Study and modeling of poly(methyl methacrylate) production process to obtain artificial bone tissue

Abstract

The generation of polymers represents a very considerable proportion of annual production of the chemical, responsible for the great growth of this sector in recent years. Among the polymers produced the Polymethyl methacrylate (PMMA) to remain a popular and frequently used material by its physical properties, versatility and reliability. PMMA is obtained from solution polymerization with free radical kinetics of the methyl methacrylate (MMA). The process is performed in a sequential BATCH reactor, which is widely used in industry for its availability and flexibility in operation. The principal objective of the industrial BATCH polymerization reactor operation is to control the reactor temperature or initiator feed rate so as to track a predetermined trajectory which is obtained a priori. In the medical specialties, the PMMA has demonstrated high potential by its qualities of biocompatibility, relative ease of manipulation and low toxicity. This is verified by its applications such as bone cement, contact and intraocular lens, screw fixation in bone, filler for bone cavities and skull defects, and vertebrae stabilization in osteoporotic patients. Through Rapid Prototyping (RP) is possible to develop Tissue Engineering (TE) to regenerate specific and functional human tissues or organs. TE characteristics and properties such as porosity, surface area to volume ratio, pore size, pore interconnectivity, structural strength, shape, or overall geometry, and biocompatibility are often considered to be critical factors in their design and fabrication. The TE is fabricated from virtual models, designed on the computer, using Computer-Aided Design (CAD) data files with STL format. Among RP techniques the Selective Laser Sintering (SLS) is very appropriate. The SLS employs a carbon dioxide laser beam to sinter thin layers of polymeric powders. During the fabrication, the laser beam is selectively scanned over the powder surface following the cross-sectional profiles, which are carried by slide data. The laser beam rises the powder temperature to the melting point, and causes the particles to be fused together to form a solid mass. Subsequent layers are built directly on the top of previously sintered layers, and new layers of powder are deposited via a roller on top of the previously sintered layer.During the post-doctoral research presented in this project will be developed following the main topics: solution polymerization of methyl methacrylate via free radical in a batch reactor with refrigeration system; formulation of a more elaborate model for a batch PMMA polymerization reactor to calculate the optimal temperature trajectory that would produce the polymer product with the desired number-and weight-average molecular weights; measurement of physicochemical properties of the polymer by DSC and rheological analysis mainly; and evaluate the potential of PMMA produced, for the fabrication of TE, via RP by SLS. The research will be performed in a total period of 4 years, on Laboratory of Optimization Project and Advanced Control (LOPCA) of School of Chemical Engineering, University of Campinas, UNICAMP, P.O. Box 6066, 13083-970, Campinas-SP, Brazil. (AU)