| Poly(propylene carbonate)(PPC) is one of carbon dioxide sourced environmental friendly thermoplastic aliphatic polycarbonate. Due to its thermoplastic, superior biodegradable, high barrier property and biocompatibility properties, PPC is widely applied in the fields such as packing and medical materials. However, the application of PPC as a material is limited because it is an amorphous polymer, and it exhibits a relatively low glass transition temperature.Therefore, it is significantly essential and practical to reinforce PPC in order to broaden its use.In order to improve its thermal property, maleic anhydride(MA), phthalic anhydride(PA), pyromellitic dianhydride(PMDA), diphenylmethane diisocyanate(MDI) and Joncryl ADR-4370(Joncryl) end-capping PPC was prepared by reactive extrusion. Structure of end-capped PPC was characterized by FTIR, titration test and intrinsic viscosity test. The properties were measured by tensile test, thermogravimetry analysis. Meanwhile, rheological responses of end-capped PPC were recorded to investigate the relationship between properties and structure. There were two types of mechanisms between PPC and anhydride. Results from FTIR spectrum showed that there existed an absorption of C=C at 1640cm-1, proving that MA was successfully end-capped with PPC. Compared with that of MA, hydrogen bonds were formed between carbonyl of PA and PMDA and terminal hydroxyl of PPC. PPC was end-capped with MDI through melt compounding and its structure was charaterized by FTIR and rheological responses. As for Joncryl, the reaction mechanism between PPC and Joncryl was complex. Because the molecular chain of Joncryl contain epoxy groups, benzene, methacrylate as well as some other polar groups. These groups may inhibit the chain unzipping scission of PPC via backbiting route.PPC/PA66 short fiber composites were prepared by a co-rotating twin-screw extruder. The structure and properties were investigated. The mechanical and thermal properties of PPC/PA66 composites were evaluated by tensile and impact tests, differential scanning calorimetry(DSC) and thermogravimetry analysis, respectively. Results of FTIR and 1H NMR tests revealed that the hydrogen bonds were formed between the carbonyl group of PA66 and hydrogen group of PPC. The properties of composites were affected significantly by the content of PA66 short fiber. The tensile and impact strength, thermal stability of composites was increased when the content of PA66 short fiber was lower than 20wt%. The increase of impact strength, decomposition temperature of 5% mass loss(T-5%) and glass transition temperature of PPC with 20wt% PA66 short fiber loading was 315.81%, 32.2℃ and 3.8℃, respectively. When the content of PA66 short fiber was 30wt%, a significant aggregation of PA66 short fiber was observed by SEM, which caused the decrease of mechanical and thermal properties for composite. This illuminated that the improvement of the mechanical properties and thermal stability for PPC with the addition of PA66 short fiber was owing to the formation of hydrogen and the characterization of PA66 short fiber.To enhance the interfacial interaction between microcrystalline cellulose(MCC) and PPC matrix, PPC/MCC composites were modified by MDI through the reactive mixing. The structure and morphology of the composites were characterized by FTIR and SEM. The properties were investigated by TGA and tensile tests. The results show that PPC chains were grafted onto the surface of MCC. As a bridging agent, MDI enhanced the interfacial interaction between MCC and PPC matrix. This result also can be concluded from the further improved mechanical properties and thermal stability. In short, PPC chains grafted onto the surface of MCC and PPC was end-capped by MDI. These two factors could improve the compatibility of PPC matrix and MCC. Moreover, nanocrystalline cellulose(NCC), prepared by TEMPO treatment of MCC and polyethylene glycol(PEG) were incorporated into PPC. The obtained PPC/PEG/NCC composites display a great improvement in thermal properties by adding 10wt% PEG and a small amount of NCC, in particular, with 0.7phr NCC incorporated. The initial decomposition temperature(T-5%) of PPC/PEG/0.7NCC composite was about 246.5 °C, 36 °C higher than that of pure PPC. The improvement of T-5% was attributed to the nano-sized NCC providing more surface area and probability to form hydrogen bonding interaction between PPC and NCC, which inhibit the chain unzipping scission of PPC via backbiting route. |
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