PS GPPS hips 525 535 Food grade PS plastic raw materials polystyrene Virgin pellet gpps hips for Disposable lunch box

General grade polystyrene is a thermoplastic resin, colorless, odorless, tasteless and shiny, transparent beads or granular solid.  Density 1.04 ~ 1.09, transparency 88% ~ 92%, refractive index 1.59 ~ 1.60.  Under the action of stress, birefringence occurs, which is called stress-optical effect.  The melting temperature of the product is 150 ~ 180ºC, the thermal decomposition temperature is 300ºC, the thermal deformation temperature is 70 ~ 100ºC, and the long-term use temperature is 60 ~ 80ºC.  At 5 ~ 6ºC lower than the thermal deformation temperature, the stress can be eliminated and the thermal deformation temperature can be increased after annealing treatment.  If a little α -methyl styrene is added in the production process, the heat resistance grade of universal polystyrene can be improved.