• Composites Research
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• 제22권3호
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• pp.35-43
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• 2009

본 연구에서는 카본블랙이 충전된 ethylene-propylene dine monomer(EPDM) 고무에 대한 가교밀도 측정법을 확립하고 EPDM 고무호스에 대해 열가속 및 산소스트레스를 가하여 가교밀도 변화를 측정하였다. 노화 초반에는 산화황가교의 형성으로 고무의 가교밀도측정값이 약간 저하하였다가 노화시간이 지남에 따라 일부 미반응 황 분자들의 가황반응으로 추가적인 가교 결합을 형성하면서 가교밀도측정값은 점차 증가하였다. 이들 가교밀도 변화거동은 인장강도의 거동과 유사하였다. $180^{\circ}C$의 고온노화에서는 노화시간이 길어짐에 따라 노화에 따른 가교밀도의 증가폭은 그다지 크지 않았으나, 인장강도와 신장률은 크게 저하하였다. 즉, 온도가 높을 수록 EPDM 고무의 가교밀도의 변동보다는 EPDM 분자사슬에서의 산화물(carbonyl groups) 형성과, 가교점의 산화황 생성으로 기계적 물성의 열화가 일어난 것이다.

• Elastomers and Composites
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• 제54권2호
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• pp.97-104
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• 2019

Emulsion styrene-butadiene rubber silica wet masterbatch (ESBR silica WMB) technology was studied to develop highly filled and highly dispersed silica compounds, involving the preparation of a composite by co-coagulating the modified silica and the rubber latex in a liquid phase. Previous studies have shown that when manufacturing ESBR silica WMB/Butadiene silica dry masterbatch (BR silica DMB) blend compounds, preparing BR silica dry masterbatch and mixing it with ESBR silica WMB gave excellent results. However, WMB still has the problem of lower crosslink density due to residual surfactants. Therefore, in this study, tetrabenzylthiuram disulfide (TBzTD) was added instead of diphenyl guanidine (DPG) in the ESBR silica WMB/BR silica DMB blend compounds and sulfur/CBS contents were increased to evaluate their cure characteristics, crosslink densities, mechanical properties, and dynamic viscoelastic properties. TBzTD was found to be more effective in increasing the crosslink density and to produce superior properties compared to DPG. In addition, with increasing sulfur/CBS contents, mechanical properties and rolling resistance were enhanced due to high crosslink density, but the abrasion resistance was not significantly changed because of the toughness.

• Corrosion Science and Technology
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• 제15권6호
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• pp.297-302
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• 2016

Water-based systems are dominating the coating market because of worldwide VOCs regulations. Research is focusing especially on waterborne polyurethane (WPU) because of its unique mechanical and chemical properties. However, commercial WPU consists of linear thermoplastic polymers with polar groups on the main chain, which do not perform as well as solvent-borne PU in a two-pack system. In this study, APTES were used as a chain crosslink agent to overcome commercial WPU's limited performance. WPUs synthesized by using a sol-gel process were evaluated with FT-IR, particle analysis, TGA, tensile tests, pull-off tests, SEM, and EIS. The results showed that WPUs with added APTES had better thermal stability, mechanical properties, and water resistance than did WPUs without added APTES. Consequently, the sol-gel process increased the crosslink density of WPUs and modified the WPU's own properties.

• Elastomers and Composites
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• 제47권2호
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• pp.148-155
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• 2012

EPDM, IIR, 그리고 BIIR 복합체를 열노화시켜 가교밀도 변화를 조사하였다. 노화 시간이 증가하거나 노화온도가 올라갈수록 EPDM 복합체의 가교밀도는 증가하였으나, 고온에서 장기간 노화된 IIR과 BIIR 복합체의 가교밀도는 감소하는 경향을 보였다. EPDM 복합체의 가교밀도 변화에 대한 활성화 에너지는 BIIR 복합체보다 높았다. 실험결과는 알릴 수소의 수, 아연 복합체의 활성화, 입체 가리움 효과, 그리고 고무 사슬의 산화로 설명하였다.

