Minglong Yuan

Effects of N-octyl lactate as plasticizer on the thermal and functional properties of extruded PLA-based films.

Films of poly(l-lactide) (PLA) plasticized with varying levels of N-octyl lactate (NOL) were prepared by extrusion. The thermal and functional properties of the blends were investigated by SEM, DSC, TGA, tensile, opacity, water vapor permeability, and water contact angle tests. The compatibility of the plasticizer with PLA was confirmed by DSC and SEM analysis. A higher plasticizing effect on the thermal properties of PLA was generally observed with the increase in NOL content. Additionally, the mechanical properties were improved with the increase in NOL content. The mechanical resistance of the films could be related to their glass transition temperature. The effect of the concentration of plasticizer on the opacity of the films was negligible. The water vapor permeability of the PLA/NOL composite films increased with the increase in the concentration of NOL; however, the values observed were still lower than the water vapor permeability of commercial LDPE films. In conclusion, the extruded PLA-based films with NOL plasticizers could be used as food-packaging materials.

Formulation and evaluation of in situ forming PLA implant containing tinidazole for the treatment of periodontitis.

Periodontitis is caused by periodontopathic bacteria and antibacterial agents are placed in a periodontal pocket with the intention of enhancing the local effect. To maximize the therapeutic effects while reducing the adverse effects, tinidazole was delivered by in situ forming system. One approach for reducing burst release rate was to testify in situ forming effect. The effect of 0%-10% (w/w) polyethylene glycol 400 and 3% (w/w) glycerol on the tinidazole release from a poly(DL-lactide) (PLA) injectable implant was evaluated. The results showed that the in vitro initial burst release rate was decreased in the presence of poly(ethyleneglycol) PEG 400 and glycerol. A formulation containing 30% (w/w) PLA (M(w) 7300) dissolved in 62% (w/w) N-methyl-2-pyrrolidone, 5% (w/w) PEG 400, and 3%(w/w) glycerol with 5% (w/w) tinidazole was shown to be optimum. Twelve adult beagle dogs were used in the periodontitis model. The treatment group I, II, and positive control group was administrated with gel containing 5%(w/w) tinidazole, 2.5%(w/w) tinidazole, and periocline, respectively. Dog studies revealed that periocline and the developed formulation could significantly decrease symptoms of periodontitis, and they were better than gel containing 2.5% (w/w) tinidazole. The developed formulation could sustain the release of tinidazole for local delivery over 7 days. These findings suggested that the developed formulation was a viable alternative to conventional drug to cure periodontitis.

Poly(lactide-co-trimethylene carbonate) and Polylactide/Polytrimethylene Carbonate Blown Films

In this work, poly(lactide-co-trimethylene carbonate) and polylactide/polytrimethylene carbonate films are prepared using a film blowing method. The process parameters, including temperature and screw speed, are studied, and the structures and properties of the P(LA-TMC) and PLA/PTMC films are investigated. The scanning electron microscope (SEM) images show that upon improving the content of TMC and PTMC, the lamellar structures of the films are obviously changed. With increasing TMC monomer or PTMC contents, the elongation at the break is improved, and the maximum is up to 525%. The water vapor permeability (WVP) results demonstrate that the WVP of the PLA/PTMC film increased with the increase in the PTMC content, whereas the WVP of the P(LA-TMC) film decreased. Thermogravimetric (TG) measurements reveal that the decomposition temperatures of the P(LA-TMC) and PLA/PTMC films decrease with increases in the TMC and PTMC contents, respectively, but the processing temperature is significantly lower than the initial decomposition temperature. P(LA-TMC) or PLA/PTMC film can extend the shelf life of apples, for instance, like commercial LDPE film used in fruit packaging in supermarkets.

Preparation and characterization of poly(l-lactide)-co-poly(trimethylene carbonate)/talc film

Poly(L-lactide)-co-poly(trimethylene carbonate) (PLLA-PTMC) composites with various talc content as food packaging materials were prepared by solvent casting method. The effect of talc filler loading (0, 1, 2, and 3 wt%) on phase morphology of PLLA-PTMC/Talc composites and improvement in resulting properties were reported. The X-ray diffraction (XRD) patterns and differential scanning calorimetry (DSC) curves indicated that the crystallinity of PLLA-PTMC/Talc composites increased. Fourier transform infrared spectroscopy (FTIR) suggested that there were strong interactions between PLLA-PTMC copolymer and talc filler. The scanning electron microscopy (SEM) image of composite films revealed certain homogeneity between PLLA-PTMC and Talc, when the talc filler did not exceed 3 wt%. The elongation at break of composite films significantly (p<0.05) improved with the addition of talc filler. Furthermore, there were 23%, 31%, and 14% improvement in water vapor barrier properties at 1, 2, and 3 wt% of talc in PLLA-PTMC/Talc composites, respectively. This had been confirmed by thermogravimetric analysis (TGA).

Effect of poly(ɛ-caprolactone-co-l-lactide) on thermal and functional properties of poly(l-lactide)

A blend of poly(L-lactide) (PLLA) with star-shaped poly(ɛ-caprolactone-co-L-lactide) (s-PCLA) at different contents (PLLA/s-PCLA=100/0, 90/10, 80/20, and 70/30, w/w) were prepared by torque rheometer. Thermal and functional properties of the blends were investigated by FTIR, SEM, DSC, TGA, DMA, tensile, optical, and water vapor permeability tests. FTIR results showed that intermolecular hydrogen bonds existed between two components in the blends. SEM indicated that PLLA and s-PCLA showed limited miscibility. DSC showed that Tg occurred at lower temperatures in the PLLA/s-PCLA blends than in neat PLLA, and the crystallinity of PLLA phase increased by the presence of s-PCLA in the PLLA/s-PCLA blends. TGA indicated that s-PCLA improved the thermal stability of the PLLA/s-PCLA blends. DMA results revealed that the storage modulus of the composites decreased with respect to the pure polymer. The result of tensile tests suggested that the PLLA/s-PCLA blends showed better elongation at break than neat PLLA. The effect of s-PCLA on the color and opacity of films could be considered as negligible. The WVP of PLLA/s-PCLA blend films increased with the increase in s-PCLA, and they were still lower than that of commercial LDPE films.

Poly(Lactic Acid) Blends with Poly(Trimethylene Carbonate) as Biodegradable Medical Adhesive Material

A novel medical adhesive was prepared by blending poly(lactic acid) (PLA) with poly(trimethylene carbonate) (PTMC) in ethyl acetate, and the two materials were proven to be biodegradable and biocompatible. The medical adhesive was characterized by 1H nuclear magnetic resonance (1HNMR), gel permeation chromatography (GPC), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The water vapor transmission rate (WVTR) of this material was measured to be 7.13 g·cm−2·24 h−1. Its degree of comfortability was confirmed by the extensibility (E) and the permanent set (PS), which were approximately 7.83 N·cm−2 and 18.83%, respectively. In vivo tests regarding rabbit immunoglobulin M (IgM), rabbit immunoglobulin G (IgG), rabbit bone alkaline phosphatase (BALP), rabbit interleukin 6 (IL-6), rabbit interleukin 10 (IL-10), rabbit tumor necrosis factor α(TNFα), glutamic-oxaloacetic transaminase (AST/GOT), glutamic-pyruvic transaminase (ALT/GPT), alkaline phosphatase (AKP), blood urea nitrogen (BUN) and creatinine (Cr) indicated that the PLA-PTMC medical adhesive was not harmful to the liver and kidneys. Finally, pathological sections indicated that PLA-PTMC was more effective than the control group. These data suggest that in addition to having a positive effect on hemostasis and no sensibility to wounds, PLA-PTMC can efficiently prevent infections and has great potential as a medical adhesive.