本研究以聚丙烯(Polypropylene)為基材,利用CF4電漿進行表面改質,探討電漿功率、電漿處理時間、不同氣體進料與基材放置位置對電漿改質後之膜材表面疏水及疏油性質之影響,並利用SEM、AFM、ESCA等儀器分析電漿改質後膜材之物理形態與化學組成變化。此外,為探討表面粗糙度對膜材疏水性及疏油性之影響,亦利用氫氣及乙烷電漿對CF4電漿改質後之膜材表面再進行改質。 首先利用CF4電漿對PP膜材進行表面改質,發現改質後之膜材表面具有超疏水( ~150∘)及疏油(~120∘)之性質,相較於單純之PTFE膜材接觸角(~110∘),顯示改質後PP膜面除了表面具有PTFE-like之化學結構外,膜材表面形態亦有明顯變化,使得表面疏水性提升。經SEM及AFM之影像結果可發現膜材表面粗糙度確實隨著電漿功率及電漿處理時間之提高而上升。另外以XPS對膜材表面進行化學元素組成分析,亦可發現改質後膜材表面之氟碳比隨著電漿功率與電漿處理時間的提高有上升後持平的趨勢。而為了探討表面粗糙度對於水接觸角之影響,本研究中利用AFM之數據求得粗糙因子(fr),並代入Wenzel以及Cassie-Baxter之計算式,結果發現經CF4電漿改質之膜材,其粗糙度之變化近似於Cassie-Baxter之模式。此外亦藉由XRD分析發現所使用之膜材具有結晶結構,推測表面粗糙度生成之原因為結晶/非結晶區段之蝕刻速率差異所造成。 使用氬氣及氧氣電漿對於膜材表面進行改質,發現改質後之膜面無法形成如CF4電漿處理後之表面粗糙度,推測表面氟化有助於提高膜面結晶/非結晶區段之蝕刻選擇性。此外氬氣與氧氣電漿改質不會提升膜材表面之疏油性質。 而對於膜材放置位置不同之探討,可發現隨著遠離電漿區,膜材表面對水接觸角有下降之趨勢,而膜材表面粗糙度之形成逐漸減少,膜材表面之氟碳比變化呈現先升後降之變化趨勢。 為了探討在不含氟之膜材表面粗糙度對接觸角之影響,本研究利用氫氣及乙烷電漿對經CF4電漿改質後之膜材再進行改質,結果發現改質後之膜材表面氟原子含量大幅降低(F/C<0.01),並保有部分表面粗糙度。改質後之膜面對水之接觸角變化取決於表面粗糙度變化與膜面氧碳比之變化,然而對於非極性液體之接觸角則呈現親油性,顯示疏油性質在本研究中,受到膜材表面化學組成之影響遠大於表面物理形態,且氟元素為影響最大之因素。 關鍵詞 : 聚丙烯、電漿表面改質、表面超疏水化、聚四氟乙烯
Super-hydrophobic and oleophobic polypropylene (PP) surfaces were prepared by surface plasma modification using tetrafluoromethane (CF4) plasma. The characteristics of surface were investigated by means of contact angle measurement, scanning electron microscopy, atomic force microscopy, X-ray diffraction (XRD) and electron spectroscopy for chemical analysis. First, the PP sheet surface showed super-hydrophobicity (~150∘) and oleophobicity (~120∘) after CF4 plasma modification, and analysis results reveal that the modified surface showed roughness enhancement and PTFE-like composition. To investigate the relation between surface roughness and water contact angle measurement, both Wenzel and Cassie-Baxter models were used. It was found that the behavior of water droplet on PP surface is close to Cassie-Baxter model. The untreated PP sheet have crystalline structure examined by XRD, it seems that the enhancement of surface roughness were based on the different etching rates between crystalline and amorphous materials. Secondly, PP sheet was modified by argon and oxygen plasma, and the surface roughness is much less than that treated by CF4 plasma. It seems that surface fluorination was helpful to enhance the selectivity of etch rate between crystalline and amorphous materials. And oleophobicity of surface was not enhanced after argon or oxygen plasma modification. By using remote CF4 plasma modification, the characteristics of PP sheet surface such as contact angle and surface roughness show decreased trend and the surface F/C ratio shows increased then decreased trend when leaving from plasma region. It reveals that ion bombardment is helpful for surface roughness enhancement.