The effect of increased crystallinity on injection molded products

The effect of increased crystallinity on injection molded products

PPS is a crystalline polymer, the crystallinity varies with the cooling temperature and rate during molding, and the maximum crystallinity can reach 85%. The material with suitable crystallinity can be selected according to the mechanical indexes required by oneself.

* The effect of increased crystallinity on injection molded products is as follows:*

Parts affected:

1) Increased heat distortion temperature

2) Increased rigidity

3) The tensile strength at room temperature is slightly reduced, but the tensile strength at high temperature is increased,

4) The bending strength below 95℃ decreases, and the bending strength above 95℃ increases

5) The impact strength is reduced;

6) Increased dimensional stability and creep resistance

7) The surface gloss of injection molded products increases (but if the surface gloss becomes worse after annealing)

8) Increased surface hardness

9) The shrinkage rate increases, and the dimensional stability at high temperature is improved

10) Reduced linear thermal expansion coefficient

2

Flow characteristics

As the temperature increases, the fluidity of PPS becomes correspondingly stronger, but if the temperature is too high or the residence time of the material is too long, the material will undergo partial oxidation and crosslinking, resulting in a decrease in fluidity.

3

Molding shrinkage

PPS molding shrinkage rate increases with the increase of mold temperature. Generally, the shrinkage rate of Polyphenylene Sulfide is small, but the shrinkage rate in the vertical direction of the flow is 2~4 times larger than the flow direction. In addition, the product thickness, shape, and injection speed are also Will have an impact on the production hands. Under normal circumstances, the thickness of the product should be uniform, and the back wall should not exceed 7~10mm. Otherwise, thick-walled polyphenylene sulfide molding products should be used.

4

Thermal stability

PPS will undergo partial oxidation cross-linking reaction at high temperature. If it stays in the barrel for a period of time, it will reduce the fluidity of the material, darken the color, and affect the physical properties of the product.

5

Water absorption

PPS has low water absorption, but the material should be pre-dried at 120~150℃-3~5 hours before processing

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