Addition of methyl methacrylate monomer to poly(methyl methacrylate) which has been polymerized with fluorenyllithium or sodium‐naphthalene in tetrahydrofuran at −78°C. produces high conversion of monomer to polymer. By a comparison of the number‐average molecular weights before and after the addition of the second monomer, it is demonstrated that no new polymer chains are formed on polymerization of the second monomer, so that the polymerization is initiated by the poly(methyl methacrylate) anion. Styrene is shown to be an inert diluent in these systems. The technique is also applied to additions of styrene and of methyl methacrylate monomer to polystyrene initiated with sodium‐naphthalene; the new polymer is demonstrated to be initiated by the polystyrene anions.
Processing aids are an important class of additives for poly(viny1 chloride) (PVC). At relatively low concentration, processing aids enable the melt processing of rigid PVC and enlarge its processing windows. Discussed in this presentation are some major functions of processing aids, such as promoting PVC fusion, modifymg PVC's melt rheology, and lubricating to prevent adherence of PVC melt to the processing equipment. Some examples are given to show the effects of processing aids on PVC die swell, melt fracture, melt viscosity, and PVC fusion. Commercial sources of various processing aids and typical PVC formulations for various applications are also discussed.
Impact modifiers are used to enhance the toughness of rigid vinyl by providing a dispersed rubbery phase to absorb impact energy and prevent fracture of the otherwise brittle matrix. MBS impact modifiers are complex core//shell polymer structures based on specially prepared butadiene/styrene rubber latices with multiple stages of acrylic and other polymers grafted to them. In addition to providing a rubbery dispersed phase to improve to improve the toughness of vinyl, these structures also maintain clarity by matching the refractive index of the rubber particles with that of the vinyl matrix. Data will be present showing the effect of the rubber morphology, particle size and refractive index on the balance of impact strength and clarity of MBS modified vinyl packaging formulations.
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