In medical injection molding production, product brittleness is a thorny issue that significantly impacts quality and performance. Medical products have extremely high requirements for strength, toughness, and stability. Brittleness not only shortens the product's lifespan but may also pose safety hazards during use. Product brittleness is influenced by multiple factors, including raw materials, injection molding processes, and molds. The following explores strategies to address this problem.

Solutions to Raw Material Problems

• Optimize Raw Material Selection: Different raw materials have distinct characteristics. For example, polypropylene (PP) materials with a narrow molecular weight distribution or low isotacticity, and polycarbonate (PC) materials with high impurity content are prone to causing product brittleness. Enterprises should strictly screen suppliers to ensure stable raw material quality. Before purchasing, request detailed quality inspection reports from suppliers to understand key indicators such as molecular weight distribution, isotacticity, and impurity content of the materials. For critical medical products, conduct spot checks on each batch of raw materials using professional testing equipment like molecular weight analyzers and impurity analyzers to ensure they meet production requirements.
• Rationally Proportion Raw Materials: When blending and modifying multiple raw materials to meet special performance requirements of products, improper proportions can lead to product brittleness. For instance, when blending PP with elastomers, it is necessary to precisely control the amount of elastomer added to form an effective sea-island structure and exert a toughening effect. At the same time, consider the compatibility of different raw materials. Compatibilizers can be added to improve compatibility and reduce phase separation. Enterprises should establish a scientific database of raw material proportions. Through extensive experiments and actual production verification, determine the most suitable raw material proportioning schemes for different products and strictly implement them during production.
• Improve Raw Material Storage Conditions: Medical injection molding raw materials are sensitive to temperature, humidity, and light. For example, nylon (PA) materials are highly hygroscopic. High humidity storage environments can cause them to absorb water, leading to product brittleness during injection molding due to hydrolysis reactions that break molecular chains. Enterprises should set up dedicated raw material storage warehouses equipped with temperature and humidity regulation devices and light control devices. Keep the warehouse temperature within an appropriate range and humidity at a low level, and avoid direct sunlight. At the same time, classify and store raw materials with clear labels for easy management and retrieval. Regularly inspect the storage status of raw materials to promptly identify and address any issues.

Improvement Methods for Injection Molding Process Problems

• Precisely Control Injection Molding Temperature: Both high and low injection molding temperatures can cause product brittleness. Excessive temperatures lead to thermal degradation of raw materials, breaking molecular chains, while insufficient temperatures result in poor raw material fluidity and the formation of weld lines. Enterprises should determine the optimal injection molding temperature range for different raw materials through experiments. During production, use high-precision temperature control equipment to monitor and adjust the injection molding temperature in real-time, ensuring it remains within a reasonable range. Additionally, provide professional training to operators to enhance their sensitivity to temperature control and operational skills.
• Reasonably Adjust Injection Molding Pressure: Insufficient injection molding pressure leads to pores and loose structures inside the product, while excessive pressure causes excessive shear forces on the material, generating internal stresses. Enterprises should determine the appropriate injection molding pressure based on the product's structure, size, and raw material characteristics through simulation experiments and actual production debugging. During production, closely monitor product quality. If signs of brittleness are detected, promptly adjust the injection molding pressure. Regularly maintain and service injection molding equipment to ensure the normal operation of the pressure control system.
• Scientifically Set Cooling Time: Insufficient cooling time results in incomplete crystallization and high internal stresses in the product, while excessive cooling time increases the production cycle and may damage the product surface. Enterprises should determine the optimal cooling time based on the product's thickness, material characteristics, and mold structure through experiments. During production, use cooling time control devices to ensure accurate cooling time. Simultaneously, optimize the cooling system design to improve cooling efficiency, such as using circulating cooling water and increasing the number of cooling channels for uniform product cooling.

Countermeasures for Mold Problems

• Reasonably Adjust Mold Temperature: Mold temperature has a direct impact on the product's crystallization and cooling process. Enterprises should determine the optimal mold temperature for different raw materials through experiments. During production, use mold temperature control equipment to adjust the mold temperature in real-time, ensuring it remains within a suitable range. Regularly inspect the operation of the mold temperature control system to promptly troubleshoot and ensure accurate mold temperature.
• Optimize Mold Structure: Improper mold runner design, inadequate venting systems, and small draft angles can all lead to product brittleness. Enterprises should hire professional mold designers to optimize the mold structure design according to the product's characteristics and production requirements. In runner design, reduce the flow resistance of raw materials and lower shear heat. In venting system design, ensure that gases in the cavity can be discharged in a timely manner. In draft angle design, ensure smooth product demolding with minimal friction and damage. During mold manufacturing, strictly control processing accuracy to ensure mold quality meets standards.