Abstract
Abstract Highly oriented natural rubber samples of Roberts and Mandelkern, prepared by racking and subsequently crosslinked using γ-radiation, undergo a spontaneous shrinkage upon melting which closely resembles the shrinkage of collagen. If the transformation is arrested by application of a tensile force, a state of equilibrium may be established between two distinct zones, or phases, one being totally amorphous (shrunken) and the other unchanged (i.e., racked). Determination of the stress τeq required for phase equilibrium at various temperatures is described. Extrapolation to τeq=0 gives equilibrium melting temperatures Tmi, which are about 8° below the temperatures Tsi for spontaneous shrinkage. The heat of transformation of racked to amorphous rubber calculated from the dependence of τeq on T is 4.5 cal g−1. Since the degree of crystallinity is only 0.24, the heat of fusion calculated for 1 g of crystalline rubber is ca. 19 cal, which agrees satisfactorily with the value 15.3 cal, deduced by Roberts and Mandelkern through use of the melting point depression method. The shrinkage of racked rubber displays all of the important features associated with the similar contraction of fibrous proteins.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
