摘要:

The Maron theory of polymer solutions was used to reexamine the data of Brown et al. and Allen et al. [1,2] on the vapor pressures of polypropylene solutions in diisopropyl and diethyl ketones. The results obtained show that the interaction parameters for these systems depend on concentration and temperature, and that these parameters are able to reproduce the observed data so long as the polymers are amorphous. However, in the presence of polymer order, deviations from theory are observed which lead to 31 and 61% crystallinity for the two polypropylene samples used in these studies.

ISSN:0022-2348    

DOI:10.1080/00222347008212501

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The morphology of glassy amorphous thin polycarbonate film cast from solution is affected by thermal treatments. Annealing above 80° C and below Tgresults in an increase in the size of the ordered regions, nodules, up to several hundred Angströms. The crystallization process from the glass, taking place at 145° C, is divided into three major steps. At first the nodules merge into patches which aggregate to form lamellar planar structures. In some cases the planar structures are well-formed single crystals. Following this, spherulitic arms develop from the planar structures as centers. These arms at first consist of aggregates of large nodules which recrystallize to form lamellae; the final morphology is spherulitic in nature. The effect of film thickness and of several substrates on the morphology has been observed. Applying stress at room temperature to the crystalline film results in a breaking up of the lamellae into small blocks.

ISSN:0022-2348    

DOI:10.1080/00222347008212502

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The crystallization of glassy amorphous thin polycarbonate films quenched from the melt has been followed. Structures similar to those observed during the crystallization of films containing small amount of adsorbed solvent are formed. However, crystallization, at the same temperatures, is much slower and more irregular. Preannealing of the samples below Tgaffects the crystallization process, increasing the nucleation rate. Annealing above Tgdoes not destroy all order gained by annealing below Tg.

ISSN:0022-2348    

DOI:10.1080/00222347008212503

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The internal friction of a series of polymethacrylates is determined by means of a computerized acoustic spectrometer between 80° and 280° K. It is found that the incorporation of tetraethylene glycol dimethacrylate as a comonomer with methyl methacrylate yields a loss peak near 180°K. This peak decreases both in strength and in temperature with decreasing divinyl content. The mechanism for this relaxation is attributed to the micro-Brownian motions of the tetraethoxy moieties. The effect of incorporating diluents in polymethacrylates is the appearance of a new “diluent peak,” which depends on the nature of the diluent. The introduction of di(ethylhexyl) adipate produces a loss peak near 140° K in the methyl, ethyl, n-propyl, and t-butyl esters of methacrylic acid. The presence of tricresyl phosphate, on the other hand, does not yield a new diluent peak. A possible mechanism for the diluent peaks consistent with these observations is the interaction of diluents with the carboxyl groups of the ester side chains.

ISSN:0022-2348    

DOI:10.1080/00222347008212504

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

In this study, X-ray diffraction has been used to determine the crystal structure of poly(vinylidene fluoride) phase II. Three principal chain conformations were considered, which included two 21helical forms [degenerate (planar) and nondegenerate] and the trans-gauche-trans-gauche' form.

ISSN:0022-2348    

DOI:10.1080/00222347008212505

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The Crystallization kinetics of molten polyethylene subjected to a constant shear stress were investigated theoretically and experimentally. The rate of crystallization depends on the difference of entropy (Δs) between the crystalline and molten state. The constant shear stress in the melt decreases Δs causing an abrupt increase in the rate of crystallization and a decrease of the thickness of the folded-chain lamellar crystals.

ISSN:0022-2348    

DOI:10.1080/00222347008212506

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Studies of chain folding in amylose employing spectroscopic techniques have led to an assignment of the 1295-cm−1band to a unique fold conformation. Irregular folds, present in single crystals, are regularized to the unique fold conformation during annealing. Annealing of solution-cast films, which initially contain a small amount of regular folding, increases the amount of regular folds. Swelling of these annealed films with water vapor destroys this unique folded conformation.

ISSN:0022-2348    

DOI:10.1080/00222347008212507

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Two infrared bands occurring at 790 and 1256 cm−1can be assigned to conformations within a metastable noncrystalline state of amylose. This metastable conformation can be transformed to a crystallizable conformation with heat or time. Both bands occur in amorphous and V-complex preparations of amylose. These two infrared bands have not been previously reported for amylose.

ISSN:0022-2348    

DOI:10.1080/00222347008212508

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Studies of the stress-strain birefringence behavior of isoprene-acrylonitrile copolymers, 2,3-dimethylbutadiene-acrylonitrile co-polymers, butadiene-acrylonitrile copolymers of three compositions, emulsion polybutadiene, and high cis-1,4-polybutadiene are reported. The stress-optical behavior of the radiation cross-linked samples was determined over the range of 30° to 110°C at small elongations. Rubber photoelasticity theory could be applied, and the optical link anisotropy and its temperature and composition dependence were determined for the copolymers. The temperature dependence of segmental anisotropy indicated in a qualitative manner the effect of substitution along the chain backbone.

ISSN:0022-2348    

DOI:10.1080/00222347008212509

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Fibrillar crystals have been prepared by the crystallization of isotactic polystyrene from stirred solutions in 1,3,5-trimethylben-zene and cyclohexanol. Similar microfibrils have been prepared in the nascent state by the polymerization of styrene in 1,3,5-trimethyl-benzene with a heterogeneous Ziegler-Natta catalyst. The microfibrils varied in width between 140 and 250 Å and were characterized by periodic lamellar overgrowths which were believed to give rise to a discrete X-ray reflection having a d-spacing of 90 A. Thermal analysis suggested that high growth temperatures favored greater crystal perfection. During crystallization from stirred cyclohexanol solutions, a fractionation of high molecular weight chains occurred which was more efficient at higher crystallization temperatures. In comparison to crystallizations under quiescent conditions, a marked facility of the crystallization process was observed in the formation of stirrer-crystallized and Ziegler-Natta polystyrene. The ease of crystallization of the shear-regenerated and nascent microfibrils has been related to a reduction in the free energy of nucleation. Mechanisms have been proposed to account for a favored nucleation process.

ISSN:0022-2348    

DOI:10.1080/00222347008212510

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor