Commonly used plastic materials and characteristics --PC (Polycarbonate)

author: YITECH

2024-10-21

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PC (Polycarbonate)

Polycarbonate is A thermoplastic resin containing - [O-R-O-CO] - chain in the molecular hair chain, according to the different ester groups in the molecular structure can be divided into aliphatic, alicyclic group, fat - aromatic type, which has practical value is aromatic polycarbonate, and bisphenol A type polycarbonate is the most important, the molecular weight is usually 300,00-100,000.

PC is a kind of amorphous, odorless, non-toxic, highly transparent colorless or slightly yellow thermoplastic engineering plastic, with excellent physical and mechanical properties, especially excellent impact resistance, high tensile strength, bending strength, compression strength; Good toughness, good heat and weather resistance, easy coloring, low water absorption.

The thermal deformation temperature of PC is 135-143℃, the creep is small, and the size is stable. It has good heat resistance and low temperature resistance, stable mechanical properties, dimensional stability, electrical properties and flame retardant in a wide temperature range, and can be used for a long time at -60~120℃; There is no obvious melting point, and it is molten at 220-230℃. Because of the rigidity of the molecular chain, the viscosity of the resin melt is high. Small water absorption, small shrinkage (generally 0.1%~0.2%), high dimensional accuracy, good dimensional stability, small film permeability; It is a self-extinguishing material; Stable to light, but not resistant to ultraviolet light, good weather resistance;

Oil resistant, acid resistant, not resistant to strong alkali, oxidizing acid and amine, ketones, soluble in chlorinated hydrocarbons and aromatic solvents, inhibit bacterial properties, flame retardant properties and anti-pollution, long-term in water easy to cause hydrolysis and cracking, the disadvantage is due to poor fatigue strength, easy to produce stress cracking, poor solvent resistance, poor fluidity, poor wear resistance. PC can be injection molding, extrusion, molding, blow molding, hot forming, printing, bonding, coating and machining, the most important processing method is injection molding.

2.PC process characteristics

PC material is more sensitive to temperature, its melting viscosity decreases significantly with the increase of temperature, the flow is accelerated, and it is not sensitive to pressure, in order to improve its fluidity, it is necessary to take a heating method. PC material before processing should be fully dry (about 120 ° C, 3 to 4 hours), moisture should be controlled within 0.02%, trace water processing at high temperature will make the product produce white color, silver wire and bubbles, PC at room temperature has a considerable forced high elastic deformation ability. High impact toughness, so it can be cold pressing, cold drawing, cold roll pressing and other cold forming process.

PC material should be molded under the conditions of high material temperature, high mold temperature, high pressure and slow speed, low speed injection for smaller gates, and high speed injection for other types of gates. It is better to control the mold temperature at about 80-110℃, and the molding temperature is appropriate at 280-320℃. PC products are easy to appear on the surface of gas flowers, water mouth is easy to produce gas lines, internal residual stress is large, easy to crack.

Therefore, the molding processing requirements of PC materials are higher. PC material shrinkage rate is low (0.5%), size change is not. The product of PC material can be annealed to eliminate its internal stress. Extrusion PC molecular weight should be greater than 30,000, to use a gradual compression screw, length-diameter ratio 1:18 ~24, compression ratio 1:2.5, can use extrusion blow molding, injection - blow, injection - pull - blow molding high-quality, high transparent bottles.

3. Typical application range:

PC's three major application areas are glass assembly industry, automotive industry and electronics, electrical industry, followed by industrial machinery parts, optical discs, civilian clothing, computers and other office equipment, medical and health care, film, leisure and protective equipment.