Polycarbonate (PC) holds an important position in the field of engineering plastics due to its excellent transparency, impact resistance, and heat resistance.However, in actual processing and application, neglecting its material properties and process requirements can easily lead to performance degradation or safety hazards. To ensure the quality and reliability of PC products, a series of precautions must be followed regarding raw material control, processing operations, environmental protection, and application matching.
First, the drying of raw materials should be given high priority. PC has strong hygroscopicity. If the moisture content is too high before molding, moisture will cause molecular chain hydrolysis under high temperature conditions, resulting in a decrease in molecular weight, weakened mechanical properties, and defects such as silver streaks and bubbles on the surface of the product. Therefore, it is necessary to dry the raw materials thoroughly at around 120℃ for 3-4 hours before processing, ensuring that the moisture content is below 0.02%. The drying equipment should be kept sealed and have hot air circulation to avoid secondary moisture absorption.
Second, temperature control during processing is particularly critical. PC melt temperature typically ranges from 260 to 300°C, but prolonged exposure to high temperatures or localized overheating accelerates thermal degradation, leading to discoloration, odor, and reduced toughness. Temperature gradients should be applied to different zones of the barrel, and nozzle temperatures should not be excessively high to prevent drooling. Maintaining a mold temperature of 80–120°C helps improve filling uniformity, reduce internal stress and warpage, and enhance surface gloss.
During molding, avoid excessive shear rates and injection pressures to prevent excessive frictional heat generation from causing degradation or stress concentration leading to product cracking. For thin-walled or complex structures, multi-stage injection and appropriate holding pressure profiles can be used to ensure complete filling and control shrinkage differences. Use mold release agents cautiously; choose types compatible with PC and use sparingly to avoid surface contamination or affecting optical properties.
After molding, annealing is recommended to eliminate residual stress. A common method is to hold the product at 100–120°C for several hours, followed by slow cooling. This step is particularly important for optical or structural components requiring high dimensional stability. In application, attention must be paid to the chemical resistance of PC. Its resistance to organic solvents is limited; prolonged contact with ketones, aromatic hydrocarbons, and strong acids and alkalis can lead to swelling or cracking. When involving food contact or medical applications, the risk of bisphenol A (BPA) migration should also be considered. Low-migration or BPA-free modified grades that comply with relevant regulations should be selected, and usage conditions should be strictly controlled.
Furthermore, the processing site should have adequate ventilation and personnel protection to avoid inhalation of potential thermal decomposition products and to prevent direct skin contact with high-temperature melts. Waste and scrap materials should be collected separately to avoid contamination and affecting recycling quality.
In summary, precautions for PC are crucial throughout the entire process, from raw material preparation and processing control to post-processing and application matching. Only by systematically adhering to material characteristics and process specifications can its performance advantages be fully realized and safe use ensured.