摘要:

AbstractMethods are reported for the separation and complete quantitative estimation of the polyorganosiloxanes prepared by the trimethylsilylation of mineral silicates. Quantitative methods for the determination of low molecular weight oligomers up to Q6M12(Q≡SiO4/2; M≡(CH3)3SiO1/2) are well known but there are no previously reported methods for the determination of high molecular weight species. This paper describes the application of gel permeation chromatography and quantitative high performance liquid chromatography to the study of these higher molecular weight species. Polyorganosiloxanes prepared from suzorite (a phlogopite) and from olivine (an orthosilicate) are used as examples. A further example is a study of the formation of higher molecular weight species on heating these polym

ISSN:0007-1641    

DOI:10.1002/pi.4980130402

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractTo improve the electret characteristics, TSD current studies of copper phthalocyanine ‐ doped polystyrene films of about 20 microns thickness have been made as a function of doping concentration, poling temperature and field. Generally the thermograms observed exhibit α and ρ peaks. The activation energy is found to decrease as the concentration of the dopant in the polymer is increased. It is established that keeping the forming field constant and by increasing the concentration of the dopant, the same polarisation can be obtained at a lower poling temperature. A Maxwell‐Wagner two‐phase model with space ‐ charge build‐up seems to provide a possible mechanism for the p

ISSN:0007-1641    

DOI:10.1002/pi.4980130403

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractDepolarisation currents have been measured of the photo‐electrets of pure and copperphthalocyanine doped polystyrene films using UV‐radiation. A hyperbolic decay law is observed suggesting bimolecular recombination process. Doped films show strong saturation with the applied field supporting a trap filling mechan

ISSN:0007-1641    

DOI:10.1002/pi.4980130404

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractPhenanthrene was treated with formaldehyde in the presence of sulphuric acid and the yields of resin obtained were dependent on the acid concentration and on the molar ration of formaldehyde to phenanthrene. All of the resins were composed of dimers, trimers, tetramers and higher oligomers. The bridges joining the phenanthryl units were mainly methylene when formaldehyde was in molar deficit relative to phenathrene, but dimethylene ether and acetal bridges were present when the formaldehyde was in molar excess.

ISSN:0007-1641    

DOI:10.1002/pi.4980130405

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThermal degradation of methyl and ethyl cyanoacrylate polymers of number‐average molecular weights 370–1350 is shown to proceed by depolymerisation at temperatures in the range 140°–180°C. Under the conditions of the thermogravimetric analysis technique employed, weight loss kinetics appear to be governed by diffusion of monomer vapour through the liquid sample. A mathematical model of this process is pos

ISSN:0007-1641    

DOI:10.1002/pi.4980130406

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractA calorimetric measuring system for continuous recording of rate of reaction and conversion in a 14 1 polymerisation reactor has been developed. The reactor was jacketed and thermostated with circulating water. The measuring signals to the calculating unit represented the temperature difference between inlet and outlet water, the water flow and the heat losse from reactor to the environment. The measuring system was constructed to calculate correctly the conversion even if the heat losses to the environment changes during the reaction. The applicability of the reactor system was demonstrated by its use in suspension polymerisation of vinyl chloride.

ISSN:0007-1641    

DOI:10.1002/pi.4980130407

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractAn attempt was made to prepare the polymer fractions having extremely sharp molecular weight distribution (MWD), by using a successive solutional fractionation (SSF) method, in which a polymer‐lean phase was separated as a fraction from a polymer‐rich phase. For this purpose a large‐scale preparative SSF apparatus was constructed. Atactic polystyrene (PS) high‐density polyethylene (PE), and cellulose di‐ and tri‐acetates (CDA and CTA) were fractionated by SSF. The fractions isolated from a quasi‐binary mixture (polymer/solvent system) have the same MWD as that predicted by the computer simulation technique. Even under the conventional fractionation conditions (initial polymer volume fractionvop= ∼ 0.01, total number of fractionsnt= 10 ∼ 20) the fractions with the ratio of the weight to number‐average molecular weightMw/Mnless than 1.1 for PS, 1.2 for PE, 1.3 for CDA and 1.4 for CTA were obtained, with exception of a few initial fractions. The advantage of the SSF method was clarified over the conventional preparative methods such as gel permeation chromatography and the column f

ISSN:0007-1641    

DOI:10.1002/pi.4980130408

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980130401

出版商:John Wiley&Sons, Ltd    

年代:1981

数据来源: WILEY