Liquid transfer molding

Resin transfer molding (RTM) and liquid transfer molding (LTM)... 

The resin transfer molding and liquid transfer molding processes are used principally for manufacturing fiber-reinforced composite parts in moderate to high volumes. The process combines the techniques of hand lay-up, liquid resin casting, and transfer molding, as discussed earlier in this chapter. 

As mentioned in Sec. 9.4.3, liquid transfer molding (LTM) is being increasingly used for reinforced plastics, or composites. Conventional transfer presses may be used in such... 

Resin transfer molding With vacuum assisted RTM, this process can be called infusion molding. RTM usually uses liquid TS plastics that is transferred or injected into an enclosed mold usually at low pressures of about 60 psi (410 kPa) in which reinforcement... 

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 repairs were performed on lower- and upper-wing skin assemblies and on a composite liquid hydrogen tank. On average, they took 50-70% of the time required for a normal thermal repair. The only process where EB carmot be used is resin transfer molding (RTM) because the electrons cannot penetrate the thick steel tooling required for it. The typical dose for this process was found to be 100 kGy. ... 

A variation of the compression molding technique is to use transfer molding. In this method the liquid polyurethane mix is placed in a pot and allowed to thicken. The polyurethane semi-gel is forced through sprues into the mold, and the air is allowed to escape through vent holes. The part is allowed to cure sufficiently so that it can be removed. Figure 5.2 shows the general layout of a compression and transfer mold. 

Resin Transfer Molding (RTM). Reinforcing fibers are distributed uniformly in the mold and the mold is closed. Liquid resin is injected into the mold until the excess comes out of the vents. The mold is pressed and heated, similarly to preform molding, until cure is complete. 

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). 

Liquid composite molding (LCM) processes such as resin transfer molding (RTM) have been long established in the automotive and aerospace industries as versatile technologies for manufacturing medium to large composite parts with complex geometries at low cost. All LCM processes involve the injection of a liquid resin into a dry fiber perform, and are... 

With RTSs, however, where the resin is liquid and requires curing, in-house mixing is the norm, especially in the hand and spray lay-up sector, and in many press-molding and resin transfer molding operations. Resin suppliers now offer resins formulated and possibly pigmented to meet a set specification, but it still requires the processor to add the reinforcement and initiate the curing reaction. 

RTM was described May 1957 (at the BPF Reinforced Plastics Conference), in a paper on work dating from 1954 at Bristol Aircraft, Filton, UK. It is basically a liquid resin version of compression transfer molding a process in which a charge of compound is placed in a transfer pot and is injected into a closed mold, usually by a plunger system. The method allows the compound to be suitably prepared melt and then transferred fast and accurately into the mold, in which the required reinforcement has already been placed, in suitable form. 

The cyanate ester monomers are available from low-viscosity liquids to meltable solids. Ciba-Geigy produces a series of cyanate esters imder the trademark AroCy L-10. Cyanate esters are used in manufacturing structural composites by filament winding, resin transfer molding, and pultrusion. 

Resin Transfer Molding (RTM) is accomplished with the use of a reinforcement system that has been preshaped to fit the mold cavity and a low-pressure resin in liquid form that is injected into a closed mold. The injection process can be assisted with the use of a vacuum system to provide for evacuation of any volatiles and to gain molded density. 

Transfer molding is used for the manufacture of small components and is particularly useful with multi-cavity tools and where small inserts are to be moulded in. Materials used are polyester and epoxide dough moulding compounds, although a new liquid resin injection technique is reported. 

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