摘要:

AbstractThe preparation of copolyhydrazides containing equimolar quantities of “bisacetyl A2” and terephthaloyl or isophthaloyl groups is described. The resulting copolymers were found to form clear colorless films which, when immersed in concentrated formic acid, softened but rehardened and turned white after subsequent immersion in water. The formic acid treatment did not bring about a morphological change from the amorphous to the crystalline state, but caused changes in the differential scanning calorimetry (DSC) traces which suggest that an α/β transformation had taken place. The possible nature of this transition is discussed. The results of tensile tests on cast film are

ISSN:0021-8995    

DOI:10.1002/app.1977.070210901

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

年代:1977

数据来源: WILEY

摘要:

AbstractBlending of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin) with a triblock butadiene–styrene–butadiene copolymer (Kraton 101) monotonically increases the softening temperature of the latter as measured by TOA. The TOA transition temperatures of the styrene/PPO resin phases closely approximate those of polystyrene/PPO resin blends having the same styrene/aromatic ether unit compositions. Uniform mixtures of the styrene blocks with the poly(2,6‐dimethyl‐1,4‐phenylene oxide) molecu

ISSN:0021-8995    

DOI:10.1002/app.1977.070210902

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe differential scanning calorimetry technique has been applied to investigate the curing of injection molding phenolic compounds. The data obtained include degree of cure, rate of curing, and heats and temperatures of curing as function of various heating rates, rate constants, energy of activation, and glass transition temperature. The curing temperature and heating rate were found to affect both the curing reaction kinetics and the final structure of the crosslinked network. The glass transition temperature changes continously with the extent of curing, approaching the cure temperature.

ISSN:0021-8995    

DOI:10.1002/app.1977.070210903

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

年代:1977

数据来源: WILEY

摘要:

AbstractDeformation of polyethylene in environmental stress cracking (ESC) agents results in changes in both the mechanism of deformation and structure of the resulting drawn material. Stress‐cracked failure surfaces are highly fibrillar, the fibrils having less elastic recovery than those in samples drawn in air. In thin films drawn in ESC agents, small blocks of the lamellae remain undrawn and attached to the fibrils drawn across micronecks. The ESC agents are suggested to weaken the cohesion between the fibrils in samples drawn beyond yield as well as the cohesion between mosaic blocks or similar structural elements in the original lamellae as they are being reoriented to form the fibrils. The stress is thus supported by a number of independent, nonuniform fibrils rather than a coherent structure; the weakest of these fibrils fail in turn as the crack propagates through the sampl

ISSN:0021-8995    

DOI:10.1002/app.1977.070210904

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe structure of melt‐spun nylon 6 filaments was studied using on‐line x‐ray diffraction and birefringence measurements. Measurements were also made on as‐spun and treated filaments. On‐line wide‐angle x‐ray scattering measurements indicated that crystallization did not occur on the nylon 6 spinline at spinning rates up to 1000 m/min when spinning was done into either ambient air of 60% relative humidity or into wet saturated air. The filaments did crystalline gradually on the bobbin to a paracrystalline pseudohexagonal (γ) form. The rate of crystallization was dependent on the molecular orientation developed in the spun filaments. Crystalline orientation factors based on hexagonal symmetry were computed as a function of take‐up velocity for fibers which were conditioned 24 hr in air at 65% relative humidity. Annealing in air or treatment in water or 20% formic acid solution causes a transformation from the pseudohexagonal form to the α monoclinic form. The tangent modulus of elasticity and tensile strength of spun and conditioned filaments increase with increasing take‐up velocity and spinline stress, while elongation to break decreases w

ISSN:0021-8995    

DOI:10.1002/app.1977.070210905

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe kinetic parameters of the polymerization of diglycidyl ether of bisphenol A with hexahydrophthalic anhydride and benzyldimethylamine as catalyst were determined using differential scanning calorimetry. The reaction was found to be first order with some variation with temperature, and the activation energy and natural log of the frequency factor were 25 kcal/mole and ∼25 sec−1, respectively. These results are discussed with respect to a steady‐state mechanism of the polymerization and compared with results reported for other epoxide–anhydride re

ISSN:0021-8995    

DOI:10.1002/app.1977.070210906

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe techniques of Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) have been used to study the locus of failure of epoxy resin joints. The effects of a long water immersion and the application of a silane‐based primer have also been studied. Results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water‐soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide. The application of the primer to the metal surface prior to bonding prevented the formation of a water‐formed oxide although fracture was then found to occur through the

ISSN:0021-8995    

DOI:10.1002/app.1977.070210907

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

年代:1977

数据来源: WILEY

摘要:

AbstractA study was conducted to determine the degree of cyclization occuring in a series of four pyrrone and two polyimide prepolymers. These materials were heated from 25° to 400°C at 2°C/min in a helium atmosphere, and the effluent was sampled at regular intervals by a gas chromatograph/mass spectrometer technique. Quantitative analysis of this effluent indicated that the pyrrone polymers were less than 80% converted under these conditions while the polyimides were essentially fully converted. Significant amounts of carbon dioxide were found to be eliminated as the pyrrone polymers cured. This evolution was attributed to the loss of carbon dioxide from intermediate stages during cure and, in some cases, to the decarboxylation of unreacted groups. Support data obtained on model compounds are also present

ISSN:0021-8995    

DOI:10.1002/app.1977.070210908

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe glass transition, crystallization, and α–β transition of the Tussah silk fibroin were studied by means of DSC (differential scanning calorimetry) and infrared spectroscopy. The endothermic shift due to the glass transition was observed at 162°C. The endothermic peak at 220°C was attributed to the α–β conformational transition from the infrared spectra. The exothermic peak due to the crystallization occurred

ISSN:0021-8995    

DOI:10.1002/app.1977.070210909

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

年代:1977

数据来源: WILEY

摘要:

AbstractPreparative gel permeation chromatography was used to produce a number of polypropylene reference samples, within the molecular weight range of 10,000–600,000, from commercial materials. Some of these materials were degraded in a controlled manner to give base materials having suitable molecular weight characteristics. A procedure has been developed using a single preparative column packed with equal quantities of Styragel with nominal exclusion limits of 102, 103, 104, and 105nm. The volume of solvent for recovery was minimized by use of higher loading factors than in analytical GPC (some 2–20 times more polymer was thus fractionated in each experiment). Under these conditions the fractions first eluted were sharpest having polydispersities of about 1.5. First fractions, from different base materials, were characterized by analytical GPC, and those of similar molecular weight and polydispersity were combined to give the reference samples. Refractionation was necessary with the highest molecular weight base material because the first stage fractions were not sharp enough. Some of these fractions were recovered at elution volumes where much lower molecular weight material was expected. Comparison with results from the other base materials indicates that the primary cause of the spreading is not overloading. This spreading is explained in terms of slower partitioning of the larger molecules between the interstitial fluid and the gel partic

ISSN:0021-8995    

DOI:10.1002/app.1977.070210910

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

年代:1977

数据来源: WILEY