Two-step grafting of methyl methacrylate(MMA) and methacrylic acid (MAA) onto commercial poly(ethylene terephthalate) (PET) film drawn biaxially has been carried out with benzoyl peroxide(BPO) as an initiator. The lst step was the pretreatment of PET with the emulsion of BPO and a swelling agent, and the 2nd step was the graft copolymerization of the monomers onto the pretreated PET in the emulsion or aqueous solution. The surface free energy of grafted PET films was determined by the two-liquid contact-angle method. From the results of contact angle measurement, the dispersion force component(γ^s_d) of surface free energy and the nondispersive interaction energy (Iⁿ_sw) between the PET film and water have been determined by the following equation; Iⁿ _sw=γ_w - γ_H + γ_Hwcosθ + 2(γ^d_s)^1/2 [(γ_H)^1/2 - (γ^d_w)^1/2 ] The dispersion component of surface free energy of MMA-g-PET increased drastically with graft yield, but the non-dispersive interaction energy between MMA-g-PET and water decreased linearly with graft yield. For MAA-g-PET film, γ_s^d values slightly decreased with graft yield, and Iⁿ _sw values increased with graft yield at the lower wt.% of MAA, but levelled off at the graft yield higher than 8%. The polar component of surface free energy was calculated from Iⁿ _sw values, using the following equation. γ^p_s =(Iⁿ _sw)² / 4γ^p_w Total surface free energy(γ_s) of MMA-g-PET was affected more dominantly by the dispersion force component than by polar force component, but that of MAA-g-PET was vice versa. This was in accordance with the chemical structure of each monomer grafted.

2축 연신한 폴리에틸렌 테레프탈레이트(PET)필름에 메타크릴산 메틸(MMA)과 메타크릴산(MAA)을 각각 그라프트 공중합시켰다. 그라프트된 필름의 포면자유에너지를 2액법을 사용하여 접촉각을 측정함으로서 분석하였다. MMA가 그라프트된 PET(MMA-g-PET)의 표면 자유 에너지의 분산력 성분은 그라프트 수율에 따라 급격히 증가하였으며, MAA를 그라프트한 PET(MAA-g-PET)의 경우 분산력 성분은 그라프트 수율에 따라 증가하다가 어떤 평형치에 도달했다. 한편 표면에너지의 극성력 성분은 MMA-g-PET의 경우는 그라프트 수율에 따라 감소하며 MAA-g-PET의 경우는 그라프트 수율에 따라 증가하였다. MMA-g-PET의 전체 표면 자유 에너지는 극성력 성분보다 분산력 성분에 의하여 더 큰 영향을 받았으며 반대로 MAA-g-PET의 경우에는 극성력에 의한 효과가 훨씬 우세한 것으로 나타났다.