Polystyrene ceiling temperature

This method was first applied by McCormick27 and by Bywater and Worsfold11 to the system a-methylstyrene/poly-a-methyl-styrene, and the free energy, entropy and heat of polymerization as well as the ceiling temperature were determined. Similar studies concerned with the system styrene/polystyrene are being carried out in our laboratories. 

FRP leads to the formation of statistical copolymers, where the arrangement of monomers within the chains is dictated purely by kinetic factors. However, reactivity of a monomer in copolymerization cannot be predicted from its behavior in homopolymerization. Vinyl acetate polymerizes about 30 times more quickly than styrene (see Table 4.2), yet the product is almost pure polystyrene if the two monomers are copolymerized together in a 50 50 mixture. a-Methylstyrene cannot be ho-mopolymerized to form high-MW polymer due to its low ceiling temperature (see Table 4.6), yet is readily incorporated into copolymer at elevated temperatures. These and other similar observations can be understood by considering copolymerization mechanisms and kinetics. 

Most monomers are above their free-radical ceiling temperature and only a single monomer unit is often added onto the polymer backbone. This is notably the case with maleic anhydride, acrylic acid, and methyl methacrylate. Styrene is an exception and one graft polymerize long polystyrene chains onto polyolefins [223]. 

Structural foam polystyrene should not be confused, however, with expanded polystyrene, well-known in the form of ceiling tiles and packaging shapes which hold their often awkward shape and fragile contents safely throughout the roughest of journeys. This lightweight material (as little as I Ib/ft ) is an excellent heat insulator below its softening temperature, which is the same as basic polystyrene, but it should be remembered that, since polystyrene dissolves in aromatic solvents, it should only be painted with emulsion paints and not spirit or oil-based ones. 

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