Biodegradation of Poly (3-hydroxybutyrate) /Eggshellsystems

In this work, biocomposites of poly (3-hydroxybutyrate) (PHB) / calcium carbonate from Rhea Americana eggshells were prepared and the effects of the addition of the inorganic filler in the polymeric matrix were assessed. The residue (powder) of the eggshell calcined at 400 ºC or in natura was inserted into a PHB solution for preparation of films via casting. Powder samples were characterized by X-Ray Fluorescence (XRF), X-Ray diffraction (XRD) and Thermogravimetry (TG/DTG) and films were characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and biodegradation tests according to the ASTM G 160-03 norm: the results were reported as weight loss and visual inspection by optical microscopy (OM). From the results of the XDR, it was perceived that the peaks in the diffractograms of the powder obtained by milling the Rhea Americana eggshells corresponded to the diffraction patterns of the Calcite crystals, which is a calcium carbonate polyform, and that the calcination preserved the crystalline structure, maintaining the calcium carbonate in the samples. For the biocomposites, a peak characteristic to the calcium carbonate in 29.57º was detected, indicating the insertion of the filler to the polymer matrix. Through SEM the presence of small agglomerates, probably due to polymer particles that were not dissolved, was observed for the pure PHB film. With the addition of the filler in natura a greater porosity was formed in the surface of the biocomposite films, and with the calcined filler, homogeneous films with reduced porosity were obtained. From the weight loss and OM results, it was observed that the filler inserted into the polymeric matrix catalyzes the biodegradation process up to 60 days evaluation in different ways, depending on the type of sample used.

本研究制备了聚(3-羟基丁酸酯)（poly(3-hydroxybutyrate), PHB）/源自大美洲鸵（Rhea Americana）蛋壳的碳酸钙生物复合材料，并探究了无机填料对聚合物基体的影响。将经400℃煅烧或保持天然态的蛋壳残渣（粉末）加入PHB溶液中，通过流延法制备复合薄膜。采用X射线荧光光谱法（X-Ray Fluorescence, XRF）、X射线衍射（X-Ray Diffraction, XRD）与热重分析法（Thermogravimetry, TG/DTG）对蛋壳粉末样品进行表征；采用X射线衍射（XRD）、扫描电子显微镜（Scanning Electron Microscopy, SEM）以及符合ASTM G 160-03标准的生物降解试验对复合薄膜进行表征，测试结果以质量损失量与光学显微镜（Optical Microscopy, OM）目视观察的形式呈现。通过X射线衍射分析发现，大美洲鸵蛋壳经研磨得到的粉末衍射峰与方解石晶体——碳酸钙的一种多晶型物——的衍射图谱完全匹配，且煅烧过程保留了其晶体结构，样品中碳酸钙晶型未发生改变。对于生物复合材料，在2θ=29.57°处检测到碳酸钙的特征衍射峰，表明填料已成功引入聚合物基体中。通过扫描电子显微镜观察发现，纯PHB薄膜表面存在少量团聚体，该现象大概率由未完全溶解的聚合物颗粒所致。添加未煅烧天然态填料的生物复合薄膜表面孔隙率更高；而添加煅烧填料的复合薄膜则形成了孔隙率更低的均匀薄膜。结合质量损失与光学显微镜观察结果可知，引入聚合物基体的填料可通过不同机制催化生物降解过程，在为期60天的评估周期内该催化效果均有体现，且具体降解模式取决于样品类型。