摘要:

AbstractThe thermal stability of a phenolic‐phosphate resin, prepared by the transesterification of triphenyl phosphate and resorcinol and cured with hexamethylene tetraamine, has been compared with that of a conventional phenolic resin. Thermogravimetric analysis (TGA) of the resins, in air, demonstrated that the phenolic‐phosphate resin had the superior thermal resistance. Accordingly, to assess the performance of phenolic‐phosphate resins as thermally stable binders in composites, long‐term heating ageing studies at 250°C were carried out on asbestos‐filled moulded test specimens. The results of these tests were less welldefined than the TGA results, for the phenolic composite had the higher flexural strength (108.5 MNm−2) initially compared with 56.7 MNm−2for the phenolic‐phosphate composite. However, after 1000 h heating at 250°C neither system retained a useful level of flexural strength, although the phenolic‐phosphate composite (18.35 MNm−2) was stronger than the phenolic

ISSN:0007-1641    

DOI:10.1002/pi.4980070202

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThree samples of polystyrene‐polybutadiene‐polystyrene block copolymers have been studied by means of the light scattering technique in several solvents. The light scattering measurements indicate the degree of heterogeneity of the samples. Further measurements which were made on the least heterogeneous of the samples in a solvent closely matching the refractive index of the centre block suggest that the two types of polymer are largely separate. In this case the angular intensity variation of the light scattering can be interpreted in terms of the scattering obtained from a “dumb‐bell” conf

ISSN:0007-1641    

DOI:10.1002/pi.4980070203

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractThe mechanisms of wear in plastics are reviewed and the properties required for high wear resistance derived. The importance of determining relevant mechanical properties at meaningful temperatures and strain rates is discussed. The particular advantages of high molecular weight polyethylene for prostheses are outlined and a typical wear test on this material described.

ISSN:0007-1641    

DOI:10.1002/pi.4980070204

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractSeries of styrene‐methyl methacrylate and styrene‐methacrylic acid copolymer latices have been prepared by emulsion polymerisation using polyoxyethylene nonyl phenyl ether as emulsifier and potassium persulphate as initiator. the effects of surfactant concentration and monomer composition on the ultimate particle size and conversion were investigated. The ultimate particle diameters decreased with increasing surfactant concentration, while the conversions were found to be almost independent of surfactant concentration. The ultimate particle diameters were notably decreased by increasing the content of methacrylic acid. Trace carboxyl groups were detected both in polystyrene latex and styrene‐methyl methacrylate copolymer latices. The number of sulphate groups on the polystyrene latex surface was about five times that of carboxyl g

ISSN:0007-1641    

DOI:10.1002/pi.4980070205

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

摘要:

AbstractLuminescence techniques can be used to study polymer systems both as an analytical tool and as a means of studying molecular behaviour. In the latter context, some very interesting information may be obtained on a variety of molecular and energy transport processes. Measurements of luminescence intensity and quenching can be used to observe electronic energy transfer processes (both along polymer chains and from polymer chains to additive molecules). These have a technical importance in that they are the photophysical processes which precede the chemical phenomena important in photodegradation or photostabilisation of polymers. The basic criteria for energy transfer are introduced and examples are given of “down‐chain” energy migration coefficients for a number of polymers. Studies of the depolarisation of luminescence can be used as a measurement of rotation in the electronic excited state of the photoactive group. Fluorescence depolarisation is introduced and examples are given of processes with nanosecond relaxation times. The concept of phosphorescence depolarisation is also mentioned, and the first use of this to study processes with millisecond relaxation times is illust

ISSN:0007-1641    

DOI:10.1002/pi.4980070206

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980070207

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980070208

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980070209

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980070201

出版商:John Wiley&Sons, Ltd    

年代:1975

数据来源: WILEY