生物可分解聚合物 (biodegradable polymers) 為包裝材料上極具潛力的替代性材料,不同於石化材料,不易造成環境汙染,生物性多醣如幾丁聚醣 (chitosan, CH) 為天然多醣材料,可溶於酸性溶劑,攜帶正電荷並具抗菌作用,成膜性好、透明度高且無毒性,但成膜之機械特性仍有許多改善空間。纖維素 (cellulose) 透過物理性方法如介質研磨法 (media-milling) 降解後得到之介質研磨纖維素 (media-milled cellulose, MC),其材料表面積增加,暴露較多之OH官能基,且表面攜帶負電荷,理論上能與結構相似、電荷相反的幾丁聚醣具良好的分子間交互作用。本實驗目的利用介質研磨降解纖維素,與幾丁聚醣,經不同比例混合形成複合薄膜,另添加固定濃度甘油 (glycerol) 塑化劑,增加複合薄膜延展性,並以三聚磷酸鈉 (sodium tripolyphosphate, STPP) 進行薄膜交聯處理,增強薄膜的機械特性,探討其物化特性與交互作用;結果顯示,與未混合MC的組別相比,當複合薄膜比例為CH/MC = 70/30時,拉伸張力增加33%;添加甘油組強度增加275%,且延展性提升11倍,掃描式電子顯微鏡 (SEM) 影像顯示,兩材料在此比例下薄膜仍呈均質的結構;交聯組拉伸張力在比例為CH/MC = 10/90時,達到所有實驗組最大值104.30 MPa;隨MC比例愈高,除甘油組外,各處理組之水氣通過率、水分含量皆呈現下降趨勢,顯示MC能夠使複合薄膜親水性下降,但MC比例上升,增加複合薄膜的不透明度;各處理組的溶解度均小於10%,顯示複合薄膜較不易溶出固形物。X光繞射儀 (XRD) 結果顯示,CH與MC材料複合成膜後,提升複合薄膜的結晶度,但無新的結晶或結晶位移產生;透過傅立葉轉換紅外線光譜儀 (FTIR) 以及介面電位分析儀 (zeta potential) 測定,顯示CH與MC兩材料之交互作用包括分子間的氫鍵與靜電力作用。
Biodegradable polymers is a potential alternative materials for packaging. These materials are environmental friendly. Some of polysaccharides, such as chitosan (CH), which is soluble and protonated in dilute acid and is positive charged. CH exhibits non-toxic, transparent, antimicrobial, and film-forming properties. However, due to its poor mechanical and barrier properties, there existed plenty of rooms for improvement. Due to size reduction media-milled cellulose (MC) exhibits more surface area, and exposed more OH functional groups, with negative charge. Theoretically, MC could composite with CH due to similar molecule structure and electrostatics force interaction. The objectives of this study were to improve the mechanical property of chitosan via the employment of media-milled cellulose and sodium tripolyphosphate (cross-linked reagent, CL), and to evaluate the interactions among components during film preparation. Results showed that, compared with the control group (without MC), at the ratio CH/MC = 70/30, the tensile strength (TS) was increased 33%. Adding 30% glycerol increased the TS by 275% and elongation by 11 folds. The composite film exhibited greatest TS of 104.30 MPa with cross-linking at the ratio CH/MC/C = 90/10. Scanning electron microscopy (SEM) showed a homogenous structure at the ratios. The hydrophilic properties (water content and water vapor permeability, WVP) of CH film significantly (p < 0.05) decreased by MC except the glycerol group. Measured by X-ray diffraction (XRD), addition of MC enhanced the crystallinity of composite film, without new crystal forming. The interactions among components included intermolecular hydrogen bonding and electrostatics force evidenced by FTIR and Zeta potential measurements.