Preparation and Characterization of Cellulose Acetate Propionate / (Poly(Butylene Terephthalate)) Blends

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.