Melt‐crystallized films of poly(L‐lactic acid) (PLLA) with Mv in the range of 3.8 ∼ 46 × 104 consisting of α‐form crystals were uniaxially drawn by solid‐state coextrusion. The effects of Mv, extrusion draw ratio (EDR), and extrusion temperature (Text) on the crystal/crystal transformation from α‐ to β‐form crystals and the resultant tensile properties of drawn products were studied. The crystal transformation proceeded with EDR and more rapidly for the higher Mv's. Furthermore, the crystal transformation proceeded most rapidly with EDR at a Text around 130 °C, independently of the Mv's. As a result of the optimum combination of processing variables influencing the the crystal transformation (Mv, Text, and drawability), highly oriented films consisting of β‐form crystals alone were obtained by coextrusion of higher Mv samples at Text's slightly below the melting temperature (150 ∼ 170 °C) and at higher EDR's > 11. Both the tensile modulus and strength increased rapidly with EDR. The modulus at a given EDR was slightly higher for the samples with higher Mv's. In contrast, the strength at a given EDR was remarkably higher for the higher M
v's. The highest tensile modulus of 8.0 GPa and strength of 500 MPa were obtained with the sample of the highest Mv of 46 × 104 coextruded at 170 °C to the highest EDR of 14.
Poly(styrene) (PST) coatings of monodispersed colloidal metal oxide particles by surface grafting to poly(N-vinyl-2-pyrrolidone) (ST-PVP) or quaternized poly(4vinylpyridine) (ST-PVPy(Me)) macromer, having a vinylphenylene end group, were investigated. Radical polymerization of styrene (ST) in ethanolic silica colloid in the presence of ST-PVP successfully led to the formation of monodispersed PST/PVP copolymerlSi0, composites. The addition of divinylbenzene (DVB) to the reaction system gave SiO, composites coated with crosslinked PST. Graft-polymerization of ST to ST-PVP also took place on T i 0 2 . CeO, and Af(OH)3 colloidal particles in ethanolic solution. However, ST-PVPy(Me) adsorbed on colloidal silica did not effectively graft PST.
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