Zero-zero-birefringence polymers which exhibit no orientational birefringence and no photoelastic birefringence may be suitable candidates for the components of optical devices. To develop zero-zero-birefringence polymers, a novel copolymerization system is required. We investigated two types of birefringence of poly(N-methylmaleimide) (PMeMI) and showed that PMeMI exhibits positive orientational and photoelastic birefringence. On the basis of the results, we calculated the optimal composition for compensating both types of birefringence by solving three equations which describe the relationship between birefringence properties and weight fraction of monomers. When the copolymer compositions were MMA/BzMA/MeMI 5 86/8/6 and 88/8/4 (wt %), zero-zerobirefringence polymers were obtained. By using MeMI as a comonomer, these zero-zero-birefringence polymers have a much higher glass transition temperature (T g ) than those of previous researches. Also, this polymer film has high transparency comparable with that of PMMA film. Therefore, we conclude that we successfully prepared zero-zero-birefringence polymers using N-substituted maleimide and that N-substituted maleimide is a promising material for zero-zero-birefringence polymers for optical devices.
Polymers that exhibit neither orientational nor photoelastic birefringence, called zero–zero‐birefringence polymers, are candidate materials for preparing optical components of liquid crystal displays (LCDs). Analyzing the birefringences for various methacrylate polymers is an issue of current importance in developing zero–zero‐birefringence polymers with appropriate characteristics for LCDs. The researchers have investigated different types of birefringence for poly(2,2,2‐trichloroethyl methacrylate) (PTCEMA) and have shown that PTCEMA exhibits negative orientational and photoelastic birefringences. By using TCEMA as a comonomer, a zero–zero‐birefringence polymer having much higher glass transition temperature (Tg) compared with previous researches has been prepared by ternary copolymerization. Moreover, the researchers have fabricated zero–zero‐birefringence polymers in a quaternary system containing TCEMA. The property analyses indicate that Tg can be controlled while maintaining the zero–zero‐birefringence property, which shows that designing a quaternary zero–zero‐birefringence polymer permits selective synthesis with the most appropriate characteristics. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
The intrinsic birefringence Dn 0 and photoelastic coefficient C of poly(methyl methacrylate), poly(2,2,2-trifluroethyl methacrylate), poly(phenyl methacrylate), and poly(2,2,3,3,3-pentafluorophenyl methacrylate) were determined. We categorized these methacrylate polymers into four birefringence-types, even though their molecular structures differed only by the substituents on the side chains. Based on the results of Dn 0 and C, novel polymers that exhibit neither orientational nor photoelastic birefringence, i.e., zero-zero-birefringence polymers, were designed and synthesized by quaternary copolymerization system. Furthermore, we confirmed that the mechanisms of orientational birefringence and photoelastic birefringence generation were different in these methacrylate polymers. The conformation of the repeat unit of the polymers was nearly constant during the generation of orientational birefringence. In contrast, the conformation of the repeat unit of the polymers changed during the generation of photoelastic birefringence in the glassy state. These findings demonstrated the reasonability of evaluating orientational and photoelastic birefringence separately, as well as the adequacy of the classification of polymers into four birefringence-types. Given these results and the fact that zero-zero-birefringence polymers could be prepared successfully by four-birefringence type monomers, we demonstrated the reasonability of the method for designing the zero-zero-birefringence polymers. POLYM. ENG. SCI., 55:1330SCI., 55: -1338SCI., 55: , 2015
EDM finishing technology has progressed recently, and very small surface roughness can be obtained by controlling the electrical discharge conditions. Also, EDM using powder mixed fluids can improve the surface characteristics. Therefore, the EDM finished surface is highly expected to be applied as a final metal mold surface. In that case, the characteristics of EDMed surface influence the molding performance and the life of metal molds. As a new surface finishing method by EDM, the characteristics of EDMed surface using a nickel powder mixed fluid was experimentally discussed in this study, since nickel coatings have been widely applied to improve the corrosion resistance and the mold releasability of metal molds. Experimental analysis clarified that the resolidified layer containing nickel content could be formed on the surface by EDM in nickel powder mixed fluid. Also, the water repellency and the releasability of molded resin from the EDM finished surface could be improved.
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