摘要:

A description of reflection boundaries in x-ray diffraction patterns from oriented and polycrystalline polymer specimens is developed. The description is based on mosaic parameters that characterize the disorientation and crystallite size in the specimen and is independent of the exact reflection shapes. This description is part of a previously described method for measuring integrated intensities from such diffraction patterns. The reliability of the method is assessed using both numerical simulations and measurements from an x-ray fiber diffraction pattern. A method for estimating the mosaic parameters from a diffraction pattern is also described. The relevance to diffraction patterns from non-crystalline oriented polymers is also discussed.

ISSN:0022-2348    

DOI:10.1080/00222348908215217

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Volume flow of polyisobutylene (PIB) (Mn= 1,283,000 and Tg= 202 K) has been measured in an Instron Capillary Rheo-meter. Elastic modulus in longitudinal compression, longitudinal volume viscosity, and retardation times are described at temperatures from about 295 K to 333 K, and at compression rates of ca. 1.00 to 200.00 × 10−5s−1The longitudinal volume viscosity decreases with increasing compression rate, decreasing volume deformation (this behavior being a typical nonequilibrium one), and decreasing temperature, the volume flow activation energy amounting to some 19.19 kJ/mol.

ISSN:0022-2348    

DOI:10.1080/00222348908215218

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In order to investigate the mechanism of freezing point depression (FPD) phenomena for polymer solutions and/or swollen rubber vulcanizates, some experiments related to this phenomenon have been carried out at a constant rate of cooling and at low temperatures. Thus far this phenomenon has not been explainable in terms of an ordinary colligative effect. In this study a new mechanism is proposed. In this mechanism, microsyneresis occurs first, because of the lowering of solvent quality with decreasing temperature, followed by crystallization of the (swelling) solvent. The measured freezing point is considered to be mainly dependent on the polymer concentration of the concentrated polymer phase formed by microsyneresis. The concept of local volume fraction is introduced in order to evaluate the polymer concentration of the concentrated polymer phase, and then Flory-Huggins' lattice model theory is extended so as to reproduce the experimental results. The physical meaning of the E-parameter used in the extension of the theory is discussed in detail. The E-parameter is associated with the changes of the excluded volume effect with decreasing temperature and might reflect the degree of formation of microsyneresis.

ISSN:0022-2348    

DOI:10.1080/00222348908215219

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We have attempted to apply the relationship found between the flexibility parameter in θ-conditions, λθ, and h*/h, h being the monomeric unit projection length, according to the wormlike theory, and h* the slope value when plotting (<r2>/L)½versus λ, to ternary systems composed of one polymer and two solvents or a solvent and a nonsolvent.

ISSN:0022-2348    

DOI:10.1080/00222348908215220

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Stress intensity factor (KI)-crack speed (c·) plots for the high-density polyethylene-10% detergent (Igepal) system have been obtained to investigate the effect of fracture mechanics test variables such as load level, specimen geometry, and dimension on the crack growth behavior. Fracture mechanics appeared to be valid at low KIlevels. However, at high KIvalues, the data showed that linear elastic fracture mechanics failed to describe the crack growth behavior. Williams' flow model was not successful in explaining a number of regions which were obtained in a KI-·c plot. Craze formation at the crack tip enhances the crack speed at high KIlevels.

ISSN:0022-2348    

DOI:10.1080/00222348908215221

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Simultaneous interpenetrating polymer networks (SINs) were prepared from nadic methyl anhydride-cured epoxy resin and bismaleimide (BMI) coreacted with triallyltrimellitate (TAT), triallylisocyanurate (TAIC), and diallylisophthalate (DAP), under the same gelling conditions for both the epoxide resin and BMI-allylester comonomer. Dynamic mechanical properties of the SINs were measured over the temperature range from room temperature to about 300°C. The rubbery modulus and glass transition temperature (Tg) due to the cured epoxy resin considerably increased with loading of BMI-allylester copolymer. The value of Tgexhibited an asymptotic behavior at high loading, the value increasing in the order of BMI-TAT, -TAIC, and -DAP. The relative modulus in the rubber state shows that phase inversion occurs in the SINs at the concentration of 30–40 wt% BMI-allylester. The increase in Tgwith loading can be explained in terms of the contributions of both an increase in crosslink density and an interaction between the epoxy resin and BMI-allylester copolymer. The increments in Tgwith loading can be correlated to the logarithm of a nominal crosslink density in the loading polymer, and the difference among the asymptotic values of Tgfor each series is discussed based on polar-nonpolar solubilities of the components. The increase in Tgwith loading can also be corre-lated to the percent densification, which exhibits a maximum at a composition of about 50%, resulting from interpenetration.

ISSN:0022-2348    

DOI:10.1080/00222348908215222

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

High-strength linear polyethylene was prepared by injection molding using an axial elongational flow component during the filling process. Microhardness (MH), tensile and bending stress ([sgrave]), optical birefringence (Δn), differential scanning calorimetry (DSC), and shrinkage measurements were used to characterize the changes in microstructure, molecular orientation, and mechanical properties, occurring throughout the range of processing temperatures used (Tm=140–200°C)

ISSN:0022-2348    

DOI:10.1080/00222348908215223

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor