摘要:

AbstractThe kinetics of the thermal degradation of cellulose and modified cellulose, namely, cellulose phosphate, cellulose carbanilate, cellulose tosylate, chlorodeoxycellulose, bromodeoxycellulose, and iododeoxycellulose in air were studied by thermogravimetry and differential thermal analysis from ambient temperature to 700°C. The various thermodynamic functions for different stages of thermal degradation had been obtained following the procedure of Broido. The activation energies for the oxidative decomposition of cellulose and modified celluloses were found to be in the range 30–399 kJ mol−1. The infrared spectra of the residues of modified celluloses gave indication of formation of a compound containing PO, POP (only in the case of cellulose phosphate), CC, and CO groups in the final residual char. The EPR signals indicated the formation of trapped and stable free radicals in the thermal degradation of all the compounds, particularly halodeoxycelluloses showed generation of large amounts of trapped free radicals during the oxidative decomposition. Scanning electron micrographs of the thermally degraded cellulose derivatives show changes in the fibrillar structure, evolution of gasesous products, and film formation depending upon the nature of the substituent in the cellulose matrix. The mechanism of thermal degradation of these compounds has

ISSN:0021-8995    

DOI:10.1002/app.1987.070330201

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe influence of certain factors on the kinetics of styrene mass transfer from polystyrene in air at elevated temperature is investigated. It is established that this process can be simulated by a model including molecular diffusion of styrene to the surface of the solid material and evaporation from that surface. The effective coefficients of molecular diffusion at different temperatures and the evaporation coefficients under different hydrodynamic conditions are determined. The data obtained can be used for estimation of the monomer removal by thermal treatment of the polymer.

ISSN:0021-8995    

DOI:10.1002/app.1987.070330202

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

年代:1987

数据来源: WILEY

摘要:

AbstractDynamic shear experiments in the linear range of deformation and extensional tests at constant strain rate have been carried out on a linear low‐density polyethylene (LLDPE) melt and on two branched low‐density polyethylene (LDPE) melts with different amounts of long‐chain branching. Both the dynamic shear moduli and the tensile stress obey the time–temperature superposition principle. A simple model based on a nonaffine generalized Maxwell model with two relaxation times is proposed to describe the rheological behavior in elongation of these melts. Close agreement between the model and the experimental data can be obtained by adjusting the two relaxation times and the “slip parameter” of entanglements. The variations of these parameters with strain rate and their relationship with molecular structure ar

ISSN:0021-8995    

DOI:10.1002/app.1987.070330203

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe dyeing kinetics of an acid dye (C. I. Acid Blue 40) in a nylon 6 film were investigated using partition‐cell and film‐roll methods at 80°C and pHs 2.3 and 3.05. The concentration dependence of diffusion coefficient of the dye in the nylon substrate measured by both methods was interpreted in terms of parallel diffusion with biomodel sorption of the Nernst and Langmuir modes. As the concentration of dye increases, the transport of dye inside the nylon film becomes dominated by pore diffusion and surface diffusion of sorbed Nernst populat

ISSN:0021-8995    

DOI:10.1002/app.1987.070330204

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

年代:1987

数据来源: WILEY

摘要:

AbstractElectrically conducting nylon 6 films was prepared by introducing amide group or cyan group into the nylon 6 film and then introducing CuxS, which is known as thep‐type semiconductor, into the grafted nylon films. The graft copolymerization of acrylamide (AM) and acrylonitrile (AN) onto nylon 6 film was investigated using ceric salt as the initiator. The graft yield was influenced by the concentration of ceric salt, sulfuric acid and monomer, and the reaction time. The optimum conditions for the introducing of CuxSwere studied. Electrical conductivity of CuxS‐treated nylon film was found to be higher by order of 109than that of the original nylon 6 film, and then properties of the resulting modified films were investiga

ISSN:0021-8995    

DOI:10.1002/app.1987.070330205

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe kinetics of tetrabutyl titanate catalyzed transesterification of dimethyl terephthalate with poly(tetramethylene ether) glycol of various molecular weight has been studied in the presence and absence of 1,4‐butanediol. Detailed analysis of experimental data with a proposed kinetic model indicates that the equal reactivity hypothesis for functional groups is valid within a wide range of experimental conditions studied. It is also found that the reactivity of hydroxyl groups of macrodiols such as poly(tetramethylene ether) glycol is independent of the chain length of the polymer. Effect of various reaction parameters on the transesterification rate and the resulting product composition is also discusse

