Thermoplastic composites containing different Ground Rubber Tire (GRT) materials, Linear Low Density Polyethylene (LLDPE) and, in some case, a coupling agent (IB‘E’, an ethylene glycidyl methacrylate copolymer) were prepared by melt blending. The impact energies of all the thermoplastic composites (normally containing 40 wt % GRT) were evaluated using an instrumented impact tester. The effects of the GRT particle-size, particle size distribution and shape, the mode of grinding, and the oxygen surface concentration were analyzed. The wet-ambient-ground GRT based composites show higher surface oxidation and give better impact energy than cryo-ground and normal air-ground GRT based composites. Smaller GRT particle size results in a small increase in the impact property of the composite and a greater influence on the melt processability of the composites. Of the different GRT surface modification techniques studied for improved composite interfacial adhesion and impact properties the composites from electron beam radiation treated GRT yield higher increases in impact energy in comparison to corona and plasma treated GRT based composites.

The impact energies of different polyethylene-ground rubber tire (GRT) composites were investigated. All the thermoplastic composites were prepared on a Haake Buchler batch mixer and injection molded test specimens were tested on Rheometrics drop weight instrumented impact tester. Addition of small amounts of functional polymers increases the impact energy of the polyethylene-GRT composite as much as 60%. The percent improvement in the impact energy for linear low density polyethylene (LLDPE) and the composites prepared from them is greater than for the corresponding high density polyethylene (HDPE) composites. Precoating of GRT particles with ethylene-acrylic acid (EAA) copolymers improves the impact energy of the composite, whereas precoating with the other functional polymers does not. An attempt has been made to identify the role of the functional polymers as to whether they act as toughening agents for the polyethylene matrix or coupling agent at the polyethylene-GRT interface. The results show the increase in impact energy resulting from the addition of styrene block copolymers is due to toughening of the polyethylene matrix while the reactive ethylene copolymers increase the impact energy by a coupling action with GRT.

SynopsisDifferent formulations of rubber with chopped coconut fiber (treated and untreated) as reinforcing agent were prepared. These reinforced systems were vulcanized at 153°C and the properties of the vulcanizates were studied by stress-strain, shore A hardness, and abrasion loss measurements. The bonding between the rubber and fillers were improved by the addition of bonding agents. The bonding effect of different bonding agents were compared. The reinforcing property of the treated fiber was compared with the untreated one. Aging resistance of the composites were studied. The fracture surfaces have been studied by scanning electronmicroscopy (SEM) and the failure mechanism has been explained.

Thermoset polyurethane (PU) elastomers were prepared using hydroxyl‐terminated polybutadiene (HTPB), toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). The effects of various diamines and diols on the mechanical and thermal properties of polyurethanes are discussed. The average molecular weight between crosslinks (M̄/c) was determined by swelling studies. The properties imparted by the extenders are explained on the basis of the groups present in the diamines and the number of methylene carbons in the diols.

SynopsisSemi-interpenetrating polymer networks of cellulose nitrate and castor oil based polyurethanes have been prepared by using excess diisocyanate for the crosslinking process. Semi-IPNs with 30% cellulose nitrate showed some degree of miscibility. Enhanced miscibility was observed by the partial replacement of cellulose nitrate with poly (vinyl chloride-co-vinyl acetate). The ternary IPNs of poly (vinyl chloride-co-vinyl acetate), cellulose nitrate, and polyurethanes showed increased tensile strength and decreased flammability than those based on cellulose nitrate and polyurethanes alone.