factors affect Modified PP material shrinakage

The shrinkage control of modified PP material is an important aspect of polypropylene modification. Good shrinkage control / control is of great significance to the popularization and application of polypropylene modified materials, and it is also an important aspect to ensure product quality. In particular, it is very important to use modified polypropylene to replace traditional engineering plastics.

Effect of mineral filling on molding shrinkage of polypropylene PP modified plastics

The mineral additives used in PP mainly include calcium carbonate, talc powder, mica powder, etc. It can be seen that mineral additives have an obvious effect on the molding shrinkage of PP modified material.

The influence of mineral additives on the molding shrinkage of polypropylene modified materials mainly includes three aspects:

First, the mineral filler itself does not shrink, and its addition reduces the shrinkage of polypropylene modified material from the overall proportion;

Second, the addition of mineral filler will inevitably affect the crystallinity of polypropylene, thus affecting the shrinkage;

Third, the addition of fine mineral agent acts as a nucleating agent, which changes the structural state of polypropylene, prevents the formation of large spherulites, and also affects the molding shrinkage of polypropylene.

Effect of glass fiber on molding shrinkage of polypropylene PP modified plastics

Glass fiber has the greatest influence on the molding shrinkage of polypropylene PP modified material. When the content of glass fiber reaches more than 30%, the molding shrinkage of polypropylene modified material decreases from 1.8 to 0.5, and the influence of surface treated glass fiber on the molding shrinkage is greater than that of untreated glass fiber. The addition of glass fiber breaks / destroys the crystallinity of polypropylene and affects the shrinkage. More importantly, glass fiber limits / limits the crystalline shrinkage of polypropylene.

Effect of polyethylene on shrinkage of polypropylene

The addition of polyethylene also affects the molding shrinkage of polypropylene modifier. Although polyethylene is also a plastic with high crystallinity and large molding shrinkage, its crystallinity is broken / damaged to varying degrees after being added to polypropylene, resulting in a decrease in the overall molding shrinkage.

Effect of mi (melt fat) change of polypropylene on molding shrinkage

The molding shrinkage of polypropylene is affected by its crystallinity, which is affected by its own molecular weight. When Mi increases, the molecular weight decreases, the crystallization rate increases and the molding shrinkage increases. The change of polypropylene Mi also has a certain effect on the molding shrinkage.

summary

① : the influence order of glass fiber, mineral, elastomer, polyethylene and MI on the shrinkage of PP modified plastics is: glass fiber > mineral > elastomer > polyethylene > MI.

② : changing the crystallinity of polypropylene is the key to control the molding shrinkage of polypropylene modifier.