摘要:

The structure of linear polyethylene filled with various solid particles (glass beads, silica, kaolin) was examined by using scanning electron microscopy. The mode of attachment of filler particles to semicrystalline polymer was of particular interest. The filler particles were bonded to polymer by polyethylene fibrillar links whose number depended upon the properties of the filler.

ISSN:0022-2348    

DOI:10.1080/00222347808212259

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

In this paper it is shown that three critical concentrations, observable through light scattering, solution and melt viscosity, exist for high molecular weight polymers: Ci, observed through light scattering, reflects the onset of intermolecular interpenetration at the point of complete space-filling, the point where all the available space is taken up by segments with no change in the intramolecular segmental density; Cep, observed through solution viscosity determination, reflects the appearance of dynamically measurable quantities of entanglements in the peripheral regio of the molecular coils; and Cec, obtained from melt viscosity measurements, reveals the appearance of such entanglements in the core regions of the coils. The relationship between these critical concentrations is Ci< Cep< Cec. This reflects the fact that intermolecular interpenetration occurs at significantly lower concentrations than intermolecular entanglements, and that the static light scattering is insensitive to entanglements while the dynamic viscosity measurements are sensitive to entanglements but do not sense intermolecular interpenetrations. A tentative explanation of these observations, based on the macromolecular domain model, is proposed.

ISSN:0022-2348    

DOI:10.1080/00222347808212260

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The molecular mobility of poly(acrylic acid) (PAAc) and its copolymers with 2-hydroxyethyl methacrylate (HEMA) was investigated by means of dynamic mechanical measurements carried out with a freely oscillating torsional pendulum (∼1 Hz). An increase in the content of AAc in the copolymers leads to reduction and eventually to complete disappearance of both the low-temperature (−135°C) and secondary (28°C) dispersion, while the glass transition temperature passes through slight maximum. In the temperature range under investigation (from −196 to 140°), PAAc exhibits only the glass transition at Ca 108°C (1 Hz). The sorbed water markedly decreases the glass transition temperature of PAAc and gives rise to a secondary dispersion near −80°C; with increasing water content, the dispersion is shifted towards lower temperatures, and its intensity increases. The effect of AAc on the temperature and intensity of the low-temperature dispersion of PHEMA was compared with that of six other comonomers; it was found that the intensity of dispersion increased approximately linearly with the volume fraction of the HEMA component, while the temperature of dispersion did not seem to be readily correlated with the comonomer composition.

ISSN:0022-2348    

DOI:10.1080/00222347808212261

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Measurements of the longitudinal acoustic (LA) Raman mode have been combined with small-angle x-ray scattering (SAXS) and nitric acid etching, followed by gel-permeation chromatography (GPC) to examine the morphology of bulk-crystallized linear polyethylene (LPE). It has been shown that in some slow-cooled samples, Raman spectroscopy can provide a direct measure of the all-trans molecular length and hence the actual thickness of the crystalline regions. For other samples (high molecular weight, slow-cooled and quenched) the Raman data taken in conjuction with those from SAXS and GPC give a direct indication of the bulk morphology provided that the differences between the different techniques are interpreted in terms of the degree of coupling between amorphous and crystalline regions. Secondly, comparison between SAXS and GPC data alone suggests that the distribution of the amorphous phase follows a completely different pattern in the two classes of samples investigated. The slow cooled samples exhibit a highly uniform morphology with all the amorphous phase distributed in series with crystals of “infinite” lateral size; the quenched samples are characterized by a heterogeneous morphology with part of the amorphous material either interrupting the lateral continuity of the crystals (crystals of finite lateral size), or being segregated at the spherulite boundaries. The insight which the present results provide on the effects of molecular weight and thermal treatment on the morphology of bulk LPE, is of value in obtaining further understanding of the drawing behavior of this polymer.

ISSN:0022-2348    

DOI:10.1080/00222347808212262

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Tests are described in which wet shrinkage is observed subsequent to strain annealing of nylon 6 fibers. The wet shrinkage studies demonstrated a large mobilizing effect by water present in the polymer structure even after very high temperature annealing treatments. Transitions in shrinkage behavior after strain-annealing treatments were experimentally observed at strains corresponding to the onset of chain rupture. The shrinkage might be attributed to chain refolding. The apparent activation energy for the processes was approximately 10 kcal/mole for the annealed nylon 6 samples, compared to published values of 14 kcal/mole for nylon 66 fibers.

ISSN:0022-2348    

DOI:10.1080/00222347808212263

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The temperature dependence of the argon permeability and diffusion coefficients in poly(vinyl fluoride) and poly(vinylidene fluoride) was determined experimentally. Two transitions were revealed as slope discontinuities in the Arrhenius plots of the transport parameters for argon in poly(vinyl fluoride). Only one transition however was observed in poly(vinylidene fluoride). A transition at 40°C reported in the literature was not observed, a third transition which has been reported by use of other techniques was below −30°C, the lowest temperature conveniently obtained in the existing experimental apparatus. The results found are consistent with dilatometry data also reported in this paper and with literature values.

ISSN:0022-2348    

DOI:10.1080/00222347808212264

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The utilization of sorption and diffusion phenomena of low molecular weight polymer swelling penetrants has been shown in the present work to make it possible to detect morphological differences in unmodified samples of polycarbonates. A suitable active penetrant has been found to bring out differences in the mobilities of areas with varying degrees of molecular ordering. These differences can then be measured by NMR.

ISSN:0022-2348    

DOI:10.1080/00222347808212265

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The method of thermally stimulated currents has been used to study the molecular relaxations in a homologous series of aliphatic polycarbonates varying in monomeric unit size from four to twelve methylene groups. The secondary β relaxation has especially been analyzed considering the complex relaxations often observed at low temperatures in other linear polyesters. In unsubstituted aliphatic polycarbonates, a significant structure in β relaxation is observed only in samples containing water; in perfectly dry samples, it appears that the TSC β peak cannot be resolved in discrete components, even by a fractional polarization technique, and is only characterized by a continuous distribution of relaxation times. On the other hand, in a substituted aliphatic polycarbonate, the β relaxation clearly appears to be structured, showing the important role played by branches for the appearance of a complex relaxation.

ISSN:0022-2348    

DOI:10.1080/00222347808212266

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Infrared and Raman spectra of poly(vinylidene chloride) (PVDC) single crystals are presented. Additionally, we report infrared spectra of a quenched, largely amorphous, sample of PVDC. Our results question the interpretation of previous vibrational studies of PVDC which conclude that the crystalline polymer chain is in the TGTG′ conformation. Strong Raman lines at 688 and 161 cm−1together with weaker lines at 3000, 345, and 143 cm−1which are either absent or, at least, extremely weak in the infrared spectrum of the crystalline polymer suggest that a planar 21helical conformation is more consistant with the vibrational data.

ISSN:0022-2348    

DOI:10.1080/00222347808212267

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0022-2348    

DOI:10.1080/00222347808212268

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor