摘要:

AbstractPoly(ethylene aspartate) [PEA] was synthesized by the melt condensation of D,L‐aspartic acid and ethylene glycol. PEA containing pendent amino and carbonyl groups in its repeating chain was used as the polymeric ligand for complexation with transition metal ions, viz. Co(II), Ni(II), Cu(II), Mn(II), Zn(II), Cd(II), Ca(II), Mg(II), Pb(II) and Hg(II). Complexation was found to be most effective in DMSO. The resulting polyester‐metal complexes were solid coloured materials which have been characterized by IR spectroscopy, elemental analysis and magnetic susceptibility measurements. The thermal stability of the polyester‐metal complexes was investigated by thermogravimetric analysis (TGA). On the basis of the physico‐chemical studies, an oxygen and nitrogen coordinated structure for the polyester‐metal complexes is

ISSN:0959-8103    

DOI:10.1002/pi.4990320302

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA large number of hydrophilic sponges were prepared by polymerisation of 2‐hydroxyethyl methacrylate in variable concentrations of water (60‐90% wt) in the initial monomer mixture. Concentration and type of crosslinking agents (ethylene dimethacrylate (EDMA) and hexamethylene dimethacrylate (HDMA)) and concentration of redox initiators were also changed. All sponges were examined in cross‐section by conventional and environmental scanning electron microscopy. Micrographs indicated that, in order to obtain sponges with characteristics appropriate for biomedical use (e.g. pores larger than 10 μm), the minimum water concentration was 75% wt with EDMA as a crosslinking agent, or 70% wt with HDMA, for contents of crosslinking agents and initiator less than 1% wt. Micrographs also showed that higher contents of crosslinking agents or initiator led to larger pores. In high concentrations of water, this effect was less evident. Microscopic details confirmed the crucial role of the phase separation during polymeri

ISSN:0959-8103    

DOI:10.1002/pi.4990320303

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractButyl acrylate was grafted onto isotactic polypropylene using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time and temperature on rates of polymerization, percentage grafting and grafting efficiency were studied. The extent of grafting achieved was 2.85%. The graft copolymers were characterized by IR, thermal, viscometric and contact‐angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymer

ISSN:0959-8103    

DOI:10.1002/pi.4990320304

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPhase separation during polymerisation was studied by taking into account in the thermodynamic analysis the generated distribution of polymer species. A model system consisting of a diepoxide based on diglycidylether of bisphenol A, a diamine and castor oil as modifier was considered. One‐and two‐step polymerisation processes were simulated (in the two‐step process a first step was carried out with an epoxy excess up to a particular conversion, stoichiometry was balanced and the reaction continued in a second step). A thermodynamic analysis for a monodisperse modifier‐epoxy/amine system was performed taking the polydispersity of the polymer into account. It was shown that the cloud point conversion was decreased when the polymerisation was carried out in two steps. This effect was enhanced for lower stoichiometric ratios (higher epoxy excesses) and higher epoxy conversions in the first step. The dispersed phase became richer in low molecular weight species than the continuous one. In particular both monomers increased their concentration in the disperse

ISSN:0959-8103    

DOI:10.1002/pi.4990320305

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPVC membranes plasticized with various concentrations of a di‐n‐alkylphthalate (methyl, ethyl, butyl or octyl) were studied for their water vapour permeation (WVP) properties. The rates of WVP through them were estimated under steady state by permeating the vapour through the membrane under the vapour pressure differential of approximately 100% to 0% relative humidities at 25°C. The rates of WVP were found to decrease with an increase in the size of the alkyl group of the phthalate but increased with its concentration. The maintenance of the property by the membranes being critical for their long‐term applications, the measurements were also repeated on the membranes aged for 250 days at intervals of 50 days. The WVP data indicate that membranes containing medium concentrations, i.e. 17.5‐20% of the plasticizers have better maintenance of the property during ageing and also in handling with good mechanical

ISSN:0959-8103    

DOI:10.1002/pi.4990320306

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractHeterogeneous sodium and potassium hydroxide‐catalysed cyanoethylation of cotton linter and viscose grade wood pulp, investigated by analysing the nitrogen content of the cyanoethylated product as a function of the time of reaction, were shown to follow a first‐order rate equation. A new procedure was elaborated and a computer program was written to estimate the number of hydroxyl groups accessible for cyanoethylation per anhydroglucose unit and the specific rate constant from the rate curves. The effect of the type of alkali, its solution‐to‐cellulose ratio, temperature of reaction, mode of agitation, and the degree of polymerisation and packing density of cellulose fibres on the kinetics of cyanoethylation reaction were inves

ISSN:0959-8103    

DOI:10.1002/pi.4990320307

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA set of 12 fully aromatic poly(amide‐hydrazides) were synthesised by the direct polycondensation phosphorylation reaction. Four different diamines containing preformed hydrazide units were condensed with three diacids in a mixture ofN‐methylpyrrolidinone and pyridine. The polymers were obtained in 70‐85% yield and characterised by infrared and elemental analysis. The thermal stability, crystallinity, density and solubility were also mea

ISSN:0959-8103    

DOI:10.1002/pi.4990320308

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTheoretical equations and a calculation method giving cloud point curve (CPC) for a multicomponent polymer 1/multicomponent polymer 2/single solvent system (i.e. quasi‐ternary system) were derived on the basis of the Flory‐Huggins solution theory. The systematic calculations based on this method were carried out to examine the effects on CPC of the type of molecular weight distribution, the polydispersity and the weight‐average degree of polymerisation of the two original polymers, and three thermodynamic interaction parameters between solvent‐polymer 1 (X01), solvent‐polymer 2 (X02) and polymer 1‐polymer 2 (X12). The shape of CPC sensitively depends on the polydispersity of the original polymer and, with an increase in polydispersity, the immiscibility region be

ISSN:0959-8103    

DOI:10.1002/pi.4990320309

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper reports a technique for the controlled bulk polymerisation of methylmethacrylate initiated by benzoyl peroxide. Due to the high exothermic nature of this polymerisation process, casting of thin sheets and profiles must generally be carried out at relatively low temperatures and over extended intervals of time at a constant rate. Curing profiles of 6‐12 h have been considered incorporating the kinetic features of polymerisation which includes a gel effect. The influence of the gel effect on the propagation and termination rate constants can be divided into two regions: one up to 20% conversion, and the other beyond it. In the first range the gel effect is independent of conversion while in the latter stage its influence is characterised by Ross‐Laurence parameters. The study indicates that no advantage is gained through the employment of two‐stage initiator loading. Curing cycles of longer duration can be generated for thicker castings from the analysis

ISSN:0959-8103    

DOI:10.1002/pi.4990320310

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTernary copolymerisations of tri‐n‐butyltin acrylate (TBTA) or tri‐n‐butyltin methacrylate (TBTMA) with itaconic acid (IA) or dimethylitaconate (DMI) andN‐vinyl‐2‐pyrrolidone (NVP) were carried out in solution at 70°C in the presence of a free radical initiator. Experimental, terpolymerisation data agreed with calculations based on the Alfrey‐Goldfinger equation. Ternary azeotropic compositions for TBTA‐IA‐NVP and TBTA‐DMI‐NVP systems were 52.60:14.80:32.60 and 56.60:26.60:16.80 mol%, respectively. Also ‘pseudoazeotropic’ regions were identified where the deviation between feed and polyme

ISSN:0959-8103    

DOI:10.1002/pi.4990320311

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY