Self-healable epoxidized natural rubber nanocomposites with halloysite nanotube and graphene oxide

Abstract

요 약

자기치유고분자는 자발적으로 기계적 발생된 손상 부위를 치유할 수 있는 스마트소재이다. 본 연구에서는 우수한 기계적물성과 자가치유특성을 갖는 고무소재를 제조하기 위한 연구를 수행하였다. 이를 위하여 고무로써는 에폭시화 천연고무(ENR)를, 나노입자로써는 튜브형태의 halloysite nanotube (HNT) 및 판상형태의 graphene oxide (GO)를 각각 이용하였으며, 이들 무기나노입자들은 밴버리믹서를 이용한 용융혼합방법으로 고무매트릭스에 1 ~ 10 phr 첨가하였다. 고무의 가교제로써는 ENR의 에폭시기와 반응할 수 있는 1,2,4‐triazole (ATA)을 이용하였으며, two-roll mill을 이용하여 배합하였다. 제조된 고무배합물의 가교 거동은 oscillating disc rheometer (ODR)을 통하여 분석하였으며, 가교시킨 고무나노복합체의 미세구조, 기계적물성 및 자가치유특성은 TEM, 동적점탄성시험(DMA) 및 인장시험을 통하여 조사하였다. ODR 분석 결과, 가교제인 ATA의 함량에 따라 또 무기나노입자의 첨가량이 증가함에 따라 가교속도가 빨라지며 가교밀도가 증가될 수 있음을 알 수 있었다. 가교시킨 고무나노복합체의 미세구조분석결과 첨가된 무기입자들은 고무매트릭스 내에 나노크기로 균일하게 분산됨을 확인하였으며, 인장시험결과 400% 이상의 파단신율값과 5% 이하의 tension set값을 나타내는 고탄성소재임을 알 수 있었으며, 소량의 무기나노입자 첨가만으로도 파단신율의 감소없이 모듈러스와 파단강도를 효과적으로 증가시킬 수 있음을 알 수 있었다. 또한, 이렇게 제조된 ATA 가교 ENR 나노복합체는 상온에서 우수한 자가치유특성을 보였으며, 면도칼로 자른 시료를 상온에서 24시간 단면을 맞댄 상태로 두었을 때, HNT 10 par, GO 2 phr 인 나노복합체의 경우 원 시료의 파단신율 대비 각각 91%와 81% 수준의 회복율을 나타내었다. 이와 같은, 기계적물성의 향상과 자가치유특성은 고무 사슬간 및 나노입자표면과 고무사슬에 존재하는 극성기들간의 광범위한 수소결합상호작용에 기인한 것으로 판단되었다. 이와같은 극성을 갖는 ENR 기반의 나노복합소재는 고무씰, 접착제, 호스 등 전통적인 고무제품에서부터 웨어러블 디바이스의 외장재, 신축성 전극 등과 같은 첨단분야에까지 다양하게 응용이 가능할 것으로 생각된다.|Abstract

Intrinsic self-healing rubbers, which are able to repair damage (scratches, cracks) spontaneously and autonomously, have received much attentions in recent years. In this study, it is attempted to develop highly elastic rubber nanocomposites having self-healing ability and robust mechanical properties via a melt blending of epoxidized natural rubber (ENR) with small amount of nanoparticles, and a subsequent curing of the nanocomposites using 3‐amino‐1,2,4‐triazole (ATA) as a crosslinker. Two different nanofillers, halloysite nanotube (HNT) and graphene oxide (GO), were employed to prepare the nanocomposites. Curing behavior of ENR/ATA compounds with the nanofillers were monitored by oscillating disc rheometer (ODR), and the morphology, mechanical properties and self-healing effects of the ATA-cured ENR nanocomposites with HNT and GO were characterized by TEM, DMA, and room temperature tensile test, respectively.

The results revealed that rubber network with covalent bonding as well as multiple hydrogen-bonding interactions between the rubber chains could be prepared by curing of epoxidized natural rubber (ENR) using ATA as a crosslinking agent. The ENR network exhibited an elongation-at-break higher than 400% along with excellent elastic recoverability. The ATA-cured ENR vulcanizates containing small amounts of inorganic nanofillers such as HNT and GO exhibited a greatly improved mechanical properties and self-healing effect at ambient condition. The nanocomposite with 10 phr HNT and 2 phr GO showed a healing efficiency of 91% and 81%, respectively. The interesting properties of the rubber nanocomposites are attributed to the hydrogen-bonding interactions between the rubber chains and functional group of surface of the nanoparticles. The ENR nanocomposites with self-healing effects and robust mechanical properties can have a variety of practical applications ranging from conventional rubber products like O-ring seal, hose, and adhesives to wearable devices and stretchable electronics.; Abstract

Intrinsic self-healing rubbers, which are able to repair damage (scratches, cracks) spontaneously and autonomously, have received much attentions in recent years. In this study, it is attempted to develop highly elastic rubber nanocomposites having self-healing ability and robust mechanical properties via a melt blending of epoxidized natural rubber (ENR) with small amount of nanoparticles, and a subsequent curing of the nanocomposites using 3‐amino‐1,2,4‐triazole (ATA) as a crosslinker. Two different nanofillers, halloysite nanotube (HNT) and graphene oxide (GO), were employed to prepare the nanocomposites. Curing behavior of ENR/ATA compounds with the nanofillers were monitored by oscillating disc rheometer (ODR), and the morphology, mechanical properties and self-healing effects of the ATA-cured ENR nanocomposites with HNT and GO were characterized by TEM, DMA, and room temperature tensile test, respectively.

The results revealed that rubber network with covalent bonding as well as multiple hydrogen-bonding interactions between the rubber chains could be prepared by curing of epoxidized natural rubber (ENR) using ATA as a crosslinking agent. The ENR network exhibited an elongation-at-break higher than 400% along with excellent elastic recoverability. The ATA-cured ENR vulcanizates containing small amounts of inorganic nanofillers such as HNT and GO exhibited a greatly improved mechanical properties and self-healing effect at ambient condition. The nanocomposite with 10 phr HNT and 2 phr GO showed a healing efficiency of 91% and 81%, respectively. The interesting properties of the rubber nanocomposites are attributed to the hydrogen-bonding interactions between the rubber chains and functional group of surface of the nanoparticles. The ENR nanocomposites with self-healing effects and robust mechanical properties can have a variety of practical applications ranging from conventional rubber products like O-ring seal, hose, and adhesives to wearable devices and stretchable electronics.