摘要:

AbstractCarboxymethyl‐2‐diethylaminoethylcellulose (CM‐DEAE cellulose) was prepared by etherification of carboxymethylcellulose with diethylaminoethyl chloride in a NaOH solution. The behaviour of CM‐DEAE cellulose in aqueous solution was studied by viscosity and GPC measurements. The degree of substitution (DS) and existing states of DEAE substituents were examined by the use of proton NMR, and those of the CM substituents were observed with FT‐IR. The results reveal that the reduced viscosity and apparent molecular size of CM‐DEAE cellulose vary with the concentration of sodium chloride and changes in pH and DS. These phenomena can be explained in terms of inter‐ and intra‐molecular ion

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340301

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractSpecimens of poly(methyl methacrylate) (PMMA): poly(chlorotrifluoroethylene) (PCTFE) polyblends with different weight percentage ratios were subjected to electron beam irradiation (1–10 Mrad). The effect of irradiation on the strength of the blend specimens was studied by measuring the surface microhardness using a Vicker's microhardness tester attached to a Carl Zeiss NU 2 Universal research microscope. Significant changes were observed in the Vicker's hardness number,Hv. An irradiation dose of 3 Mrad was found to enhance greatly the microhardness level of the specimens. An increase of approximately 78% in microhardness was observed as the radiation dose was increased from 1 to 3 Mrad. Electron irradiation was also found to induce crosslinking and degradation in the material. The degree of crosslinking was found to be maximum at a dose of 3 Mrad. Specimens incorporating 10 wt% PCTFE were found to exhibit the highest level of microhardness at all radiation dose

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340302

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractSmall‐angle X‐ray scattering (SAXS) data have been used to deduce the localization of organic additives in the bulk of isotactic polypropylene (iPP). The results have shown that changes in the thickness of a transition layer are not directly connected with the introduction of additives but with the content of the hexagonal β‐form. This leads to the conclusion that the additives are placed in the amorphous phase in spite of their crucial influence on the formation of the crystalline phase

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340303

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe flow behaviour of a polyester in various solvents was studied at temperatures ranging from 10 to 80°C. The practical data obtained from the temperature dependence of limiting viscosity number [η] were used to calculate unperturbed dimensions and interaction parameters of the polyester resin in poor, moderate and good solvents. The data provided information regarding conformational transitions in the polymer chains in terms of exothermic or endothermic local ordering of solvents on resin segments and their fixation on polymer coils. The temperature dependence of unperturbed dimensionsKe, Flory–Huggins interaction parameter χ12, the second virial coefficientA2, entropy parameterU1, enthalpy parameterK1, and viscosity expansion factor αn, has been used to estimate the solvent quality for the

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340304

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractInterpenetrating polymer networks (IPNs) of castor oil‐based polyurethanes and polystyrene were prepared by simultaneous polymerization. The liquid prepolyurethanes were formed by reacting the hydroxyl functionality of castor oil with isophorone diisocyanate using different stoichiometric NCO/OH ratios. These prepolyurethanes were mixed with styrene monomer and subsequently polymerized by free radical polymerization initiated by benzoyl peroxide in the presence of the crosslinker 1,4‐divinyl benzene. The interpenetrating polymer networks. PU/PS IPNs, were obtained as tough and transparent films by the transfer moulding technique. These IPNs were characterized by the static mechanical properties (tensile strength, Young's modulus and % elongation), thermal properties and morphology. The dielectric relaxation properties (σ,E′,E″ and tanδ) of the IPNs at different temperatures wer

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340305

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

Abstract2‐Pyrimidyl acrylamide (2PA) monomer was prepared by the reaction of 2‐aminopyrimidine with acryloyl chloride. Its structure was confirmed by IR,1H NMR, and MS spectroscopy. Binary copolymerizations of this new monomer with methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BuA), methyl methacrylate (MMA), vinyl acetate (VA), and acrylonitrile (AN) were performed in tetrahydrofuran, using 1 mol% azobisisobutyronitrile as initiator at 65°C. N analysis and1H NMR spectroscopy were used to determine the composition of the copolymers. Copolymerization parameters for each system were calculated by both the Fineman&Ross and Kelen&Tüdös methods. The monomer reactivity ratios for the systems 2PA–MA, 2PA–EA, 2PA–BuA, 2PA–MMA, 2PA–VA, and 2PA–AN were found by the Kelen&Tudos method to ber1= 0.58±0.042,r2= 1.26±0.086;r1= 0.63±0.041,r2= 1.04±0.072;r1= 0.88±0.051,r2= 0.99±0.069;r1= 0.43±0.021,r2= 1.60±0.094,r1= 0.69±0.051,r2= 0.084±0.088; andr1= 0.065±0.008,r2= 2.54±0.220, respectively. The averageQandevalues for 2PA were found to

