In:
Rubber Chemistry and Technology, Rubber Division, ACS, Vol. 23, No. 4 ( 1950-12-01), p. 770-785
Abstract:
The generally observed stiffening of elastomers at low temperatures may be supplemented by the occurrence of crystallization if the elastomers have sufficient regularity of molecular structure and other conditions are favorable. To study these effects, observations of the progressive stiffenings of elastomer compounds at low temperatures were made by measurements of the relative torsional modulus of test strips mounted in racks which were stored at low temperature. The periods of observation extended over 30 to 60 days with temperatures in the range from −59° to −18° C. A correlation was found between density changes due to crystallization as determined dilatometrically and torsional stiffness changes. Factors studied in addition to temperature included compounding variables such as cure and plasticizer content. Some data were obtained to show the acceleration of crystallization due to compressive stress. Progressive stiffening due to crystallization was observed for vulcanizates of Hevea, Neoprene Type GN, and Butyl rubber, as well as for an 85-15 butadiene-styrene redox-type copolymer. The results were interpreted in accordance with concepts of crystal nucleation and growth with necessary modifications due to the molecular structure of elastomers. Although the phenomenon of spontaneous crystallization of elastomers was found to be complicated by many factors, a useful degree of generality appears in some of the results.
Type of Medium:
Online Resource
ISSN:
1943-4804
,
0035-9475
Language:
English
Publisher:
Rubber Division, ACS
Publication Date:
1950
