Márquez Yolanda, Franco Lourdes, Turon Pau, Martínez Juan Carlos, Puiggalí Jordi
Chemical Engineering Department, Escuela d'Enginyeria Barcelona Est (EEBE), c/ Eduard Maristany 19, Barcelona 08930, Spain.
B. Braun Surgical S.A., Carretera de Terrassa 121, Barcelona 08191, Spain.
Polymers (Basel). 2016 Sep 28;8(10):351. doi: 10.3390/polym8100351.
Non-isothermal crystallization kinetics of polydioxanone (PDO), a polymer with well-established applications as bioabsorbable monofilar suture, was investigated by Avrami, Mo, and isoconversional methodologies. Results showed Avrami exponents appearing in a relatively narrow range (i.e., between 3.76 and 2.77), which suggested a three-dimensional spherulitic growth and instantaneous nucleation at high cooling rates. The nucleation mechanism changed to sporadic at low rates, with both crystallization processes being detected in the differential scanning calorimetry (DSC) cooling traces. Formation of crystals was hindered as the material crystallized because of a decrease in the motion of molecular chains. Two secondary nucleation constants were derived from calorimetric data by applying the methodology proposed by Vyazovkin and Sbirrazzuoli through the estimation of effective activation energies. In fact, typical non-isothermal crystallization analysis based on the determination of crystal growth by optical microscopy allowed secondary nucleation constants of 3.07 × 10⁵ K² and 1.42 × 10⁵ K² to be estimated. Microstructure of sutures was characterized by a stacking of lamellae perpendicularly oriented to the fiber axis and the presence of interlamellar and interfibrillar amorphous regions. The latter became enhanced during heating treatments due to loss of partial chain orientation and decrease of electronic density. Degradation under various pH media revealed different macroscopic morphologies and even a distinct evolution of lamellar microstructure during subsequent heating treatments.
聚对二氧环己酮（PDO）是一种有着成熟应用的生物可吸收单丝缝合线聚合物，采用阿弗拉米法、莫法和等转化率法对其非等温结晶动力学进行了研究。结果表明，阿弗拉米指数出现在相对较窄的范围内（即3.76至2.77之间），这表明在高冷却速率下为三维球晶生长和瞬间成核。在低冷却速率下，成核机制变为分散型，两种结晶过程都在差示扫描量热法（DSC）冷却曲线上被检测到。由于分子链运动的减少，随着材料结晶，晶体的形成受到阻碍。通过应用维亚佐夫金和斯比拉祖奥利提出的方法，通过有效活化能的估算，从量热数据中得出了两个二次成核常数。事实上，基于光学显微镜测定晶体生长的典型非等温结晶分析得出二次成核常数估计为3.07×10⁵K²和1.42×10⁵K²。缝合线的微观结构特征是垂直于纤维轴堆叠的片晶以及片晶间和原纤维间无定形区域的存在。由于部分链取向的丧失和电子密度的降低，后者在加热处理过程中变得更加明显。在各种pH介质下的降解揭示了不同的宏观形态，甚至在随后的加热处理过程中层状微观结构有明显的演变。
