon in agglomeration of TPV particles: particles can be dispersed with little force, instead of agglomeration of some TPE-S, where particles deform and soften together. Of course, if TFE particles are compressed for a long time and hardness of TFE is particularly low (eg less than 35A), particles between agglomerates will need a relatively large force to loosen.

    4. How to improve agglomeration of TPV particles in winter?

    First, based on above analysis, it is difficult to completely improve caking phenomenon of TPV in winter because we cannot change inherent shrinkage rate of TPV materials. If shrinkage rate exists, adhesion will not disappear, and eventually lead to low hardness TPV will agglomerate.

    4.1. Increase amount of external TPV lubricant used appropriately, but not too much. Too much can easily precipitate and cause problems in some applications such as TPV flocking;

    4.2. Increase cure rate of TFE accordingly, but cure rate cannot be 100%;

    4.3. Increase proportion of TPV filler accordingly, but usually proportion of filler is fixed;

    4.4. Properly increase high temperature drying time of TPV particles so that external lubricant has enough time to migrate to surface of particles;

    4.5. Mix several release agents with TPV particles;

    Above, relatively speaking, plan 4.4 is better, and plan 4.5 will generate a certain amount of dust.

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