摘要:

AbstractChanges in the lamellar structure of polypropylene during biaxial orientation by hydrostatic extrusion have been examined. Examination of etched surfaces in the transmission electron microscope has revealed that up to a draw ratio of about 1.5 × 1.5 the primary mechanism is lamellar rotation into the plane of orientation, At higher draw ratios breakup of the lamellae is observed with formation of a granular structure. Thermal measurements suggest that localized melting and recrystallization may accompany the process of lamellar breakup. These morphological observations confirm the previous interpretation of SAXS and permit a more detailed model of the hierarchical structure to be proposed. Stress strain measurements show a gradual change from sharp necking to uniform deformation as the draw ratio is increased. On the other hand, the structural change at a draw ratio of about 1.5 × 1.5 Is accompanied by a large increase in the tensile impact strengt

ISSN:0032-3888    

DOI:10.1002/pen.760271202

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe deformation of biaxially oriented polypropylene sheet produced by the BeXor process has been examined in terms of the hierarchical solid state structure described previously. The mechanical properties have been examined over a range of temperatures and strain rates. The anisotropic nature of uniaxial tensile deformation was analyzed from simultaneous measurements of longitudinal extension and lateral contraction in the width and thickness directions, by determining the shape of uniaxially deformed spherulites, and by examining fracture surfaces in the scanning electron microscope (SEM). It was determined that deformation proceeds by elastic extension of the amorphous network and plastic shear deformation of the crystalline regions in the plane of the sheet, and in the thickness dimension, by voiding with induced fibrillation. It is suggested that the property improvements, particularly at low temperatures and high strain rates, which are achieved by the BeXor process, result from changes in the hierarchical structure at the size scale of the crystalline lamellae. Specifically it appears that the small crystalline blocks formed by breakup and recrystallization of lamellae are more easily deformed than the original large coherent lamellae.

ISSN:0032-3888    

DOI:10.1002/pen.760271203

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe orientation development in elongational flow (spinning) of liquid crystal polymers (LCP) has been studied and a physical model derived which relates the modulus development and extensional deformation. The model defines an orientability parameter, λ, which in addition to the total elongational deformation (drawdown ratio) are related to the orientation (modulus) level of the final spun fiber. Five LCPs were included in the study—a lyotropic polymer: Poly (p‐phenylene‐terephthalamide) and four wholly aromatic naphthalene‐containing polyesters. The experimental results have shown good agreement with the proposed model and indicate that λ is independent of the spinneret size and is characteristic of the orientability in elongational flow of each of the polymers inv

ISSN:0032-3888    

DOI:10.1002/pen.760271204

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractBiaxially oriented poly(ethylene terephthalate) (PET) films have been characterized by small angle and wide angle x‐ray scattering. The films were studied at various rotational angles to the impinging beam and orientations relative to axes in three directions in the film were obtained. Pole figures were developed for both the major small angle scattering peak and wide angle diffraction peaks. These are used to interpret structural changes in the films associated with various degrees of biaxial stretching and subsequent constrained annealin

ISSN:0032-3888    

DOI:10.1002/pen.760271205

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractMeasurements of thermal diffusivity were carried out with semicrystalline and amorphous polymers stretched in the solid and in the molten state to different elongations. For semi‐crystalline materials two regions in the curves of the diffusivity versus the elongation can be detected. The change occurs at an elongation of 1.4 for the polymers stretched in the solid state and at an elongation of 3 for the polymers stretched in the molten state. For amorphous polystyrene the shape of the curves of thermal diffusivity versus elongation also depends on the mode of stretching. Along with thermal diffusivity measurements, wide angle X‐ray scattering investigations were also performed and give explanations for the differences in thermal behav

ISSN:0032-3888    

DOI:10.1002/pen.760271206

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe drawing of an amorphous copolyester based on poly(ethylene terephthalate) and poly(1,4 cyclohexylene‐dimethylene terephthalate) has been studied at temperatures from 20° to 100°C and various strain rates. The tensile properties, densities, and stress whitening of the stretched samples depend on whether the drawing temperature is below or above the glass transition temperat

ISSN:0032-3888    

DOI:10.1002/pen.760271207

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractOrientation in injection moldings of polypropylene (PP), polyethylene (PE), polyamide 6 (PA‐6), and polystyrene (PS) was investigated by transmission and reflection infrared spectroscopy. Orientation of the surface was measured by the reflection method, the depth profiles of orientation and of the fraction of the crystalline phase were measured by the transmission spectroscopy of microtome sections. The maximum of orientation of PP lies in the subsurface layer (ca. 250 μm); the crystalline phase is oriented more than the amorphous one. The maximum of the depth profile of orientation corresponds to the minimum of the fraction of the crystalline phase in PP. The profile of orientation of PE Is similar; at the beginning (to a depth of about 500 μm) the parallel orientation of thecaxis of the crystalline phase is the most distinct one, towards the center the orientation of the a axis passes from the perpendicular to the parallel one. Under the described molding conditions PA‐6 is not significantly oriented, the fraction of the crystalline phase increases towards the center of the molding. Unoriented PA‐6, the surface layer of which was removed by milling, has a highly oriented surface due to its mechanical treatment. No pronounced orientation of PS was observed under the molding conditio

ISSN:0032-3888    

DOI:10.1002/pen.760271208

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760271201

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY