摘要:

AbstractThe stress‐strain properties of three different rubbers have been measured using two different techniques, in order to evaluate the relative internal energy contribution to the total stressfe/fand the corresponding value ofMe/Mover a range of strain and temperatures. Two different experimental techniques have been designed; one is to allow measurement in simple extension of the length of a rubber sample in relation to the temperature at constant force, and the other is to measure the variation of torsional coupleMin a cylinder of rubber (subjected to combined torsion about the axis and extension in the axial direction) with temperature. The thermoelastic results obtained for natural rubber and butyl rubber do not contain any surprising features, and are found to be in good agreement with other reported experimental results for these rubbers. Values offe/fandMe/Mobtained forcis‐transpolybutadiene rubber show different trends between the two techniq

ISSN:0007-1641    

DOI:10.1002/pi.4980180302

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis research programme has been concerned with the technology of phenol‐formaldehyde resins and of moulding powders based on them. This paper reports the characterisation of the prepolymer (Novolak) and concentrates on the results obtained by gel permeation chromatography with an infrared detector. A variety of frequencies have been employed, corresponding to different components in the resin, and the best separation was obtained by monitoring the phenolic hydroxyl at 3400 cm−1. It has been concluded that both commercial Novolak and prepolymer extracted from moulding powder contain a substantial fraction of high molecular weight mater

ISSN:0007-1641    

DOI:10.1002/pi.4980180303

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThree poly(arylene sulphones) have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1and isothermally at a number of temperatures. The level of stability found compared favourably with that of other heat‐resistant materials, for example the addition type polyimides. The polymers have also been examined by pyrolysis gas chromatography mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the sample was subjected to successive pyrolyses at the same temperature inter

ISSN:0007-1641    

DOI:10.1002/pi.4980180304

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractHydrolysis of poly(6,8‐(1,5‐dichloro‐2,4‐dioxa‐3‐keto)bicyclo[3.3.0]octylene vinylene) results in the formation of poly(4,5‐bis‐hydroxy‐1,3‐cyclopentadienylene vinylene), a new conjugated polymer. This new system can be generated as a surface layer on its precursor polymer. The conversion process has been studied with the aid of infrared and optical spectroscopy, elemental analysis, microscopy and conduc

ISSN:0007-1641    

DOI:10.1002/pi.4980180305

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe polymerisation of methylmethacrylate initiated by alkali alkoxides is greatly promoted in the presence of macrocyclic compounds, cryptands and crown ethers. The solubility in toluene and the reactivity of alkoxides is enhanced by these complexing agents. Polymerisations have been carried out in a non‐polar solvent in the homogeneous phas

ISSN:0007-1641    

DOI:10.1002/pi.4980180306

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractHigh resolution13C n.m.r. data are presented for a series of model compounds generated by the acid catalysed reaction of either phenol or cresol with formalin. The pure compounds prepared for this study allow unambiguous identification of features associated withortho‐ortho, ortho‐para and para‐paralinked moieties, and hence allow analysis of the sequence structure in the typical resin. To aid assignment of the spectra a comparison is made between the predictions of the spectra using simple additivity relationships and the experimentally observed shifts. It is found that the differences between theory and experiment vary systematically with structure, and averaged correction factors are presented for various characteristic struc

ISSN:0007-1641    

DOI:10.1002/pi.4980180307

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe reactions of mono‐ and difunctional tertiary amine ended polybutadienes with mono‐ and difunctional living cationic poly THF have been studied. It is shown that the reaction to form quaternary ammonium linking groups takes place rapidly in all cases, and AB. ABA, BAB and (AB) block copolymers have been prepared. The efficiency of the process is extremely high and the degree of conversion is essentially controlled by the efficiency with which the terminal tertiary amine groups can be introduced on to the polybutadiene. The block copolymers show anomalous behaviour on gel permeation chromatography columns and this has been related to a specific interaction of the created ionic groups with polar species on the column packing. This effect is greatest with (AB) block copolymers where substantial proportions are retained indefinitely on the colu

ISSN:0007-1641    

DOI:10.1002/pi.4980180308

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractUltrasonic velocity and isoentropic compressibility measurements are reported on aqueous solutions of polyethylenoxide of different molecular weights and different concentrations using pulsed ultrasonic apparatus operating at 2 MHz and 310 K. The data obtained as a function of concentration indicate the magnitude of the contribution due to relaxation of the backbone of the ethylene group. The results show a linear increase of density, velocity and viscosity values with increasing molecular weight and concentration of PEO. In contrast, the isoentropic compressibility decreases with increasing of molecular weight and concentration of PEO. A mathematical equation correlating isoentropic compressibility and molecular weight of the polymer is suggested. This was applied to the calculation of the molecular weight of unknown samples of PEO from their measured isoentropic compressibility; the results obtained agreed well with those obtained from osmometry.

ISSN:0007-1641    

DOI:10.1002/pi.4980180309

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe flow characteristics of styrene‐butadiene‐styrene thermoplastic rubbers have been studied and the results compared with earlier static measurements. Computer best‐fitting shift factors and inverse Melt Flow Index were plotted according to two mathematical models, Arrhenius and Vogel. Fulcher, Tamman and Hesse (VFTH). One transition was observed in both models, with appreciable reduction in the apparent activation energy of flow above this transition. This melt transition was associated with the temperature above which the PS chains can be removed from the PS rich phase by the rubbery chains. This allows rearrangement of the domain structure in a static condition or facilitates flow. Birefringence measurements support the model pro

ISSN:0007-1641    

DOI:10.1002/pi.4980180310

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractContinuation of work on the curing characteristics of an epoxy resin which is widely used as a composite matrix is reported. Results are given of study of the cure of the resin with dicyandiamide as hardener and diuron as accelerator, using differential scanning calorimetry to monitor the cure. The effect of diuron on the cure of the resin with an aromatic amine curing agent is also described. Distinctive effects of composition are found and values of the apparent activation energy of the curing reaction are derived.

ISSN:0007-1641    

DOI:10.1002/pi.4980180311

出版商:John Wiley&Sons, Ltd    

年代:1986

数据来源: WILEY