GAS COUNTERPRESSURE

INCREASING THE DIMENSIONAL STABILITY OF PRODUCTS MADE FROM FOAMED AND FILLED THERMOPLASTICS BY THE USE OF GAS COUNTERPRESSURE INJECTION MOULDING Piperov N L... 

The gas counterpressure IM method uses a sealed mold pressurized to 2.8 to 3.5 MPa (400 to 500 psi) with an inert gas, sufficient pressure to suppress foaming as the plastic mix enters the mold cavity. After the measured shot is injected, the mold pressure is released, allowing the instantaneous foaming to form the core between the already formed... 

Figure 8.5 (a ) Schematic of gas counterpressure foam injection molding (Cashiers Structural Foam patent)... 

Structural foam molding, gas counterpressure structural foam molding, and co-injection molding. The high cost of tooling is the factor which governs access... 

Gas counterpressure structural foam molding and co-injection structural foam molding generally follow the same design rules as structural foam molding, although co-injection molding differs somewhat and... 

Techniques have been developed for producing smooth-faced mouldings but involves added process sophistication and increased cost. At the present time the gas counterpressure is the most popular technique. 

Both roughness mechanisms are controlled in coinjection and gas counterpressure molding. The smooth surface and spherical cells are made by both methods. However, both methods have less weight reduction and high cost of hardware. The best surface quality is achieved by co-injection molding. The gas counterpressure tested for smooth surface of microcellular foam with lowest gas pressure 1.73 MPa successfully. In addition, a new overlapped smooth surface on the foamed bottom layer has been developed. 

Figure 6. Morphology pictures of PC with gas counterpressure molding (a) gas pressure on (b) gas pressure off. 

MICROCELLULAR INJECTION MOLDING OF PP AND PC/ABS WITH PRECISION MOLD OPENING AND GAS COUNTERPRESSURE... 

H. Naguib, C. Park, S. Wong, University of Toronto, Mechanical Industrial Engineering MICROCELLULAR INJECTION MOLDING OF PP AND PC/ABS WITH PRECISION MOLD OPENING AND GAS COUNTERPRESSURE. 

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