摘要:

The fusion behavior of lightly cross-linked polyethylene films isothermally crystallized at various temperatures and extensions has been examinedonadifferential scanning calorimeter (DSC). Ameans to hold the specimen at fixed elongation during the melting was devised. At large extensions, a separate higher-temperature endotherm was observed in addition to the major peak, indicating a two-phase nature of the crystal morphology. In addition, crystallization experiments performed on the DSC show the crystallization process to consist of two stages. In contrast to reported results for natural rubber and polychloroprene, the melting temperature for polyethylene was not found to be strongly dependent on crystallization temperature or extension. The reason for the differences between polymers is not presently understood, but they may reflect variations in morphological details.

ISSN:0022-2348    

DOI:10.1080/00222347008212481

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Free volume quantities proposed earlier by Boyer and Simha in connection with the glass transition are reformulated by taking into account the temperature dependence of the thermal expansivities αland αgfor the liquid and the glass, respectively. This necessitates an extrapolation of the liquid to temperatures below Tg which is performed by means of the reduced volume-temperature function established and given a theoretical foundation previously. For the glass, low temperature experimental data, encompassing all relaxations occuring below Tg, are required.

ISSN:0022-2348    

DOI:10.1080/00222347008212482

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor