摘要:

AbstractA series of highly oriented tapes has been prepared from a blend consisting of equal proportions of polyethylene and polypropylene. The mechanical properties and the structure and morphology of the samples have been investigated using DSC, optical microscopy, and wide angle and small angle diffraction, including measurements of crystal strain on samples under stress. It has been confirmed that the blend is incompatible, and a structural model has been proposed which is consistent with the observation that the polyethylene and polypropylene components act essentially independently in their response to external macroscopic stress.

ISSN:0021-8995    

DOI:10.1002/app.1991.070430801

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractUsing the free volume theory, general relations between viscometric and volumetric properties of polymers as functions of temperature and deformation conditions (shear rate or shear stress) have been derived. In particular, it has been shown that thermal expansion of polymers can be calculated from viscometric data. The obtained relations have been applied for description of the rheological behavior of polymer blends. Theoretical predictions have been compared with experimental data. Good agreement between theory and experiment has been stated if rheological properties of blends were compared at a constant shear rate.

ISSN:0021-8995    

DOI:10.1002/app.1991.070430802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis article describes the effect of stirring on epoxy network morphology and physical properties. Several different mechanical stirrer speeds, from 45 rpm to 800 rpm, were employed for the mixing of diglycidyl ether of bisphenol A resin with 2‐ethyl‐4‐methyl imidazole catalytic curing agent. The investigation indicated that the glass transition temperature, room temperature density, low temperature relaxation, tensile mechanical properties in the rubbery state, and nodular morphology are significantly affected by the stirrer speed used. Transmission electron microscopy has revealed that the extent of homogeneity for the dispersion of nodule domain in the low crosslinking matrix improved with increasing stirrer speed. However, an optimum stirrer speed condition is needed for achieving the most homogeneous system. In addition, it is shown that the room temperature tensile mechanical properties are independent of the mixing condition. This independence is ascribed to the fact that the glassy state mechanical properties are closely related to the intermolecular forces rather than to the network stru

ISSN:0021-8995    

DOI:10.1002/app.1991.070430803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe purpose of this research is to prepare high solute permeability membranes for hemodialysis by plasma depositing hydrophilic monomers onto chemically treated or O2plasma etched Nylon 4 substrate. The factors that affect the performances of membranes, such as deposition conditions and chemical or plasma etching conditions, were studied. The monomers used in this study were 1‐vinyl‐2‐pyrrolidone (VP), 2‐Hydroxyethyl methacrylate (HEMA), and Methyl methacrylate (MMA). The permeabilities of NaCl, urea, vitamin B12, and albumin were measured, as were the water content, hydration, diffusivity, partition coefficient, and protein adsorption ratio of fibrinogen to albumin by membrane surface of plasma deposited membranes.The permeabilities of NaCl, urea, vitamin B12, and albumin of HEMA 5 w‐1 h plasma deposited onto chemical treated Nylon 4 membranes were 2.896 ± 0.192, 3.301 ± 0.325, 0.010 ± 0.007, and 0.000 x 10−5cm2/min, respectively. The mole ratio of adsorbed fibrinogen to adsorbed albumin (F/A) is 0.26 ± 0.05, which is much lower than that of the pure Nylon 4 membrane (0.94 ± 0.06) and the Gambro® membrane (0.90 ± 0.15). The HEMA deposited membrane possesses the highest feasibility as hemodialysis material among those plasma deposited me

ISSN:0021-8995    

DOI:10.1002/app.1991.070430804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractCompression ultrasonic velocity, longitudinal ultrasonic absorption, and heat of mixing for NR‐BR, NR, NBR, and NR‐IIR rubber blends were measured. Results show the applicability of examining the compatibility degree by using longitudinal ultrasonic absorption techniques. Results showed that NR‐BR blends are compatible, whereas NR‐NBR and NR‐IIR blends are semicompatible and incompatible, res

ISSN:0021-8995    

DOI:10.1002/app.1991.070430805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractPoly(4‐vinylpyridine) (P4VP) microgels with a narrow size distribution have been prepared by a special emulsion polymerization method. This is to say that P4VP, to which cation and double‐bond were introduced with iodomethane and chloromethylstyrene, by quarternization reaction was used as a polymer emulsifier. Divinylbenzene was used as a crosslinking agent. It was found that the microgel became larger with the increase in monomer concentration, and became smaller and softer with the enhancing emulsifer/monomer ratio. Microgels, with the diameter of between 70–700 nm, were obtained by varying the monomer concentration from 1.0 wt % to 5.0 wt %, and by varying the emulsifier/monomer (unit/unit) ratio from 0–10.0 mol %. Compared with conventional emulsion polymerization with surfactant or hydrophilic monomer, this method provides an advantage in that monoingredient microgels can be o

ISSN:0021-8995    

DOI:10.1002/app.1991.070430806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractCure kinetics of tetraglycidyl 4,4′‐diaminodiphenyl methane resin formulations with diaminodiphenylsulfone as hardener and borontrifluoride‐ethylamine adduct as accelerator has been studied by differential scanning calorimetry (DSC) technique both dynamically and isothermally. The DSC scans show multiple exotherm peaks, indicating the complex nature of reaction. The curing exotherms obtained have been analysed to derive the kinetic parameters associated with the curing process. The heat of reaction shows a decreasing trend with increasing catalyst concentr

ISSN:0021-8995    

DOI:10.1002/app.1991.070430807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractMeasuring the fiber lengths of the broken pieces and estimating the mean tensile strength from the length just before the final fragment length in tension, efforts were made to estimate the axial compressive strengths of carbon fibers when the tensile strength varies with the length. The estimated compressive strength of carbon fibers decreases with increasing temperature. This decrease in compressive strength may be accounted for by a decrease in the radial compressive force owing to a decrease in the residual thermal stress and a decrease in Young's modulus of the resin matrix. There is a linear relationship between the estimated compressive strength and radial compressing force in the temperature range from room temperature to 80°C. The real compressive strength of the fibers, determined by extrapolating this straight line until the radial compressing force is zero, is about 20% higher than the compressive strength estimated by assuming that the tensile strength is uniform. It is approximately 10–50% of tensile strength. A linear relationship between the fiber axial compressive strength and compressive strength of the unidirectional composites is found. The experimental values agree with the values calculated by the rule of mixtur

ISSN:0021-8995    

DOI:10.1002/app.1991.070430808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe interaction between several polymeric materials, typical of those that have application as parenteral product containers, and 16 marker solutes was evaluated. Polymers used included polypropylene, polyvinyl chloride, ethylenevinyl acetate, an olefin rubber, a polyester ether block copolymer, and various composites of these materials. In addition, the partitioning of solutes between two common PVC plasticizers (dioctyl phthalate and butyryl hexyl citrate) and water was also examined. Correlation between equilibrium interaction constants (Eb) (which describe the equilibrium distribution of a solute between contacting polymer and solution phases) and solute octanol‐water (Po‐w) or hexane‐water (Ph‐w) partition coefficients were in general poor for all materials studied. However, a bivariate linear interaction model relatingEbto both partition coefficients:\documentclass{article}\pagestyle{empty}\begin{document}$$ \log E_b = a\left( {\log P_{{\rm o} - {\rm w}} } \right) + b\left( {\log P_{{\rm h} - {\rm w}} } \right) + c$$\end{document}effectively mimicked the interaction behavior of all materials evaluated. The utilization of the developed models to facilitate container compatability assessments is discussed. In addition, the use of a critical ratio of binding constants for a pair of solutes is introduced as a means of qualitatively assessing the effectiveness of a particular solvent as a polyme

ISSN:0021-8995    

DOI:10.1002/app.1991.070430809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe objective of this study was to improve the durability and stability of urea‐formaldehydebonded wood products by decreasing the internal stress developed during resin cure and by improving the ability of the cured system to withstand cyclic stresses. Urea‐formaldehyde resins were modified by (i) incorporating urea‐terminated di‐ and trifunctional flexible amines into the resin structure, (ii) curing the resins with the hydrochloride derivatives of some of these amines (in place of ammonium chloride), or (iii) using both processes. The cyclic stress resistance of solid wood joints and the internal bond strength and thickness swell of particleboards made with these resins were compared with these properties in joints and particleboards made with an unmodified resin and a commercial urea‐formaldehyde resin. The strength of joints and the internal bond strength of particleboards made with resins modified with urea‐terminated hexamethylenediamine, bishexamethylenetriamine, and poly(propylene oxide) triamine at modifier contents of 13, 16, and 28 wt %, respectively, showed excellent stability even after repeated wet‐dry cycles. Similar stress resistance was shown by wood joints and particleboards bonded with the unmodified resin cured with the hydrochloride salts of hexamethylenediamine and triethyleneaminetriamine. In contrast, solid wood joints and particleboards bonded with the unmodified resin cured with ammonium chloride showed lower resistance to cyclic stress. Particleboards that possessed good cyclic stress resistance also showed less th

ISSN:0021-8995    

DOI:10.1002/app.1991.070430810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY