E. M. Abdel-Bary

Mechano-Chemical Reclamationof Waste Rubber Powder andIts Effect on the performanceof NR and SBR Vulcanizates

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.

Recycling of polyethylene films used in greenhouses—Development of multilayer plastic films

Abstract Recycling of greenhouse plastic films was carried out by coextruding two-layer plastic films. The top layer consists of a blend of virgin thermoplastic resins stabilized with different stabilizers. The bottom layer was composed mainly of PE waste in combination with virgin resins and other ingredients. The two-layer films produced were subjected to accelerated UV ageing and to outdoor weathering in two different locations for almost 1 year. The results obtained revealed that the optimized two-layer films can be successfully used as greenhouse films.

Radiation-Induced Graft Copolymerization Of Some Vinyl Monomers Onto Waste Rubber Powder

Abstract Rubber powder was subjected to graft copolymerization with different vinyl monomers such as acrylamide (AAm), acrylic acid (AAc), and acrylonitrile (AN). Graft copolymerization of these monomers onto rubber powder was carried out using gamma radiation. The effects of different parameters such as monomer concentration, radiation dose, inhibitor concentration, and type of reaction solvent on the graft yield were studied. It was found that the maximum graft yield obtained is 90%, 24%, and 42% for AAc, AAm, and AN, respectively. The grafted rubber powder obtained was tested as ion exchanger for copper and lead, and its capacity for ion recovery was found to be dependent on the type of monomer and graft yield. For instance, polyacrylamide and sodium salt of polyacrylic acid grafted onto rubber powder are more efficient as ion exchangers for both copper and lead ions than polyacrylonitrile. Amidoxime derivative of polyaerylonitrile is more efficient as ion exchanger than the parent polyaerylonitrile.

The photodegradation of cis-1,4-polybutadiene, polystyrenebutadiene and polyisoprene

Abstract The photodegradation of the synthetic rubbers cis -1,4-polybutadiene, polystyrenebutadiene and polyisoprene was studied. The chemical structure of the polymers as well as the effect of changing the solvent and the additive were particularly taken into consideration. The polychloroprene rubber in this study was irradiated either as a film or in solution. The presence of methylene blue affects the endothermic peaks observed in its differential scanning calorimetry diagrams. Methylene blue acts as a photostabilizer dye in solutions and films of polychloroprene. Mixtures of methylene blue, β-carotene as a singlet oxygen quencher and Fmbanox as a known anti-oxidant showed synergystic behaviour.

Evaluation of some organic compounds as antioxidants in rubber

Three different classes of organic compounds, namely triazole, oxazoline and p-phenylenediamine derivatives, were synthesized and investigated in natural rubber and styrene-butadiene rubber mixes and vulcanizates. It was found that the efficiency of triazole derivatives increased with the introduction of electron withdrawing substituents in the para position of the benzene ring. The only exception is the p-amino derivative which shows a higher efficiency relative to other substituents. In contrast, it was found that the efficiency of p-phenylenediamine derivatives increased with the increasing inductive effect of the substituents. A correlation between the Hammet constant and the efficiency of triazole derivatives was established.

Effect of some curatives on the properties of ethylene propylene diene rubber/polyethylene blends

A series of ethylene propylene diene rubber/polyethylene (EPDM/PE) blends has been prepared containing different weight fractions of PE up to 0.66. The blends were vulcanized with a sulphur system N-cyclohexyl-2-benzthiazol sulphenamide/sulphur (CBS/S), and a non-sulphur-system dicumyl peroxide (DCUP). The concentration of the latter has been changed from 1.5phr up to 6phr calculated on the total weight of the blend composition. It has been found that the maximum torque obtained from rheographs for blends vulcanized with the CBS/S system decreases markedly with increasing PE concentration in comparison with those vulcanized with peroxide. The E modulus obtained from the stress-strain diagram at 110°C showed the role played by the crosslinking of PE, the E modulus for blends vulcanized by peroxide being higher than for samples vulcanized with CBS/S. In contrast, the values of E modulus of both samples are practically the same at room temperature and attain more than 40MPa depending on the composition. The tensile strength at room temperature strongly increases with increasing the weight fraction ofPE. It has also been confirmed that the melting point of the crystalline phase of PE decreases with increasing crosslinking density of PE. The shear modulus obtained from dynamic mechanical measurements is in accordance with that obtained from static mechanical measurements.

