Tham khảo tài liệu 'plastic product material and process selection handbook part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 474 Plastic Product Material and Process Selection Handbook There are also flexible RP. These RTP elastomeric materials provide special engineered products such as conveyor belts mechanical belts high temperature or chemical resistant suits wire and cable insulation and architectural designed shapes. Fabricating process Different processes are used. About 5wt of all plastic products produced worldwide are RPs. Injection molding consumes over 50wt of all RP materials with practically all of it being thermoplastics Chapter 4 . The different processes range in fabricating pressures from zero contact through moderate to relatively high pressure 2 000 to 30 000 psi to 207 MPa at temperatures based on the plastic s requirements that range from room temperature to over room temperatures. Equipment may be low cost to rather expensive specialized computer control of the basic machine with auxiliary equipment. In turn labor costs range from very high for low cost equipment to very low for the high cost Each process provides capabilities such as meeting production quantity small to large quantities and or shapes performance requirements proper ratio of reinforcement to matrix fiber orientation reliability quality control surface finish materials used quantity tolerance time schedule and so forth versus cost equipment labor utilities etc. . There are products when only one process can be used but there can be applications where different processes can be used. Preform Process The preform process has been used since the 1940s. As time passed significant improvements occurred processing-wise equipment-wise plastic-wise and cost-wise. This is a method of making chopped fiber mats of complex shapes that are to be used as reinforcements in different RP molding fabricating processes rather than conventional flat mats that may tear wrinkle or give uneven glass distribution when producing complex shapes in a mold. Most of the reinforcement used is glass fiber .
