聚對苯二甲酸丁二酯與纖維素醋酸丙酸酯摻合物薄膜、纖維及其性質分析

Abstract

本研究主要針對聚對苯二甲酸丁二酯(PBT)與纖維素醋酸丙酸酯(CAP)兩相高分子依不同組成比例進行一系列摻合物加工與其性質研究，並藉由低分子量聚乙二醇(PEG)作為相容化劑，期間透過雙螺桿混練設備進行混摻造粒，再以熱壓成型與熔融紡絲不同加工程序製備該摻合物薄膜或其纖維，並探討摻合物成分間相容性變化及摻合物薄膜與纖維之熱性質、結晶行為、微結構、親水性與機械性質。 論文內容包含三大部分，第一部分係以PBT為連續相，而CAP扮演分散相，其添加比例由5~15wt%，相關研究結果彙整於第三章。其次，第二部分為第一部分內容延伸，於兩相高分子系統中導入低分子量PEG作為相容化劑，整體摻合系統實際變為三相高分子而較為複雜，相關分析結果彙整於第四章。最後，第三部分則係以CAP為連續相，PBT則轉換為分散相，其添加比例一樣為5~15wt%，但因CAP為主的摻合物於混練造粒、熱壓成膜與紡絲階段皆因無法連續成型，因此相關研究僅揭露逕行添加低分子量PEG的摻合系統進行分析，相關討論彙整於第五章中。 研究證實PBT與CAP為不相容的摻混系統，因為各自的玻璃轉化溫度(Tg)皆不隨組成不同而改變，然而若有小分子的PEG加入，會使兩者Tg皆降低，意即摻合物轉變為部分相容系統。此外，CAP由於其化學結構剛硬與側鏈多，因此加工過程中不易形成結晶，而CAP與PEG的存在會影響連續相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且降低PBT結晶度；反之，當PBT作為分散相時在高溫下難以成核結晶，因此需要到CAP的Tg溫度之下藉由異相成核來結晶，結晶溫度則明顯由190°C降至110°C。其次，透過偏光顯微鏡進行摻合物恆溫結晶行為觀察，以PBT連續相時恆溫結晶，會產生緻密的球晶形態，其大小會隨著CAP或P-CAP添加量增加而變大；而P-CAP為連續相時恆溫結晶則多為非結晶形態，僅有少量細小的PBT球晶存在。而透過掃描式電子顯微鏡進行摻合物薄膜微結構觀察，發現分散相皆以球形顆粒存在於薄膜中，但當摻合物經過紡絲延伸加工後，分散相均變形為棒狀或纖維狀。 而就摻合物纖維研究結果顯示，PBT組分在纖維中的結晶度均較薄膜大，主要原因在於摻合物經過順向延伸後，PBT分子鏈的規則排列增加所導致，並且其結晶結構由α形態轉變為β形態。以PBT為連續相的纖維，隨著CAP或P-CAP的加入會使拉伸強度降低，但斷裂伸長率卻有大幅的提升；此外，以PBT為分散相的纖維，經由丙酮溶除連續相，可以製備出直徑為50~70nm之間的PBT奈米纖維。

This study is devoted to develop a series binary blends of poly(butylene terephthalate) (PBT) and cellulose acetate propionate (CAP) as a thermoplastic and renewable material, which could be applied for melt-spun fibers or other engineering plastics in the future. In order to improve the interfacial strength and miscibility between these two polymers by using a low-molecular-weight poly(ethylene glycol) (PEG) as a potential compatibilizer. A twin-screw extruder was applied to melt-compound these components to prepare the CAP/PBT, P-CAP/PBT, and PBT/P-CAP blends which were further processed into films and fibers by compression-molding and spinning, respectively. The morphology and crystallization behavior of the prepared films and fibers were examined. Moreover, their thermal, miscibility, and mechanical properties were also investigated. There are three major parts in the thesis. The first part：the CAP, as a dispersed phase, was mixed with the PBT in the composition range of 5 to 15wt%. Their related results were reported in the chapter 3. The next part：the content extension of the first part, a low-molecular-weight PEG as a compatibilizer, was introduced into previous binary blends systems. Their related results were summarized in the chapter 4. The third part, the binary blends of CAP and PBT were exchanged roles, which CAP be a continues phase. However, these binary blends could not be compounded smoothly and spun continuously, so we can't measure and analyze these specimen. Thus we tried again to blend CAP-PBT with PEG, and hopefully developed the films and fibers from the blends. Their related results were discussed in the chapter 5. The presence of two invariant glass transition temperatures corresponding to the CAP and PBT components implied that the CAP/PBT blends were immiscible. However, CAP/PBT blends became partially miscible after a low-molecular-weight PEG, as a compatibilizer, was added. In addition, the CAP in the blends could not crystallize during the cooling process from the molten state because of its rigid structure and thus existed in the amorphous state. This suggests that the presence of the amorphous CAP component and low-molecular-weight PEG hinders the arrangement of PBT component, leading to the reduction of the crystallization temperature of the PBT component. However, the crystallization temperature of the PBT component decreased greatly from 190°C for the neat PBT to 110°C, 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. From the isothermal crystallization behavior observation, it can be clearly found that PBT all form dense spherulites and collide with each other under various compositions. These spherulites become larger with more P-CAP added in the blend. From the SEM observation, the CAP component domains deform from the dispersed particles in the compression-molded films to the rods in the spun-fibers owing to the spinning orientation. Moreover, the crystallinity of the PBT component was higher in the spun fibers than in the films, possibly owing to the chain orientation in the spinning process. In the blend systems of PBT as a continuous phase, the presence of the amorphous CAP or low-molecular-weight PEG in the spun fibers caused a decrease in the tensile strength and an increase in the elongation at break. However, in the blend systems of CAP as a continuous phase, the ultra-fine PBT nanofibers with diameters in the range of 50 ~ 70nm were observed after removing the P-CAP matrix with acetone from the fibers, owing to the formation of PBT nanofibers during spinning and orientation processes. This method thus could successfully produce nano-scale PBT fibers with fineness comparable with the nanofibers developed via electrospinning technology.