By studying the physical properties of natural rubber compounds cured by compression in a test mold which has a unidirectional outer flow of excess rubber from the mold when vulcanization starts, we found that the tear strength of the test pieces where the direction of the stretching was parallel to the outer flow was lower than that of the test pieces with the direction perpendicular to it. Similar anisotropies were also observed in tensile strength, modulus, tanδ, Payne's effect, etc. Some anisotropies similar to the experiments were observed in the OCTA calculation with a non-crosslinked natural rubber model. The causes of anisotropies were considered.

抄録全体を表示

The ethylene (Et) - styrene (St) - divinylbenzene (DVB) terpolymer was synthesized from Et, St, and small amount of DVB using rac-isopropylidenebis(4,5-benzindenyl) zirconium dichloride/MAO coordination polymerization catalyst system. The terpolymer obtained highly keeps a pendant aromatic vinyl group from self cross-linking, which is considered to be a useful building block for the branching copolymer synthesis.
The branching copolymers are synthesized from the Et-St-DVB terpolymer and styrene using anionic polymerization. The resulting copolymers showed uniformnano-scale phase separated structure corresponding to the main chain Et-St copolymer phase as soft segment and side chain polystyrene (PS) phase as hard segment. Mechanical strength and transparency increase with DVB content from 0.05 to 0.11 mol% of the Et-St-DVB terpolymers employed, with keeping good processability (MFR value). The mechanical properties are changed from thermoplastic elastomer to plastic by changing the weight ratio of the soft/hard segment, as well as the morphologies of the sea/islandstructure.

抄録全体を表示

The relationship between distribution of antioxidant and degradation of polymer is investigated on EPDM compounded with IPPD that is a typical amine type antioxidant for vulcanized rubber. IPPD in EPDM homogeneously-dispersed by kneading is used. Because of decomposition by heat while molding and volatilization from surface of vulcanized rubber, more IPPD exists inside of rubber than the surface. At the depth of 0 ~ about 50μm, percolation of water contained with residual chlorine and polymer degradation occur at the same time, IPPD disappears because of its dissolution into the water and consumption by trapping radical generated polymer degradation caused by residual chlorine and heat. In this area the rubber degradation occurs easily, so almost on the surface oxidation degradation progress even though antioxidant exists enough in vulcanized rubber.

抄録全体を表示

Electron spin resonance measurements under the tensile deformation and transmission electron microscopy observations were carried out for silica filled SBR and polyisoprene vulcanizates to discuss on the mechanism of stress softening effect (Mullins effect).
It was found that for unfilled vulcanizates, the breakdown of crosslinks and/or chain scission of rubber molecules are responsible for the Mullins effect. By the incorporation of silica into rubber, the Mullins effect was enhanced possibly due to the partial breakdown of silica agglomerates.

抄録全体を表示

Fullerenes are the carbon materials that only 60 or more carbon atoms are covalently bounded. Since such greatly unique materials were discovered, many researches of fullerenes have been carried out. On the other hand, the unique carbon soot (CS) is yielded at production of fullerene, but it is not really investigated. However, we think that the application of CS is extremely important from the perspective of fullerene research and of market expansion. In this study, we prepared the composites by adding CS to styrene block copolymer (SBC), and then investigated the additional effect by measuring dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and tensile properties. It was found that tensile modulus and heat-aging resistance of the SBC improved by adding CS.

抄録全体を表示

This review reports on hierarchical structures formed by complex polymeric materials such as block copolymers and/or polymer blends. The topics and their principal achievements are as follows. The polymer components used are polyiosprene(I), polystyrene(S), poly(2-vinylpyridine)(P) and poly(4-hydroxystyrene)(H), and almost all the polymer samples were prepared by anionic polymerizations and therefore have narrow molecular and composition distribution. 1) Complex structures from multiblock terpolymer: Undecablock terpolymers of the PISISISISIP type and hexablock terpolymers of the PISISI type with both have much different block chain lengths show hierarchical structures with double periodicity. 2) Periodic and aperiodic tiling structures from star-shaped terpolymers: Bulk structures of I_XS_YP_Z star-shaped terpolymers were observed and simply periodic Archimedean tiling structures and quasicrystalline tiling structures with dodecagonal symmetry have been found. 3) New self-assembly manner of block copolymer/homopolymer blend: A polystyrene-b-poly(2-vinylpyridine)(SP) diblock copolymer and H homopolymer can be mixed together to form periodic two-phase structures because of hydrogene bonding interaction between P and H components. 4) Supramacromolecular self-assembly by ionic bonding interaction: Polystyrene with 13 styrene sulfonic acid units on one chain end and polyisoprene with amino group on one chain end tend to form periodic two-phase structures due to acid/base ionic bonding depending on compositions.

抄録全体を表示