Structural reaction injection-molded

C. F. Johnson, Resin Transfer Molding and Structural Reaction Injection Molding in Engineering Materials Handbook, Vol. 2, ASM, International, USA (1988). 

Liquid Composite Molding (LCM) is the common name for several similar processes for the manufacturing of polymeric fiber reinforced composites. Widely used processes that belong to this class are Resin Transfer Molding (RTM), Vacuum-Assisted Resin Injection (VARI), and Structural-Reaction Injection Molding (S-RIM). 

The latest trend in foamed composites is automotive structural parts produced by the SRIM (structural reaction-injection-molding) process. The SRIM process is a method of the reactive liquid injection molding (i.e., LIM). LIM includes RIM (reaction injection molding), RRIM (reinforced RIM) and RTM (resin transfer molding). IX M (Liquid Composite Molding) is a relatively new technical term which includes SRIM, RRIM and RTM (Resin Transfer Molding). 

Structural reaction injection molding (SRIM) maybe considered as a natural evolution ofRIM. It is a very attractive composite manufacturing process for producing large, complex structural parts economically. The basic concepts of the SRIM process are shown in Figure 2.57. A preformed reinforcement is placed in a... 

FIGURE 2.57 Schematic of structural reaction injection molding (SRIM). 

SRIM structural reaction injection molding T E test and evaluation... 

Sheet-Molding Compound) or SRIM (Structural Reaction Injection Molding) manufacturer, the surface quality or roughness is influenced by the type of reinforcement used (fibers, mats, roving), the particle size of the filler and the surface quality of the mold. 

Polyurethanes (PU or PUR) and polyureas are classified as TS resins, but their chemistry is so flexible that they can be formulated different ways. There are moldable solid and expanded TSs, with (RPUR) or without reinforcement, flexible and rigid foams, elastomers and thermoplastic molding compounds. As RPs they are important in reinforced reaction injection molding (RRIM) (Chapter 5) and are also available as reinforced thermoplastic molding compounds. A variant on the process employs a structural preform of the reinforcement that is placed in the mold cavity and is called structural reaction injection molding (SRIM). 

Structural reaction injection molded (SRIM) sandwich panel composites incorporating recycled RRIM granulate have been developed in Europe, comprising two layers of glass reinforcement on either side of a core layer of granulated RRIM. The filling can be composed of either painted or unpainted material and can be preformed to shape before resin injection. 

The first such method was structural reaction injection molding (SRIM), as described above, in which the fiber reinforcement is in the form of a mat, which is usually preformed and laid into the mold before the polyurethane mix is injected from the mixing heads. This, however, introduces the additional operation of preforming the reinforcement, so adding to cost. 

---