Saeed Ostad Movahed

A novel chemical technique for compatibility of ethylene-propylene-diene monomer rubber and styrene-butadiene rubber in their blends

The market for commercial polymer blends has grown steadily. A good blend should have strong interphases between different parts of the constituted polymers. Lack of strong interphases is a classical problem of the blend industry. Ethylene-propylene-diene monomer rubber (EPDM)/styrene-butadiene rubber (SBR) blends have a very good aging resistance and good compression sets. However, these rubbers are partially miscible. To improve the miscibility of EPDM and SBR in their blends, a Lewis acid, AlCl3, was used to form EPDM–g–SBR copolymer through Friedel–Crafts reactions. The existence of covalent bonds between EPDM and SBR macromolecules was studied by the cure traces of the blends, that is, ΔTorque, Fourier transform infrared spectrums, differential scanning calorimetry (DSC) heat flow curves, thermogravimetric analysis curves, and scanning electron (SEM) micrographs. Subsequently, several blends with EPDM/SBR ratio of 40/60 and with various AlCl3 amounts were prepared and after curing, their mechanical properties were measured and compared. The results showed covalent bonds formed between SBR–EPDM and SBR–SBR macromolecules. An exothermic change in heat flow in the DSC curve was observed around 111.28°C, which can be attributed to the formation of carbocations in Friedel–Crafts reactions. Adding 2 phr AlCl3 had an efficient effect on EPDM–SBR and or SBR–SBR linkages. The mechanical properties of the cured blends, that is, tensile strength were lower when compared with corresponding values for prepared compound with SBR. Excellent compatibility between the two polymers and strong interphases were observed in SEM micrograph of the cured blend with 1 phr AlCl3.

Devulcanization and recycling of waste automotive EPDM rubber powder by using shearing action and chemical additive

In automotive applications, ethylene-propylene-diene rubber (EPDM) is used to manufacture various components and therefore recycling scrap rubber is a major issue. The primary aim of this study was to develop a new method for devulcanizing waste automotive EPDM rubber powder by using shearing action and chemical additive and recycle the devulcanized powder. A semi-industrial twin screw extruder with a shearing action and reactor along with 2-mercaptobenzothiazole-disulfide (MBTS) chemical were used to devulcanize the waste powder at two different feed screw speeds and main rotor speeds at a constant temperature of 220°C. To recycle the devulcanized powder, different amounts of the devulcanized powder were mixed with a commercial EPDM-based automotive rubber strips compound to produce blends. The blends, commercial compound and devulcanized powder were cured with a semi-efficient (SEV) vulcanization system and their viscosity, cure and mechanical properties measured. For the blends, the Mooney viscosity was unchanged with 40 wt%, crosslink density with 20 wt%, tensile strength and elongation at break with 10 wt%, and compression set with 20 wt% of the devulcanized powder. Interestingly, the hardness benefitted from 50 wt% of the devulcanized powder in the blends. The scorch and optimum cure times shortened and the cure rate index rose when the loading of the devulcanized powder in the blends was raised. This new method offered a major new route for devulcanizing and recycling the waste powder.

A New Formulation for Polymeric Separator Gels for Potential use in Blood Serum Separator Tubes

Blood serum separator tubes (SST) are used for collecting blood samples for performing clinical chemistry assays. Some SSTs have separator gels inside the tube which enable them better separation of the blood serum from packed cells during centrifugation. The cost, weak performance and interaction with blood ingredients are the most concerns of the available commercial gels. A commercial and cheap silicone oil as a polymeric base of the gel was chosen and formulated without and with several fillers. Subsequently, the compounds were crosslinked through a free radical crosslinking mechanism using dicumyl peroxide (DCP). The crosslinking took place in both, an oven and as well as under microwave irradiation in normal and under pressure conditions. The FTIR spectrometer analysis showed that both chain ends of the used silicone oil were terminated with a vinyl group. It also revealed that blood serum separator gel can be produced from selected silicone oil type. Among of different curing apparatus, curing in an oven was preferred due to less curing time and electrical energy consumption. The curing in normal pressure showed better results when compared with curing under pressure. Increasing the filler and DCP with various amounts had positive effect on gel densities. Silica was the most efficient filler among of the studied fillers. The cured compound filled with 10 and 8 phr silica and DCP, respectively, was chosen as appropriate gel for SST due to suitable density and thixotropy. The selected gel was cured in oven under normal pressure for 30 minutes at 160°C.