Yukio Onouchi

Rubber elasticity at very large elongation

SummaryThe rubber elasticity increases in general at very large elongation and sometimes it is ascribed to the strain-induced crystallization. However, the authors found that a steep increase takes place in an ordinary Mooney-Rivlin plot not only for natural rubber but also for non-crystallizable rubbers such as SBR, NBR, EPDM and polyurethane, and the upturn for non-crystallizable rubbers disappears if data are examined with the theoretical equation derived taking the limited extensibility of chains into consideration. In the ordinary Mooney-Rivlin plot the elongation inducing the stress upturn due to the limited extensibility of chains increases with decreasing degree of vulcanization and sometimes it does not appear before the upturn of the rubber of low degree of vulcanization. The strain-induced crystallization can bring about the steep increase of elastic force, but it is not always adequate to ascribe the upturn to the strain-induced crystallization. The upturn also occurs due to the limitation of extensibility of chains.

Oxidative Polymerization Behavior of Diphenylamine with Bridged Structure

For convenient synthesis of polydiphenylamine with a bridged structure, oxidative polymerizations of diphenylamine with a bridged structure were carried out. Polymer was obtained when dibenzazepine (Azep) was used as a monomer, but oxidative polymerization of phenothiazine (Phen) did not afford polymer. Therefore, oxidation behavior of Phen was examined. From the result, it was suggested that oxidation of Phen affords S-oxide-type compound rather than formation of polydiphenylamine-type polymer.

Fluorescent additive for estimation of compatibility of polyester blend by imipramine-containing polymer

ABSTRACT The effects of adding imipramine-containing polymer (PImip-Fl) in two kinds of polyester/lysine triisocyanate (LTI) blends were investigated. PImip-Fl was prepared by Suzuki–Miyaura coupling reaction of dibromoimipramine hydrochloride and dioctylfluorene diboronic acid. The addition of PImip-Fl gave fluorescence to resins [poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL)], and its fluorescent maximum wavelength (λmax) depended on the resin. PImip-Fl was used as a functional additive for the estimation of compatibility of PLA/PCL blend composite. The addition of LTI to the resins/PImip-Fl blend composites afforded a shorter wavelength shift of the fluorescent λmax. This suggested that the method using PImip-Fl is adaptive for the estimation of compatibility of the blend composite.

Study on High Damping Rubbers. Part 1. Development of High Damping Rubbers by Structural Modification of Natural Rubber.

The High damping rubber for seismic bearing was developed by the structural modification, cis-trans isomerization, of natural rubber (NR). Dimethyl sulfoxide (DMSO), tetramethylene sulfoxide (TMSO), and tetramethylene sulfone, (TMSN) were used for modifiers. The isomerization rates of NR were compared by using the three modifiers. The isomerization rate was -19% in a whole amount for NR. The isomerization of NR gave a high hysteresis loss and lower compression set. The DMSO was more significant for the degree of an activity on the modifiers than that of TMSO and TMSN. Hysteresis loss of the isomeric rubber was about 2.0 times bigger than that of the control (NR), and the compression set of the isomeric rubber was smaller than that of the control. Vulcanization was also remarkably accelerated.

Analysis of vulcanization of rubbers with an oscillating die vulcanometer. (2). Analysis of vulcanization of SBR with various vulcanizing agents.

振動式レオメータを用いて種々の加硫剤によるSBRの加硫曲線を測定した. これらのトルクと時間の関係を, 加硫過程を分子論的に三つの段階に分けて誘導した理論式に基づいて解析し, 理論式の適合性を検討した.種々の加硫促進剤-硫黄加硫系における解析結果から, 三つの理論式に基づく直線関係が成立する領域を認めた. したがって, ゴムの加硫は, 初期では分子鎖間の結合による分枝ポリマーの発生, 中期では網目構造の形成, 終期では架橋間分子鎖の結合, の順で進行することがかなり明確になった. 一方, 過酸化物加硫系における解析結果から, 加硫促進剤-硫黄加硫系の場合と同様に中期及び終期に対する理論式の適合性を認めたが, 初期に対する理論式の適合性はほとんど認められなかった. このような加硫系による理論式の適合性の差は, 加硫反応の機構や形成する架橋構造の違いによるものと推察された.

VULCANIZATION OF RUBBERS WITH SLUDGE INVOLVING CHROMIUM

クロムを主成分とするめっきスラッジの有効利用として, 粉砕及び熱処理したスラッジを天然ゴムあるいは合成ゴムに配合し, いろいろな立場からスラッジの効果を検討した. その結果, スラッジの配合によってゴムのムーニー粘度は著しく低下し, 特にNR, IRに対してその効果が大であった. また, NBR, CRのような極性ゴムに対してスラッジは加硫促進効果を示し, 加硫剤あるいは加硫助剤として使用することができる. 加硫ゴムの引張特性, 接着性もスラッジの添加によってかなり向上し, 更に, 耐熱老化性も無添加のものと比べて大差がないことがわかった. したがって, カーボンプラックに代わる充てん剤としても使用できる.