Evaluation of Sulfonated Rubber Powder as Ion Exchange Resin

Ground rubber powder was treated with both concentrated sulfuric acid and chlorosulfonic acid. The treatment conditions as well as the parameters affecting the degree of sulfonation were investigated. It is assumed that the sulfonation reaction occurs on the benzene ring as well as on the double bond of the butadiene unit in styrene butadiene rubber (SBR). Evaluation of the ion exchange capacity of both the acidic form and the neutralized form was carried out. It was found that the ion exchange capacity of the neutralized form is higher than that of its corresponding acidic form.

Recovery of some metal ions using gamma-radiation induced grafted waste rubber powder

Waste rubber powder was grafted with different vinyl monomers by using gamma-radiation. The monomers used for grafting were acrylic acid, acrylamide and acrylonitrile. The sodium salt of grafted polyacrylic acid as well as the amidoxime derivative of grafted polycacrylonitrile were also obtained. Evaluation of the efficiency of the products obtained to the recovery of some metal ions such as cobalt and nickel as well as to phenol was carried out. It was found that the grafted waste rubber powder is able to recover cobalt and nickel ions from their corresponding salts depending on the type of monomers used. It was also found that phenol can be reasonably recovered by using rubber powder grafted with acrylamide and amidoxime derivative.

Radiation-Induced Grafting of Vinyl Monomers Onto Polymer Blends. I. Effect of Vulcanizing Systems on the Grafting of Acrylonitrile onto Epdm/Pe Blends

Abstract Ethylene propylene diene terpolymer (EPDM) was blended with high-density polyethylene (HDPE) in the ratio 1:1. The blends obtained were vulcanized with sulfur or with peroxide vulcanizing systems. The vulcanized samples were subjected to radiation graft copolymerization with acrylonitrile (AN). The parameters affecting graft yield, such as irradiation dose, monomer concentration, and type of solvent, were investigated. It was found that sulfur-vulcanized blends are less susceptible towards graft copolymerization than peroxide-vulcanized blend even after purification from residual additives. Thus, the maximum graft yield was found to achieve 5% and 45% for sulfur-and peroxide-vulcanized samples, respectively. In addition, the graft copolymerization of AN onto EPDM/PE blend improves its solvent resistance depending on graft yield, exceeding 8%. Also, the mechanical properties of the blends obtained were improved markedly at low graft percentages not exceeding 14%.

Homogeneous Photoinduced Graft Copolymerization of 4-Vinyl Pyridine onto Ethyl Cellulose. 1. Influence of Biacetal and Acetonaphthone Derivatives

Abstract Homogeneous photoinduced graft copolymerization of 4-vinyl pyridine (4-VP) onto ethyl cellulose (EC) in the presence of three photosensitizers such as 1-acetonaphthone (1-An), 2-acetonaph-thone (2-An), and biacetal (Bi) in benzene solution was extensively investigated. Ultraviolet (UV) irradiation in the range 310 to 460 nm was used. The U V spectra of the mentioned photosensitizers showed n-π∗ transitions. Grafting parameters such as grafting percentage (GP) and grafting efficiency (GE) were determined as functions of the irradiation time and the concentrations of monomer, substrate, and initiator. The IR spectrum of the EC-g-4-VP copolymer shows the appearance of new peaks between 1600 and 1690 cm-1 indicating the presence of poly-4-vinyl pyridine (p-4-VP) grafted chains. The rate of copolymerization of 4-VP onto EC in the presence of 1-An, 2-An, and Bi was determined as 0.98% min-1, 0.88% min-1 and 0.042% min-1, respectively. A good correlation was observed between the change in absorbance at ...