Injection molding improve stability

Smoothness of extmdates and calendered sheets Dimensional stability of extmdates and calendered sheet Air inclusion in soft conqrounds Flow in injection molding (improvement depends on compounding)... 

Processing Stability. Despite its improved properties, the polymer based on PPG 2000 was found to be impractical because of instability at processing temperatures. Retention of the polymer melt at 204°C. in the barrel of an injection molding machine for times as short as 10 minutes gave molded parts with reduced tensile strength and loss of impact resistance. Ineffectiveness of antioxidants and nitrogen blankets in preventing this breakdown indicates that it is thermal and not oxidative. 

There is a great diversity of polyimides (PI) having = 180-420°C. Several were blended with PC to improve its stiffness, HDT and strength. PEEPC blends were commercialized in 1992 as Ultem LTX, for injection molding or extrusion. They show higher impact resistance than PEI and higher heat resistance than PC, as well as they retain the stain, chemical resistance, and the hydrolytic stability of PEI. 

PP/EPDM Blends To improve impact properties of PP, the resin is usually modified by incorporation of an elastomer. Since the performance depends on morphology, radiation crosslinking was used in its stabilization [van Gisbergen et al., 1989a] (Table 11.9). The blends were made either in a two-roll miU, at 185°C, then compression molded into 1-mm-thick sheets, or in a co-rotating twin-screw extruder, then pelletized. The irradiations (100 kGy) were done using a 3-MeV electron accelerator. Irradiated and non-irradiated pellets were injection-molded. Eor the DSC measurements, the samples were melted at 200°C, quenched to 110°C, and then heated at a rate of 10°C/min. 

One of the growing areas for PAB blend applications under the hood is in electrical and electronic connectors and systems for power distribution and control. Such applications often require low melt viscosity at injection molding temperatures to fill the intricate tooling that may be designed for up to hundreds of individual electrical connections. Practical toughness is required for snap-fit of the connections. Furthermore, glass-reinforcement of these PAB s may be required to improve modulus and dimensional stability. Typical blends suitable for these applications include PBT/PC, PA/PPE and PPS/PEI. 

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