ISSN:0007-1641    

DOI:10.1002/pi.4980010101

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractFor most applications of polymer products, the modulus or stiffness, i.e. resistance to deformation under load, is of prime importance. The mechanical losses or damping reveal molecular movements of small groups of atoms, which movements can be significant for the impact strength.This review illustrates the effect of crosslinking, polarity, and steric features of both side‐groups and main molecular chain on both shear modulus and damping as functions of temperature.The examples are mainly taken from commercial or recently developed polymers.It is concluded that the most promising way of increasing the softening temperature of thermoplastics is to introduce rings into the main molecular chai

ISSN:0007-1641    

DOI:10.1002/pi.4980010102

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA technique has been developed by which molecular weight averages and distributions may be obtained for polymer fractions of high molecular weight.For glassy amorphous polymers, very dilute solutions in solvent‐precipitant mixtures are atomised on to a thin carbon substrate, shadowed with platinum‐carbon mixture and examined in the electron microscope. A solvent is chosen which is more volatile than the precipitant, so that on the path from the atomiser system to the substrate, and on the substrate itself, preferential evaporation of the solvent takes place. Contacts between polymer segments become more favourable than polymer‐solvent contacts, resulting in the progressive contraction of the molecular coils, and the deposition of single spherical self‐supporting molecules, the diameters of which can be determined from the lengths of the shadows cast by them.Molecules of polymers having glass transition temperatures below room temperature, or even slightly above, show varying degrees of collapse when prepared at room temperature. A device has been constructed which allows such polymer molecules to be deposited and shadowed at temperatures down to −100°, at which temperature molecular collapse is not apparent. Molecular diameters may then be measured as for glassy polymers. An atomiser‐separator system was constructed, which produced small droplets containing, essentially, one or zero polymer molecules, when a fraction of high molecular weight was used. All the solvent was evaporated from the droplets on the path to the cooled substrate, allowing the deposition of solvent‐free molecules.Molecular weight averages and distributions are presented for a series of high‐molecular‐weight polymer fractions, in the glass transition temperature range from 100° to —73°. The high precision of the results from this technique is demonstrated, together with the close agreement between molecular weight averages obtained by electron microscopy, and those obtained by light‐s

ISSN:0007-1641    

DOI:10.1002/pi.4980010103

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe possible course of methylotation and subsequent crosslinking steps in melamine‐formaldehyde resins has been investigated by using two model compound systems, viz., 2‐amino‐4, 6‐diphenoxy‐s‐triazine and 2‐amino‐4, 6‐diphenyl‐s‐triazine. The reactions of these models with formaldehyde and the secondary thermally induced condensation reactions have been examined, in particular, by the use of thin‐layer chromatography and by nuclear magnetic resonance and infra‐red spectroscopy. Methylolated products crosslink by forming ether and methylene bridges at ∼120°, the former being readily converted to the latter when the temperature is varied to ∼135°. Ether bridge degradation releases formaldehyde which further reacts in part at available N—H sites. The conversion of ether bridges to methylene bridges is enhanced by the attachment of p

ISSN:0007-1641    

DOI:10.1002/pi.4980010104

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractPrevious work has shown that the intermediates in the formation of resins from phenol and formaldehyde— the 2,2′‐, 2,4′‐ and 4,4′‐dihydroxydiphenylmethanes can only be isolated from the reaction products in small yields and with difficulty.It is now shown that after distillation of excess phenol and formaldehyde from the initial reaction mass at atmospheric pressure, a further high‐temperature steam distillation yields approximately 60% of the remaining product as white crystalline dihydroxydiphenylmethanes, 20% as triphenylols varying from hard crystalline masses to slowly crystallising oils, and 20% of fusible and soluble novolac resin of high melting point.Some lens‐shaped crystals w

ISSN:0007-1641    

DOI:10.1002/pi.4980010105

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe adhesion of PVC to various steel surfaces has been studied using a simple peel test apparatus. The effects of surface cleanliness, phosphate coatings, and oxide films on adhesion have been studied, and studies of oxide film thickness indicate that forces other than those usually considered in models of adhesion may be operative.

ISSN:0007-1641    

DOI:10.1002/pi.4980010106

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractA Fischer—Tropsch paraffin wax of high molecular weight, congealing point 205°F (96·1°C), was crosslinked with dicumyl peroxide as initiator. At peroxide/wax molar ratios of less than 1·15 : 1, crosslinked waxes with molecular weights up to approximately double that of the starting material are obtained. These products are characterised by an increase in elasticity. At peroxide/wax ratios greater than 1·15 : 1 insoluble and infusible gels are formed. The efficiency and fate of the initiator and possible side reactions are dis

ISSN:0007-1641    

DOI:10.1002/pi.4980010107

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractTwo weakly basic anion exchangers have been investigated for the selective uptake of cations. The cashewnut‐ shell liquid ‐ tetraethylene pentamine resin absorbs copper, nickel and cobalt at different pH of external solution. The unbuffered melamine‐based resin was specific for copper, which could be separated from nickel and cobalt compl

ISSN:0007-1641    

DOI:10.1002/pi.4980010108

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980010109

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY