摘要:

AbstractSynthesis of a series of novel terpolymers, consisting of two electron‐donating monomers, viz.N‐vinyl pyrrolidone (N‐VP) (heterocyclic polar monomer) and styrene (Sty) (non‐polar monomer), with one electron‐accepting polar monomer, i.e. acrylonitrile (AN), using α,α'‐azobisisobutyronitrile as radical initiator and benzene as diluent at 60°C, has been extensively surveyed. Besides the synthesis, an attempt has been made to study the kinetics and various properties of the terpolymers, such as softening temperature and chemical resistance. The system follows non‐ideal kinetics and the kinetic equation for the present system can be written asThis non‐ideality can be explained on the basis of significant initiator‐dependent termination through primary radicals and degradative chain transfer to acrylonitrile monomer. The overall energy of activation is 72.4 kJ mol−1andkp2/ktis 0.26 × 10−3litre mol−1s−1.The effects of various additives such as imidazolium‐p‐chlorophenacylide (ICPY) and ZnCl2were also studied. ICPY functions as a chain transfer agent (Ctr= 0.43 × 10−4), whereas ZnCl2accelerates the rate of reaction. IR spectroscopy was used to conf

ISSN:0959-8103    

DOI:10.1002/pi.4990310302

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWater resistance of particulate fly‐ash‐epoxide composites, cured at low temperature by means of synthetic polyalkylenepolenepolyaminophenolic products, was tested at room temperature. Siliceous fly‐ash (20% w/w) as filler reduces water penetration into the matrices, while saturation with water does not strongly affect the properties of the composites. The low value of the water diffusion coefficient through the material and the high mechanical properties of the particulate composites suggest further experimentation for its application in the confinement of low and medium activity nuclear wastes or of toxic chemical w

ISSN:0959-8103    

DOI:10.1002/pi.4990310303

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFree‐radical‐initiated linear cyclopolymerization of a symmetrical non‐conjugated divinyl monomer, viz.N,N'‐methylenebisacrylamide, was carried out using cerium sulphate as initiator and malic acid as activator, in an inert atmosphere at 25 ± 0.1°C. A gel‐free polymer was formed under the experimental conditions. The order with respect to malic acid and monomer was found to be 1 and 2, respectively. The rate of polymerization was found to be inversely proportional to the concentration of Ce(IV). The overall energy of activation was found to be 25.5 kJ mol−1. An intramolecular cyclization prior to propagation is proposed in formulating a suitable mechanism to explain the ki

ISSN:0959-8103    

DOI:10.1002/pi.4990310304

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDi(2‐hydroxy propane methacrylate) ester of adipic acid (DAP) was prepared by reacting adipic acid with glycidyl methacrylate using triphenyl phosphine as catalyst. The kinetics of bulk polymerization of the prepared compound using benzoyl peroxide as initiator were determined using isothermal differential scanning calorimetry (DSC). The kinetic order of the reaction (order exponentnand autocatalytic exponentm) and apparent reaction rate constant (k) were determined. The kinetics of radical‐initiated photo‐polymerization of DAP were also studied by differential photocalorimetry (DPC), using benzophenone as initiator. The rate of reaction was found to be much higher in radical‐initiated photo‐polymerization than in radical‐initiated thermal pol

ISSN:0959-8103    

DOI:10.1002/pi.4990310305

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects on chemical and physical properties of PET (poly(ethylene terephthalate)) film surfaces as a result of microstructuring induced by KrF‐laser (248 nm) radiation were investigated. On irradiation, the properties of film surfaces changed in proportion to radiation flux intensity. Close to threshold values, bulbous swellings appeared on the surface, which showed hydrophilic properties. At the threshold and above, regular rippling was seen, and the surface showed hydrophobic properties. Excimer laser irradiation induced chemical modification of the surface, decrease in the O/C ratio, dissociation of ester binding and amorphism as observed by X‐ray‐induced photoelectron spectroscopic and Fourier‐transform infrared a

ISSN:0959-8103    

DOI:10.1002/pi.4990310306

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA novel approach is proposed for estimating the average molecular weight between crosslinks (M̄c) from the functionality distribution of hydroxyl‐terminated polybutadiene (HTPB). The functionality distribution of four free‐radically polymerisedHTPBprepolymers of varying hydroxyl content and molecular weight was determined by a combination of preparative and analytical gel permeation chromatography. The gumstock properties of the samples cured with stoichiometric amounts of toluene diisocyanate were not correlatable with the relative amounts of difunctional chain extender and multifunctional crosslinker present, unlike the case ofHTPBwith similar hydroxyl content and molecular weight. However, the mechanical properties and sol content could be correlated with the average molecular weight between crosslink sites, M̄c, of the cured polymer. The M̄cvalues derived by our method compare well with those of classical methods, and the observed differences are attributed to segmental entanglement. These M̄cvalues give consistently good correlation with all the gumstock properties, confirming the validity of our approach and the soundness of the techniques developed for the determination of the functionality distribution

