High-pressure reinforced plastics

High performance composites may be laminates wherein veils of carbon fiber ate treated with an epoxy resin, stacked up to the desired final product thickness, and then laminated together under heat and pressure (see Composite materials Carbon and graphite fibers). Simply mixing together carbon or glass fibers and polymeric resins to form a reinforced plastic leads to a composite material, but this is not a laminate if not constmcted from discrete phes. 

In the reinforced RIM (RRIM) process a dry reinforcement preform is placed in a closed mold. Next a reactive plastic system is mixed under high pressure in a specially designed mixing head. Upon mixing, the reacting liquid flows at low pressure through a runner system to fill the mold cavity, impregnating the reinforcement in the process. Once the mold cavity is filled, the plastic quickly completes its reaction. The complete cycle time required to produce a molded thick product can be as little as one minute. 

Asia Pacific Coatings Journal 14, No.6, Dec. 2001, p.557-63 DECOMPOSITION OF FIBER REINFORCED PLASTICS USING FLUID AT HIGH TEMPERATURE AND PRESSURE Sugeta T Nagaoka Otake K Sako T... 

Pressure vessels are constructed from plain carbon steels, low and high alloy steels, other alloys, clad plate, and reinforced plastics. 

Because of high capital costs and potential HE of steel pipelines for high-pressure hydrogen transport, the investigation of fiber reinforcement or other plastic composites as substitutes for steels is one of the major R D tasks within the DOE hydrogen delivery program. The purpose of the work is to achieve reduction in installation costs, better reliability, and safer operation of hydrogen pipelines. 

The effects of processing will be illustrated by considering injection moulding of a semicrystalline polymer. The molten plastic is injected into the mould under high pressure and temperature. The edges of the mould retard flow and cool more rapidly, leading to a boundary layer of high shear, which in semicrystalline polymers leads to orientation of the polymer chains and of short fibre reinforcements parallel to the direction of flow. At the centre the structure is less oriented. Where two separate flow streams meet, there is a... 

Reinforced plastics differ from high-pressure laminates in that little or no pressure is employed. For instance, in making formed shapes, impregnated reinforcing material is cut to a desired shape, the various layers are added to a mold, which is then heated. This process is favored over the high-pressure process because of the use of a simpler, lower cost mold and production of strain-free products. 

The molds in a RIM-process plant are located in a separate assembly, which has devices for opening and clamping a mold and, in some cases, for changing it. The pressure in the RIM-process is considerably lower than in traditional injection molding of thermoplastics thus, the requirements for the mold material are less rigid. Molds may be made from aluminum or reinforced plastics, since high-strength steel is not necessary. 

Appendix A contains a materials selection guide for aerated freshwater systems. As indicated in Note 27 of Appendix A, in freshwater systems, admiralty brass should be limited to a maximum pH value of 7.2 from ammonia and copper-nickel alloys and should not be used in waters containing more sulfides than 0.007 mg/L The materials selection guide is also satisfactory for seawater, although pump cases and impellers should be a suitable duplex stainless steel or nickel-aluminum-bronze (properly heat treated). Neoprene-lined water boxes should be considered. For piping, fiber-reinforced plastic (up to 150 psi [1,035 kPa] operating pressure) and neoprene-lined steel should also be considered. Titanium and high-molybdenum SS tubes should be considered where low maintenance is required or the cost can be justified by life expectancy. 

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