Research on the Comprehensive Performance of Gradient-Hardness Polycarbonate-Based Polyurethane Through Different Molding Methods

Thermoplastic polycarbonate polyurethane (PCU) has been applied in numerous biomedical applications owing to its superior properties. The objective of this study is to obtain the comprehensive performance of PCU materials with different hardness processed through various molding methods. The performance will be compared with that of natural intervertebral discs to assess their degree of match, with the expectation of further enhancing the application of PCU in the field of elastic intervertebral disc products. PCU materials with four different hardness grades, namely 75A, 85A, 95A, and 55D, were prepared through injection molding (IM), compression molding (CM), and fused deposition modeling in three-dimensional printing (3D). Material property analysis and mechanical performance characterization were conducted on the PCU materials. The PCU materials processed through the three different molding methods exhibited similar results in terms of hardness, scanning electron microscopy (SEM) images, X-ray energy-dispersive spectroscopy (EDS) spectra, and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectra, indicating that the materials did not degrade or introduce impurities during the molding process and the molding methods used in this study were acceptable. Differences were observed in the tensile and compressive properties of PCU materials. The mechanical properties of 85A- and 95A-hardness materials processed by CM and 3D molding were relatively close to those of natural intervertebral discs. In terms of water contact angle, under the same hardness condition, the materials processed by CM molding exhibited the largest water contact angle, while those processed by IM and 3D molding were similar. The PCU materials with 85A and 95A hardness processed through IM, CM, and 3D exhibited properties that were close to the performance requirements of natural intervertebral discs. There is a high potential for their application in intervertebral disc products to enhance product performance, replace diseased natural discs, and promote the development of cervical total disc replacement (TDR) surgery.