• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.147-147
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• 2004

폴리메틸메타크릴레이트(polymethylmethacrylate, PMMA)는 아크릴레이트계 고분자이자 열가소성 플라스틱으로써 LCD용 도광판, 콘택트렌즈, 치과용 레진, DVD 디스크용 소재, 나노임프린트용 피가공재, 나노리소그래피 공정용 레지스트 등 많은 분야에서 활발히 사용되고 있다. PMMA 와 같은 점소성 점탄성 소재의 기계적 성질 측정 및 가공을 위해서는, 응력완화 (stress relaxation), 크립 (creep)등과 같은 시간의존적 변형거동에 대한 연구가 선행되어야 한다.(중략)

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.89-96
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• 2018

Purpose: The aim of this study was to evaluate the effect of delayed time, surface treatment, and repair materials on repair of bis-acryl composite resin through comparison of shear bond strength and to evaluate the utility of bis-acryl composite resin repair using polymethyl methacrylate resin. Materials and Methods: A total of 90 bis-acryl composite resin specimens were fabricated and classified into 9 test groups, each of 10 pieces according to delayed time, surface treatment and repair material. The shear bond strength of each specimen was measured using a universal testing machine immediately after fabrication and analyzed using a statistical analysis program (IBM SPSS statistics 20). After the shear bond strength measurement, the fracture surface of the specimen was observed. Results: The highest shear bond strength ($17.54{\pm}3.14MPa$) was observed in the experimental group bonded immediately with a light-curing flowable composite resin using a bonding agent. Conclusion: When repairing bis-acryl composite resin, it is necessary to consider whether to remake according to the delayed time. For effective repair, it is desirable to consider appropriate materials and surface treatment methods according to the site or purpose of use.

• Polymer(Korea)
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• v.36 no.4
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• pp.531-535
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• 2012

Conductive polyaniline (PANI) nanofibers in UV-curable resin were used for a transparent conductive film. The emeraldine-salt PANI (ES-PANI) nanofibers were prepared by chemical oxidation polymerization of aniline, which could be changed into emeraldine-base PANI by dedoping. EB-PANI nanofibers as a precursor for conductive fillers were thereby transformed into re-dpoed PANI (rES-PANI) by dodecylbenzenesulfonic acid in the UV-curable resin solution. rES-PANI nanofibers have high conductivity and long-term stability in the solution without a defect of nanostructure. The resulting conductive resin solution was proved to be highly stable where no precipitation of rES-PANI fillers was observed over a period of 3 months. The transparent film was spin-casted on a poly(methyl methacrylate) sheet of thickness ca. $5{\mu}m$. A surface resistance of $6.5{\times}10^8{\Omega}/sq$ and transmittance at 550 nm of 91.1% were obtained for the film prepared with a concentration of 1.4 wt% rES-PANI nanofibers in the solution. This transformation process of rES-PANI from ES-PANI by dedoping-redoping can be an alternative method for the preparation of an antistatic protection film with controllable surface resistance and optical transparencies with the PANI concentration in UV-curable solution.

• Korean Journal of Dental Materials
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• v.44 no.4
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• pp.311-318
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• 2017

The purpose of this study was to examine the effects of the curing sequence and polymerization temperature on the flexural strength and microhardness of two provisional resins (Bis-acryl resin composite and polymethyl methacrylate (PMMA)). Polymerization was carried out under various conditions, in air at $25^{\circ}C$ (control) and in hot water (40, 50, 60, 70, and $80^{\circ}C$). The flexural strength test was conducted according to ISO-4049. The Knoop hardness was measured. For the Bis-acryl resin, the temperature up to $50^{\circ}C$ did not increase the flexural strength nor the hardness of the bis-acryl resin composite (p>0.05) but higher temperatures increased the strengths. For the PMMA resin, flexural strength increased with temperatures up to $70^{\circ}C$ and then decreased slightly. Bis-acryl resin composite had higher mechanical properties than the PMMA resin. The effect of heat was more pronounced in the bis-acryl resin composite than in the PMMA resin (p<0.05).

• Journal of Oral Medicine and Pain
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• v.35 no.1
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• pp.75-81
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• 2010

By repeating nocturnal bruxism occlusal appliance's wearing condition that is used to cure temporomandibular disorders into the vitro experiment, research aims to find out how moisture infiltrated and drying cycle process affects on the surface microhardness of the resin for occlusal appliance and flexural strength. By utilizing resin for occlusal appliance which is the main component of poly methyl methacrylate, bar shaped sample was produced. For the resin sample utilized as the controlled group 1, the sample was infiltrated in the moisture for 7 days in the temperature of 37C. Then, the resin sample of the controlled group 2 was maintained in a dry condition for 7 days in the normal temperature. After that, each sample's surface microhardness and flexural strength were measured. For the resin sample that is utilized as the experimental sample, the sample was infiltrated in the moisture for 7 days in the temperature of 37C. Then, it was inundated for 8 hours a day and dried in the normal temperature for 16 hours with the continuous process of moisture infiltration and dry cycle process for 30 days. During this cycle process, sample's surface and flexural strength were measured in the 1st day, 7th day, and 30th day. Then, it was statistically analyzed to find out the difference of controlled and experiment group's surface microhardness and flexural strength. Results are 1. For the experimental and controlled group's surface microhardness of the resin for the occlusal appliance, it did not show any significant differences after moisture infiltration and dry cycle process repetition. 2. In case of the flexural strength for resin for the occlusal appliance, experimental group with moisture infiltration and dry cycle for 30 day process had greater effect than the experimental group at the 1st day and controlled group These results can be considered to be utilized from the patients of the temporomandibular disorders towards occlusal appliance used and maintained method.