摘要:

AbstractExposure of aluminium‐epoxide bonds to methanol, ethanol, ammonia and formamide has shown that the hydrogen bonding ability of the ‘solvent’ plays little part in determining the effect on bond strength. The strength of the bonds may be increased by short‐term exposures to the alcohols. A mechanism is proposed to explain t

ISSN:0007-1641    

DOI:10.1002/pi.4980020111

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractA study of the ratio of the glass temperature to the melting point of 132 polymers is described. Contrary to some other workers' observations on smaller numbers of polymers there is no sharp division between the ratios observed for symmetrical and unsymmetrical polymers. The arithmetic mean of the ratio is 0·63 and 0·69 respectively, but the combined standard deviation is 0·11. There is no correlation between the ratios and the crystalline forms of polyme

ISSN:0007-1641    

DOI:10.1002/pi.4980020112

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020113

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractHexamethylene tetramine (hexamine) in phenol‐formaldehyde and urea‐formaldehyde moulding compounds can be determined by non‐aqueous titration in acetic acid solution with perchloric acid. Phenolic compounds may be dissolved directly in glacial acetic acid and the hexamine may be titrated. However, hexamine must first be extracted from dry urea‐formaldehyde samples with chloroform before titration as the resin interferes with the titration. Nuclear magnetic resonance spectroscopy may also be used to determine the hexamine content of the extracted s

ISSN:0007-1641    

DOI:10.1002/pi.4980020114

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe reaction between chlorophosphazenes and silicon alkoxides has been studied as a means of preparing temperature‐stable thermosetting resinous materials. If the silicon alkoxide is polyfunctional in straight‐chain lower alkoxy groups the usual reaction is elimination of alkyl chloride and formation of a thermosetting resinous product. The mechanism of this reaction is discussed. Other reactions occurring in the treatment of chlorophosphazenes with silicon alkoxides are also discussed. Asbestos laminates which retain much of their strength when heated to 500° for 50 hours in air can be prepared from the thermosetting resinous products resulting from the reaction between chlorophosphazenes and silicon alkox

ISSN:0007-1641    

DOI:10.1002/pi.4980020115

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractElectron microscopy can only yield information about polymers in the solid state. Preparative methods have been developed which consisted of replica techniques; thin films stained with uranyl acetate, sodium tungstate or phosphotungstic acid; and extraction replicas. Results suggest an ordered sequence of structures from: (i) the stereochemically defined chain molecule which tends to form; (ii) a folded structure to minimise free energy; (iii) a structure which can be resolved in the electron microscope and is roughly spherical in shape‐this structure is dependent on molecular weight up to a certain figure after which it is independent as is a constant for the material; and (iv) aggregates of structure (iii), either in the form of chains resembling a string of pearls or a pile of aggregated sphere

ISSN:0007-1641    

DOI:10.1002/pi.4980020116

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020117

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020119

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020120

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020121

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY