How to solve the crystallization point of the injection molding machine to produce plastic film?

Date：2016-07-21 10:56:12

What is the crystallization point of the film is believed to make friends "crystallization point" must be very familiar with the term, simply put, it is a product defect.

Academically it is explained: the polymer molecular weight higher than the molecular weight of the polymer around the same species, and over-produced polymer.

Reason crystallization point generated

Crystal Point is usually caused by machinery, processing technology, materials, etc. caused. But the mechanism to produce the polymer crystallization point is due to over-produce polymers, so long may have been dimer are likely to cause crystallization point.

The impact of raw materials

He said that the impact of raw material injection molding machine is in fact refer to the effect of residual catalyst raw materials.

When polymer production will be some residual catalyst in molding experience, viscous polymer melt containing the catalyst in the production of equipment surfaces, at high temperatures, residual catalyst polymer continuous catalytic polymerization, the polymerization will form over thereof.

Not the same polymeric resin manufacturers equipment and technology are not the same, there are differences in the processing of residual catalyst purity, its crystallization point of the resulting polymer does not have the same impact in a film, for example, low residual catalyst content of the polymer, the device structure well, the raw material itself contains crystallization point less.

Influence of polymer oxygen

If when the processing temperature is higher, the polymer oxidation radical oxygen will adsorb at the die wall, a radical initiator as an active center of the other polymer molecule chain reaction, a high concentration of the polymer formed is unstable at the child, in high temperature become variegated points.

Adding a certain amount of antioxidants, there is an effect of oxygen to prevent crystallization point.

Effect of processing technology, equipment

If the master control process temperature and other factors, raw materials for a long time to heat, excessive polymerization, degradation will lead to the crystallization point production.

In fact, a lot of time is a result of equipment, such as:

Injection molding machine parts die poor design, the presence of the dead, causing a small amount of raw materials for a long time to heat, excessive polymerization, degradation;

The aspect ratio of the injection molding machine configuration, die design and other poor;

Screw top or barrel inner wall above the long-term because of the accumulation of things that have some charring, charring and these things can be used as the gel point, continue impurities adsorbed more to it, but also to continue the film gets top resulting in a so-called crystallization point.

All in all, molding equipment cleaned regularly helps to reduce crystallization point production.

Fillers, masterbatch and other effects

Currently injection molding machines film production habits add masterbatch, masterbatch will result in poor dispersion of grain and other undesirable point defects, such as masterbatch pigment surface treatment chosen is unstable in the masterbatch processing experience, "Reunion", a " powder point "; masterbatch carrier resin with poor film-forming material compatibility.

Reduce or eliminate the crystallization point method

Learn more crystallization point of causes, can be easier to control, you list the following four methods:

1, a good selection of raw materials purification resins, to reduce the impact of the catalyst;

2, the film forming process increases the filter fineness, frequently changes the screen (especially obsolete equipment), is conducive to the crystallization point reduction;

3, antioxidants and other appropriate amount;

4, add a surface lubricant in steel production experience, reduce viscous polymer melt in the surface of the device;

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