醋酸丙酸纖維素/聚對苯二甲酸丁二酯摻合物之製備及其性質分析

Abstract

本研究分為三大部分，第一部分以由天然纖維素藉著有機酸當介質、硫酸當催化劑、酸酐為酯化劑的非均相法合成醋酸丙酸纖維素(CAP)，藉由凝膠層析儀(GPC)、液態超導核磁共振儀(NMR)、微差掃描熱分析儀(DSC)、熱重分析儀(TGA)和X光繞射儀(XRD)探討反應時間、反應溫度以及丙酸酐/乙酸酐的莫爾比的改變，對CAP的分子量、化學結構、熱性質與結晶性的影響。研究發現，隨著反應時間與反應溫度的增加，CAP的丙醯基取代度和結晶度皆上升，而其分子量、結晶溫度、熔融溫度和裂解溫度則下降。而當丙酸酐/乙酸酐的莫爾比增加時，CAP的丙醯基取代度、分子量、熔融溫度、結晶溫度、結晶度和裂解溫度皆為上升。 第二部分及第三部分為將聚對苯二甲酸丁二酯(PBT)與CAP以不同的組成摻混，並透過熱壓成型加工成薄膜。第二部分以CAP為分散相PBT當連續相的組成，第三部分則相反，以PBT為分散相CAP當連續相，兩部分的產品皆藉由掃描式電子顯微鏡(SEM)、接觸角測量儀、XRD、偏光顯微鏡(POM)、動態機械分析儀(DMA)、DSC和TGA來探討摻混材料的微結構、親水性、結晶行為、相容性、熱性質與機械性質。對照兩組的研究結果可知，PBT與CAP為不相容的摻混系統，因為各自的玻璃轉化溫度(Tg)皆不隨組成不同改變，然而若有小分子的聚乙二醇(PEG)作為塑化劑加入，則變為部分相容摻混系統。CAP與PEG的存在會影響PBT的結晶行為，因此隨著CAP或PEG的含量增加，PBT的結晶溫度會向低溫移動，其中當PBT為分散相時，PBT需要降溫至CAP的Tg溫度之下藉由異相成核才能結晶。CAP由於其化學結構較剛硬、側鏈較多以及分子量較大，因此不易形成結晶。CAP較PBT疏水且裂解溫度較低。分散相的成分在摻合物薄膜中會形成球狀顆粒。

Three divided parts were contained in this thesis. In the first part, cellulose acetate propionate (CAP) was synthesized by using acid anhydride as an acylating agent, sulfuric acid as a catalyst and acid as a dispersion medium from natural cellulose through heterogeneous esterification. The effects of reaction temperature, reaction time and the molar ratio of propionic anhydride to acetic anhydride on esterification were investigated. The molecular weight, chemical structure, crystallization behavior and thermal properties of CAP were investigated using gel permeation chromatography (GPC), nuclear magnetic resonance spectrometer (NMR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). As the reaction time and temperature increased, the melting point, crystallization temperature, molecular weight and degradation temperature of CAP decreased; however the substitution degree of propionyl group and crystallinity of CAP increased. As the the molar ratio of propionic anhydride to acetic anhydride increased, the melting point, substition degree of propionyl group, crystallization temperature, molecular weight, degradation temperature and crystallinity of CAP increased. In the second and third parts, blends of CAP with poly(butylene terephthalate) (PBT) were prepared in the form of film by melt compounding. The CAP was a dispersed phase in the second part while PBT was a dispersed phase in the third part. The microstructures, crystallization behavior, hydrophlilicity, miscibility, thermal and mechanical properties were investigated using scanning electron microscope (SEM), polarized optical microscope (POM), XRD, contact angle system, DSC, dynamic mechanical analysis (DMA), and TGA. The CAP/PBT blends was immiscible because of the presence of two invariant glass transition temperatures (Tg) corresponding to the CAP and PBT components. However, CAP/PBT blends became partially miscible after low molecule weight poly(ethylene glycol) (PEG), as a plasticlizer, were added. During the cooling from the molten state, the PBT crystallization peak shifted to lower temperature with increasing the CAP or PEG content, indicating that the presence of CAP or PEG has some effect on the crystallinity of the PBT component in the blends. The PBT component was crystallized at the temperature below the Tg of CAP as it was a dispersed phase in CAP/PBT films through heterogeneous nucleation. The CAP component could not undergo crystallization owing to its rigid structure, alkyl substituents and high molecular weight. The degradation temperature and the hydrophlilicity of CAP/PBT films decreased gradually with increasing the CAP content. For the CAP/PBT films, the dispersed phase was present as dispersed particles in the matrix.