Standardization Study on the Method of Measuring the Tensile Strength of Contact Lenses

본 연구는 콘택트렌즈에 관한 표준화 규정에 인장강도 규격의 필요성을 평가하기 위해 기본적인 하이드로젤 콘택트렌즈 재료에 강도가 우수한 탄소나노튜브와 친수성 물질을 첨가하여 제조된 콘택트렌즈의 물성을 비교 및 분석하고자 하였다. 첨가제인 탄소나노튜브는 화학적 구조가 서로 다른 SW_CNT(carbon nanotube, single-walled), SW_CCNT(carbon nanotube, single-walled, carboxylic acid functionalized), SW_CPNT(carbon nanotube, single-walled, poly(ethylene glycol) functionalized)을 사용하였다. 또한 친수성 물질인 MA(methacrylate), PEGMA(Poly ethylene glycol methacrylate)을 함께 사용하여 함수율과 인장강도의 상관관계를 평가하였다. 제조된 렌즈의 물성을 정리하면 다음과 같다. REF에 비해 탄소나노튜브가 첨가된 렌즈의 함수율은 감소하고, 인장강도는 다소 증가하였다. 그리고 탄소나노튜브에 PEGMA와 MA가 첨가한 경우, MA가 PEGMA에 비해 함수율이 증가하여 큰 차이를 보였다. 그러나 SW_CCNT와 SW_CPNT군에 첨가한 경우, 두 친수성 물질의 인장강도 결과는 큰 변화가 없었다. 따라서 함수율의 결과와 인장강도의 결과는 항상 비례한다고 할 수 없으며, 인장강도는 렌즈의 내구성을 평가할 수 있는 중요한 지표로써 인장강도를 표준화시켜 정확한 성능 평가를 위해 규격 제정이 필요하다고 판단된다.

This study was conducted to evaluate the necessity of the tensile strength in the standardization for contact lenses by comparing and analyzing the properties of contact lenses manufactured by adding carbon nanotubes with high strength and hydrophilic materials to the basic hydrogel contact lens material. For the carbon nanotubes (the additives), SW_CNT (carbon nanotube, single-walled), SW_CCNT (carbon nanotube, single-walled, carboxylic-acid-functionalized), and SW_CPNT (carbon nanotube, single-walled, poly- [ethylene glycol]-functionalized) were used as the ones with different chemical structures. In addition, hydrophilic materials (MA [methacrylate] and PEGMA [polyethylene glycol methacrylate]) were used to evaluate the correlation between the water content and the tensile strength. The physical properties of the manufactured lens are summarized as follows. Compared to REF, the water content of the carbon-nanotube-added lens decreased while its tensile strength increased. In addition, when PEGMA and MA were added to the carbon nanotube, the water content of MA increased more than that of PEGMA, showing a big difference. When PEGMA and MA were added to the SW_CCNT and SW_CPNT groups, however, the tensile strength of the two hydrophilic materials did not change significantly. Therefore, it is considered that the water content and tensile strength results may not always be proportional, and that the tensile strength is an important index for evaluating the durability of lenses. Therefore, a tensile strength standard should be established by standardizing the format for evaluating it for accurate performance evaluation.