ISSN:0021-8995    

DOI:10.1002/app.1987.070330206

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

年代:1987

数据来源: WILEY

摘要:

AbstractSterically hindered amine groups were incorporated into poly(methy1 methacrylate) and poly(ethy1 methacrylate) by copolymerizing 2,2,6,6 tetramethylpiperidinyl methacrylate (TPMA) with MMA and EMA. The replacement of the pendant alkyl groups of the polymethacrylates by SHA groups reduced their miscibility with poly(styrene‐co‐acrylonitrile) (SAN) and with poly(α‐methyl styrene‐co‐acrylonitrile) (MSAN). The cloud points of the miscible blends indicated that the effective interaction parameter B of a blend became less negative with increasing TPMA content in the copolymer, and B was more negative for SAN blend than for a corresponding

ISSN:0021-8995    

DOI:10.1002/app.1987.070330207

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

年代:1987

数据来源: WILEY

摘要:

AbstractFor the purpose of enhancing the reinforcement–matrix interaction in carbon‐fiber‐reinforced polymer composite, mechanical and spectroscopic studies were made on the epoxy resin composite reinforced with the carbon fiber coated with thin Layer of polyimide resin. On the loss modulus and loss tangent vs. temperature curves, a subtransition appears at a temperature above the primary transition. The T‐peel strength of a laminated specimen and the fiber efficiency factors for modulus and strength are larger than those of the composite reinforced with nonpolyimide treated fiber. These results show the increased interaction between the epoxy resin and the carbon fiber coated with polyimide resin. The occurrence of specific interaction between an epoxy resin and the polyimide resin are recognized on fourier transform infrared

ISSN:0021-8995    

DOI:10.1002/app.1987.070330208

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

年代:1987

数据来源: WILEY

摘要:

AbstractEffect of polymerization temperature on the phase‐separated structure of the composite materials [P(St‐DVB)/PVC systems] prepared by copolymerization of styrene (St) and divinylbenzene (DVB) in the presence of fine poly(vinyl chloride) (PVC) powder was studied by electron microscopy and dynamic mechanical test. P(St‐DVB)/PVC systems have the two‐phase nature with a styrene‐divinylbenzene copolymer as the continuous phase [P(St‐DVB) phase) and a PSt/PVC composite as the dispersed phase (PSt‐PVC phase), in which PSt penetrates into the PVC domain. The crosslinking density of the P(St‐DVB) phase is larger than that estimated from the recipe in the feed, suggesting that there exists a difference of the diffusion constants of styrene and divinylbenzene into the PVC particles on the paste formation and the polymerization process. The changes of the phase‐separated structure of P(St‐DVB)/PVC systems polymerized at various temperatures are also explained on the basis of the difference between the diffusion behavior of styrene and that of divinylbenzene into fine PVC particles at

ISSN:0021-8995    

DOI:10.1002/app.1987.070330209

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

年代:1987

数据来源: WILEY

摘要:

AbstractNylon‐6 grafted polyacrylamide (NYgAM) membranes were modified by crosslinking and/or annealing with 65% aqueous solution of formic acid at room temperature. The permselectivity properties of the treated NYgAM membranes to a number of ionic solutes of varying molecular size ranging from HBr to tetrabutylammoniumbromide (Bu4NBr) were studied in the temperature range of 27–47°C. The temperature dependence of the permeation coefficients through the cross linked membranes indicates an apparent energy of activation of 6.6 and 11.3 kcal/mol for HBr and Bu4NBr, respectively. In the crosslinked and annealed membranes the corresponding activation energy values were found to range from 4.4 to 5.6 kcal/mol, reflecting the increased water uptake of the annealed membranes. The flux of water and bromide solutes through the 135 μm thick crosslinked and annealed NYgAM membranes at 332% graft yield was found to be approximately equal to that of 18 μm thick cellophane films. The permeability coefficients of urea, uric acid, raffinose, and inulin through the crosslinked annealed NYgAM membranes were determined in order to establish the potential applicability of the modified membranes to clinical separation of metabolites. The flux of all four solutes, especially that of uric acid, through the modified NYgAM membranes at 100% graft yield was found to be higher than through the cellophane films. In addition, the flux of inulin was found to be strongly affected by variation in graft

ISSN:0021-8995    

DOI:10.1002/app.1987.070330210

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

年代:1987

数据来源: WILEY