Natural rubber thermodynamic properties

Lord Kelvin s close associate, the expert experimentalist J. P. Joule, set about to test the former s theoretical relationship and in 1859 published an extensive paper on the thermoelastic properties of various solids—metals, woods of different kinds, and, most prominent of all, natural rubber. In the half century between Gough and Joule not only was a suitable theoretical formula made available through establishment of the second law of thermodynamics, but as a result of the discovery of vulcanization (Goodyear, 1839) Joule had at his disposal a more perfectly elastic substance, vulcanized rubber, and most of his experiments were carried out on samples which had been vulcanized. He confirmed Gough s first two observations but contested the third. On stretching vulcanized rubber to twice its initial length. Joule ob-... 

Meier [23] has derived equations relating block copolymer morphology to thermodynamics using lattice models. His model explains quantitatively the observations of Merrett [24] on the influence of preferential solvents on the mechanical properties of graft copolymers. Merrett found that, depending on the solvent used in casting films of a natural rubber/poly(methyl methacrylate) graft copolymer, he could obtain either a hard stiff film characteristic of poly(methyl methacrylate) or a soft, flexible film typical of natural rubber. He interpreted these results as follows a solvent for poly(methyl methacrylate) collapsed the... 

The above features of rubbery materials have long been known. The quantitative measurements of mechanical and thermodynamic properties of natural and other elastomers go back to 1805 and some of the studies were conducted by luminaries like Joule and Maxwell. The first molecular theory in polymer science dealt with the rubber elasticity (9-12). 

The properties of elastomeric materials are controlled by their molecular structure which has been discussed earlier (Section 4.5). They are basically all amorphous polymers above their glass transition and normally crosslinked. Their unique deformation behaviour has fascinated scientists for many years and there are even reports of investigations into the deformation of natural rubber from the beginning of the nineteeth century. Elastomer deformation is particularly amenable to analysis using thermodynamics, as an elastomer behaves essentially as an entropy spring . It is even possible to derive the form of the basic stress-strain relationship from first principles by considering the statistical thermodynamic behaviour of the molecular network. 

The above-mentioned general features of elastomeric materials have long been known and, in fact, the area of rubber-like elasticity has had one of the longest and most distinguished histories in all of polymer science (1,2,16). Forex-ample, quantitative measurements of the mechanical and thermodynamic properties of natural rubber and other elastomers go back to 1805, and some of the earliest studies have been carried out by such luminaries as Joule and Maxwell. Also, the earliest molecular theories for polymer properties of any kind were, in fact, addressed to the phenomenon of rubber-like elasticity. 

---