Thermo-mechanical properties of devulcanized rubber/high crystalline polypropylene blends modified by ionizing radiation

Short nylon tire cord and gamma irradiation impact on SBR/ultrasonic and mechanochemical devulcanized rubber blends

Devulcanization of discarded tire rubber (WR) has remained of prior attention to numerous researchers, aiming for unlimited commercial profits upon modification, especially to serve as a substituent for virgin rubber. In this concern, composites of styrene butadiene rubber (SBR) and devulcanized waste rubber, developed via two techniques: mechanochemical (DRm) and ultrasonic (DRus), and reinforced with short nylon tire cord (SNF), namely at a filling ratio of 3 and 5 phr were fabricated. All prepared specimens were exposed to various gamma radiation doses, namely 50, 100, and 150 kGy. The post-radiation characterization was investigated by FTIR and SEM techniques. Radiation-induced crosslinking density of the polymer composites was calculated and correlated with the different mechanical features. Furthermore, the TGA technique and activation energy measurement were implemented in studying the thermal behavior of the products. Incorporation of 5 phr SNF set out the thermal stability order: SBR/DRm/5 SNF > SBR/DRus/5 SNF > SBR/5 SNF. Ionizing irradiation of all composite–SNF formulations derived to a marked improvement in TS data as a result of creating further crosslinking within the polymeric matrix, reaching a maximum by the integral dose 150 kGy. The results were appreciably compared to a recently published study that applied reinforced tire fiber with polyester, as another cord utilized in the manufacture of tires. It is found that TS data observed by irradiation with 150 kGy of SBR/3 SNF, SBR/DRm/3 SNF, and SBR/DRus/3 SNF are respectively as follows: 3.7, 2.5, and 2.4 MPa, whereas the corresponding reported values for PTC reinforced counterpart blends were: 2, 1.7 and 1.8 MPa. Similarly, the TS respective values of SBR/5 SNF, SBR/DRm/5 SNF and SBR/DRus are 2.5, 1.9, and 2.2 MPa, whereas their counterparts reinforced with 5 phr PTC recorded 1.6, 1.8, and 1.2 MPa. SNF-reinforced SBR, SBR/DRm, and SBR/DRus were superior in their properties to PTC-reinforced counterpart specimens.

Low-Temperature Mechano-Chemical Rubber Reclamation Using Terpinene as a Swelling Agent to Enhance Bond-Breaking Selectivity

Common swelling agents used in the mechano-chemical rubber devulcanization process usually require high temperatures to achieve satisfactory swelling effects, which results in severe production of pollutants and reduces the selectivity of bond scissions. This work presents an environmentally friendly swelling agent, terpinene, which can swell the rubber crosslink structures at low temperatures. Both a rubber swelling experiment and a rubber reclaiming experiment with a mechano-chemical devulcanization method are conducted to explore the swelling effects of terpinene. After soaking in terpinene at 60 °C for 90 min, the length elongation of the rubber sample reaches 1.55, which is much higher than that in naphthenic oil and is comparable to that in toluene. When adding 3 phr of terpinene for every 100 phr of waste rubber during the reclaiming process, the bond scissions exhibit high selectivity. After revulcanization, the reclaimed rubbers have a tensile strength of 17 MPa and a breaking elongation of 400%. Consequently, the application of terpinene as the swelling agent in the LTMD method can greatly improve the properties of reclaimed rubbers, thereby enhancing the dual value for the economy and environment.

