Slivka M A, Chu C C
Department of Textiles and Apparel, Cornell University, Ithaca, New York 14853, USA.
J Biomed Mater Res. 1997 Dec 5;37(3):353-62. doi: 10.1002/(sici)1097-4636(19971205)37:3<353::aid-jbm6>3.0.co;2-k.
In this study, a new visual characterization method was developed using laser scanning confocal microscopy (LSCM) to study morphologic properties, particularly at the fiber-matrix interface, by optical sectioning of bioabsorbable single-fiber composites. The interface gap width (IGW) between the fiber and matrix, and the changes in IGW after in vitro hydrolysis, named the gap rate (Rg), were measured from images obtained using the LSCM. Higher values for IGW and Rg showed faster degradation of the fiber-matrix interface. These parameters were used to investigate the effects of strain, wicking, different reinforcing fibers, and gamma-irradiation on the fiber-matrix interface morphology. The component materials used were nonbioabsorbable AS4 carbon (C) fibers, bioabsorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), and chitin fibers, and bioabsorbable poly(L-lactic acid) (PLLA) matrix. The application of strain on CaP/PLLA composites increased the IGW up to about 15%, after which there was no change up to 25%. The Rg for CaP/PLLA composites with the fiber ends exposed in vitro (permitting wicking) was greater than for CaP/PLLA with the fiber ends embedded completely within the matrix (preventing wicking). Open-end C/PLLA composites had the slowest rate of interface degradation in vitro, followed by chitin/PLLA, PGA/PLLA, and CaP/PLLA. The exposure of closed-end CaP/PLLA composites to 4 Mrad of gamma-irradiation, in air at room temperature or in vaccuum at 77K, accelerated the rate of interface degradation in vitro. In conclusion, an effective new visual characterization method was developed using LSCM, and it was used to show that (a) moderate strain could accelerate the degradation of the interface, (b) fiber-matrix interface wicking could accelerate the rate of degradation of the interface, (c) the rate of interface degradation depends on the type of fiber used, and (d) gamma-irradiation could accelerate the rate of interface degradation. Furthermore, the results of LSCM analysis of different reinforcing fibers with a PLLA matrix agree with measurements of interfacial shear strength (IFSS) and single-fiber tensile strength reported in Part I of this study.
在本研究中，开发了一种新的视觉表征方法，即使用激光扫描共聚焦显微镜（LSCM），通过对生物可吸收单纤维复合材料进行光学切片来研究其形态特性，特别是纤维 - 基体界面处的形态特性。从使用LSCM获得的图像中测量纤维与基体之间的界面间隙宽度（IGW）以及体外水解后IGW的变化，即间隙率（Rg）。IGW和Rg值越高，表明纤维 - 基体界面的降解速度越快。这些参数用于研究应变、芯吸作用、不同增强纤维以及γ射线辐照对纤维 - 基体界面形态的影响。所使用的组成材料包括非生物可吸收的AS4碳纤维（C）、生物可吸收的磷酸钙（CaP）、聚乙醇酸（PGA）和几丁质纤维，以及生物可吸收的聚（L - 乳酸）（PLLA）基体。对CaP/PLLA复合材料施加应变会使IGW增加约15%，此后直至25%都没有变化。纤维末端暴露于体外（允许芯吸作用）的CaP/PLLA复合材料的Rg大于纤维末端完全嵌入基体内（防止芯吸作用）的CaP/PLLA复合材料。开口端C/PLLA复合材料在体外的界面降解速率最慢，其次是几丁质/PLLA、PGA/PLLA和CaP/PLLA。将封闭端CaP/PLLA复合材料在室温空气中或77K真空中暴露于4 Mrad的γ射线辐照下，会加速其在体外的界面降解速率。总之，使用LSCM开发了一种有效的新视觉表征方法，并用其表明：（a）适度应变可加速界面降解；（b）纤维 - 基体界面芯吸作用可加速界面降解速率；（c）界面降解速率取决于所使用的纤维类型；（d）γ射线辐照可加速界面降解速率。此外，对具有PLLA基体的不同增强纤维进行LSCM分析的结果与本研究第一部分中报道的界面剪切强度（IFSS）和单纤维拉伸强度的测量结果一致。
