This thesis presents a detailed study of the simultaneous biaxial stretching of isotactic polypropylene (iPP) films in the partly molten state. Four commercial grades of isotactic PP (PP1--PP4) were investigated. The first three resins differed principally in isotacticity levels, which were 94.8%, 98.6%, and 99.5%, and the fourth resin had molecular weight and isotacticity levels similar to those of PP2, but differed in crystallization behavior. The four iPP resins were extruded and cast under similar conditions. The severity of the cooling was varied for PP4. The cast films were stretched on the laboratory film stretcher, that simulates closely the stretching conditions encountered in the industrial tenter-frame stretching process. The morphology of the cast films and the final stretched films was characterized by differential scanning calorimetry and wide-angle X-ray diffraction. The reflection technique was used for the X-ray measurements. Finally, the mechanical and optical properties of the films were determined, and the results were correlated with the film morphology and orientation. The effects of drawing temperature, stretching ratio, strain rate, initial morphology, and chain tacticity on deformation behavior, stretched film morphology, and end-film properties were studied, and correlations were sought. / Simultaneous equibiaxial stretching was found to be homogeneous for sufficiently high deformation rates ( 3&d2;H > 0.1 s-1). The stiffness and the thermal stability of the crystallites played an important role in deformation behavior. In fact, the biaxial yield stress showed linear dependence on the crystallite size. Upon simultaneous equibiaxial deformation, crystallinity and especially orientation increased, while crystallite size decreased. The isotacticity content was found to influence greatly the thermal stability of the initial morphology. Increasing isotacticity leads to an increase in DSC melting peak temperature of the initial morphology, overall stress of deformation, and in the final crystallinity, orientation, elastic modulus, and tensile strength of the end film. Finally, it was concluded that the crystalline phase, that melts during preheating prior to stretching forms a "structured melt" phase. The amount of structured melt is related to the tensile strength at break of the end film. Finally, it was showed that an optimal gloss is obtained, if the cast film is stretched about 15°C below its melting point.

Thesis (Ph. D.)--Ohio University, March, 1992. / Title from PDF t.p.

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 1998. / Includes vita. Includes bibliographical references (leaves 139-143).

Thesis (M.S.)--Rochester Institute of Technology, 1984. / Typescript. Includes bibliographical references (leaf 31).

Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. Includes bibliographical references (leaves 120-124).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 239-251).

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 144-149).

No description available.

An investigation into the structure and properties of poly(1-butene) monofilaments was carried out. Eight commercial grades of poly(1-butene) were thoroughly characterized and compared by a wide range of techniques: DSC, GPC, C13nmr, melt rheology, optical and electron microscopy, crystallization rates and crystallinity were also measured. Both qualitative and quantitative information was obtained on additives, blends, copolymers and polymer tacticity. To compare the mechanical properties of the materials in the absence of molecular orientation at various levels of crystallinity compression moulded sheets were produced.