摘要:

AbstractThe cooling power of aqueous solutions of polyvinylpyrrolidone are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. The dependences of the cooling rates at each temperature on polymer concentration and solution viscosity are established and empirical laws of variation are given.

ISSN:0021-8995    

DOI:10.1002/app.1991.070431201

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe cooling power of aqueous solutions of ethylene oxide‐propylene oxide copolymers are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. For temperature T>400°C, the viscosity plays the predominant role; for T<400°C, the cooling is controlled by the polymer precipitation and the cooling rate decreases by lowering the cloud point of the polymer solution. This work demonstrates the possibility of adjusting the cooling curves by taking into account the thermodynamical properties of the poly

ISSN:0021-8995    

DOI:10.1002/app.1991.070431202

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

年代:1991

数据来源: WILEY

摘要:

AbstractSolvent penetration into nonaqueous dispersions (NAD) of poly(methyl methacrylate) (PMMA) sterically stabilized by PIB were studied by ESR spectroscopy. These colloidal particles were exposed to dilute solution of spin probe 3‐carbomoyl 2,2,5,5‐tetramethyl 3‐pyrolin‐1‐yloxy and the bimodal distribution of ESR spectra of this probe molecules were carefully monitored as a function of time. Fickian type diffusion of spin probes into the particles was observed and a spherical model was employed to obtain the diffusion coefficients(D)in various solvents.Dvalues were found around 10−15cm2/s, and interpreted as the parameter, inversely proportional to the apparent viscosity of the environment inside the colloid particle. Maximum amount of diffused solvent molecules(M∞) into the PMMA particle was found inversely proportional to polymer‐solvent interaction through the solubility parameters. The interconnected network of PIB was found to be responsible for the penetration of spin‐probe (i.e., solvent) molecules into the glassy PMMA phase and/or P

ISSN:0021-8995    

DOI:10.1002/app.1991.070431203

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe aging phenomenon of highly filled rubber in humid environment was investigated. HTPBD was reacted with MDI and mixed with salt at the same time. The mixture was then hot‐pressed for 24 h at 90°C to prepare the sample. The changes in mechanical properties and glass transition temperature of the sample were followed when they were subjected to different humidity at 30°C for 7 days. Furthermore, the effects of humidity on chemical structures were studied with IR.The results showed that unfilled rubber suffered no changes in mechanical properties after 7 days in environment of high humidity (RH 97). However, for NaCl‐Filled rubber, its strength decreased because of a loss of stiffness of salt after salt deliquesced. The glass transition temperature of unfilled rubber seems not to be affected by various humid conditions, but the Tgof filled rubber decreased slightly. From SEM pictures, we observed that interior holes were left after salt deliquesced. This was the main cause for the reduction in mechanical properties of filled r

ISSN:0021-8995    

DOI:10.1002/app.1991.070431204

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

年代:1991

数据来源: WILEY

摘要:

AbstractJute stick was bleached with sodium chlorite and alkaline hydrogen peroxide solutions. The infrared (IR) spectra of bleached samples and jute stick were analyzed and compared. The bleached samples were characterized by higher absorbance intensity ratios(Av/A2900) of the bands attributed to hemicellulose. Among the bleached samples the chlorite‐bleached sample showed higher intensity for the bands mentioned. The bands attributed to lignin are either absent or very weak in the chlorite‐bleached jute stick as compared to that of peroxide‐bleached jute stick, although some residual lignin was present in the substrate. The 1635 cm−1band attribute to the vibration of adsorbed water molecules in the noncrystalline regions in cellulose appears as a sharp peak in chlorite‐bleached jute stick and as a shoulder in peroxide‐bleached jute stick. This can be attributed to the difference in the nature of the two bleachin

ISSN:0021-8995    

DOI:10.1002/app.1991.070431205

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

年代:1991

数据来源: WILEY

摘要:

