摘要:

AbstractThe scope of thermal methods and their application to polymeric substrates are reviewed. The general application of these methods to polymers is discussed and illustrated by reference to: (i) the problems associated with thermal methods and the apparatus used to obtain thermal responses; (ii) the problems associated with calibration and the standardisation of reporting procedures; (iii) the specific problems associated with polymeric materials. Problems associated with crystallinity determinations and thermal stability assessment are also discussed.

ISSN:0007-1641    

DOI:10.1002/pi.4980110302

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractRates and extents of cure at different times and temperatures are determined for a modified epoxy resin system and related to gel time measurements. An empirical equation based on time‐temperature superposition determines cure time as a function of degree and temperature of cure. The dependence of glass transition temperature on degree of cure, and heat capacity measurements on the cured resin, are discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980110303

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980110304

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe heat capacity of an amorphous polymer is insensitive to molecular and processing variables except in the glass transition region. Here DSC shows a variety of potentially confusing curves that result from a coupling of instrumental‐ and sample‐based rate effects. The curves can be simply analysed to give true glass temperatures that characterise the method of glass format

ISSN:0007-1641    

DOI:10.1002/pi.4980110305

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractDifferential scanning calorimetry (DSC) has been used in the study of a series of hydrogels in an attempt to correlate water binding and transport properties. DSC and oxygen transport studies were carried out on a series of styrene‐2‐hydroxyethyl methacrylate copoly‐mers. The transport of dissolved oxygen through those copolymers that contained no freezing water was found to be negligible in comparison to those in which both freezing and non‐freezing water was present. This correlates well with the observation that the dense layer of asymmetric cellulose acetate reverse osmosis membranes was found to contain little or no free water.On this basis, the use of DSC in the design of a hydrogel that contains little or no freezing water (to promote salt rejection) with a reasonably high total water content (to maximise water flux) for use in reverse osmosis, is described. The resultant copolymer of acrylamide, methacrylic acid and styrene has a total equilibrium water content (30 per cent) that is twice that of a typical dense cellulose acetate used in reverse osmosis and a very low (<1 per cent) freezing water content.Examination of the fine structure of the melting endotherms and freezing exotherms associated with various hydrogels shows several interesting features which are interpreted in terms of the existence of a continuum of water states. These range from water that is unaffected by its polymeric environment to water (on average two or less molecules per monomer repeat unit) that is hydrogen bonded to functional groups in the

ISSN:0007-1641    

DOI:10.1002/pi.4980110306

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractMethods for determining the crystallisation characteristics of polymer by differential scanning calorimetry are discussed, particularly in terms of their limitations. Isothermal and non‐isothermal crystallisation thermogrphs are analysed to determine crystallisation mechanism and compared with other techniques. The inadequacies of current theories of crystallisation rates are developed. Melting studies on oligomers and polymers are developed in terms of recent theories of melting, and a method suggested for quantifying the quality of crystallinity in polymeric material in terms of the averages of the lamellae thicknes

ISSN:0007-1641    

DOI:10.1002/pi.4980110307

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractAn examination of the effect of various inorganic and organic additives on the crystallisation behaviour of polyethylene terephthalate has been made. Various methods of mixing the polymer and additives were also investigated and one involving screw extrustion was finally adopted. Crystallisation studies were carried out using Differential Scanning Calorimetry under dynamic and isothermal modes covering both normal and cold‐crystallisation conditions. Using screw extrusion mixed material it was found that almost all additives produced some nucleating effect as indicated by an increase in the rate of crystallisation. In particular, sodium benzoate and sodium stearate (1 per cent w/w) had the greatest effect, decreasing the initial cold‐crystallisation temperature and increasing the temperature of equivalent half‐times of isothermal crystallisation, both by about

ISSN:0007-1641    

DOI:10.1002/pi.4980110308

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980110309

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe experimental requirements for ultraviolet and fluorescence microscopy are briefly discussed. The application of these techniques to polymers usually depends upon the use of some form of staining reagent to develop contrast within the polymer and three variations of this principle are described. In the first, ultraviolet absorbing or fluorescent additives are monitored during spherulitic crystallisation of a polymer with quantitative results which demonstrate rejection of the additive by the crystalline polymer and allow the diffusion coefficient for the additive in the molten polymer to be estimated. In the second application, the equilibrium distribution of absorbing additives after crystallisation is used to reveal crystallinity variations within the sample and to study the influence of non‐crystallisable fractions upon these variations. Finally, reaction of carbonyl groups, with fluorescent or absorbing reagents, in oxidised polymers, has been investigated as a way of revealing uneven oxidation in polypropylen

ISSN:0007-1641    

DOI:10.1002/pi.4980110310

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980110311

出版商:John Wiley&Sons, Ltd    

年代:1979

数据来源: WILEY