In Vitro Degradation Characteristic Of Carbon Fiber Reinforced Polylactide (C/PLA) Composite Under Pulsed Electromagnetic Field

Carbon fiber reinforced poly(lactic acid)(C/PLA) composite is considered to be a promising degradable implanted material used for internal fracture fixation, and attracts wide spread attentions. However, due to the complex and changeable environment in the human body, there are some significant discrepancies for the requirements of C/PLA degradation characteristics in different physical people, different fracture parts, and even different periods of fracture healing. Presently, the starting point of solving the above problems focuses on the biodegradable material itself, namely, the degradation charateristics of C/PLA composite is adjusted only through the matrix modification and the surface treatment of the reinforced part. In this work, the pulsed electromagnetic fields(PEF) is introduced into in vitro C/PLA degradation process, PEF treatment should change the external environment of C/PLA degradation, and it is supposed to propose an assistive technology used for the biodegradable composite, the corresponding mechanism is explored basically.In this work, the preparation of C/PLA was optimized. Based on the good C/PLA samples, PEF was introduced into in vitro C/PLA degradation, it was studied the influences of PEF parameters on the pH value, water absorption, weight retention and mechanical properties during C/PLA degradation, and the interface changes of these composites were observed by SEM.The results indicate that the crystallinity of PLA decreases with the increasing hot-pressing temperature: the hot-pressing temperature has little influence on the Tg and Tm of PLA sample, however, for the PLA sample with so called “granular interface”, the Tg and Tm decrease obviously; furthermore, the bending strength and modulus increase at first then decrease with the increasing hot-pressing temperature, and obtain the maximum value at 195℃.PEF treatment has various influences on pH value(PBS solution), water absorption, weight retention, flexural strength and shear strength of C/PLA samples, and the impacts of those are related to the pulse and frequency of PEF. PEF treatment is considered to have minor effect on the PLA matrix degradation, and mainly affects the interface degradation of C/PLA composite. SEM observation indicates that after the PEF treatment, PLA matrix located in the interface exhibits some caves, which probably results from an accelerated degradation. A proposed mechanism model denotes that PEF treatment should affect the diffusion behavior of the positive and negative ions in the degradation solution, and lead an appearance of the degradation accelerating region for the PLA matrix at the interface. PEF voltage and frequency can alter the distribution of high ion concentration area at the interface of C/PLA. Therfore, under the given PEF equipment, adjusting the voltage and frequency can effectively control the in vitro C/PLA degradation process. This work is bound to facilitate the investigation of external auxiliary treatment instrument for the degradable fracture internal fixation device.