No abstract

Waste rubber powder (RP) was subjected to chemical modification by using different concentrations of oxidizing agents such as nitric acid and 30% hydrogen peroxide solution. This treatment leads to introducing some functional groups onto the surface of RP. The chemically modified RP was incorporated in natural rubber mixes either alone or in combination with carbon black (HAF). The physicomechanical properties of NR vulcanizates obtained were studied and compared to NR vulcanizates filled with untreated RP. It was found that the chemically modified RP improves tensile strength and aging resistance of NR vulcanizates compared with untreated RP.

Waste rubber powder (RP) was processed in a Brabenderpremixer under various conditions in the presence of reclaiming agents toconvert the RP into plastic mass (reclaimed rubber), then the obtained reclaimwas blended with both NR and SBR in different ratios. It was found that thebehavior of the reclaim in both NR and SBR is the same. The rheometriccharacteristics show that by increasing the reclaim ratio, the curing time wasdecreased and consequently the cure rate index was increased. Also themaximum torque of the same rubber compounds was decreased. The physico-mechanical data of the reclaim/NR and reclaim/SBR blends showthat the tensile strength as well as elongation at break were decreased withincreasing the reclaim ratio in the blend. On the other hand the equilibrium swellingwas increased. However one can replace about 10–30% of NR or SBR by thereclaim without sacrificing the essential characteristics of the rubber vulcanizates.

New bio‐composite, semi‐interpenetrating biopolymers (obtained from hydrolyzed carboxymethyl cellulose grafted polyacrylonitrile [h‐CMC‐g‐PAN] and sodium alginate [Na‐Alg] using CaCl2 as a cross linker; semi‐interpenetrating biopolymers [s‐IPNs]) have been prepared and fully characterized using spectroscopic (FTIR, scanning electron microscopy, EDS), elemental analysis, and thermal analysis measurements measurements. The morphology and structure of these s‐IPNs are different from those obtained with solely h‐CMC‐g‐PAN and Na‐Alg indicating successive functionalization. The availability of the functional‐rich bio‐composites has afforded an excellent opportunity to test them as sorbents for the uptake of toxic Cd(II) ions from aqueous media. Subsequently, the uptake of Cd(II) ions was shown to be dependent on the pH, shaking time, temperature, amount of sorbent, and the initial concentration of the Cd(II) ions. The maximum Cd(II) ion uptake was 99.5% at pH 6, using 50 mg of sorbent with 120 min shaking time at 25°C. The adsorption isotherm fitted well with Langmuir model, with calculated maximum adsorption capacity 49.75 mg g−1. The kinetic studies were modeled using a pseudo second‐order reaction. The thermodynamic parameters (ΔHo, ΔGo, and ΔSo) of the uptake of Cd(II) ions onto s‐IPNs were found to be −13,176.07 Jmol−1, −4,572.7 Jmol−1, and 28.87 J K−1 mol−1, respectively, verifying spontaneous exothermic process. Successive desorption and reusability of s‐IPNs for the uptake of Cd(II) indicated, its high efficiency over three cycles.

The thermal properties (thermal conductivity, thermal diffusivity, and specific heat capacity) of nitrile rubber (NBR)/poly(vinyl chloride) (PVC) blends were measured in the temperature range of 300-425 K. The incorporation of graphite into the NBR/PVC (30/70) matrix improved its thermal properties. Moreover, these properties slightly changed with the temperature. The thermal conductivity values of the prepared samples were compared with values modeled according to the MaxwellEucken, Cheng-Vachon, Lewis-Nielsen, geometric mean, and Agari-Uno models. The Agari-Uno model best predicted the effective thermal conductivity for the whole range of blend ratios and for the whole range of graphite contents in NBR/PVC (30/70)/graphite composites.