摘要:

AbstractDrawing of quenched polyethylene at 60°C transforms the spherulitic sample into a material with fibrous structure. As a consequence, the sorption and still more the diffusion of C2Cl4vapours are drastically reduced. Annealing at 120 and 125°C increases the crystallinity and hence reduces the amount of the amorphous component. In spite of that, it enormously increases the transport properties. It restores the sorption per unit volume of amorphous component to a value which, corresponding to completely relaxed amorphous component, is even higher than that of the starting undrawn but quenched material. The diffusion constant after annealing is a little smaller than in the undeformed original sample and shows the same small dependence on concentration in striking contrast with the drawn material. One concludes that the restoration by annealing of the sorption and diffusion coefficients for drawn polyethylene to the values of the undrawn material is a consequence of the complete relaxation of polyethylene chains, in particular of tie molecules, in the amorphous component which completely overcompensates the effects of a reduced amorphous fraction and the increase in crystal perfectio

ISSN:0007-1641    

DOI:10.1002/pi.4980040402

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe introduction of very sensitive detectors and the use of phase modulation has enabled interferometric spectroscopy to be extended downwards in frequency until the spectral coverage overlaps that provided by microwave dielectric methods. The radiometric precision available has been steadily improved by taking advantage of both instrumental and computational advances and the accuracy which can now be attained is comparable to that of dielectric or mid‐infrared methods. Both the real and the imaginary components of the complex dielectric constant (or the complex refractive index) can now be obtained for moderately transparent materials over the millimetre and submillimetre bands for a wide range of specimen temperature, and reflectance methods have been developed for the study of heavily absorbing specimens. The far infrared band is particularly appropriate for the study of high polymers. With these instrumental innovations considerable advances may be expected in the understanding of molecular motion in these material

ISSN:0007-1641    

DOI:10.1002/pi.4980040403

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractBy means of a disc centrifuge it is possible quickly and easily to separate the components of particulate mixtures of polymers and copolymers having different densities. The technique has been applied to mixtures and copolymers of PVC and PMMA, and PE and PVAc, but is believed to be of general application.

ISSN:0007-1641    

DOI:10.1002/pi.4980040404

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractPolyamide–polydimethylsiloxane block copolymers were made by the BuLi or LiOSi(CH3)2OSi(CH3)2OLi catalysed polymerisation of hexamethylcyclotrisiloxane terminated by and using this substituted siloxane to initiate the polymerisation of lauryllactam or caprolactam in toluene solvent in the presence of lithium aluminium hydride as the catalyst.One or 2% of the polycaprolactam‐polydimethylsiloxane block copolymers were mixed with nylon 6 and discs moulded. The presence of silicone in the surface was demonstrated by determining the critical surface tensions of wetting using ethanol–water mixtures as the contact‐angle test liquids. A polylauryllactam–polydimethylsiloxane block copolymer compatible with polyethylene was similarly studied.An important application for such composites is to provide a dry lubricated surface, therefore the kinetic coefficients of friction of steel against these copolymer‐treated nylon 6 samples were determined demonstrating at best a reduction to one third that of the untrea

ISSN:0007-1641    

DOI:10.1002/pi.4980040405

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe application of polyelectrolyte flocculants as primary coagulants, coagulant aids and sludge conditioners in the treatment of water for public supply is discussed. Laboratory techniques that have been used to evaluate commercial polyelectrolytes for these uses are described and exemplified with results. The difficulty of defining floc characteristics is emphasised.

ISSN:0007-1641    

DOI:10.1002/pi.4980040406

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThermovolatilisation analysis has been used as part of an investigation of the flammability of an insaturated polyester resin. It was clearly possible to distinguish two reaction stages which were attributed to breakdown of the styrene and polyester chains respectively and in neither case did flame retardants affect the reaction very much.

ISSN:0007-1641    

DOI:10.1002/pi.4980040407

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe nature of the catalysts for the ring‐opening polymerisation of cycloolefins is reviewed with particular reference to the production of trans‐polypentenamer. The roles of the components of the catalyst systems are discussed and a mechanism for the ring‐opening polymerisation of cycloolefins is pro

ISSN:0007-1641    

DOI:10.1002/pi.4980040408

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractAn apparatus is described which permits reasonably uniform heat treatment of fairly large samples of PVC blends in controlled atmospheres, at preset temperatures, and for predetermined lengths of time. Experiments are described in which portions of a plasticised PVC blend, and also portions of an unplasticised PVC blend, were heated under nitrogen at 180 °C for various lengths of time up to those stages when Congo Red tests showed hydrogen chloride to be liberated. Each blend contained the basic lead carbonate “plumbonacrite”, 6PbCO3. 3Pb(OH)2.PbO, as stabiliser, and stearic acid as milling lubricant. Carbon dioxide evolved during the stabilising reactions was measured, and the crystalline solids in each heated PVC blend sample were studied by X‐ray diffraction.The results obtained show that the plumbonacrite stabiliser in each PVC blend was used continuously and completely during the effective stabilisation period. The rates of carbon dioxide evolution were found to differ markedly between the plasticised and unplasticised blends, but in each case they could be described in terms of first order reaction kinetics. Correlation of these carbon dioxide measurements with the X‐ray diffraction results led to the conclusion that the stabilising reactions in the plasticised PVC blend took place mainly in solution, whereas these reactions in the unplasticised PVC blend seemed to take place within the plumbonacrite crystals themselves.It is shown that these findings are consistent with previous work in these laboratories which has led to the idea that soluble lead compounds are formed by reaction of the basic lead stabiliser crystals with stearic acid milling lubricant, and that these compounds are in some way responsible for stabilising polyvinyl chloride against thermal decomposition. Further, it is suggested that the present results show that basic lead compounds act as thermal stabilisers for PVC in the true sense of the word. Considering in particular a radical chain mechanism for the thermal dehydrochlorination of polyvinyl chloride, a theory is proposed which explains how basic lead compounds can stabilise this

ISSN:0007-1641    

DOI:10.1002/pi.4980040409

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040410

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040412

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY