Highly toughened poly (lactic acid)/poly (butylene adipate-terephthalate) blends in-situ compatibilized by MMA-co-GMA copolymers with different epoxy group content.

Poor compatibility limits the wide application of biodegradable poly (lactic acid)/poly (butylene adipate-terephthalate) (PLA/PBAT) blends in packaging industry. How to prepare compatibilizers with high efficiency and low cost by simple methods is a challenge. In this work, methyl methacrylate-co-glycidyl methacrylate (MG) copolymer with different epoxy group content are synthesized as reactive compatibilizers to resolve this issue. The effects of glycidyl methacrylate and MG contents on phase morphology and physical properties of the PLA/PBAT blends are systematically investigated. During melt blending, MG migrates to the phase interface, and then grafts with PBAT to form PLA-g-MG-g-PBAT terpolymers. When the molar ratio of MMA and GMA in MG is 3:1, the reaction activity of MG with PBAT is the highest and the compatibilization effect is the best. When the M3G1 content is 1 wt%, the tensile strength and the fracture toughness are increased to 37. 1 MPa and 120 MJ/m3, which increase by 34 % and 87 %, respectively. The size of PBAT phase decreases from 3.7 µm to 0.91 µm. Therefore, this work provides a low-cost and simple method to prepare the compatibilizers with high efficiency for the PLA/PBAT blend, and provides a new basis for the design of epoxy compatibilizers.

[Histopathological changes of three kinds of bone grafts in vivo].

OBJECTIVE: To evaluate the tissue response induced by three kinds of bone transplantation materials implanted in rat so as to provide proper evidence for their clinical application. METHODS: Thirty-six healthy mature Sprague-Dawley rat, weighing from 229 g to 358 g, were randomly assigned to groups A and B (n=18). Three kinds of materials were implanted into muscles of rats. Calcium sulfate (CS) granular preparations and allogeneic demineralized bone matrix (DBM) were transplanted into the left (group A1) and right (group A2) thigh muscle pouches of group A. Respectively, whereas xenogenic DBM were transplanted into the left (group B1) thigh muscle pouches of group B and the right (group B2) sites were taken as control without implant. The samples (n=6) were collected to make the observation of gross and histology and to analyze histological score after 2, 4, and 6 weeks. RESULTS: The gross observation: implanted materials were gradually absorbed at late stage in group A1. No obvious degradation and absorption, but fibrosis of tissues were observed in group A2 and B1. The inflammatory reactions were more severe in groups A2 and B1. In group B2, only the changes of scar were seen at operative site. The histological observation: no obvious inflammatory reactions were seen in group A1, CS were gradually absorbed and completely absorbed at 6 weeks, while fibrosis of tissues increased at late stage. Inflammatory reactions in group A2 and group B1 were alleviated gradually, no obvious absorption and degradation were observed. The different two DBM could induce granulation tissues and bone formation at different sites and secondary fibrosis with no obvious immune response was observed. In group B2, there was an increase in collagen fiber density and angiogenesis at late stage. The scores of inflammatory infiltration were significantly higher in groups A2, B1 than in groups A1, B2 (P < 0.05), and the scores of fibrosis was larger in groups A1, A2 and B1 than in group B2 (P < 0.05). CONCLUSION: CS has rapid dissolution and good biocompatibility. It is a good replaceable packing materials of bone defects in some upper limb's or acute bone fracture. Both of two DBM have biocompatibility and osteoinductive potential, which dissolution are very slow. Due to these capacity, they can be served as an ideal materials in treatment of lower limb's bone defect and nonunion.