Conventional Compression Mold

This mold design is disadvantageous for conventional compression molds because of the severe wear that can result. 

It is well known that by applying minor modifications, the conventional compression molding process can be nsed for manufacturing of plastic foams, as depicted in Figure 2. 

The isosorbide polyurethanes based on the aromatic diisocyanates P(I-TDI) and P(I-MDI), possess more rigid structures with both polymers forming brittle films and brittle compression moldings. Their glass transition temneratures are above their decomposition temperature of 260°C. The thermostability of isosorbide polyurethanes correspond to that of conventional polyurethanes with similar structure based on 1,4-cyclohexanedimethanol for which degradation temperature of 260°C has been determined. 

Solution blends of 20-25% by weight were formed in DM Ac, with conventional dry spinning and film casting techniques used to produce blend fiber and film, respectively. Blend powders were prepared by precipitating the dope with a non-solvent (water). All materials were extensively washed in methanol or water to reduce residual solvent to less than 1 wt %. Neat resin tensile bars and plaques were compression molded from both powder and fiber. 

Because of its high melt viscosity it has no useful melt flow index. Conventional screw plasticizing extrusion and injection molding can noy process them. The processing methods used are compression molding, ram extrusion, ram injection, and warm forming of extruded slugs from powdered plastic. In turn many components are machined from semifinished products. 

Since the plastic entering the cavities is melted it requires less force to fill the cavities than compression molding With conventional CM there is more force in the cavities as the solid plastic is melted. The result is that more intricate parts can be molded as well as encasing intricate devices such as electronic. 

Usually called injection-compression molding (ICM). Details are in Chapter 4. The essential difference when compared to IM lies in the manner in which the thermal contraction in the mold cavity that occurs during cooling (shrinkage) is compensated. With conventional injection... 

Usual method of molding BMC is by compression molding. BMCs can also be injection molded in much the same way as other plastic compounds using ram, ram-screw, and, for certain BMC mixes, conventional reciprocating screw injection molding techniques (Chapter 4). 

Fig. 14 Spherulitic structure of compression molded samples (core) obtained with different cooling rates a rapid, b conventional and c slow...

---