Читать книгу Plastics Process Analysis, Instrumentation, and Control - Группа авторов - Страница 26

A carbide-bonded graphene coating on silicon insert was proposed to realize rapid thermal cycling (RTC) in injection molding. A continuous and dense carbon-bonded graphene coating was prepared on the surface of the silicon cavity through chemical vapor deposition (32, 33).

Serving as a thin film resistance heater, the graphene coating was able to heat the mold cavity rapidly to above the glass transition temperature of the polymer, even if the applied power source was of relatively low voltage. When the voltage was 240 V, the coating was heated up to 145.6°C in a short period of 10 s. So, the average and transient heating rates were able to be as high as 11.6 ^◦C s^–1 and 16.1 ^◦Cs^–1, respectively.

This injection molding technique of RTC could be successfully implemented to produce plate samples with uniform sizes at a thickness of 600 μm (32).

Also, the influence of RTC on the weld line, internal stress, and replication fidelity was investigated. Compared with CIM, the here described method was able to mold products with smaller weld mark, less internal stress, and better replication fidelity. The tensile strength and elongation at yield of the products were also enhanced by 37.77% and increased by 265.11%, respectively, with much less energy consumption (32).

The graphene heater with a 48 Ω surface resistance made by a 60 min coating time proved to be the best choice for rapid heat cycle molding with regard to the heating efficiency (33).

The graphene heater was used in the rapid heat cycle molding of long-glass-fiber-reinforced PP composites to reduce the width and depth of the weld lines, decrease the floating fiber phenomenon, and improve the surface quality (33).