ISSN:0959-8103    

DOI:10.1002/pi.4990310307

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThermal properties of a new semicrystalline polyimide synthesized from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and 2,2‐dimethyl‐1,3‐(4‐aminophenoxy)propane (DMDA) have been studied. Heat capacities in the solid and liquid states ofBTDA‐DMDAhave been measured. The heat capacity increase at the glass transition temperature (Tg= 230°C) is 145 J/°Cmol for amorphousBTDA‐DMDA. The equilibrium heat of fusion of theBTDA‐DMDAcrystals has been obtained using wide‐angle X‐ray diffraction and differential scanning calorimetry measurements, and is 75.8 kj/mol. Based on the information on crystallinity and the heat capacity increase atTg, a rigid amorphous fraction is identified in semicrystallineBTDA‐DMDAsamples, which represents an interfacial region between the crystalline and amorphous states. In particular, this fraction increases with the crystallinity of the sample, which should be associated with crystal sizes, and therefore with crystal morphology. It has also been found that this polymer has a high‐temperature crystal phase upon annealing above its original melting temperature. The thermal degradation activation energies ofBTDA‐DMDAin nitrogen and air are determined to be

ISSN:0959-8103    

DOI:10.1002/pi.4990310308

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe template polymerization of chromium acrylate (CrA3) with poly‐(vinyl acetate) (PVAc, M̄v= 56 265) at 90 ±0.1°C for 2 h in dimethylformamide has been studied dilatometrically to examine the effects of concentration and average molecular weight of template, and of monomer concentration upon the kinetics and mechanism of template polymerization. The viscometric measurements showed that the complexation between poly‐CrA3and PVAc was at a maximum when the template/polymer ratio was 1:1, and the time required for complete complexation was 8 min. The value of the coefficient of interaction (KAB) between the two polymers was high for DMSO, medium for DMF and low for dioxane, and is a direct function of the polarity of the solvent. TheKABvalues indicate that an interaction, which consists of van der Waals forces and hydrogen bonding, exists between the polymers. The overall activation energy was 72.1 and 57.3 kJ mol−1in the absence and presence of PVAc, resp

ISSN:0959-8103    

DOI:10.1002/pi.4990310309

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPhenol novolac/4‐hydroxyphenylmaleimide (HPMI) homopolymer (PHPMI) blends or phenol novolac/HPMI‐styrene copolymer (HPMI‐St) blends were used as the hardener of epoxy resins. Curing behaviour of the above systems and thermal and mechanical properties of the cured epoxy resins were studied. It was not necessary to use a curing accelerator for this system because PHPMI or HPMI‐St had an accelerating effect on the curing reaction. Curing behaviour was investigated by measurement of gelation time(JIS K 6910) and differential scanning calorimetry thermogram (JIS K 7122). Test pieces made from neat resins and from reinforced resins with glass fibre or fused silica were evaluated in terms of thermal and mechanical properties, respectively. It was found that the heat resistance and the mechanical properties improved with increase of PHPMI or HPMI‐St content in the

ISSN:0959-8103    

DOI:10.1002/pi.4990310310

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe influence of thermoplastic polyurethane (TPU) elastomer on the rigidity of polyacetal (polyoxymethylene, POM) was studied by determining heat deflection temperature (HDT). The higher the content of TPU in the POM/TPU blend, the lower the HDT of the blend, as would be expected. A comparative study of the recycle capability of POM and the blends was carried out by measuring melt flow index (MFI) on each successive extrusion. Stress‐strain behaviour of the virgin material and that obtained after fourth‐time extrusion was analysed for POM and the blends. The effect of γ‐radiation on the mechanical behaviour of the blends was investigated. The kinetics of thermal degradation of POM, TPU and their blends was studied. The kinetic parameters, viz. activation energy and the order of reaction, were established. The values of the activation energy of the blends were found to be higher than those of the POM and TPU, indicating improved stability of the resultant

ISSN:0959-8103    

DOI:10.1002/pi.4990310311

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY