Performance and Structure Characterization of Poly(lactic acid)/Zinc Oxide Pillared Organic Saponite Nanocomposites by Solution Intercalation

Weijun Zhen,Shengzhen Bian,Jinlu Sun,Xi Xi 한국고분자학회 2016 폴리머 Vol.40 No.2

Zinc oxide (ZnO) pillared organic saponite was synthesized with cetyltrimethylammonium bromide (CTAB) via a microwave hydrolysis method. Moreover, poly(lactic acid) (PLA)/ZnO pillared organic saponite nanocomposites were prepared by solution intercalation. The microstructure analysis suggested that ZnO pillared organic saponite appeared at an exfoliated or partially intercalated nanometer layer, which dispersed homogeneously in PLA matrix. The experimental results showed that ZnO pillared organic saponite improved the mechanical properties and thermal stabilities of PLA/ZnO pillared organic saponite nanocomposites. Differential scanning calorimetry (DSC) results demonstrated that the ZnO pillared organic saponite eliminated the cold crystallization process, decreased the crystal size and obviously promoted the crystallinity of PLA, which was in accordance with XRD analysis results. At the same time, the properties of UV absorbance and antibacterial properties of nano ZnO were introduced into PLA.

The Effects of Structure of Inclusion Complex between β-Cyclodextrin and Poly(L-lactic acid) on Its Performance

YuFang Zhou,Weijun Zhen,YaNan Song,WenTao Wang 한국고분자학회 2015 Macromolecular Research Vol.23 No.12

The partial inclusion complexes (ICs) between poly(L-lactic acid) (PLLA) with high molecular weight and β-cyclodextrin (CD) were prepared and characterized by 1H nuclear magnetic resonance spectra (1H NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), respectively. The thermal results demonstrated that the crystallization performance of ICs were significantly improved, and the decomposition temperature of ICs were increased compared with PLLA. The mechanical tests indicated that the mechanical performance of ICs was improved, and the β-CD-PLLA ICs exhibited a higher non-Newtonian effect than PLLA. The degradation rate for the partial ICs in phosphate buffer solution accelerated as the ratio of β-CD increased, meanwhile, the partial ICs had a good shape memory behavior. The wetting measurements suggested the hydrophilicity of ICs was also enhanced markedly in comparison with the bulk PLLA.

Enhancement of Mechanical and Antimicrobial Properties of Thermoplastic Poly(lactic acid)/Quaternized Chitosan-Saponite Nanocomposites

Xi Xi,Weijun Zhen,Shengzhen Bian,Wentao Wang 한국고분자학회 2015 폴리머 Vol.39 No.4

Water-soluble N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared with 2, 3-epoxypropyl trimethyl ammonium chloride grafting to the amino groups of chitosan. Then, chitosan quaternary ammonium intercalated saponite (HTCC-saponite) was synthesized with HTCC and saponite by ultrasonication intercalation. Compared with chitosan, HTCC had a good antibacterial effect. Thermoplastic poly(lactic acid) (PLA)/HTCC-saponite nanocomposites were prepared with HTCC-saponite and PLA by melt intercalation. Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) showed that HTCC was successfully synthesized by a modified method of two-step reaction. Moreover, X-ray diffraction (XRD) and scanning electron microscope (SEM) also showed that saponite was intercalated or nearly exfoliated by HTCC. It was shown the mechanical properties of PLA/HTCC-saponite nanocomposites attained the optimum when the content of HTCC-saponite was 1 phr. The studies of thermal stability, crystallization and rheological behavior of PLA/HTCC-saponite nanocomposites demonstrated that PLA/HTCC-saponite nanocomposites exhibited high performance compared with PLA.

Preparation, the Chain-extending Reaction Kinetics and Thermal Degradation of Poly(D-lactide) by Reactive Extrusion Process

Zhongbo Song,Weijun Zhen 한국고분자학회 2017 폴리머 Vol.41 No.6

The chain-extended poly(D-lactide) (PDLA) was prepared from D-lactide under optimum polymerization conditions of 1 wt% stannous octoate, at 170 ℃, 10 rpm for 15 min or 10 min with the addition of chain extender (4,4"- diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI)) by reactive extrusion process. The molecular weight of PDLA-MDI and PDLA-HDI was 45376 and 47238 g/mol, respectively, which had been significantly improved compared with PDLA (Mw=20730 g/mol). Furthermore, differential scanning calorimetry (DSC) results showed that the crystallinity of PDLA-MDI and PDLA-HDI was increased by 66.04 and 78.60%, respectively, compared with PDLA. Moreover, the rheological results and thermal decomposition kinetics results showed that the MDI and HDI had restricted the mobility of PDLA chains and enhanced the apparent activation energy (Ea) of thermal degradation of PDLA.

