Ming Long Yuan

Physical Properties and Antimicrobial Activity of a Poly(Lactic Acid)/Poly(Trimethylene Carbonate) Film Incorporated with Thymol

Thymol (TH), which has antimicrobial effect on many food pathogens, was incorporated as antimicrobial agent into composite poly (lactic acid)/poly (trimethylene carbonate)(PLA-PTMC) films. Antimicrobial active films based on PLA-PTMC were prepared by incorporating thymol at five different concentrations: 0, 3, 6, 9 and 12 %(w/w). The mechanical characterization, water vapor permeability (WVP), and antimicrobial activity of all formulations composite film were carried out. A decrease in elastic modulus was obtained for the active composite film compared with neat PLA-PTMC film. The presence of thymol decreased water vapor permeability, with a significant antimicrobial activity. Antimicrobial activities of films were tested against Escherichia coli, Staphylococcus aurous, Listeria, Bacillus subtilis, and Salmonella. Increasing amount of the thymol in the film caused a significant increase in inhibitory zones. These results suggest that thymol incorporated PLA-PTMC films have a prospectively potential in antimicrobial food packaging.

The Preparation and Property Research on Laponite-Poly (L-Lactide) Composite Film

The laponite-poly (L-lactide) composite films are prepared by the method of solution blending with polylactide (PLA) and laponite. The result shows that the homogeneous and smooth composite film is prepared with 1, 4-dioxane. Thermogravimetry analysis (TG) and tensile strength studies demonstrate that the thermal stability and tensile strength are improved with the laponite added. The scanning electron microscopy (SEM) measurement indicates that the pores of composite films get uniform and network structure is more and more compact with compared to pure PLA film. The present study reveals that the laponite as a complexing agent can improve the mechanical properties and thermal stability of PLA.

Preparation and Characterization of poly(L-lactide) /poly (ε-caprolactone) Composite Films for Food Packaging Application

Poly (L-lactide) (PLLA) and poly (ε-caprolactone) (PCL) were produced by solution mixing and cast into films. The films were characterized by morphological, mechanical, and barrier behavior tests to evaluate the effect of the PCL. The micrographs of the fractured surfaces showed the morphology of the phase separated system, with the dispersed PCL phase higher than 30%. The elongation at break of PLLA was improved significantly (p<0.05) in the blends while the tensile strength decreased significantly (p<0.05) with increase of PCL content. WVP of PLLA/PCL films significantly decreased (p < 0.05) by blending with PCL. When the ratio of PLLA/PCL increased from 100/0 to 50/50, WVP of PLLA/PCL films decreased from 1.85±0.15 (×10-14 kgm/m2sPa) to 1.27±0.06 (×10-14 kgm/m2sPa). The results showed that PLLA/PCL blend can be a novel composite film for food packaging applications.

Preparation and Characterization of Poly(L-Lactide-Co-ε-Caprolactone) Copolymer for Food Packaging Application

Biodegradable poly (L-lactide-co-ε-caprolactone) (PLA-PCL) copolymers were synthesized via solution polymerization by varying the feed composition of L-lactide (LLA) and ε-caprolactone (ε-CL) (LLA/ ε-CL= 1/0, 1/1, 1/2, and 1/3). PLA-PCL film was produced by solution mixing. The films were characterized by thermal property, mechanical property, and barrier behavior tests to evaluate the effect of the PCL. The differential scanning calorimetry analyses revealed the micro-domain structure in the copolymer. The elongation at break of PLLA was improved significantly (p<0.05) in PLA-PCL copolymer while the tensile strength decreased significantly (p<0.05) with increase of PCL content. WVP of PLA-PCL films significantly decreased (p< 0.05) when compared with that of neat PLLA film. When the feed ratio of PLA-PCL copolymer increased from 1/0 to 1/3, WVP of PLA-PCL films increased from 1.85±0.15 (×10-11 gm/m2sPa) to 2.83±0.26 (×10-11 gm/m2sPa). The results showed that PLA-PCL copolymer can be a novel film for food packaging applications.

