摘要:

AbstractThe sorption of bromine from bromine water on cis‐1,4‐polyisoprene film and the initial stages of bromination are studied at concentrations of 0.002–0.1 mol/l and temperatures of 15–35°C. The diffusion coefficient of bromine into natural rubber (NR) is 1.3–2.0 × 10−6cm2/sec for the total sorption and 5–13 × 10−7cm2/sec for the irreversible sorption. The partition coefficient of bromine between water and rubber increased from 17.3 at 15°C to 37.1 l/kg at 35°C. The chemical potential, enthalpy and change in entropy of partition are, at 25°C, respectively: −1.9 kcal/mol, 6.6 kcal/mol and 28.4 cal/mol. K. The irreversible sorption is due to a charge‐transfer complex between bromine molecules and double bonds of the rubber. The complex is the first stage of the addition reaction, which becomes noticeable at concentrations above 0.012 mol/l. With increasing bromine concentration the concentration of the complex decreases and the added bromine increases. The charge transfer complex appears to change the conformation of the cis‐NR chains so that the bromine addition occurs in the trans‐conformation, as shown by FT–IR spectra. The bromination is accompanied by a marked crystallization effect as illustrated by thermal

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040801

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPhotosensitive copolymers have been obtained by chemical modification of natural rubber. The introduction of the photoreactive cinnamoyl group in different conversions has been carried out by the reaction of natural polyisoprene with maleic anhydride, followed by ring opening and condensation with some oxyalkylcinnamate esters. These reactions gave rise to five polymer series. Each series, for which the anhydride content was kept constant, is constituted of five copolymeric products, differing from each other in the size of the aliphatic chain between the chromophore and the main chain. The photosensitive products were submitted to UV irradiation, and their kinetic behavior has been investigated in order to correlate structural dissimilarities with the dimerization rate constants.

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040802

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractResults on polycondensation of poly(1.4 benzamide) (PBA) and 2.5.DCIPDAcoTPA in solutions of poly(vinylpyrrolidone) (PVP) will be presented. For polycondensation, the method of OGATA, using triphenylphosphine and hexachloroethane, and the low‐temperature solution polycondensation of dicarboxylic acid dichlorides and diamines, were applied. It is shown that the molar mass of PBA depends strongly on the PVP:PBA ratio. To explain this dependence, one has to take into account the phase behavior of the ternary rigid rod polymer/flexible coil polymer/solvent system and the influence of the matrix polymer. An enhancement of the molar mass of the PBA produced can be observed when the PVP:PBA is high enough to prevent an association of the PBA, i.e. when one stays in the isotropic one‐phase area of the phase diagram. Under these circumstances, it is possible to obtain one‐phase systems in nonsolvents for the ara

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040803

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractVinylchloride–vinylacetate–maleic acid terpolymer (VMCH) and nitrocellulose (NC) were blended at 10% (W/V) concentration is cyclohexanone at different weight fractions. Compatible blends were obtained at all weight fractions. This paper reports the mechanical behavior of solvent cast blend films of VMCH and NC. The films were prepared by solution blending and subsequent casting on a mercury surface. Depending on the composition, the tensile behavior ranged from brittle to ductile. The effect of the blend ratio on the properties shows that within the Hookeian region the modulus and strength have a positive deviation from linearity, whereas the elongation has a negative deviation. The effect of the blend ratio on the ultimate properties of the materials shows a positive deviation in strength up to 63 wt% VMCH composition and a negative deviation in elongation and toughness. The tensile fractography of the pure VMCH and VMCH/NC blends shows the presence of peaks, foldings of fibrils along with cavities or voids, which indicate a ductile mode of failure with craze‐initiated fracture. Fractography of the pure NC Indicates a brittle mode of failure wit h craze‐initiated fra

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040804

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThick films of tetra‐N‐glycidyl epoxy resin of p,p′‐diaminodiphenyl methane (TGDDM) were prepared using p,p′‐diaminodiphenyl methane (DDM), p,p′‐diaminodiphenyl sulfone (DDS) and diethylene triamine (DETA) as curing agent with or without the epoxy fortifiers PGEHA and VCDRC (at 20 phr level). These thick films were used to evaluate various physical, mechanical, chemical resistant and dielec

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040805

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPoly(vinyl alcohol) (PVA) bearing N‐(1‐pyridinio)benzamidate (PB) was synthesized through acetalization of PVA and 4‐dimethoxymethyl‐N‐(1‐pyridinio)benzamidate (DMPB) in water. The PB groups in PVA–PB had almost the same proportion of DMPB to the starting PVA. The UV spectrum of PVA–PB shows an absorption band of pyridinium ylide as a shoulder around 300 nm in water, and as a maximum at 315 nm in a film on a quartz plate. These absorption bands decreased on irradiation at 313 nm. The photoreaction of the PVA–PB film proceeds much faster than that of PVA–PB in water. The solution, of PVA‐bearing high‐PB content, became slightly turbid during irradiation. After irradiation the film became insoluble in water, and the soluble fraction of polymer (P̄ = 1700) was 3% at a PB content of 1 mol% and less than 1% at that of more than 2 mol%. This polymer can be applied as a water‐so

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040806

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040807

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:1042-7147    

DOI:10.1002/pat.1993.220040808

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY