• Composites Research
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• v.33 no.2
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• pp.39-43
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• 2020

Recently, fabrication process of thermoplastic polyamide-based composites with recyclability as well as impact, chemical, and abrasion resistance have been widely studied. In particular, thermoplastic reactive resin transfer molding (TRTM) in which monomer with low viscosity is injected and in-situ polymerized inside mold has received a great attention, because thermoplastic melts are hard to impregnate fiber preform due to their very high viscosity. However, it is difficult to optimize the processing conditions because of high reactivity and sensitivity to external environments of the used monomer, ε-caprolactam. In this study, viscosity as an important process parameter in TRTM was measured during in-situ anionic polymerization of ε-caprolactam and the solutions for problems caused by high polymerization rate and sensitivity to moisture and oxygen were suggested. Reliability of the improved measurement technique was verified by comparing the viscosity behavior at various environmental conditions including humidity and atmosphere, and it is expected to be helpful for optimization of TRTM process.

• Polymer(Korea)
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• v.25 no.1
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• pp.1-5
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• 2001

Monomer casting nylons were synthesized by casting anionic polymerization of ${\varepsilon}$-caprolactam. Polymerization rates, molecular weights of the products and the conversions were determined while varying the content of catalysts in the range of 0.2~0.6 mol% and 0.1~1.0 mol% for initiator. The polymerization rates were enhanced as the ratio of catalysts to initiator increased. The maximum molecular weight was observed when the ratio of catalysts to initiator was 0.8, and as the ratio increased the molecular weight decreased. On the other hand, when the ratio of catalysts to initiator was below 0.8, the conversions and the molecular weights were abruptly diminished due to the termination of growing chains.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.268-277
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• 1999

In order to make an advanced dry-friction engineering material, wax-impregnated nylons were synthesized by anionic polymerization of $\varepsilon$-caprolactam in the presence of apraffin wax. DNX-125S, which has lowest melting point among four different kinds of waxs investigated, showed excellent miscibiility with $\varepsilon$-carprolactam and no effect on the polymerization reaction. Five different kinds of wax-impregnated nylons from of DNW-125S content 0% to 8% were synthesized and tested. Among the samples, wax-free nylon has the highest yield and tensile strength and hardness, while the specimen with2% wax has the largest elongationi and energy absorption to break. The wax-impregnated nylon with a wax content 6% showdd the smallest friction coefficient under slow sliding speed and low load. Bus as the sliding speeds were increased to high, thespcieimen with 8% wax has better friction property.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.424-430
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• 1976

Isocyanate-terminated SBR-prepolymers were prepared from SBR-diol and excess toluene diisocyanate. These prepolymers were then used as initiators for the sodium-catalyzed polymerization of ${\varepsilon}$-caprolactam. The resulting block copolymers, presumably the structure of nylon 6-SBR-nylon 6, were confirmed from their IR spectra. The viscosities of these polymers were measured in phenol/tetrachloroethane and the molecular weights were estimated. The polymerization reaction was not affected by the change in concentration of catalyst, but significantly faster at $185^{\circ}C$ than at $150^{\circ}C$. And the initiator concentration of 0.5 mole % gave good results.

• Polymer(Korea)
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• v.29 no.1
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• pp.14-18
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• 2005

Nylons were synthesized by anionic polymerization of ${\varepsilon}$--caprolactam while varying the content of catalyst. Polymerization rates, molecular weights, mechanical properities and frictional properties of the nylons were investigated. As the ratio of catalyst to initiator was increased up to 1.0%, the polymerization rate, conversion and molecular weight were found to increase, and mechanical properties except impact strength were improved. Frictional properties were affected mainly by tensile strength and hardness. According to the study on the friction coefficient, product of stress (P) and velocity (V), PV limit, and abrasive wear rate, nylon synthesized at 1.0% of the ratio of catalyst to initiator showed the best performance for sliding machine elements.

• Polymer(Korea)
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• v.38 no.6
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• pp.714-719
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• 2014

Bio-based nylon 6-morpholinone random copolymers were prepared by the anionic ring opening polymerization of ${\varepsilon}$-caprolactam and morpholinone, both of which were prepared from lysine and glucose, respectively. From this work, a new biomass based nylon 6 with improved hydrophilicity was prepared. Optimizing the polymerization condition, copolymer with a viscosity-average molecular weight of 30000 g/mol was prepared, with a yield of 80%. It was possible to improve the hydrophilicity of nylon 6 by its copolymerization with morpholinone. The prepared nylon 6-morpholinone random copolymers were then characterized using several analytical methods such as DSC, TGA, XRD, viscosity measurement with U-shaped glass capillary viscometer and contact angle measurement.

• Microbiology and Biotechnology Letters
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• v.34 no.3
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• pp.204-210
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• 2006

Ethyl (S)-4-chloro-3-hydroxybutyrate is a useful intermediate for the synthesis of Atorvastatin, a chiral drug to hypercholesterolemia. In this research, two 4-chloro-3-hydroxybutyro-nitrile-degrading strains were isolated from soil sample. They were identified as Rhodococcus erythropolis strains by 16S rRNA analysis. The nitrile-degrading enzyme(s) were suggested to be nitrile hydratase and amidase rather than nitrilase from the result of thin layer chromatography analysis. The corresponding genes were obtained by PCR cloning method. The predicted protein sequences had identities more than 96% with nitrile hydratase ${\alpha}-subunit$, nitrile hydratase ${\beta}-subunit$, and amidase of R. erythropolis. The 4-chloro-3-hydroxybutyronitrile-hydrolyzing activities in both strains were increased dramatically by ${\varepsilon}-caprolactam$ which was known as good inducer for nitrile hydratase. Both intact cells and cell-free extract could hydrolyze the nitrile compound. So, the intact cell and the enzymes could be used as potential biocatalyst for the production of 4-chloro-3-hydroxybutyric acid.