In the field of plastic industry, the classification of crystalline and amorphous plastics is the underlying logic determining material properties and processing behaviors, essentially stemming from the difference in the arrangement of polymer molecular chains during solidification. This core distinction not only affects the macroscopic characteristics such as material appearance and heat resistance but also directly guides material selection and process optimization in industrial production.

    Crystalline plastics such as polyethylene (PE) and polypropylene (PP) form crystalline regions through regular and ordered stacking of molecular chains during cooling, coexisting with amorphous regions, with a crystallinity usually between 30% and 80%. Their advantages lie in high density, strong barrier properties, excellent rigidity, wear resistance and heat resistance, making them suitable for manufacturing high-strength products such as gears and toolboxes. However, they have a large molding shrinkage rate and anisotropy, which are prone to warping and deformation, requiring the control of cooling rate to regulate the crystallization process.
    Amorphous plastics such as polycarbonate (PC) and polystyrene (PS) have molecular chains in a state of disorderly entanglement without a fixed melting point. These materials have good light transmittance, high dimensional stability and uniform shrinkage, making them ideal for manufacturing water cups, light boxes and complex structural parts, but their rigidity and heat resistance are relatively weak.
     In terms of processing technology, the mold temperature is a key parameter for crystalline plastics: rapid cooling can improve toughness and shorten the cycle, while slow cooling can increase crystallinity and dimensional accuracy; the cooling process of amorphous plastics is simpler, and the mold temperature mainly affects production efficiency and internal stress.
    During material selection, precise matching is required according to needs: amorphous plastics are preferred for high transparency and low shrinkage; crystalline plastics are the first choice for high rigidity and chemical resistance. This classification system provides a clear selection logic for thousands of plastic grades, promoting the efficient development of injection molding, molding and other industries.

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