AbstractThermal aging and strain endurance experiments on a filled rubber were performed at several temperatures. The rubber was polyurethane (PU) made from hydroxyl‐terminated polybutadiene (HTPB) with 4,4′‐diphenyl methane disocyanate (MDI). The filler was sodium chloride. The mechanical properties, glass transition temperature, dynamic viscoelasticity, and chemical structures were investigated for filled and unfilled PU under an aging period at 60 and 80°C and 50% relative humidity. We found that at 60°C the chemical structures of the filled and unfilled rubbers had no changes in 30 days during aging. But moisture had some effects on the filled PU and changed its mechanical properties. At 80°C, the chemical structures of the filled and unfilled PU had changed due to the thermal oxidation of polybutadiene in aging. The deterioration was more apparent for the filled rubber than for the unfilled. The prestraining would dewet the filler from the samples and it increased t

ISSN:0021-8995    

DOI:10.1002/app.1991.070431206

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

年代:1991

数据来源: WILEY

摘要:

AbstractFine particles of poly(glycidyl methacrylate) (PGMA) were prepared by suspension polymerization and crosslinked via the ring‐opening reaction of the epoxide group with formic acid. A fraction of the spherical gel particles averaging about 70°m in diameter was examined under an optical microscope with its swelling behavior in a number of solvents. Equilibrium degrees of swelling were established with accuracy to show that this polymer gel has rather unusual affinities for solvents: (i) It is swollen (and, without the crosslinks, soluble in most cases) in many types of solvents, (ii) it cannot be represented by a single value of solubility parameter, and (iii) it is not swollen at all in water nor in aliphatic alcohols, in spite of the presence of hydroxy groups in the cha

ISSN:0021-8995    

DOI:10.1002/app.1991.070431207

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

年代:1991

数据来源: WILEY

摘要:

AbstractMaterials which may be classified as interpenetrating polymer networks have been prepared by thein situpolymerization of styrene in natural rubber latex using azobisisobutyronitrile (AIBN) as the initiator. The resulting materials have been characterized by electron microscopy, Soxhlet extraction coupled with proton nuclear magnetic resonance spectroscopy, dynamic mechanical analysis, and stress‐strain analysis. The styrene polymerizes within the natural rubber latex particles to give a relatively fine phase‐separated morphology with some evidence for a limited degree of segmental mixing. Moreover, it is clear that AIBN, despite what is stated in the literature, does lead to some grafting of polystyrene, and, in addition, causes significant degradation of the natural rubber molecules when the styrene content is

ISSN:0021-8995    

DOI:10.1002/app.1991.070431208

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

年代:1991

数据来源: WILEY

摘要:

AbstractNew polyesters were obtained by interfacial polycondensation of bis(4‐hydroxyphenyl) ether with phthaloyl, isophthaloyl, and terephthaloyl chlorides. The initial reaction conditions were as follows: the aqueous to organic phase ratio 1 : 1, reaction temperature 25°C, the rate of chloride addition about 10 min, and molar ratio of the reagents diol/acid dichloride 1 : 1.1, benzene‐hexane as an organic phase. To determine the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: organic phase, excess of sodium hydroxide as an acceptor of HCl, contribution of benzyltriethylammonium chloride as a catalyst, and contribution of an emulsifier, Mersolan. The structure of all polyesters was determined by elemental analysis and infrared spectra. Initial decomposition and initial intensive decomposition temperature were defined by the curves of thermogravimetric analysis. Some mechanical and electrical properties of isophthaloyl polyester, only partly soluble in organic solvents, were determ

ISSN:0021-8995    

DOI:10.1002/app.1991.070431209

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

年代:1991

数据来源: WILEY

摘要:

AbstractCatalase was immobilized in a polyion complex from poly(sodium 2‐acrylamide‐2‐methyl‐1‐propanesulfonate) and poly[2‐(trimethylammonioethyl) methacrylate chloride]. Polyion complex formation between the two polyions was found to proceed stoichiometrically by the turbidimetric titration. Immobilization of catalase was achieved by conducting the complexation in the presence of the enzyme, which was established to be incorporated in the polyion complex networks. The fixed catalase showed higher thermal stability than the original enzyme. Furthermore, the stability and the activity of the fixed catalase were improved by annexing inert components such as albumin, histone, or lecithin at the time of polyion comple

ISSN:0021-8995    

DOI:10.1002/app.1991.070431210

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

年代:1991

数据来源: WILEY