The Mechanical Properties and Hydrophilicity of Poly(L-Lactide)/Laponite Composite Film

Abatract: The poly (L-lactide)/laponite composite films are prepared by the method of solution blending with polylactide (PLA) and laponite. The results show that when laponite content was lower than 0.2 %( mass w/w), laponite can be uniform dispersed in PLA and the composed material had good stability. Fourier transform infrared spectroscopy (FTIR) study demonstrates that PLA was successfully incorporated with laponite by Si-O bond. The mechanical measurement reveals that the tensile strength of PLA/laponite composite film has been increased with compared to pure PLA. The water contact angle (WCA) tests indicate that the hydrophobicity of the laponite modified PLA films can be improved. The present study reveals that the laponite as a complexing agent can improve the mechanical properties and hydrophilicity of PLA.

Adsorption Thermodynamics Study on CCl2F2 over Solid Base Na2O/ZrO2

Catalytic hydrolysis decomposition of dichlorodifluoromethane (CCl2F2) in the presence of water vapor and oxygen was studied over solid base Na2O/ZrO2 using a fixed-bed reactor. The CCl2F2 adsorption was multilayer chemical adsorption and its process was corresponding with Freundlich model. Its adsorption heat was from 43.74 to 76.31 KJ.mol-1, and the CCl2F2 adsorption over solid base Na2O/ZrO2 was exothermic and chemical.

Physical Properties and Antimicrobial Activity of a Poly(lactic acid)/poly(ε-caprolactone) Film Antimicrobial Coating with Chitosan

In this work a preliminary study on the physical properties and antimicrobial activity of environmentally friendly active films to be produced is presented. Chitosan (CH), which has antimicrobial effect on many food pathogens, was coated as antimicrobial agent into composite poly (lactic acid)/poly (ε-caprolactone)(PLA-PCL) films. Antimicrobial active films based on PLA-PCL were prepared by coating five different chitosan concentrations: 0, 2, 4, 6 and 8 %(w/w). The mechanical characterization, water vapor permeability (WVP), and antimicrobial activity of composite PLA-PCL film coating with chitosan were carried out. The mechanical characterization, water vapor permeability of composite PLA-PCL films coating with chitosan was uninfluenced. Antimicrobial activities of films were tested against Staphylococcus aurous, Escherichia coli, Bacillus subtilis, Listeria, Salmonella. The antimicrobial activity of films were significantly increase with the chitosan concentration. The results of this work suggest that chitosan coated composite PLA-PCL films have a prospectively potential in antimicrobial activity food packaging.

Reaction Mechanism for CCl2F2 Catalytic Decomposition over MoO3/ZrO2

Catalytic hydrolysis decomposition of dichlorodifluoromethane (CCl2F2) in the presence of water vapor and oxygen was studied over a series of solid acids using a fixed-bed reactor. Solid acid MoO3/ZrO2 displayed the highest activity, over which the conversion of CCl2F2 reached 100 % at 250 °C. CO2 was the main-product and the selectivity to CClF3 remained lower than 28.0 %. CO was not detected as by-product. The decomposition activity depended on the calcination temperature and the ZrO2 content. The activity of solid acid MoO3/ZrO2 correlates well with its specific surface area and the amount of medium-strong acid sites on the surface. To explain the reaction mechanism for CCl2F2 catalytic decomposition over MoO3/ZrO2, a surface intermediate, Osurface-CF2-Osurface is proposed.

Chrysotile-Asbestos Decomposition by CCl2F2-Decomposed Acidic Gas

Asbestos was widely used in numerous materials and building products duo to its desirable properties. However, it is well known that asbestos inhalation causes health damage and its inexpensive decomposition technique is necessary to be developed for pollution prevention. Dichlorodifluoromethane (CCl2F2) must be decomposed before being liberated into the atmosphere. Acidic gas (HF and HCl) generated from the decomposition of dichlorodifluoromethane (CCl2F2) in the presence of water vapor and oxygen, was reacted with chrysotile-asbestos fibers. At high temperature beyond 300 °C, chrysotile-asbestos fibers were completely decomposed, and sellaite and hematite were detected in the decomposed products.

Synthesis of Poly(ethylene glycol) Derivatives

To expand the extent of conjugation with biologically active molecules (biopolymers, peptides, drugs, etc.) and biomaterial substrates, we synthesized a serial of poly (ethy1ene glycol) (PEG) derivatives (PEG-2000-NH2, MPEG-1200-NH2, and APEG-1200-NH2) in three efficient steps. The end groups were characterized by 1H NMR spectroscopy.