Plastic mold manufacturer, analysis of crystallization of thermoplastic materials
Plastic mold maker, analysis of crystallinity of thermoplastic materials, thermoplastic materials are materials that are malleable within a certain temperature range, they can be softened by heating and keep their shape after cooling. In injection mould factories, Thermoplastic are divided into crystalline and amorphous plastics according to whether they crystallize when they condense. The appearance criteria for these two types of plastics are usually determined by observing the transparency of thick-walled plastic parts, generally speaking, the crystalline materials are opaque or translucent (such as POM, etc.) , and the amorphous material is transparent (such as PMMA, etc.) . However, there are some exceptions, such as poly (4)-methyl-xylene as a crystalline plastic but with high transparency, and ABS as an amorphous material but not transparent.
In mold design and selection of injection molding machine, injection mold factory needs to pay attention to the characteristics and requirements of crystalline plastics. First, crystalline plastics require more heat to heat up to the molding temperature, so equipment with greater plasticizing capacity is needed. Second, the crystalline plastic releases more heat during cooling and recycling, so it needs to be cooled adequately. In addition, due to the large proportion difference between the molten and the solid state, the molding shrinkage of crystalline plastics is large, prone to shrinkage and porosity. In addition, the cooling rate of the crystalline material is faster, the crystallinity is lower, the shrinkage is smaller and the transparency is higher. The degree of crystallinity is related to the wall thickness of the plastic parts. The cooling rate of the plastic parts with larger wall thickness is slower, the degree of crystallinity is higher, the shrinkage is bigger and the physical property is better. Therefore, for the crystalline material, the mold temperature needs to be controlled according to the requirements. In addition, crystalline plastics have obvious anisotropy and high internal stress, and the uncrystallized molecules have the tendency to continue crystallizing after demoulding. Finally, the crystallization temperature range is narrow, and it is easy to inject the unmelted material into the mold or block the inlet.
The crystallization analysis of thermoplastic materials is very important for injection mould factory to know the crystallization of thermoplastic materials for mould design and selection of injection molding machine. Through the understanding of the characteristics and requirements of crystalline plastics, we can better deal with different types of plastic materials, improve production efficiency and product quality.
