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The analytical model proposed for poly-α-olefins has been tested on polyisobutene. Relaxation modulus E(t) and distribution of relaxation times have been predicted from dynamic experiments and agree with literature data.

SEVERAL theories for the description of the long-term transients of stress relaxation of rubber-like polymers have been put forward1 which require complex distribution functions of relaxation and retardation times. Tobolsky and Aklonis1 have postulated that such a complex relaxation modulus arises from torsional vibrations and internal rotations of the chain molecules as well as motions of the entangled rubbery networks. The difficulty inherent in all these theories is either that they fail to explain why the relaxation and retardation spectra do not drop very rapidly or that they require very complex assumptions such as cooperative changes of configuration involving whole groups of polymer strands which become dominant at long intervals of time2.

In order to determine the characteristics of the glassy-state relaxations of poly(bisphenol-A carbonate) which are closely overlapping each other, shear relaxation modulus was measured from 10 sec to 900 sec at temperatures ranging from ca. -180°C to 0°C. Three relaxations named β, γ and δ in the order of descending temperature were observed separately and master curves were determined by the method of reduced variables. The activation energies of the β, γ and δ relaxations were estimated to be ca. 30, 25 and 9 kcal/mol, respectively. Theoretical considerations suggest that the molecular motions for the β, γ and δ relaxations are the local-mode motion of main chain, the flip motion of a phenylene with a carbonate group, and the rotational motion of a pair of methyl groups belonging to neighboring chains and coupled by van der Waals force.

In order to clarify the effect of branching on the α-loss band in polyethylene, the shear relaxation modulus of samples with various degrees of branching is measured from 5 sec to 900 sec, between -90°C and 60°C. Two relaxations named α1 and α2 in order of ascending temperature are observed separately and reduced to master curves by the method of reduced variables. The activation energies for the α1- and α2-relaxations are ca. 26 kcal/mol, and 46 kcal/mol respectively. The activation energies and the shapes of the relaxation spectra for these relaxations are independent of the crystallinity and degree of branching. As the degree of branching increases, the relaxation strength for the α1-relaxation increases and that for the α2-relaxation decreases, while both relaxations shift to lower temperatures. These results are compared with the existing molecular theories.

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.