Free radical suspension copolymerization of styrene (St) with methyl methacrylate (MMA) in the presence of n-pentane was investigated. The batch polymerization was performed in a stirred reactor via a two-stage process. First, free radical suspension polymerization of St and MMA in aqueous media was carried out at about 80—90°C with the aid of a monofunctional initiator to the monomer conversions up to about 70%. Second process, called impregnation stage, consisted of a high temperature—high pressure cycle (110—120°C and 10 bars) in which the blowing agent was charged in the reactor and polymerization was carried out with the aid of a high temperature initiator. Fine particles of micron sizes of St/MMA copolymer were synthesized by manipulation of some experimental parameters governing the copolymerization system. Polymerization was carried out at different agitation rates, suspending agent and aqueous phase initiator concentrations as well as emulsifier amounts, while keeping constant the MMA/St ratio. To reach a desired bead size, the above parameters were optimized using the Taguchi method for experimental design and the relative importance of the mentioned parameters was analyzed. Particles with a spherical shape of 250—350 μm were formed. The obtained copolymers were also characterized in terms of molecular weight, polydispersity index, copolymer composition, morphology of the polymer beads, thermal behavior, and particle size and particle size distribution.
Parts cast of metals using expandable polystyrene foams may have an unacceptable amount of surface defects, such as lustrous carbon. The use of foams made of styrenic/acrylic copolymers can improve the quality of foam molds and metal parts made using such molds. Lost foam copolymer was synthesized by suspension copolymerization of styrene and methyl methacrylate. The polymerization was carried out in the presence of blowing agents. The decomposition products of lost foam beads were studied by a method composed of the thermogravimetry/differential thermal analysis (TG/DTA) and gas chromatography/mass spectrometry (GC/MS). With these systems, the TG/DTA data can be combined with a GC separation and MS identi-fication methods. This combined method improves the analysis of the decomposition products of lost foam beads and enables the precise identification of the amount and the nature of volatile organic compounds (VOCs) trapped during suspension polymerization. The results obtained from the combined method were verified for the nature and amount of VOCs with the results of time-conversion studies for copolymerization of monomers in the presence of different concentrations of blowing agent. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: 4711-4720, 2012
ABSTRACT:The wear properties of low modulus polymer-based friction materials were studied. The wear equation W ϭ K P a V b t c was used to correlate the wear of polymer-based friction material sliding against cast iron with the wear coefficient (K), load (P), speed (V), and time (t). The parameters were determined experimentally by varying only one variable at a time and keeping the other two variables constant. The wear rate of selected polymerbased friction material was compared with cast iron friction material.
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