共擠製微米層厚高分子多層膜的特性之探討

Abstract

單層設計的高分子薄膜已經漸漸無法滿足人類對於薄膜功能性多樣化的需求，多層化薄膜應運而生並大量運用在包裝、光學等用途。而目前應用多層化高分子薄膜，大多使用的是層數較少層厚較厚的薄膜，近年來奈米材料的發展研究，微/奈米層厚高分子多層膜儼然成為新的研究方向。 本研究的目的是在探討當多層膜在厚度維持不變、內部層數大幅提升使得層厚大幅下降至微/奈米等級時，其層厚均勻性、層數、層間介面對於多層膜的機械特性、氣體阻障能力之影響。研究中首先設計、製造了一套層倍增模具，用以將共擠製過程中的高分子膜反覆交疊，以二的冪次逐漸增加層數同時減低層厚至數微米等級；其次，利用光學顯微鏡(OM)對實驗製得之多層膜進行結構分析。 最後，採用體積排除法進行多層膜的氣體穿透能力實驗，歸納分析多層膜之氣體阻障能力與層數、層厚之關聯，初步建立一氣體穿透模型。 研究結果顯示，具有水氣阻障能力的PP其水氣阻障能力隨單位膜厚內的層數之增加而明顯增加；而具有氧氣阻障功能的PA特性亦相仿 。整體而言，高分子多層膜的氣體穿透能力與多層膜膜內層數之間存在明顯的關聯性。本研究結果可供未來探討高分子多層膜的功能性機制時之參考。

Since single-layer polymer film do not meet the requirements of new applications of packaging and optical components, multi-layer polymer films are widely used. However, most current applications of multi-layer polymer films use a small number of layers but with increased thickness. Recent studies of nanomaterials show that multi-layer polymer films with layer thickness in micrometer and nanometer scale has become a new trend of technological development. This study investigated how of layer thickness, number of layers, and the interface between layers affect the mechanical characteristics and gas barrier ability while layer thickness does not change the thickness of multi-layer films, increasing the number of layers significantly decreases layer thickness to the micron scale. This study developed a new mold design that can separate and expand co-extruded polymer films by using a co-extrusion system that has been described previously. The mold enables repeated overlay of two polymer layers to reduce layer thickness and increase the number of layers. The specimen are then compared by optical microscope, and a gas permeability experiment is performed to determine the relationships among number of layers, layer thickness, and gas barrier ability in the multi-layer films. Finally, a gas permeability experiment is performed using size exclusion method to generalize the relationship between gas permeability, numbers of layers, and layer thickness, and to establish a numerical model of gas permeability. The experiments indicate that polypropylene is an effective water vapor barrier, and its oxygen barrier characteristics resemble those of polyamide. Overall, gas permeability revealed a strong correlation with the number of layers of multilayer films. The experimental results of this study provide a reference for further study of the functional mechanisms of polymer multilayer films.