{"id":35591,"date":"2025-02-12T08:40:04","date_gmt":"2025-02-12T16:40:04","guid":{"rendered":"https:\/\/www.linquip.com\/blog\/?p=35591"},"modified":"2025-02-18T06:20:40","modified_gmt":"2025-02-18T14:20:40","slug":"how-to-improve-the-transparency-of-plastic-products-lets-explore-the-relationship-between-materials-and-injection-molding-processes","status":"publish","type":"post","link":"https:\/\/www.linquip.com\/blog\/how-to-improve-the-transparency-of-plastic-products-lets-explore-the-relationship-between-materials-and-injection-molding-processes\/","title":{"rendered":"How to Improve the Transparency of Plastic Products? Let’s Explore the Relationship Between Materials and Injection Molding Processes"},"content":{"rendered":"

Due to its advantages of being lightweight, tough, easy to form, and cost-effective, plastic is increasingly replacing glass in modern industrial and everyday products, especially in optical instruments and packaging industries, where it has seen rapid development. However, as plastic products need to meet high demands for transparency, wear resistance, and impact toughness, significant work must be done on the plastic\u2019s composition, the entire <\/span>injection molding process<\/span><\/a>, equipment, and molds to ensure that these plastics (hereafter referred to as transparent plastics), used to replace glass, have good surface quality and meet usage requirements.<\/span><\/p>\n

Currently, commonly used transparent plastics include polymethyl methacrylate (PMMA, also known as acrylic or organic glass), polycarbonate (PC), polyethylene terephthalate (PET), transparent nylon, acrylonitrile-styrene (AS), polysulfone (PSF), and others. Among these, PMMA, PC, and PET are the most frequently encountered. We will discuss the properties of transparent plastics and the injection molding process using these three materials as examples.<\/span><\/p>\n

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  1. Properties of Transparent Plastics<\/b><\/li>\n<\/ol>\n

    Transparent plastics must first have high transparency. Additionally, they need to have a certain level of strength, wear resistance, impact resistance, heat resistance, chemical resistance, and low water absorption. Only by meeting these requirements can the plastic maintain its transparency and functionality over time. PC is an ideal choice, but due to the high cost of raw materials and the more complex injection molding process, PMMA is still primarily used for products with general requirements. PET, on the other hand, needs to undergo stretching to achieve good mechanical properties, so it is mostly used in packaging and containers.<\/span><\/p>\n

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    1. Common Issues in the Injection Molding of Transparent Plastics<\/b><\/li>\n<\/ol>\n

      Since transparent plastics require high light transmittance, their surface quality must meet stringent requirements. The products must be free from defects such as streaks, air pockets, whitening, fogging, black spots, discoloration, or poor gloss. Therefore, special attention and strict requirements must be applied to the raw materials, equipment, molds, and even product design throughout the entire injection molding process.<\/span><\/p>\n

      Furthermore, because transparent plastics often have high melting points and poor flowability, it is necessary to make fine adjustments to process parameters such as barrel temperature, injection pressure, and injection speed to ensure that the mold is filled without causing internal stress, which could lead to deformation or cracking of the product.<\/span><\/p>\n

      Key Considerations Regarding Equipment, Molds, and Process Parameters<\/b><\/p>\n

      Drying of Materials<\/b><\/p>\n

      The preparation and drying of materials is critical, as any impurity in the plastic can affect its transparency. During storage, transportation, and feeding, it is essential to ensure that materials are sealed and kept clean, especially if there is moisture in the raw materials. Heating moisture-laden materials will lead to material degradation, so they must be thoroughly dried. During injection molding, a drying hopper should be used for feeding. Also, it is recommended that the air used for drying be filtered and dehumidified to avoid contaminating the material.<\/span><\/p>\n

      Cleaning of the Barrel, Screw, and Attachments<\/b><\/p>\n

      To prevent material contamination and to ensure that no old materials or impurities remain in the screw and attachments, particularly in areas with poor heat stability, it is necessary to clean these parts with a screw cleaning agent before use or after stopping the machine. If a cleaning agent is not available, other resins like PE or PS can be used to clean the screw.<\/span><\/p>\n

      During temporary shutdowns, to prevent material degradation due to prolonged exposure to high temperatures, the temperature of the drying machine and barrel should be lowered (for materials like PC and PMMA, the barrel temperature should be reduced to below 160\u00b0C, and for PC, the hopper temperature should be lowered to below 100\u00b0C).<\/span><\/p>\n

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      Considerations in Mold Design (Including Product Design)<\/b><\/p>\n

      To prevent issues such as poor flow or uneven cooling, which can lead to molding defects and surface flaws, the following should be considered in <\/span>mold design<\/span><\/a>:<\/span><\/p>\n