A comparison was made of the room temperature strain-crystallization of naturally-occurring cis-1,4-polyisoprenes having varying non-rubber content. A variety of measurements were employed to assess crystallization, including stress relaxation, optical birefringence, and the infrared absorption spectrum. All methods yielded the same result: The strain required to induce crystallization is less for polyisoprenes having larger concentrations of impurities. The ability to crystallize at lower orientation presumably underlies the superior failure properties of guayule rubber and the poorer grades of natural rubber (NR) in comparison to deproteinized NR.

Inherent flaw sizes were determined from fatigue lifetimes, and from the crack length dependence of the strain energy to break, for four cis-1,4-polyisoprenes compounded to have the same crosslink density and low strain hysteresis. Both techniques indicated that the flaws intrinsic to guayule rubber (GR), and to a lesser extent conventional natural rubber, are larger than those found in deproteinized NR. This result may not be surprising; however, the failure properties of the elastomers, expected to depend on flaw size, were surprising. The guayule rubber and a natural rubber of relatively low purity (SMR-10) had the highest tensile strengths, tear strengths, breaking energies, and fatigue lifetimes, while DPNR exhibited the worst failure properties. Such an inverse correlation between flaw size and failure performance is due to the dominant effect of strain-induced crystallization. GR and SMR-10 have the highest propensity for strain-induced crystallization, while DPNR is the least strain-crystallizable. Interestingly, all rubbers exhibited the same isotropic crystallization behavior.

The ability of elastomers to store large quantities of energy, which can subsequently be recovered very quickly, makes them attractive materials for propulsion devices. Recently the U.S. Navy has developed a torpedo ejection system based on an elastomeric mechanical capacitor. The criteria governing selection of a material for this application include high elastic energy, sufficient fatigue life, minimal creep, and resistance to deterioration by seawater. This paper describes various approaches to obtaining these material properties.

This study examined the relationship among PsyCap(positive psychological capital), psychological empowerment, personal creativity and verified the mediated effects of intrinsic motivation in this relationship using the SEM (Structural Equation Model). For this study, the data was collected through on/off-line surveys of members and managers from 12 different enterprises. Among the 418 answers from voluntary participating employees, 332 answers were finally used for statistical analysis. The results were as follows. First, PsyCap had a positive influence on the intrinsic motivation and personal creativity. Second, Psychological Empowerment had a positive influence on intrinsic motivation, but psychological empowerment has no influence on creativity. Third, intrinsic motivation had a meaningful influence by partially mediating PsyCap and personal creativity but completely mediated psychological empowerment and personal creativity. This study focused on intrinsic motivation among the internal factors that have influences on showing personal creativity and has importance in the point that it has suggested the statistical significance by analyzing the psychological/emotional mechanism to reinforce this intrinsic motivation in a positive way. Positive analysis on the relationships among these variables suggests a theoretical meaning on providing a future direction for the study and practical meaning on providing ideas to reinforce the employees' personal creativity. The details of this study are followed in the main text.