Papers by Author: Ping Zhang

Abstract: This paper concerned nanocrystalline cellulose(NCC)’s isolation from microcrystalline cellulose(MCC) by sulfuric acid hydrolysis, meanwhile centrifuging, ultrasonic treatment and freeze-drying were carried out afterwards. It covered the effect of reaction conditions on the yield of NCC. It indicated that hydrolysis time was the factor that matters most and it was possible to obtain the largest yield with hydrolysis time being 108min, hydrolysis temperature being 43oC and sulfuric acid concentration being 33%. It also investigated the microcosmic morphology of NCC by Transmission Electronic Microscopy(TEM). MCC and NCC’s thermal properties were studied further.

Abstract: The paper describes the production and the mechanical characteristics of composites made completely from renewable raw materials, the corn straw fiber and the biodegradable plastic, poly(lactic acid). The effect of straw fiber content on the mechanical properties of the composites was studied and the optimum mass fraction was 15%. To enhance the mechanical properties of the composites, two different methods were tested. Maleic anhydride as the compatilizer was introduced into the composites but the changes of the mechanical properties were small. While the other method, pre-treatment for straw fiber before blending, the mechanical properties increased obviously. The tensile strength and the impact strength were 35.6 MPa and 1.67 kJ/m2, respectively.

Abstract: Biodegradable aliphatic-aromatic copolyesters nanocomposites were designed and prepared via direct melt polycondensation of terephthalic acid (TPA), 1,4-butanediol (BDO), poly(L-lactic acid) oligomer (OLLA) and nano-SiO2 or nanostructured cage POSS reagent (POSS). The morphologies and dispersions of two nanofillers and their comparative effects on the mechanical properties of the nanocomposites were investigated. TEM characterizations confirmed that both nano-SiO2 and POSS took good dispersions in the copolyesters matrix. Due to the presence of flexible PEG tails and inorganic-organic nanocaged hybrid structures, POSS showed rather better dispersions and formed more strong interactions with the matrix than nano-SiO2. The experimental results indicated that incorporation of nano-SiO2 or POSS-PEG was a simple and rather effective way to greatly enhance the mechanical and thermal properties of the nanocomposites. Comparative studies of the effects between nano-SiO2 and POSS demonstrated that the introduction of POSS-PEG not only remarkably improved the tensile strength from 6.4 MPa to 11.2 MPa and Young’s modulus from 9.6 MPa to 70.7 MPa, but also dramatically increased the elongation at break from 190 % to 350%.

Abstract: In situ melt copolycondensation was proposed to prepare biodegradable copolyester nanocomposites based on degradable components poly(L-lactic acid) (PLA), rigid segments poly(butylene terephthalate) (PBT), and nanoparticles polyhedral oligomeric silsesquioxanes (POSS). The morphologies and dispersions of two POSS nanoparticles (POSS-NH₂ and POSS-PEG) in the copolyester PLABT matrix and their effects on the mechanical properties were investigated. The results demonstrated that the morphologies and dispersions of POSS-NH₂ and POSS-PEG showed quite different characteristics. POSS-PEG took better dispersion in the PLABT, while POSS-NH₂ had poor dispersions and formed crystalline microaggregates. Due to the good dispersion and strong interfacial adhesion of POSS-PEG with the matrix, the tensile strength and Young’s modulus were greatly improved from 6.4 and 9.6 MPa for neat PLABT up to 11.2 and 70.7 MPa for PLABT/POSS-PEG nanocomposite. Moreover, the incorporation of POSS-PEG could impart macromolecular chains good flexibility and improve the mobility of the chains, so the the elongation at break of PLABT/POSS-PEG nanocomposite dramatically increased from 190 to 350 % compared with neat PLABT.

Abstract: The aromatic polyester from diphenolic acid and isophthaloyl chloride was synthesized by interfacial polycondensation with tetrabutylammonium chloride as phase transfer catalyst. The structure was characterized by means of FTIR. The poly(DPA-IPC) solution was titrated by aqueous HCl solution. The titration curves were obtained. The trend of reduced viscosity of solution with concentration was studied. Besides, the stability of poly(DPA-IPC) in aqueous basic solution was discussed.

Abstract: Aromatic polyesters bearing pendent carboxyl functionalities were prepared by interfacial polycondensation of diphenolic acid, bisphenol A and isophthaloyl chloride with tetrabutylammonium chloride as phase transfer catalyst. The copolyester composition was confirmed with HPLC analysis. The polymerization process and composition of the copolyesters were examined by considering influences of reaction temperatures, time, ratio of feeds, agitation speeds.

Abstract: In this paper, we have studied the hot forming process of composites made by polylactic acid (PLA) and corn straw fiber. In order to obtain the composite cushioning material with ideal density and expansion ratio, the parameters of processing was optimized. It showed that the optimum condition as follows: the hot-press time was 5min, the pressure was 15MPa and the temperature was 200°C. The structure of the composite was characterized by FTIR.