PC(polycarbonate) is a polymer containing carbonate esters in the molecular chain, according to the structure of the ester group can be divided into aliphatic, aromatic, aliphatic - aromatic and other types, is currently the five major engineering plastics in the fastest growing general engineering plastics.

Advantages and disadvantages of PC materials

Polycarbonate is colorless and transparent, heat resistant, impact resistant, flame retardant BI class, and has good mechanical properties in ordinary use temperatures. Polycarbonate has good impact resistance, high refractive index, good processing performance, and has UL94 V-0 flame retardant performance without additives. The main performance defects of PC are not high enough hydrolysis stability, sensitive to notch, organic chemical resistance, poor scratch resistance, long-term exposure to ultraviolet light will turn yellow. PC, like other resins, is also susceptible to corrosion by some organic solvents. Polycarbonate has poor wear resistance, and some polycarbonate devices used for easy wear applications require special surface treatment.

PC(polycarbonate) processing conditions

The comprehensive performance of polycarbonate is excellent, especially suitable for the manufacture of small parts with precise size, complex shape, light load or less impact load. During the processing process, the viscosity decreases with the increase of temperature, and the three major conditions of raw material drying, injection temperature and mold temperature need to be strictly controlled.

(1) Raw material drying

Polycarbonate is highlighted by its sensitivity to trace moisture at high temperatures, coupled with high melting temperature, large melting viscosity, often due to improper handling and cracking and other quality accidents, so it must be strictly and thoroughly dried before injection molding. After drying, the moisture content of plastic should not be greater than 0.02%, the presence of trace water can cause destructive degradation of polycarbonate, the viscosity decreases, the release of carbon dioxide and other gases, the plastic discoloration, and the performance deteriorates. The disc products are easy to bring silver wire, bubbles, and even crack. The higher the water content, the more serious the destructive degradation phenomenon.

(2) Injection temperature

Polycarbonate has two thermal processing characteristics: high thermal stability and a wide molding temperature range; The viscosity changes greatly due to the change of temperature and little due to the change of shear rate.

That is, the melting fluidity of polycarbonate (PC) is greatly affected by the change of temperature, and the influence of pressure is not significant. Therefore, it has always been the adjustment of injection molding temperature as an effective means to smoothly carry out molding and control the quality of parts.

However, if the temperature is too low, the viscosity is large, and the supply is insufficient, it will lead to the surface shrinkage, wrinkles, dull, and silver wire disorder. The temperature is too high or higher than 320 ° C and the residence time is too long, it will cause serious degradation, resulting in a flash, dark brown, silver filaments, spots and traces on the surface, internal bubbles, and a significant decline in physical properties.

(3) Mold temperature

Polycarbonate has high viscosity, poor fluidity, insensitivity to shear action, fast cooling speed, and is easy to produce defects on the surface of the parts and form internal stresses.

If the mold temperature is too low, it is difficult to fill the mold cavity, or there is a large shrinkage rate, ripples, hair spots, filaments, voidings and other apparent defects, which will increase the residue of the product.

If the mold temperature is too high, the cooling of the parts is slow, the molding cycle is long, and the surface luster is poor, it will cause the sticking mold, making the ejection and stripping difficult, and the bridge area and warping deformation of the parts.

Injection pressure of PC(polycarbonate)

The influence of injection pressure on the performance of the parts is mainly manifested in the holding time. The pressure holding time is short, the parts shrink, or there are shrinkage holes and vacuum bubbles; Lengthening the holding time, especially for large-area thick-walled parts, can increase its density, eliminate true voids and improve dimensional stability; If the pressure holding time is too long, the parts will produce internal stress and crack easily.

PC(polycarbonate) application

PC is widely used in building materials, automobiles, medical, aviation, aerospace, electronic appliances, packaging and other fields.

Building materials industry: PC sheet has good light transmission, impact resistance, dimensional stability, molding processability and ultraviolet resistance, which has obvious technical performance advantages over traditional inorganic glass.

Automotive field: polycarbonate has good impact resistance, thermal distortion resistance, and good weather resistance, high hardness, so it is suitable for the production of various parts of cars and light trucks, its application is mainly concentrated in the lighting system, instrument panel, heating plate, defroster and polycarbonate alloy bumper.

Medical devices: Because PC products can withstand steam, cleaning agents, heating and large doses of radiation disinfection, and do not occur yellow and physical properties decline, it is widely used in artificial kidney hemodialysis equipment and other medical equipment that needs to be operated under transparent and intuitive conditions and need to be repeatedly disinfected. Such as the production of high pressure syringes, surgical masks, disposable dental appliances, blood separators and so on.

Aerospace: With the rapid development of aviation and aerospace technology, the requirements for various components in aircraft and spacecraft continue to improve, making the application of PC in this field is also increasing. According to statistics, there are 2,500 polycarbonate parts used in only one Boeing aircraft, and the single machine consumes about 2 tons of polycarbonate. On the spacecraft, hundreds of different configurations and fiberglass reinforced polycarbonate components are used, as well as astronaut protective equipment.

Packaging: A new growth point in the packaging field is the various models of water bottles that can be re-sterilized and used. Because polycarbonate products have the advantages of light weight, impact resistance and transparency, and do not deform and remain transparent when washed with hot water and corrosive solutions, the use of PC bottles is very common.

Electronic appliances: Because polycarbonate has good and constant electrical insulation in a wide range of temperature and humidity, it is an excellent insulating material. At the same time, due to its good flame resistance and dimensional stability, it is widely used in the electronic and electrical industry, including power tool shell, body, bracket, refrigerator freezer drawer and vacuum cleaner parts. PC materials are also used in many important parts of computers, video recorders and color TV sets.

Optical lens: Polycarbonate occupies an extremely important position in this field because of its unique characteristics of high light transmittance, high refractive index, high impact resistance, dimensional stability and easy machining. Optical lenses made of optically grade polycarbonate can not only be used for cameras, microscopes, telescopes and optical testing instruments, but also for movie projector lenses, photocopier lenses, infrared autofocus projector lenses, laser beam printer lenses, as well as various prisms, multi-sided mirrors and many other office equipment and home appliances. In the eyewear industry, PC materials are also playing a big role in the lens materials for children's glasses, sunglasses and safety goggles and adult glasses.