摘要:

AbstractProcedures for the determination of the log molecular weight vs. elution volume calibration relation are reviewed for linear homopolymers. The calibration curve is readily established with narrow molecular weight distribution fractions. For broad molecular weight distribution fractions the peak molecular weight at the peak elution volume of a fraction's gel permeation chromatogram has to be calculated from average molecular weights. When well‐characterised fractions of the polymer requiring analysis are unavailable, a calibration curve can be established by procedures which assume that the hydrodynamic volume of a polymer molecule in solution controls fractionation in gel permeation chromatography. These universal calibration procedures require information on Mark‐Houwink viscosity constants or polymer unperturbed dimensions. The validity of hydrodynamic volume as the universal calibration parameter is discussed with special reference to the goodness of the solvent for a polymer and polymer polarity. Examples are given of the various calibration procedures which are employed in the determination of molecular weight distribution and average molecular weights for poly(methylmethacrylate), polyethylene and polyisopr

ISSN:0007-1641    

DOI:10.1002/pi.4980040202

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe reaction between chlorophosphazenes and triethyl, tri‐n‐butyl and acid ethyl phosphates has been studied as a means of preparing temperature‐stable thermosetting resinous materials. Ethyl orn‐butyl chlorides were eliminated (together with hydrogen chloride in the case of acid ethyl phosphate) and thermosetting resinous products were obtained. The products are film forming when stoved in air. Asbestos laminates, which retain up to 64% of their strength when heated to 500 °C for 50 h in air, have been made with the thermosetting resinous products obtained from the reaction between a chlorophosphazene and triethyl or tri‐n‐buty

ISSN:0007-1641    

DOI:10.1002/pi.4980040203

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractDetermination of the sedimentation–diffusion equilibrium is one of the methods furnishing data on the thermodynamic parameters of polymer solutions. By means of this procedure measurements can be performed over a considerable range of concentrations.The equilibria in the ultracentrifuge have been determined for five polystyrene samples of narrow distribution covering the molecular weight range 2 × 104to 2 × 106, at concentrations up to 40 wt‐% and at temperatures of 30, 45 and 65 °C.The results are expressed in the data for the chemical potential of the solvent, the number‐average chemical potential of the polymer and the interaction parameter ξ. The results are compared with those obtained from osmotic pressure, light scattering and critical miscibility measurements. At very low concentrations the molecular weight dependence of the interaction parameter is in agreement with literature values derived from osmotic pressure and light scattering figures. At higher concentrations this molecular‐weight dependence decreases sharply but remains noticeable up to 40% co

ISSN:0007-1641    

DOI:10.1002/pi.4980040204

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractIt has been observed that cyclic phosphoramidites react more slowly than triphenylphosphine with diallyldisulphide and do not give a quantitative yield of monosulphide. Therefore, contrary to expectation, these reagents are unsuitable for use as chemical probes for determining the structure of sulphurvulcanised rubber. It appears that, like triphenylphosphine, the cyclic phosphoramidites react with allylic disulphides by a SNi' mechanism.

ISSN:0007-1641    

DOI:10.1002/pi.4980040205

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractElastic fibres soluble in dimethylformamide were made from essentially linear polyester‐ and polyetherurethanes. The molecular structures of the polyurethanes were varied by using as chain extenders aliphatic diamines with a successively increasing number of carbon atoms. Mechanical investigations resulted in modulus, stress relaxation and creep data which oscillated with increasing number of carbon atoms of the diamines used. These results and the temperature‐ and time‐dependence of these data can be explained by a model proposing the existence of hard segment domains in a matrix of soft but crystallisable polyester or polyether mat

ISSN:0007-1641    

DOI:10.1002/pi.4980040206

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA model is developed for the degradation of fibre‐forming high polymers. Overall degradation is divided into three types of degradation: (i) thermal degradation based on the mean residence time; (ii) thermal degradation in the boundary layers caused by a prolonged residence time at the walls; (iii) degradation induced by mechanical effects (this type of degradation occurs, in particular, at low temperatures, i.e. at high dynamic viscosities, since it is proportional to the shear stress). In an example, the degradation in a pipe is reduced to a minimum. It is stated that an optimum value can always be fixed for the tube diameter and the operating temperatur

ISSN:0007-1641    

DOI:10.1002/pi.4980040207

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe similarity of frequency and behaviour of a band showing increased intensity on heating in the spectrum of polyvinyl acetate observed at 1126 cm−1to one previously observed in polyvinyl alcohol at 1142 to 1146 cm−1is described. Several vinyl polymers of similar structure and the behaviour of the band in a copolymer structure have also been exami

ISSN:0007-1641    

DOI:10.1002/pi.4980040208

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040209

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040210

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980040211

出版商:John Wiley&Sons, Ltd    

年代:1972

数据来源: WILEY