Thermo-Mechanical Properties of P(HB-HV) Nanocomposites Reinforced by Nanodiamonds

Several studies of biodegradable polymers and copolymers have been carried for different applications in the biomedical area. This current study aims to develop a biocomposite to be used as an orthopedic device, using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(HB-HV), a biodegradable copolymer, with 94%HB and 6%HV, as matrix; and nanodiamonds (ND) with primary grains of 4-6nm, as reinforcement. The nanodiamonds were previously encapsulated by P(HB-HV) and specimens were prepared using a hydraulic press and injection molding machine, in order to evaluate which method presents a better performance. Thermal and mechanical analyses were done to compare their behavior. The biocomposite and pure P(HB-HV) samples were analyzed by flexural testing, nanoidentation, DMA, XRD, TGA. The distribution of nanodiamonds on the specimen fracture surface were investigated by SEM. The SEM micrographs allowed us to concluded that the encapsulation of nanodiamonds by P(HB-HV) was successfully performed, promoting a better interface and distribution in the polymeric matrix. The presence of ND in the polymeric matrix decreased the P(HB-HV) crystallinity, inhibiting the crystallite growth. The mechanical properties obtained from flexural test, nanoidentation and DMA of the injection-molded specimens were superior to compression-molded, due to its homogeneous and continuous structure. In vitro analysis was performed to evaluate the samples cytoxicity.

针对生物医用领域的各类应用，已有诸多关于可降解聚合物及共聚物的研究报道。本研究旨在开发一种可应用于骨科器械的生物复合材料：以含94%羟基丁酸酯单元与6%羟基戊酸酯单元的可降解共聚物聚(3-羟基丁酸酯-co-3-羟基戊酸酯)[poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(HB-HV)]作为基体，以一次晶粒尺寸为4~6nm的纳米金刚石(nanodiamonds, ND)作为增强相。此前已通过P(HB-HV)对纳米金刚石进行包覆处理，并分别采用液压压制成型与注塑成型两种工艺制备试样，以对比两种成型方法的性能优劣。为对比两类试样的性能表现，本研究开展了热学与力学性能分析：对生物复合材料及纯P(HB-HV)试样分别进行弯曲测试、纳米压痕(nanoindentation)、动态力学分析(Dynamic Mechanical Analysis, DMA)、X射线衍射(X-ray Diffraction, XRD)以及热重分析(Thermogravimetric Analysis, TGA)。通过扫描电子显微镜(Scanning Electron Microscopy, SEM)观察试样断面上的纳米金刚石分布情况。SEM显微图像结果证实，P(HB-HV)对纳米金刚石的包覆工艺成功实现，有效改善了纳米金刚石在聚合物基体中的界面结合与分散均匀性。聚合物基体中纳米金刚石的引入降低了P(HB-HV)的结晶度，抑制了晶粒生长。得益于均匀连续的微观结构，注塑成型试样的弯曲测试、纳米压痕及动态力学分析所得力学性能均优于压制成型试样。此外还开展了体外细胞毒性试验，以评估试样的细胞毒性。