Gel coats processing

The hand lay-up or spray-up process, used universally for the production of laminar composites incorporating glass fiber reinforcement, is most efficient for the manufacture of large parts, such as boats, bathtubs, tanks, architectural shapes, and recreational accessories. Resins intended for spray-up processes are usually modified with thixotropic additives, such as fumed siHca (1%), to reduce the risk of drainage when appHed over large vertical mold surfaces. Molds are also made from ERP for short-mn products usually surfaced with a tooling gel coat to provide consistent surface quaHty and appearance. 

A special attribute of these processes is the abiHty to pre-position reinforcement, inserts, and core materials for stiffening ribs. Gel coatings can be apphed to the mold surface to eliminate post-mold finishing. Because both surfaces of the part are formed in a mold to close tolerances, accurate assemblies are possible, which is a requirement for many automotive or tmck body appHcations. 

This process is carried out at low pressure and at ambient temperature. The fiber is placed in the tool in the form of a mat and the resin is poured in. The mold is closed, and the resin spreads through the reinforcement thereby impregnating and fully wetting out the fiber strands. The process is done on an hydraulic press. Pressure levels required for molding are typically around 10 MPa. Gel coat can be applied to the mold faces before the molding operation commences. 

Gel coat In RP processing a gel coat on the outer surface can be used to ensure a smooth surface appearance and a tough surface. It could contain a thin synthetic fiber veil to improve performance of the gel coat and/or a surfacing mat. It is a quick setting plastic and gelled prior to reinforcement layup. The gel coat becomes an integral part of the finished RP product. 

Gel-based activated aluminas, 2 397-398 Gelcasting, ceramics processing, 5 652 Gel coats, 20 116... 

Sol—gel, alumina derived from, 23 76—78 Sol-gel bioactive glasses, 23 82-83 Sol-gel chemistry aerogels, 1 749-753 ceramics processing, 5 642 Sol-gel coatings, 5 665... 

Other coating processes involving fluoridated apatite have been investigated to improve the long-term adhesion and promote osteointegration of cementless titanium-based metal implants pulsed laser deposition, electron beam deposition and ion beam sputter deposition techniques, and sol-gel methods, for example. They lead to fluor-containing calcium phosphates (apatites in most cases) with different compositions and crystallinity states. 

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