394 HANDBOOK OF TROUBLESHOOTING PLASTICS PROCESSES
• Greatest uniformity in molded properties
• Most versatile process with relation to quantities and component complexity
• Relatively simple to understand and control.
18.7.3 Disadvantages
• Thermosets have poor fracture resistance.
• Thermoset materials are brittle, hence recommended minimum part wall thick¬ness are necessary
• Relatively labor intensive, with more material handling involved.
• Material losses due to the flash allowances and general waste.
• Secondary operations for flash removal are generally required.
• Poor part thickness and weight control.
• Cannot mold around delicate inserts or pins.
18.7.4 Future Trends
Compression molding is highly recommended for high impact, downy materials, because of the difficulty in feeding the compound from a hopper to the press or performer. Typical formulation for compression molded parts includes ingredients such as:
• inorganic fillers
• thickeners
• curing agents
• internal mold release
• plus a carrier resin and
• a low profile agent [481.
The formulation flexibility leads to variety of end-use properties for molded parts, in turn, brings about a wide spectrum of commercial application [49-50] .
Compression molding is widely used and will continue to be employed for manufactur¬ing thermoset polymeric materials particularly to produce parts that are:
• large
• thin
• light weight
• strong and
• stiff.
This technique will continue to be used for:
• automotive
• trucking
• agricultural equipment
• rail cars
• high speed civil transportation
• off-shore and in-marine
• sporting goods