The objective of this study was to characterize and evaluate the performance of various fiber-matrix composite systems by studying the mechanical, thermal, and physical properties of the fiber and matrix components, and by studying the fiber-matrix interface adhesion strength using both microbond and fragmentation methods. The composites studies were poly(L-lactic acid) (PLLA) matrix reinforced with continuous fibers of either nonabsorbable AS4 carbon (C), absorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), or chitin. Carbon and CaP single fibers had high Young's moduli and failed in a brittle manner. PGA and chitin single fibers had relatively lower Young's moduli and relatively higher ductility. Upon in vitro hydrolysis, CaP fibers retained 17% of their tensile strength and 39% of their Young's modulus after 12 h, PCA fibers retained 10% of their tensile strength and 52% of their Young's modulus after 16 days, and chitin fibers retained 87% of their tensile strength and 130% of their Young's modulus after 25 days. PLLA films had much lower strength and Young's moduli, but much higher ductility relative to the single fibers. Using the microbond method, the initial fiber-matrix interfacial shear strength (IFSS) of C/PLLA and CaP/PLLA microcomposites was 33.9 and 12.6 MPa, respectively. Upon in vitro hydrolysis, C/PLLA retained 49% of IFSS after 15 days and CaP/PLLA retained 46% of IFSS after 6 h. Using a fiber fragmentation method, the initial IFSS of C/PLLA, CaP/PLLA, and chitin/ PLLA was 22.2, 15.6, and 28.3 MPa, respectively. The performance of carbon fibers and C/PLLA composites was superior to the other fibers and fiber/PLLA systems, but the carbon fiber was nonabsorbable. CaP had the most suitable modulus of the absorbable fibers for fixing cortical bone fracture, but its rapid deterioration of mechanical properties and loss of IFSS limits its use. PGA and chitin fibers had suitable mechanical properties and their retention for fixing cancellous bone fractures, but likely had insufficient stiffness for applications such as bone plates for fixing cortical bone fractures.

Abstract:The objective of this study was to characterize strength (IFSS) of C/PLLA and CaP/PLLA microcomposites and evaluate the performance of various fiber-matrix comwas 33.9 and 12.6 MPa, respectively. Upon in vitro hydrolysis, posite systems by studying the mechanical, thermal, and C/PLLA retained 49% of IFSS after 15 days and CaP/PLLA physical properties of the fiber and matrix components, and retained 46% of IFSS after 6 h. Using a fiber fragmentation by studying the fiber-matrix interface adhesion strength usmethod, the initial IFSS of C/PLLA, CaP/PLLA, and chitin/ ing both microbond and fragmentation methods. The com-PLLA was 22.2, 15.6, and 28.3 MPa, respectively. The perforposites studied were poly(L-lactic acid) (PLLA) matrix reinmance of carbon fibers and C/PLLA composites was superior forced with continuous fibers of either nonabsorbable AS4to the other fibers and fiber/PLLA systems, but the carbon carbon (C), absorbable calcium phosphate (CaP), poly(glyfiber was nonabsorbable. CaP had the most suitable modulus colic acid) (PGA), or chitin. Carbon and CaP single fibers of the absorbable fibers for fixing cortical bone fractures, had high Young's moduli and failed in a brittle manner. PGA but its rapid deterioration of mechanical properties and and chitin single fibers had relatively lower Young's moduli loss of IFSS limits its use. PGA and chitin fibers had suitable and relatively higher ductility. Upon in vitro hydrolysis, CaP mechanical properties and their retention for fixing canfibers retained 17% of their tensile strength and 39% of their cellous bone fractures, but likely had insufficient stiffness Young's modulus after 12 h, PGA fibers retained 10% of their for applications such as bone plates for fixing cortical bone tensile strength and 52% of their Young's modulus after 16 fractures. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, days, and chitin fibers retained 87% of their tensile strength 36, [469][470][471][472][473][474][475][476][477] 1997. and 130% of their Young's modulus after 25 days. PLLA films had much lower strength and Young's moduli, but much higher ductility relative to the single fibers. Using the

Protein sorption from raw rennet whey at pH 3.0 onto S-type (strong acid), and at pH 7.2 onto Q-type (strong base), ion exchange beads and membranes was measured. The data were used to analyze protein binding capacities, percentage recoveries, production rates, and design parameters for a commercial-scale process. Performance of S-type beads was superior to Q-type beads, but Q-type and S-type membranes performed comparably, except that the S-type membranes lost capacity during repeated cycling without cleaning, while the Q-type membranes did not. Performance of the S-type membranes was increased by microfiltration of the whey before loading, but this was partially offset by the lower protein content of the microfiltered whey. Increasing the flow rate through the cartridge increased productivity, but the percentage protein recovery decreased. This 1437