Processing characteristics of PPS plastics

The PPS provided by the resin manufacturer is a white powder with low relative quality (4000~5000) and high crystallinity (75%). This pure PPS cannot be directly plasticized and can only be used for spraying. PPS used for plasticizing must be cross-linked to increase the viscosity of the melt. Generally, the melt index after crosslinking should reach 10-20; The melt index of glass fiber reinforced PPS can be larger, but it cannot be greater than 200.

There are two cross-linking methods of PPS: thermal cross-linking and chemical cross-linking. At present, thermal cross-linking is the main method. The crosslinking temperature of thermal crosslinking is 150~350 ℃, no crosslinking occurs below 150 ℃, and highly crosslinking occurs above 350 ℃, which leads to processing difficulties.

Chemical crosslinking requires the addition of crosslinking promoters, including zinc oxide, lead oxide, magnesium oxide, cobalt oxide, phenolic compounds, hexamethoxymethyl melamine, hydrogen peroxide, alkali metal or alkaline earth metal hypochlorite, etc.

Although PPS is cross-linked, its liquidity is not much reduced; Therefore, the waste can be reused three times; PPS itself is demoulding, so it is unnecessary to add mold release agent; The crystallinity and thermal deformation temperature of PPS can be increased after heat treatment. The post treatment conditions are: temperature 204 ℃, time 30 min.

PPS plastic processing method

(1) Injection molding: general injection molding machine can be used, and the melt index of glass fiber reinforced PPS should be 50. The process conditions for injection molding are: barrel temperature, 280~330 ℃ for pure PPS and 300~350 ℃ for 40% GFPPS; Nozzle temperature: 305 ℃ for pure PPS and 330 ℃ for 40% GFPPS; Die temperature 120-180 ℃; Injection pressure, 50-130 MPA.

(2) Extrusion: exhaust extruder is adopted, and the process is: the temperature of feeding section is less than 200 ℃; The barrel temperature is 300-340 ℃, the connecting temperature is 320-340 ℃, and the die temperature is 300-320 ℃.

(3) Moulding: suitable for large products, using twice compression, first cooling, then hot pressing. The preheating temperature of hot pressing is about 360 ℃ for 15 min for pure PPS and 380 ℃ for 20 min for GFPPS; The molding pressure is 10~30Mpa, and it is cooled to 150 ℃ for demoulding.

(4) Spray molding: suspension spraying method and suspension spraying and dry powder thermal spraying mixed method are used to spray PPS onto the metal surface, and then obtain the coating after plasticizing and quenching treatment; The coating treatment temperature of PPS is above 300 ℃, and the heat preservation is 30min.