Functional gradient hydroxyapatite reinforced polyetheretherketone is one of the most promising orthopedic implant biomaterials. In this study,functional gradient hydroxyapatite reinforced polyetheretherketone biocomposites were prepared by layer-by-layer method with the incorporation of hot press molding technology. Studies on the flexural mechanical properties of the functional gradient biocomposites revealed that the flexural stress–stain behavior of the biocomposites presented linear elastic characteristics. The fracture mechanism of the functional gradient biocomposites was predominated by brittle rupture. Furthermore,both flexural strength and break strain of the functional gradient HA/PEEK biocomposites obviously decreased with the rise of the total HA content. The effect of hydroxyapatite concentration difference between adjacent layers(HCDBAL) on the flexural strength obviously relied on the level of HCDBAL and total HA content in the functional gradient HA/PEEK biocomposites. The higher the total HA content in the functional gradient biocomposites is,the less the influence degree of HCDBAL on the flexural strength is. Moreover,total HA content and HCDBAL played synergistic influence on the flexural modulus of the functional gradient HA/PEEK biocomposites.
Super plasticizer was synthesized by using coal coking by product washing oil and industrial naphthalene.The results show that sulfonationt time(2.5 h),sulfonation temperature(160 ℃) and condensation time(5.0 h) are key factors.Adding oxidizing agent MO in the course of synthesis can decrease the emission of SO2 in exhaust(20%).Compared with NF,NF-30 have some advantages in lower cost,high water reducing rate(19.7%) and optimum early strengths.Moreover,TGA-DTA and SEM analysis were adopted to research the NF-30 modified concrete on hydyation mechanism.The analysis show that,compared with NF,there are a large number of hydration products such as Ca(OH)2,C-S-H,AFt etc of NF-30,the structure of NF-30 is dense and the performance is good.
Functional gradient materials provided us a new concept for artificial articular cartilage design with gradient component and gradient structure where one side of the material is high free water content thereby providing excellent lubrication function and the opposite side of the material is high hydroxyapatite content,thereby improving the bioactivity of the material and stimulating cell growth.The goal of the present study was to develop a multi-layered gradient HA/PVA gel biocomposites through layer-by-layer casting method combing with freeze/thaw cycle technology.The various influence factors on the compressive strength and modulus of the multi-layered gradient biocomposites were investigated.The results showed that the compressive mechanical characteristics of the biocomposites were similar to that of natural articular cartilage.Both the compressive strength and modulus of the multi-layered gradient HA/PVA gel biocomposites increased exponentially with the rise of compressive strain ratio.Both the compressive strength and average compressive modulus of the biocomposites improved with the rise of freeze/thaw cycle times and total concentration of HA particles in the biocomposites,but they showed decreasing tendency with the rise of HA concentration difference between adjacent layers.
