Waste tire powder, as waste rubber WR was subjected to grafting with styrene (St) and maleic anhydride (MA). Hydrogen peroxide H2O2 was used to initiate the free radical copolymerization of St onto WR. A thermal initiation was used in case of grafting of MA onto WR. Effect of initiator and monomer concentrations together with the influence of reaction temperature and reaction time were investigated. The grafting was estimated by weight, and the grafted copolymers were characterized by FT/IR, DSC and SEM to prove the grafting. It has found that the grafting increases with increase monomer and initiator concentrations. The increase in the reaction temperature and time also causes increasing levels of the grafted St and MA.
Vulcanized waste rubber especially the scrap tires, cause several environmental problems. Recycling of waste rubber by grafting or blending with polymeric material has become an important in last decades. Surface modification of ground waste tire powder by chlorination and amination reactions, and by photo grafting using UV energy, have been studied [1-3]. Recently authors are modified the surface of rubber crumb with ozone [
Modification of different kinds of rubber using maleic anhydride (MA) is useful to enhance compatibility of immiscible blends as well as improving interfacial adhesion in polymeric composites [
In this work, powdered waste tires (as waste rubber), were used as a polymer backbone for the grafting reaction with styrene and maleic anhydride.
The effect of monomers (St or MA), initiator concentration (H2O2) (in case of St) as well as the reaction time and reaction temperature was studied. The surface chemistry of untreated and treated waste rubber (WR) was characterized by FT/IR spectroscopy, DSC thermal analysis and by scanning electron microscope (SEM).
The ground scrap tires with an average particle size 0.2 - 0.4 mm was prepared from waste tires SBR (styrenebutadiene rubber), USA, which contain about 60% SBR and 40% various additives. Styrene and maleic anhydride (Aldrich) are used without further purification. H2O2, fuming H2SO4 (Fluke). The other chemical solvents and reagents used are of analytical pure grade.
The appropriate quantities of WR and St were added in a special designed steel reactor. The requisite amount of H2O2 (initiator) were added and the reactor closed tightly at the required temperature for certain demand time. After the reaction completed, reactor is cooled and opened carefully, then the polymerization mixture was poured into acetone and leaved for 24 h. Washing of grafted polymer carried using chlorobenzene, followed by drying at 40˚C for two days to constant weight.
The above procedure was used for grafting of MA onto WR without using chemical initiator, only by thermal initiation. Sulfonation of WR and WR-g-St was carried using fuming conc. H2SO4 at 80˚C for 8 h. All treated waste rubber material was dried in an oven at 40˚C for 24 h prior to further use.
Grafting yields were characterized by the following parameters:
Grafting percentage: Gp% = (A – B/B) × 100 Weight conversion: Wc% = (A ÷ B) × 100 where A and B are the weights of the grafted product and WR respectively.
FT/IR spectra were recorded using JASCO FT/IR 460 plus spectrophotometer. Scanning electron microscope (SEM) 6360 (LA) were used to investigate the microstructure of the polymers. Thermal date was obtained by using Shimadzu DSC-50 instrument.
The grafting of St or MA onto WR was performed at various conditions to get the most suitable conditions for grafting. The variables studied were temperature, time, and the amounts of monomers and initiator.
The graft copolymerization of St onto WR was carried out at four different temperatures ranging from 75˚C to 150˚C. The initiator and WR concentration were 0.5 and 0.25 g/ml respectively, for three days. In