Conditions Optimization and Physiochemical Analysis of Oil Obtained by Catalytic Pyrolysis of Scrap Tube Rubber Using MgO as Catalyst

Motor vehicles scrap tires and tube rubbers generate a large amount of waste with different characteristics and compositions, contaminating the environment when not properly disposed. Waste inner tube rubber (isobutylene isoprene) representing a threat to the environment can be used as valuable source of energy. Waste inner tube rubber was pyrolyzed thermally under atmospheric pressure both with and without catalyst. Parameters of temperature, time, and catalyst weight were optimized for catalytic and thermal pyrolysis of isobutylene-isoprene rubber into liquid fuel, using MgO as catalyst. It was found that one-hour heating time at 350 °C using 2 g catalyst (MgO) constitutes a suitable parameter for the maximum conversion of scrap inner tube rubber into oil. The oil obtained was characterized by physical and chemical tests. Among the physical tests, Density, specific gravity, viscosity, kinematic viscosity, analine point and flash point were determined according to IP and ASTM standard valves. The physical tests indicate the presence of aromatic and olefinic hydrocarbons. Among the chemical tests, the phenol test, bromine number, bromine water test, and KMnO4 tests were conducted. The chemical tests are also the support of physical tests conducted. The physical and chemical tests indicate that the oil obtained is a mixture of kerosene, diesel, and light oil and could be used for fuel purposes.

Effect of gamma irradiation and oxidized bitumen on the performance of the modified crumb rubber for various applications

The objective of this study is to enhance the properties of crumb rubber (CR) derived from the tread and sidewalls of passenger and truck waste tires by adding bitumen (B) and oxidized bitumen (OB). On this context, CR was activated and modified by adding different chemical ingredients to convert it into modified crumb rubber (MCR). OB was irradiated at 25 kGy to get irradiated oxidized bitumen (IOB) with the aim of study the effect of irradiation on the samples in the presence and absence of sulfur element. The crosslinking density, mechanical parameters and thermal stability of the developed blend were examined. Furthermore, chemical resistance behavior, vibration tests which reflecting the velocity level and sound proofing performance were discussed. Remarked improvement in the mechanical, thermal and various applications of MCR were achieved by the incorporation of OB especially at 10 phr and gamma irradiation.

Investigation of physico-mechanical properties of flexible poly (vinyl chloride) filled with antimony trioxide using ionizing radiation

Composites of polyvinyl chloride (PVC) with 2% calcium carbonate, 2% diethyl phthalate, 2% paraffin wax and 2% lead sulphate and different contents of antimony trioxide (Sb₂O₃) prepared by melting and irradiated with gamma ray have been considered. Assessment of the mechanical and thermal properties of the unirradiated and irradiated flexible polyvinyl chloride (FPVC) were completed utilizing elasticity (TS), Elongation at break (Eb) and thermogravimetric analysis measurements. TS and thermal stability of FPVC displayed advanced improvement after addition of additives and this approach highlighted the efficiency of those ingredients on PVC. The compounding of FPVC with Sb₂O₃ in various extents was examined by FTIR, X-ray diffraction and scanning electron microscope methods. It is obvious that the presence of Sb₂O₃ begins impacting oxidative degradation, leading to a decrease in mechanical properties up to 10%. Moreover, a slight increase in the thermal stability of composites by exposure to ionizing radiation is apparently due to cross-linking of FPVC chains.

Thermoplastic vulcanizates based on waste truck tire rubber and copolyester blends reinforced with carbon black

Devulcanized rubber (DR) was prepared from waste truck tire rubber via thermo-chemical devulcanization process. Thermoplastic vulcanizates (TPVs) based on blending of DR and copolyester (DR/COPE) were prepared. Effects of carbon black loading on microstructure, mechanical properties and elastomeric behaviors of dynamically cured DR/COPE blends were investigated. It was found that increasing of the carbon black loadings leads to transformation from co-continuous phase structure to dispersion of smaller vulcanized rubber domains in the COPE matrix. Furthermore, the carbon black was well dispersed in the DR/COPE matrix up to 10 wt% and then the aggregates slightly occurred with increasing of carbon black loadings. In addition, dynamic experiments proved that a progressive non-linear behavior was more pronounced with increasing of carbon black loadings. Also, tan δ_max of the DR phase decreases with increasing carbon black concentration indicating mainly localization of filler in rubber phase. Moreover, it was found that increases of CB loadings resulted in increase of tensile strength and hardness while the elongation at break was slightly decreased. Additionally, the rate of stress relaxations was found to be increased with increasing CB loadings.