Effects of Ingredients on Thermal and Mechanical Properties of Acrylic Bone Cements

There is a very delicate relation between the amounts of all the ingredients present in the cement composition and the properties of the product. In this study, homogeneous poly(methyl methacrylate) (PMMA) microspheres were prepared by suspension polymerization technique, and used in cement formulations. Various acrylic cements with different compositions were prepared by using PMMA microspheres, methyl methacrylate (MMA) monomer, radiopaque agent of barium sulfate (BaSO4), inorganic particles of hydroxyapatite (HA), initiator and chain stopping agent of 1-dodecyl mercaptan (DDM). The effects of these additives on mechanical and thermal properties of the resultant cements were examined. Addition of 8% HA relative to the solid parts caused an increase in both tensile and compressive strengths from 20.40 to 25.20 MPa, and from 84.04 to 89.57 MPa, respectively, while curing temperature was decreased about 3 degrees. Chain stepping agent of DDM caused a sharp decrease about 30 degrees in the curing temperature. Radiopaque agent of barium sulfate caused inverse effect on mechanical and thermal properties. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 4077-4084, 200

Synthesis and characterization of polycaprolactone-based segmented polyurethanes

Segmented polyurethanes were synthesized by the reactions of poly(epsilon-caprolactone) (PCL)-diol and 1,6-hexamethylene diisocyanate through bulk polymerization without using solvent, initiator, or catalyst. Phase separation and hydrogen bond formation between hard segments or between hard and soft segments were examined by Fourier transform infrared spectroscopy (FTIR)-ATR and X-ray diffraction (XRD), while physical and mechanical properties were studied by atomic force microscope, differential scanning calorimeter, dynamic mechanical analysis, and tensile tester. When the diisocyanate content was increased, deconvolution results of FTIR-ATR in C = O and N-H regions demonstrated better miscibility of the segments and XRD results showed a significant decrease in the crystallinity of soft segments. Samples having strong hard segment interactions displayed better mechanical properties

Preparation and Characterization of Chitosan and PLGA-Based Scaffolds for Tissue Engineering Applications

Three dimensional (3D) biodegradable porous scaffolds play a crucial role in bone tissue repair. In this study, four types of 3D polymer/hydroxyapatite (HAp) composite scaffolds were prepared by freeze drying technique in order to mimic the organic/inorganic nature of the bone. Chitosan (CH) and poly(lactic acid-co-glycolic acid) (PLGA) were used as the polymeric part and HAp as the inorganic component. Properties of the resultant scaffolds, such as morphology, porosity, degradation, water uptake, mechanical and thermal stabilities were examined. 3D scaffolds having interconnected macroporous structure and 77-89% porosity were produced. The pore diameters were in the range of 6 and 200 mm. PLGA and HAp containing scaffolds had the highest compressive modulus. PLGA maintained the strength by decreasing water uptake but increased the degradation rate. Scaffolds seeded with SaOs-2 osteoblast cells showed that all scaffolds were capable of encouraging cell adhesion and proliferation. The presence of HAp particles caused an increase in cell number on CH-HAp scaffolds compared to CH scaffolds, while cell number decreased when PLGA was incorporated in the structure. CH-PLGA scaffolds showed highest cell number on days 7 and 14 compared to others. Based on the properties such as interconnected porosity, high mechanical strength, and in vitro cell proliferation, blend scaffolds have the potential to be applied in hard tissue treatments. (C) 2014 Society of Plastics Engineer