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Crystallinity PPS is a kind of crystalline polymer, and its crystallinity is changed with the cooling temperature and rate when it is molding. The maximum crystallinity of PPS could be up to 85%. The customer can choose resin with proper crystallinity according to the Mechanics of machinery index required. The effect of crystallinity on the injection mold product is shown as following:： • Thermal deformation temperature increased; • Stiffness increased; • Tensile strength improved under room temperature; • Flexural strength under 95℃ decreased, but that above 95℃ increased; • Impact strength decreased; • Dimensional stability and resistance to creep enhanced; • Surface brightness of injection mold product increased (but the surface brightness got poor after anneal treatment); • Surface rigidity improved; • Shrinkage ratio increased, with high dimensional stability under elevated temperature; • Linear expansibility reduced. |
Flow characteristics With temperature increased, the flow of PPS increased. But under too high temperature or too long standing time, resin maybe be partial oxidized and cross-linked, then lead to the reducing of flow ability. |
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Shrinkage The shrinkage of PPS increased with the temperature. In general, the mold shrinkage rate of PPS is small, but that of vertical direction is 2-4 times as that of flow direction. In addition, the thickness and shape of product and rate of injection also influence the shrinkage. The thickness of product should be uniform with the wall thickness not exceeding 7-10mm. Or else PPS resin for thick wall mold should be chosen. | |
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Thermal stability Under elevated temperature, PPS resin may be partial oxidized and cross-linked. Long time standing in machine barrel will lead to flow ability reduce, color and luster become dark, and product property be influenced. | |
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Water absorption The water absorption rate of PPS is quite low. But before processing, it should be pre-dry under 120-150℃ for about 3-5 hours. |
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