Thermosets composites, molding processes

Key words polymer matrix composites, short-fiber composite molding processes, polymer nanocomposites, thermoplastics, thermosets. 

The rigidi d thermoplastic sheet - Tiocess combines thermoplastic sheet vacuum forming with a spray-up or cold press molding process to add a thermoset composite stmctural backing to a decorative thermoplastic skin. Large parts such as bathtubs, hot tubs, recreation vehicle components, and camper tops have been produced by this process. 

SCRIMP process This Seeman Composites Resin Infusion Process (SCRIMP) is described as a gas-assist resin transfer molding process. As an example glass fiber fabrics/ thermoset vinyl ester polyester plastic and polyurethane foam panels (for insulation) are placed in a segmented tool. A vacuum is pulled with a bag so that a huge amount of plastic can be drawn into the mold (Marco process approach). Its curved roof is made separately and bonded to the box with mechanical and adhesive fastening. It is similar to various reinforced plastics molding processes. 

The other difference [21] is fhaf fhermosef composife shows higher balanced sfrength and toughness compared to thermoplastic composite, with a little brittleness. Thus, thermoset composite plates can be fabricated relatively thinner and have more applications. On the other hand, as mentioned before, a well developed injection molding process has been applied as the fabrication process of thermoplastic-based composite plates to assure high quality and low cost. 

Table 1 Typical molding processes in thermoset composites...

Phenol-formaldehyde molding compositions are traditionally processed on compression- and transfer-molding machines with a very small amount being extruded. However, the injection-molding process as modified for thermosetting plastics is being increasingly used and it is today the most common method used to process phenolic compounds. The shorter cycle times and low waste factor available with... 

Reactive Melt Polymerization. The liquid composite molding (LCM) method is established for the fahricarion of thermosets. In contrast, reac-rive thermoplastic LCM processes are developed to only a few engineering polymers. The technique was applied to low-melting PA 6T/6I oligo-... 

Chapters 9 through 11 all belong to a class of processes called liquid composite molding (LCM). In this class of processes, one usually transfers the resin from a reservoir into a network of fibers. The fiber network is formed from any type of reinforcement from random mat to woven, stitched, noncrimp and bidirectional fabrics. This class of processes is very attractive as one can make net shape parts from composites using continuous fibers and have good control over the orientation of the fibers so one can tailor the properties as required by the design. Usually thermoset matrices are used... 

Fig. 1. Very large parts can be produced by the patented Seaman Composites Resin Infusion Molding Process (SCRIMP), in which dry reinforcements are vacuum bagged before thermoset resin is introduced into the lay-up. Courtesy Hardcore Composites, New Castle, Del.

Fig. 4. Matched composite molds are locked together between steel housings in patented thermoset-injection-molding-type process to produce an entire boat hull. Courtesy of VEC Technology, Greenville, Penn.

The materials presented in this chapter will be used in the discussions on the processing of thermosets in Chapters 11-13 of Volume 2, which cover reaction injection molding, pultrusion of thermoset/fiber composites and compression molding of thermoset/fiber composites, respectively. 

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