The effect of crystallinity on the characteristics of perforation in breathable polypropylene film made by laser ablation was studied and it was related with the characteristics of oxygen transmittance in the film. It was found that the increase of laser power resulted in the increase of the diameter of perforation while the spatter interval and height decreased. This phenomenon was relatively dominant in the film having thick thickness. The crystallinity controlled by cooling condition in melt casting film process affected the characteristic of perforation, as a result, the transparent film having smaller crystallite had a lager diameter of perforation with less spatter interval and height when similar laser power was applied. Oxygen transmittance was controlled by the shape of perforation and it was confirmed that less crystalline film having larger diameter of perforation showed higher oxygen transmittance. The dramatic increase of oxygen transmittance was found in the thinner film because the complete perforation through the film thickness occurred when high laser power was applied on the film.

폴리프로필렌 필름의 결정화도가 레이저 절제에 의하여 제조된 통기성 필름 천공 특성에 미치는 영향과 이에 따른 산소 투과도 변화에 대하여 살펴보았다. 레이저 파워 증가는 필름에 형성된 천공 직경을 증가시키는 반면, 천공의 간격 및 높이를 감소시킴을 확인하였다. 이러한 현상은 필름의 두께가 두꺼울수록 더 두드러짐을 확인하였다. 천공 형태 변화는 냉각 조건에 의하여 형성된 결정화도에 따라 달라지며 결정 크기가 작아 투명한 필름은 천공 직경이 증가되는 반면, 천공 간격 및 높이는 감소되었다. 필름에 형성된 천공 모양은 필름의 산소 투과도에 영향을 주어 천공 직경이 크고, 결정화도가 낮은 필름에서 높은 산소 투과도를 보였다. 두께가 얇은 필름에서 레이저 파워가 커지면 완전 천공 현상에 의하여 산소투과도가 급격히 증가되었다.

Keywords: breathable film, laser ablation, perforation, oxygen transmittance