Microparticle Size and Quantities Effect on the Mechanical Features of End of Life Tires in Thermoplastic Composites

Currently, the huge use of tires generates large quantities of waste material which represents a severe environmental problem. The common technique used for processing waste tires is crushing using mechanical methods and separating tire components like fibers, metals, and rubber from the used tire. The aim of this research is the recycling of this rubber from crushed tires, called ground tire rubber (GTR). With this aim, the manuscript analyses key mechanical properties of the thermoplastic composites produced by blending of crushed and micronized small particles of waste rubber tires with several industrial thermoplastic polymers. These types of composites are defined based on the total amount GTR in percent by weight, in the composite, and also, the particle sizes used in each case, so these aforementioned two variables (microparticle size and amounts) along with seven common industrial polymers define a series of composites for which the mechanical properties were tested, studied, analyzed and finally presented. Finally, the results obtained show that this proposed recycling method could be a way to enhance some specific polymer properties and could contribute to reducing the total of end of life used tire stocks environmental problem.

ENCAPSULATION AND RELEASE PROFILE OF PROTEIN CAGE FROM A POLYMERIC MATRIX

Protein cages have been widely investigated as molecular drug carrier. E2 protein from Bacillus stearothermophillus forms a dodecahedral cage structure of approximately 24 nm in diameter. To formulate a sustainable release profile, E2 protein was further encapsulated into poly(lactide-co-glycolide) (PLGA) microparticles to form a composite structure using water-in-oil-in-water (W/O/W) double emulsion method. The influence of fabrication parameters on microparticle morphology and E2 protein release profile were investigated. The microparticle size increased when the stirring speed of the second emulsification decreased. Decrease in the volume of external aqueous phase led to the reduction of microparticle size without affecting its porosity. The higher ionic concentration of external aqueous phase in the presence of surfactant resulted in microparticles with closed pores on surface. Increase in polymer concentration also led to the formation of less porous microparticles. The E2 protein was not dissociated upon encapsulation into PLGA microparticles based on the unchanged particle size of E2 protein. E2 protein release was studied in phosphate-buffered saline solution at 37°C. The initial burst and release rate were lowered as the surfactant concentration in external water phase during the fabrication process was increased from 0.1% to 1% (w/v). After 14-day incubation, no observable polymer degradation was found while the surface of microparticles appeared to be smoother than before incubation.