The shift from petroleum based plastics to biomass based plastics is one solution that can’t be avoided forthe global warming issues by reduction of CO2 emission in recent years. In the polyurethane market, naturaloil (biomass) based polyols have been applied in this market for a long time. On the other hand, biomass basedisocyanates haven’t almost been commercialized and applied due to the difficulty of the molecular design ofisocyanate. In recent years, new biomass feedstock have been available for the production of isocyanates. Inthis review, we explain about the development of new biomass based polyurethanes centering on biomassbased isocyanates. 1,5-penthamethylete diisocyanate (1,5-PDI; STABiO^TM PDI^TM) derived from L-lysine exhibitsimproved reactivity with alcohol compared to those of petroleum based 1,6-hexamethylene diisocyanate (HDI)and the other commercialized aliphatic and alicyclic isocyanates. In addition, the polyurethane coatings basedon 1,5-PDI derivatives shows improved chemical resistance and mechanical properties than those of HDI basedones.

Stress analysis by finite element method was performed to study a rounding the edge of the adheringsurface of the round bar adherend and using an analytical model of butt adhering shape to estimate the tensilestrength of the butt joint. The tensile strength of the round bar butt joint, which adhesive surface had a roundedge, was calculated. Furthermore, the butt joint was actually made with the same shape as the analysis, andthe tensile test was carried out to show the validity of the analysis. The tensile test of the same shape butt jointwas conducted experimentally to confirm the result of the finite element method. As a result, it showed thatit is possible to reduce the influence of stress specificity by providing roundness on the edge of the bondingsurface. The influence of the stress singularity can also be decreased by adding the round edged surface. Themaximum value of the maximum principal stress in the adhesive layer was made equal to the strength of theadhesive using a joint model with rounded radius of 0.2 mm or more. It is found that the analysis value andthe breaking load value by experiment agreed well. The calculated value coincided with the experimentalvalue when the edge at the adhesive surface was more than 0.2mm and the maximum principal stress was thesame as the strength of the adhesive. In other words, by providing a radius of 0.2 mm or more on the edgeof the adhesion surface of the round bar adherend, round bar butt joints subjected to tensile loads using thestress-strain relationship and the finite element method of the adhesive to be used It is shown by analysis andexperiment that the strength evaluation is possible. This indicates that the strength of the adhesive round buttjoint, which has more than 0.2mm round adhesive surface edge, can be estimated using the relation betweenstress and strain of adhesive and the infinite method.

There are several natural systems related to adhesion and adhesives in the field of biomimetics. Focusingon gecko adhesion, one of its remarkable features is reversibility of the adhesion. Although geckos adhere to awall using molecular interaction, they cannot walk or run without detaching their foot easily from the surface.Understanding the mechanism of easy detachment is important to achieve gecko-like reversible adhesion.In this paper, detachment mechanism of gecko adhesion is investigated. Using simplified adhesion model ofgeckos’ foot hairs, directional dependency of adhesion force at detachment is theoretically derived. Then, itis clarified that anisotropy of adhesion force is generated by the hair structure. Additionally, gecko-inspiredadhesive devices are created and the anisotropy is experimentally verified. Finally, manipulation system usingthe adhesive device is proposed and pick-and-place of a glass plate is succeeded.