• Elastomers and Composites
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• 제55권2호
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• pp.108-113
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• 2020

Wear particles of the model tread compounds for bus and truck tires were made using a laboratory abrasion tester and characterized based on their size distributions, shapes, and crosslink densities. The influence of the carbon black contents and rubber compositions (NR= 100 and NR/BR= 80/20) on the production of wear particles was investigated. The wear particles were separated according to size using a sieve shaker. The shape properties of the wear particles were analyzed using an image analyzer and scanning electron microscopy (SEM). Their shapes were observed as tiny stick cookies or sausages with bumpy surfaces. The particle size distribution tended to be smaller with increasing carbon black content. Moreover, the particle size distributions of the NR = 100 samples were larger than that of the NR/BR blend samples. There were different filaments in the wear particles. The filament diameters tended to be thinner with increasing carbon black content. The crosslink density increased with increasing carbon black content, and the crosslink densities of the NR= 100 samples were lower than those of the NR/BR blend ones. The particle size distribution tended to be smaller with increasing crosslink density. Based on the experimental results, the wear particles can be produced by detaching debris from the main body through repetitive strain and recovery.

• Elastomers and Composites
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• 제46권3호
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• pp.237-244
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• 2011

비보강, 카본블랙, 카본블랙과 실란커플링제, 실리카, 실리카와 실란커플링제 등 5가지의 다른 충전 시스템을 갖는 NR 복합체를 열노화시켰으며, 가속 열노화에 의한 가교밀도 변화를 연구하였다. 가교밀도는 충전 시스템과 관계없이 노화 시간이 경과함에 따라 증가하였다. 노화 온도가 높아질수록 가교밀도는 눈에 띄게 변하였다. 카본블랙으 로 보강된 NR 복합체의 경우, 실란커플링제는 가교밀도를 증가시켰다. 하지만 실리카로 보강된 NR 복합체의 경우에는 $60^{\circ}C$와 $70^{\circ}C$ 노화에서는 가교밀도 증가분이 감소하였으며, $80^{\circ}C$와 $90^{\circ}C$에서는 거의 영향을 주지 않았다. 카본블랙으로 보강된 NR 복합체의 가교밀도 변화에 대한 활성화 에너지는 로그 함수 형태로 지속적으로 증가한 반면, 실리카로 보강된 NR 복합체의 경우에는 노화 시간 30-150일 구간에서는 거의 변화가 없었다. 비보강 시험편의 활성화 에너지 는 노화 시간에 따라 지수 함수 형태로 증가하였다. 실험 결과는 실란커플링제로부터의 황 제공, 실란커플링제에 의한 충전제의 표면 개질, 실리카 표면에서의 가교제 잔류물의 흡착, 그리고 흡착된 가교제 잔류물의 방출 등으로 설명하였다.

• Applied Biological Chemistry
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• 제34권2호
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• pp.86-93
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• 1991

CDDP는 $100\;{\mu}M$ 이하의 농도에서 BTV 캡시드 단백질에 crosslink를 형성하지 않는다. 밀도구배초원심분리 결과에 의하면 캡시드 단백질과 RNA사이의 crosslink도 일어나지 않는다. CDDP를 처리한 BTV RNA를 폴리아크릴아마이드 겔에 전기연동하면 RNA이동 패턴이 변한다. 이 결과는 BTV core에 없는 RNA중합효소의 불활성화가 CDDP에 의한 BNA RNA의 구조변화에 의함을 가리킨다.