Preparation, Structure and Performance of Poly(lactic acid)/Poly(lactic acid)-γ -Cyclodextrin Inclusion Complex-Poly(glycidyl methacrylate) Composites

Ya Li,Weijun Zhen 한국고분자학회 2018 Macromolecular Research Vol.26 No.3

Poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(glycidyl methacrylate) (PLA-IC-PGMA) was synthesized with poly(lactic acid) (PLA) and γ-cyclodextrin inclusion complex via surface initiated atom transfer radical polymerization. Then, the PLA/PLA-IC-PGMA composite was prepared by melt blending using PLA-IC-PGMA as additive. Structure and properties of PLA-IC-PGMA and PLA/PLA-IC-PGMA composites were confirmed by X-ray diffraction patterns, 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), polarized optical microscopy, rheological analysis, etc. Mechanical testing analysis showed that the tensile strength, elongation at break, and impact strength of PLA/ (1 wt%) PLAIC- PGMA composites were improved by 2.3%, 10.8%, and 52.5%, respectively, compared with pure PLA. Scanning electron microscopy analysis demonstrated that the toughness of PLA/PLA-IC-PGMA composite was improved. The results of DSC and TG showed that the cold crystallization peak of PLA composites after the addition of PLA-IC-PGMA disappeared, and its crystallinity was increased by 25% compared with PLA. Furthermore, the thermal stability of PLA/PLA-IC-PGMA composite was improved. Dynamic mechanical analysis showed that the glass transition temperature of PLA/PLA-IC-PGMA composites decreased by 8 oC, which indicated that the flexibility of the chain of PLA was greatly improved. Therefore, the addition of PLA-IC-PGMA improved the comprehensive performance of PLA.

Surface Functionalization of Graphene Oxide via Activators Regenerated by Electron Transfer for Atom Transfer Radical Polymerization and Its Effect on the Performance of Poly(lactic acid)

Lang Zheng,Weijun Zhen 한국고분자학회 2018 폴리머 Vol.42 No.4

An improved Hummers method was used to prepare graphene oxide (GO). Then, the orthogonal experiment design methods were used to select the optimum conditions of preparation for graphene oxide-polymethyl methacrylate (GO-PMMA) via activators regenerated by electron transfer for atom transfer radical polymerization (AGET-ATRP). The optimum preparation conditions were determined by orthogonal tests. Furthermore, poly(lactic acid) (PLA)/GO-PMMA nanocomposites were prepared by melt blending to improve the comprehensive performance of PLA. Analysis results indicated that methyl methacrylate (MMA) was successfully grafted onto GO, and the addition of 0.3 wt% of GO-PMMA increased the tensile strength, elongation at break, and impact strength of PLA/GO-PMMA nanocomposites by 7.82, 40.66, and 50.62%, respectively, compared with PLA. Moreover, GO-PMMA eliminated the cold crystallization of PLA matrix and improved the crystallinity of PLA by 27.55%. In all, this study provided an effective and feasible method for improving the comprehensive performance of PLA.

Superior adsorption of Re(VII) by anionic imprinted chitosan-silica composite: Adsorption performance, selectivity and mechanism study

Ying Xiong,Lisha Xie,Long Zhu,Yuejiao Wang,Weijun Shan,Zhenning Lou,Junshuo Cui,Haibiao Yu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

In this study, a three-dimensional chitosan/mesoporous silica composite material (I-CTS-KIT-6) was successfullysynthesized by one-step method using ion imprinting technology. To overcome the enormouscost problem, MoO4 2 with similar radius to ReO4was selected as template ion. In addition, the adsorbentwas prepared by using glutaraldehyde and chitosan as crosslinking agents and monomers and TEOS assilicon source in the process of imprinting. The effects of pH values, mass of chitosan and templateion, contact time, temperature and concentration on Re(VII) adsorption were studied. The resultsrevealed that the I-CTS-KIT-6 has the saturated adsorption capacity of 368.8 mg g1 at pH 3.0 for Re(VII), and the adsorption process corresponded to Langmuir isotherm and pseudo-second-order kinetics. Especially, the I-CTS-KIT-6 has higher selectivity for rhenium ions compared with the non-imprintedadsorbent. To verify the adsorption mechanism, density functional theory (DFT) was adopted to analyzethe binding patterns of Re(VII) with the I-CTS-KIT-6. The test analysis and calculation results further mentionedthat the adsorption mechanism is mainly three N atoms of I-CTS-KIT-6 coordinated with threeoxygen atoms of ReO4, which provides the theoretical foundations and explanations for adsorptionprocess.