Liquid composite compression molding

Materials and Processing. Copolyesters of poly(ethylene terephtha-late) (PET) and para-oxybenzoic acid (FOB) were supplied by the Tennessee Eastman Corporation. Past work Indicates the copolyesters form thermotropic liquid crystalline phases at compositions containing more than 30 mole% POB (26,27,28). The composition of the copolyester studied here contains 60 mole% POB. Quiescent liquid crystalline films were made by compression molding the copolyester at 210, 230, 255, and 285 C, and followed by a quench Into Ice water, ambient air, or cooled In the press with the power off. Film thicknesses ranged between 0.05-0.15 mm. Another sa(q>le of the 40/60 PET/POB copolyester was melted at 270 °C In a Mettler hot stage, manually sheared between glass slides, and then ambient air cooled. 

By compression-molding in heated molds it is possible to process composites containing large amounts of the liquid-phase components (up to 50 wt %). Liquid plasticizers are able to lower the polymer melting point and, consequently, that of the composite processing, together with the compaction pressure due to high fluidity of the composite melt. 

Pillai, K. M., Tucker, C. L. and Phelan, F. R., Numerical simulation of injection/ compression liquid composite molding. Part 2 Preform compression . Composites Part A Applied Science and Manufacturing, 32(2), 207-220, 2001. 

Derieth et al. (2008) immersed injection-molded polypropylene-bonded and PPS-based compression-molded composite bipolar plates. The authors exposed some sets of composite bipolar plates to different liquids (10 per investigation). Deviations in weight, thickness, surface topography, and electrical as well as mechanical properties were determined before and after exposure. Furthermore, to identify leachant ionic and organic species, the liquids were analyzed. 

Five wt% MWNT-filled polycarbonate composites (untreated and treated) were prepared through a solution method described elsewhere [23] and compression molded at 220°C under a pressure of 1 ton for 40 minutes to produce samples with a dog-bone geometry and dimensions W x W x Vi The samples were tensile stretched on an Instron machine in liquid nitrogen. This created a sharp fracture surface. Some samples were coated with gold and examined in a field emission scanning electron microscope (FESEM) under 12 kV. 

Transfer, or plunger molding, is a process in which high-flow B-stage resins, such as epoxies, are liquefied under heat and pressure in a transfer pot, after which the resultant liquid resin is transferred under pressure into mold cavities. The transferred resin is then heated to form cured, final parts that are then removed from the mold. Although compression and transfer molding are used principally with thermosetting compounds, the processes are occasionally used with thermoplastic material, often thermoplastic composites. 

Isayev AI, Modic M (1987) Self-reinfOTced melt processible polymer composites extrusion, compression, and injection molding. Polym Compos 8 158 James SG, Donald AM, MacDonald WA (1987) Blends of a liquid crystalline copolyester with polyethersulphone. Mol Cryst Liq Cryst 153 491 Jerman RE, Baird DG (1981) Rheological properties of copolyester liquid crystalline melts. I. Capillary rheometry. J Rheol 25 275... 

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