• Elastomers and Composites
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• 제50권1호
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• pp.1-6
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• 2015

Polybutadiene rubber (BR) has been well known that its physical and chemical properties are changed when it is exposed to ultraviolet light undergoing photooxidation. In this study, photooxdiation process of BR vulcanizate was investigated using a high pressure mercury lamp used as an outdoor lighting, which has high UV radiation efficiency and reasonable cost. Discoloration and crack formation of photooxdized BR vulcanite surface were examined using an image analyzer. Change of chemical functional groups of BR vulcanite surface by photooxidation was investigated using ATR-FTIR, and variation of the crosslink density with the UV irradiation time was investigated. By increasing the UV irradiation time, the crosslink density steeply increased after a period of time and did not increase any more. Formation of hydroxyl (~OH) and carbonyl (~C=O) groups on the BR vulcanizate surface increased and the1,4-cis unit was converted to the 1,4-trans unit as the photooxidation was proceeded.

• Elastomers and Composites
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• 제48권4호
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• pp.288-293
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• 2013

무수말레산-그래프트 EPDM (MAH-g-EPDM)/산화아연 복합체를 디클로로아세트산(DCA)/톨루엔 공용매로 처리하고 추출 온도에 따른 무게 감소와 가교밀도 측정을 이용하여 가교 특성을 조사하였다. 감쇠전반-후리에변환 적외선분광법(ATR-FTIR)을 이용하여 화학적 변화를 분석하였다. 상온 추출보다 고온($90^{\circ}C$) 추출에 의한 무게 감소가 월등히 높았으며, DCA/톨루엔 공용매 추출에 의한 무게 감소는 톨루엔 추출에 의한 무게 감소보다 5배 이상 높았다. 용매 추출 후 가교밀도를 측정하였으며, 1차 가교밀도보다 2차 가교밀도가 높았다. 1차 가교밀도는 추출온도가 높은 경우 더 낮았고 DCA/톨루엔 공용매로 추출한 것이 톨루엔으로 추출한 것보다 훨씬 낮았다. 2차 가교밀도는 DCA/톨루엔 공용매로 추출한 것이 톨루엔으로 추출한 것보다 높았다. 고온에서 DCA/톨루엔 공용매로 추출하면 강한 가교 그물망만 남는 반면, 상온에서 톨루엔으로 추출하면 미가교 고분자 사슬이 추출되는 등 추출 용매와 온도에 따라 추출되는 성분이 달랐다. 따라서 추출 용매와 온도에 따른 추출 성분의 비교와 연속 가교밀도 측정에 의해 MAH-g-EPDM/산화아연 복합체의 가교 특성을 분석할 수 있다.

• Elastomers and Composites
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• 제54권1호
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• pp.54-60
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• 2019

The rapid development of the automobile industry is an important factor that led to the dramatic development of synthetic rubber. The tread part of tire that comes in direct contact with the road surface is related to the service life of the tire. Rubber compounds used in tire treads are often blended with SBR (styrene-butadiene rubber) and BR (butadiene rubber) to satisfy physical property requirements. However, when two or more kinds of rubber are blended, phase separation and silica dispersion problems may occur due to non-uniform mixing of the rubber. Therefore, in this study, we synthesized an SBR copolymer with the same composition as that of a typical SBR/BR blend compound by controlling butadiene content during ESBR (emulsion styrene-butadiene rubber) synthesis. Subsequently, silica filled compounds were manufactured using the synthesized ESBR, and their mechanical properties, dynamic viscoelasticity, and crosslinking density were compared with those of the SBR/BR blended compound. When the content of butadiene was increased in the silica filled compound, the cure rate accelerated due to an increased number of allylic positions, which typically exhibit higher reactivity. However, the T-2 compound with increased butadiene content by synthesis less likely to show an increase in crosslink density due to poor silica dispersion. In addition, the T-3 compound containing high cis BR content showed high crosslink density due to its monosulfide crosslinking structure. Because of the phase separation, SBR/BR blend compounds were easily broken and showed similar $M_{100%}$ and $M_{300%}$ values as those of other compounds despite their high crosslink density. However, the developed blend showed excellent abrasion resistance due to the high cis-1,4 butadiene content and low rolling resistance due to the high crosslink density.