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340306

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractPolymerizations of methyl methacrylate (MMA) and acrylonitrile (AN) were carried out in aqueous nitric acid at 30°C with the redox initiator system ammonium ceric nitrate–methyl cellosolve (MC). A short induction period was observed, as well as the attainment of a limiting conversion for polymerization reactions. The consumption of ceric ion was first order with respect to Ce(IV) concentration in the concentration range (0.5–3.0) × 10−3MCe(IV), and the point at higher concentration deviated from the graph. Plots of the inverse of the pseudo‐first order rate constant for ceric ion consumption, [k′]−1, versus [MC]−1gave straight lines with non‐zero intercepts for both monomer systems, suggesting complex formation between Ce(IV) and MC. Complex formation between Ce(IV) and reducing agent was also detected by a shift in the absorption maximum of Ce(IV), using a Beckman spectrophotometer. The rates of polymerizations increased with increase in Ce(IV), MC and monomer concentrations; however, at higher concentration of AN (0.2187M) a steep fall inRpwas observed for AN polymerization. The orders with respect to Ce(IV), MC and monomer for MMA polymerization were found to be 0.22, 0.35 and 1.73 respectively. The orders with respect to Ce(IV), MC and monomer for AN polymerization were found to be 0.56, 0.30 and 1.30 respectively. Maintaining constant nitrate ion in the reaction medium did not significantly change the rate of polymerization with [Ce(IV)], but a fall inRCewas observed. A kinetic scheme involving oxidation of MC by Ce(IV) via complex formation, whose decomposition gives rise to a primary radical, initiation, propagation, and termination of the polymeric radicals by bimolecular interaction, is proposed. An oxidative termination of primary radicals by Ce(IV)

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340307

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper deals with protein microencapsulation by coacervation of poly(lactide‐co‐glycolide) solutions in CH2Cl2induced by the addition of silicone oils of various viscosities.This coating technique proceeds along three steps: phase separation of the coating polyester, adsorption of the coacervate droplets around the protein phase, and hardening of microparticles. Size distribution, surface morphology and internal porosity of the final microspheres clearly depend on the main characteristics of the coacervate, particularly the viscosity, in a direct connection with the CH2Cl2content. Indeed, the whole porosity (which may be as high as 80%), average pore size and broadness of pore size distribution decrease as the coacervate is more viscous. Hardening of the coacervate droplets is thus so fast that the organic solvent is entrapped within the polymer matrix and predetermines the internal porosity. Finally, size distribution of microspheres is bimodal in a clear relation with the coacervate viscosity. A less viscous coacervate favours smaller microspheres (within the 7–90 μm range), contaminated with a minor population of microparticles belo

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340308

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTransesterification of polycarbonate/poly(ethylene‐terephthalate) (PC/PET) blends and the reaction extent were investigated by DSC, FTIR,1H NMR and Soxhlet extraction. A new characteristic peak appeared in the FTIR spectrum of PC/PET blends after heat treatment, which indicates that new copolymers were formed in the transesterification of the PC/PET blends. The reaction extent was characterized by the absorbance ratios of the FTIR characteristic bands. The reaction extent was associated not only with the reaction conditions but also with the composition of the blends. These results were confirmed by chemical analysis of the extracted products in CH2Cl2solvent and FTIR analysis. For all the blends studied, the blend with 50/50 wt% had the highest reaction extent. The reaction mechanisms and extent were also confirmed by1H NMR analysi

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340309

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of transesterification on the compatibility of polycarbonate poly(ethylene terephthalate) (PC/PET) blends and the crystallization and melting behaviour of PET was studied. The results show that with increase of the reaction extent, the compatibility of the blends was enhanced during melt‐processing, from completely incompatible to partially compatible, then to complete compatibility. In addition, with the increase of reaction extent, the crystallization ability and crystallinity of PET decreased. A new endotherm peak was discerned in DSC thermograms and its position and peak area were closely related to the reaction conditions, which was explained by the changes in the crystalline regions in the PC/PET blends. The effect of transesterification on the multiple melting behaviour of PET in PC/PET blends is also discusse

ISSN:0959-8103    

DOI:10.1002/pi.1994.210340310

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY