Study On Preparation, Structure And Properties Of Thermal Plastic Biodegradable Polymers Based On Lignocellulose

Polymer materials from renewable resources have attached an increasing attention recently and cellulose is the richest renewable resources in the world. It was very important to prepare cellulose-based blend plastic for the replacement of petroleum in polymer material by biomass. Compatibility between blends was the basis of the performance improvement of cellulose-based thermoplastics. The block copolymer prepared from the ring-opening polymerization was adopted as the macromolecule compatibilizer of polycaprolactone-based or polylactide acid-based blending plastics. The structure and performance of compatibilized blends were characterized and compared to those of cellulose-based blending plastics without compatibilizer. The rules of interfacial compatibilization were also summarized. These results of research were as follow:1. The preparation and characterization of cellulose-based reinforced blending plasticsThe introduction of cellulose material had no influence on the crystallization behavior of polycaprolactone. All samples of blending plastic had the same melting point and crystalline degree with polycaprolactone. There was no particular signal in X-ray diffraction spectrum of blending plastics. It was demonstrated that polycaprolactone had different crystalline structure in blends. There was only the relaxation transition of polycaprolactone in the DMA spectrum of cellulose-based reinforced blends. The temperature of glass transition of polycaprolactone in blends was the same as the pure polymer. The storage modulus had drastic increase in samples with more than 20 % microcrystalline cellulose. The wood flour even had greater effect on storage modulus of blends. The blend 40 % wood flour and microcrystalline cellulose could be almost six and three times the modulus value of polycaprolactone, respectively, although tensile and impact strength of blend decreased.The tensile, modulus and impact didn't change after freeze aging. Samples with microcrystalline cellulose had better modulus after humid aging while the modulus decreased after soak aging. The modulus of samples with wood flour decreased under both conditions. The weight gain of blends in water bath reached the highest value within three weeks and samples with wood flour had the highest weight gain.2. The preparation of cellulose-based compatibilized blending plasticsHydrogen atom linked with carbonyl in compatibilizer showed new signal in nuclear magnetic resonance. It could be concluded that the product of caprolactone condensated with maleic anhydride was a block polymer. The compatibilized blends had satisfied tensile performance while the compatibilizer amount was between 8% and 10%. The tensile strength of polycaprolactone-based compatibilzed blends was increased by 12% while the cellulose ratio was lower than 60%. The reinforcement was greater in polylactide acid-based compatibilzed blends.The preparation technology of compatibilized blends was also investigated. It was found that the torque decreased to a stable value after the first three minutes of extrusion. Blending plastics could have satisfied extrusion and mechanic performance at 160°C and 100rpm. The addition of polycaprolactone to blending plastics could decrease the torque and had no influence on the extrusion pressure. The addition of macromolecule compatibilizer could decrease the torque and extrusion pressure. The structure of polymer in blends was the main factor to affect the shear force of screw and melt flow.3. The structure and characterization of cellulose-based compatibilized blending plasticsThe crystallinity and melting point of polycaprolactone decreased while the percentage of polycaprolactone decreased. Part of crystalline structure had no fusion after annealing treatment in the cellulose-based compatibilized blending plastics.The glass transition temperature of cellulose and polycaprolactone in blends moved closer to each other. This illuminated that cellulose-polycaprolactone compatibilized blending plastic was partly miscible. The distribution of relaxation transition broadened while phase dispersion increased. The blend with higher crystallinity had higher storage modulus. The dynamic mechanic character of blends was mainly decided by the continental phase in blend. The blend with 10% compatibilizer had high storage modulus.There was only one relaxation transition in the polylactide acid-cellulose compatibilized blends. It demonstrated that polylactide acid was miscible with cellulose in compatibilized blends.The feather-like and stripe-like image in transmission electron microscope represented polycaprolactone phase and cellulose phase, respectively. The morphology of blends changed according to the ratio of polycaprolactone in the blend. The flake-like structure in polylactide acid-cellulose compatibilized blends represented the interface phase.The contact angle of water on blends surface increased while the cellulose ratio in blends was lower than 60% and decreased after that ratio. The surface tension also reached the minimum while polylactide acid ratio in blends was 60%.The addition of cellulose acetate propionate could decrease the max decomposition rate of polycaprolactone in blends. The decomposition activation energy of CAP was lower than that of polycaprolactone and decreased by the addition of macromolecule compatibilizer. The decomposition activation energy of CAP and polycaprolactone both decreased to the minimum value while the amount of macromolecule compatibilizer was 10%.