Polyethylene/styrene copolymerization reaction under high temperature-high pressure conditions

MARTINI, RAQUEL; BARBOSA, SILVIA; BRIGNOLE, ESTEBAN

Ischia, Italia.

Conferencia; 8th Conference on Supercritical Fluids and their applications.; 2006

Graft copolymers have found applications in diverse fields like adhesives, paint or coating materials, emulsifiers to molding materials, and biomedical applications. Other very important area of application is its use as compatibilizing agents in blends. In this work, graft copolymerization of styrene onto lineal low-density polyethylene (LLDPE) was carried out in high pressure-high temperature n-heptane medium. The reaction was a Friedel-Crafts alkylation and the catalyst used was aluminum chloride (AlCl3). By this reaction, a hydrocarbon chain can be chemically bonded to the styrene ring through an aromatic electrophilic substitution. The principal advantage of this method of reaction is that the polyethylene was solubilized by the near critical alkane at these conditions, and then, the polymer chains were more available to react than in a melt blend. The graft reaction was corroborated using Fourier transform infrared spectroscopy (FTIR), after a careful phase separation of the reaction product by selective soxhlet extraction using tetrahydrofuran (THF). Besides of FTIR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscopy (SEM) were techniques used for characterization of the reaction products and quantification of polystyrene grafted. The effect of the amount of catalyst added was studied varying the content from 1 to 5-wt% of AlCl3 on the same PE/styrene relation.