摘要:

Nylon 6 filaments of different draw ratios were subjected to swelling treatments with benzyl alcohol, aqueous solutions of phenol, and formic acid. The change in lateral order and orientation was followed by x-ray diffraction methods. The shrinkage in the swelling medium and residual shrinkage were also studied. The increase in lateral order and decrease in residual shrinkage values in the treated samples show that it is possible to effect stabilization of the structure at low temperature. This behavior is analogous to thermal treatment. The increase in lateral order has been explained as due to the growth of crystallites in the amorphous regions.

ISSN:0022-2348    

DOI:10.1080/00222348008241377

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Poly(methyl methacrylate) (PMMA) and a series of three methacrylic copolymers have been studied in the temperature range from-196°C to about 200°C by the thermally stimulated current (TSC) and the thermally stimulated creep (TSCr) techniques; the same samples have been the object of an earlier phosphorescence study by Somersall, Dan, and Guillet. The comparison of the dielectric, mechanical, and optical results has helped resolve ambiguities which arise when only a single technique is employed, and has revealed hitherto unreported characteristics of molecular motions in methacrylic polymers. The most important among these pertains to the β relaxation (rotation of the ester side groups): both TSCr and TSC have revealed the existence of at least four submodes, but in the case of TSC spectra the “structure” of the β peak appears only if the sample is polarized in a relatively low-intensity (≲ 20 kV/cm) electric field. These sub-modes, each of which is characterized by a single relaxation time τ have been analyzed in detail by TSCr for PMMA and its copolymer with naphthyl methacrylate (NMA). Although they all obey either an Arrhenius or a Vogel equation, τ values for PMMA are several orders of magnitude smaller (while the activation energy E is larger) than for PMMA-NMA. This has been attributed to interactions between primary and secondary transitions.

ISSN:0022-2348    

DOI:10.1080/00222348008241378

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A method of preparing solid solutions of chemically different polymeric molecules in the crystalline state is reported. The characteristic feature of the method is the high longitudinal flow gradient in which one can achieve very high rates of crystallization as well as supercooling at constant temperature. In the present study, isotactic polypropylene-polybutene-1 blends of different compositions were investigated, and solid solutions were observed up to 20% on each side of the phase diagram. The resultant crystalline blends were investigated by using transmission electron microscopy (TEM) and electron diffraction, wide-angle x-ray diffraction, differential thermal analysis, and mechanical testing. Structural studies reveal the presence of needle-like crystals within the blends. The thermal stability of the blended crystals is unexpectedly high with no major changes in the structure upon annealing. The mechanical properties exhibit only small changes for the different blends.

ISSN:0022-2348    

DOI:10.1080/00222348008241379

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Single crystals of poly(tetramethylene adipate) (PTMA,-[O-(CH2)4-O-CO-(CH2)4-CO]n-) have been prepared by precipitation from solution and by epitaxial deposition on suitable substrates. The crystals grown from solution exhibited two distinct morphologies: most of the crystals were diamond-or truncated diamond-shaped, but a few were approximately hexagonal. These two morphologies yielded different diffraction patterns from which the polymorphic structures could be identified. Comparison of the electron diffraction patterns with the equatorial d spacings in the x-ray fiber diagrams indicated that the diamond and hexagonal morphologies correspond to β-and α-PTMA, respectively. The growth faces are the 110 planes for the β single crystals and both the 010 and 110 planes for the α single crystals. Epitaxial crystals were produced by deposition from the melt on trioxane and both from the melt and from solution on potassium halide crystals. The electron diffraction patterns of these crystals indicate that the PTMA chains are oriented parallel to the substrate surface. The crystals grown from the melt on potassium iodide are identified as the β-form and the layer line spacing is determined to be 14.67 Å, which defines the chain conformation as planar zigzag. In the same manner, the crystals grown from the melt on trioxane are identified as α-PTMA.

ISSN:0022-2348    

DOI:10.1080/00222348008241380

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In the present paper the mechanical and photomechanical behavior of two ethylene-propylene copolymers of different ethylene contents has been analyzed. This microstructural difference gives rise to differences in physical behavior. In particular, the physical properties of the sample of higher ethylene content are strongly temperature-dependent in the temperature range investigated. The results are discussed in terms of intermolecular interactions or aggregations and show a direct relationship between interaction phenomena, mechanical hysteresis, and deviations from the ideal Gaussian behavior of a rubberlike network.

ISSN:0022-2348    

DOI:10.1080/00222348008241381

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A series of PDMS networks were prepared by endlinking reaction of α, ω-functional precursor polymers. The erosslinking reaction and the influence of incomplete reaction on formation of pendent chains are discussed. Equilibrium concentration and light spectroscopy measurements have demonstrated a decrease of the mesh size of the network with increasing concentration at which the latter is formed. These results are interpreted as a consequence of trapped entanglements.

ISSN:0022-2348    

DOI:10.1080/00222348008241382

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Isotactic polypropylene samples were cold-drawn to a draw ratio of 5.5 at 23°C and then annealed at temperatures between 60 and 160°C for 1 and 30 min, with ends kept free. The density, the long period, and the thickness of the crystal core increased with increasing annealing temperature and time, but the thickness of the amorphous layer hardly changed. From measurements of the dynamic mechanical behavior along the fiber axis, the intensity of the crystalline absorption αcdecreased with increasing annealing temperature and time, but the intensity of the primary absorption αaincreased with increasing annealing temperature and time. Thus, it is considered that the transformation from the fiber structure obtained by cold drawing to the new sandwich structure with lamellar crystals and amorphous layers oriented nearly perpendicularly to the fiber axis, and production of taut tie molecules, are caused by annealing. Under applied forces in the fiber direction, most of the stresses are accommodated selectively by the taut tie molecules of all the interlamellar tie molecules, and the taut tie molecules play an important role in the transmission of the applied stress, while the relaxed tie molecules, caused by annealing, no longer transmit applied stress.

ISSN:0022-2348    

DOI:10.1080/00222348008241383

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The dynamic tensile modulii E' of cold-drawn and subsequently annealed polypropylene film samples were measured as a function of annealing temperature. The modulus E' at 23°C along the draw direction was found to decrease with an increase in the annealing temperature, but the degree of crystallinity of the samples became greater with increasing annealing temperature. This conflicting behavior can be explained on the basis of the volume fraction of tie molecules. Tie molecules must sustain a large portion of the applied stress, and their volume fraction decreases with an increase in the annealing temperature, in spite of the increase in the degree of crystallinity. The decrease in volume fraction of tie molecules results in the formation of folded chain lamellar crystals, leaving only a small portion of the original tie molecules in the amorphous region.

ISSN:0022-2348    

DOI:10.1080/00222348008241384

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The polarized and unpolarized far-infrared (460-30 cm−1) spectra of poly(p-phenylene terephthalamide) (PPTA) fabric and fiber arrays are reported. These spectra are discussed and tentatively analyzed on the basis of the internal and external modes of the repeat unit of PPTA. To assist in band assignments, the spectra of potassium triiodide-treated PPTA fibers and of benzanilide and its benzene solution are also reported.

ISSN:0022-2348    

DOI:10.1080/00222348008241385

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor