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The purpose of this paper is to study the efficiency of lignin/silica and calcium lignate/calcium silicate as natural antioxidants in styrene-butadiene rubber (SBR) vulcanizates.

It has been found that thermal aging data of the aged sample revealed that SBR vulcanizate undergoes crosslink reactions that lead to embrittlement and ultimately failure. Incorporation of lignin/silica or calcium lignate/calcium silicate, however, resulted in significant improvement of the degradation profile of the vulcanizates at 90±1°C. Loss of tensile strength and flexibility during aging of the SBR compounds with 8 phr lignin/silica or calcium lignate/calcium silicate was mild relative to unfilled polymer, indicating a restricted degradation due to the presence of the investigated compounds. The results obtained revealed that the investigated compounds are good antioxidant, and the evaluation was confirmed by physico-mechanical properties of the vulcanizates, FT-IR spectroscopy, transmission (TEM) and scanning (SEM) electron microscope.

It was noticed that SBR vulcanizates having 8 phr of lignin/silica or calcium lignate/calcium silicate exhibited the best mechanical properties in comparison with other concentrations (1, 2, 4, 6 and 10 phr). Also, results revealed that the lignin/silica derivatives are efficient antioxidants in SBR vulcanizates compared to vulcanizates containing conventional antioxidants used in rubber industry, namely polymerized 2,2,4-trimethyl-1, 2-dihydroquinoline (TMQ), and N-isopropyl-N'-phenyl-P-phenylenediamine (IPPD).

All these results indicated that lignin/silica and calcium lignate/calcium silicate in SBR had good heat resistance and aging resistance, calcium lignate/calcium silicate has an application limitation as not all vulcanizates need to use CaCO₃/calcium salts.

Lignin is usually seen as a waste product of pulp and paper industry and is often used as fuel for the energy balance of the pulping process. It is simple isolation along with silica from rice straw and using it as an antioxidant added further practical utility for this waste.

The importance of lignin/silica derivatives is arisen from their biodegradability and their ease availability from rice straw black liquor.

Some organo‐metallic pigments namely copper phthalocyanine, metal and metal free biphthalocyanines, halogenated copper phthalocyanine and two inorganic pigments (red and yellow iron oxides) were incorporated into styrene butadiene rubber mixes (SBR). The rheometric characteristics and mechanical properties of the compounded rubber were investigated. The antioxidant efficiency of the above mentioned pigments were evaluated. Beside their good colouring effect the synthesized copper and nickel biphthalocyanines and the commercial red iron oxide have a significant effect on the properties of rubber vulcanizates after ageing. In addition, nickel biphthalocyanine and red iron oxide can be successfully used as ultraviolet stabilizers for rubber vulcanizates.

The purpose of this paper is to study the effect of incorporating some inorganic fillers, namely aluminium oxide and aluminium hydroxide on the rheological, mechanical and thermal behaviour of acrylonitrile‐butadiene rubber (NBR) vulcanizates.

For improving physico‐mechanical properties of NBR vulcanizates, various compositions were made by incorporating different concentrations of employed fillers with NBR. These properties included the torque, cure time, tensile strength, elongation at break, swelling, diffusivity, as well as thermal behaviour of the loaded and unloaded NBR with fillers were characterised.

The incorporation of the two investigated fillers improves the thermal behaviour of the vulcanizates, especially aluminium hydroxide. All samples showed more or less a first order decomposition kinetics, for which the activation energy ranged from 177 to 187 kg/mol.

NBR is extensively used industrially for its single, most important property, which is an exceptional resistance to attack by oils and solvents. However, incorporation of fillers in (NBR) leads to the development of improved, competitive properties of the vulcanizate. A further study must be carried out on the flame retarding effect of the fillers, beside the effect of surface treatment of the fillers on the dispersibility and physico‐mechanical properties of the vulcanizates.

The use of two investigated fillers provided a simple and practical solution to improving the resistance to swelling in motor and break oil as well as the thermal behaviour of the NBR.

The use of these fillers was novel and could be used in many rubber industries especially in gasket and oil seals.

Itaconic acid was reacted with phenylene diamine (ortho, meta and para) and o‐tolidine in boiling dekalin, using Dean and Stark apparatus. The polymers prepared were evaluated for their suitability as antioxidants for natural rubber vulcanizates. The amide polymers prepared showed high efficiency as antioxidants for rubber vulcanizates, exceeding the performance of commercial antioxidants. In addition, the results obtained are encouraging and support the use of these polymers from both the environmental and economical points of view.

Evaluation of uracil and/or benzothiazol derivatives as antioxidants in natural rubber mixes.

Cyanoacetylurea 1, as a precursor, was prepared at a good yield from widely available, low‐cost chemicals. Compound 1 was treated with triethylorthoformate and amine derivatives in one pot reaction affording the target uracil derivative 3. Replacement of the cyano group in 1 by benzothiazol led to obtaining the interesting N‐hydroxy uracils containing benzothiazole moiety 5 at a good yield. Some of the compounds prepared was selected and were evaluated as antioxidants in natural rubber mixes. The rheometric characteristic of the compounded rubber and the physico‐mechanical properties of the vulcanizates were determined.

The cure rate index, tensile strength and modulus increased while the equilibrium swelling decreased, i.e. compound 5 behaved as a secondary accelerator. The rubber vulcanizates were subjected to thermal oxidative ageing at 90°C for up to seven days. It has been found that uracil and/or benzothiazol derivatives can protect natural rubber vulcanizates against oxidative deterioration.

The compounds prepareds were difficult to dissolve, they needed solvents with high boiling points, e.g. DMF, DMSO to be dissolved and even then they are not completely dissolved.

Uracil and or benzothiazol derivatives have many industrial applications.

The new compounds were prepared from very cheap and widely available chemicals. The compounds synthesised showed good antioxidant behaviour in comparison with the commercial antioxidant (phenyl‐β‐naphthyl amine) industrially used.

A new method for modifying the properties of aluminium oxide had been developed which allowed alumina to be used as a white, reinforcing filler in various rubber composites to replace carbon black, producing high performance white rubber vulcanizates comparable to those loaded with carbon black that could be coloured if needed.

Alumina was treated with small amounts of ammonium molybdate. Characterisation of modified aluminium oxide was carried out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Also, evaluation of the pigments prepared, in terms of oil absorption, specific gravity, and bulking value using international standard testing methods was performed. The morphology of the natural rubber composites loaded with the new modified alumina were studied using SEM. Kraus equation was used to analyse the extent of polymer‐pigment interaction, while Mooney‐Rivlin relation was employed to study the near equilibrium stress‐strain behaviour.

The results showed that, the pigment had a significant effect on the rheological characteristics (scorch, cure time, etc.), mechanical properties, stress and strain at yield and at rupture of white rubber vulcanizates prepared resulting in high performance.

As concentration of molybdenum oxide increased in the alumina crystals, the reinforcing effect in rubber composites also increased till an optimum concentration where such a reinforcing effect reversed. However, investigation of the application of these pigments in other systems such as an anticorrosive pigment in paint formulations and reinforcing filler in polyester composites could also be interesting.

The pigments prepared could be used as reinforcing filler in plastic composites and also as anticorrosive pigment in paint formulations.

Aluminium oxide is a cheap compound. The originality of the work lay in the finding that by adding trace amounts of molybdenym to it, aluminium oxide's properties changed dramatically resulting in more effective action in reinforcing rubber composites filled with such modified alumina, producing white rubber composites with comparable properties to those loaded with carbon black, and may exceed them in some cases. This allowed the preparation of coloured rubber with good rheological and physical properties.

In continuation to the previous work on copper (lignin/silica/fatty acids) (Cu-LSF) complex as a natural antioxidant/electrical conductivity agent for nitrile-butadiene rubber (NBR), this study aims to perform further investigations for NBR vulcanizates loaded with different concentrations of Cu-LSF complex, including swelling behavior and hardness properties, as well as evaluating their thermal stability via thermogravimetric analysis.

The behavior of Cu-LSF complex in NBR matrix was compared with that of the standard commercial antioxidants (2,2,4-trimethyl-1,2-dihydroquinoline/N-isopropyl-N′-phenyl-p-phenylenediamine [TMQ/IPPD]).

Results revealed that Cu-LSF complex can act as an effective reinforcing and hardening agent, with exhibiting fluid resistance, even when compared with the commercial antioxidants. In comparison with the previous studies on its Zn and Ca analogues and their behavior in different rubber matrixes, Cu-LSF complex showed higher values of hardness and less susceptibility for swelling, respectively. Moreover, Cu-LSF antioxidant activity becomes in accordance with the previous work.

The new Cu-LSF complex could be used as a green alternative to the commercial antioxidants (TMQ/IPPD) with introducing further advantages to the rubber matrix, such as hardening, fluid resistance and thermal stability.

The purpose of this paper is to study the effect of new heterocyclic compounds on styrene butadiene rubber (SBR) mixes.

It has been found that the starting material 1 could react with cyromazine (2) and/or 4‐aminoantipyriene (4) as amino compounds in the presence of triethylorthoformate and in the boiling dioxane to yield triazine‐3 and/or pyrazolo 5 derivatives, respectively. The chemical structures of the new products 3 and 5 have been established by their elemental analyses spectroscopic data IR, Ms and 1H, 13C NMR. These two compounds were evaluated as antioxidants in SBR, and this evaluation was confirmed by physico‐mechanical properties of vulcanizates, IR spectra and scanning electron microscope.

The difference between maximum torque MH and minimum torque ML (ΔM), tensile strength, modulus and elongation at break increases in the presence of prepared antioxidants while the equilibrium swelling decreased. The rubber vulcanizates were subjected to thermal oxidative aging at 90°C for up to seven days. It has been found that new compounds 3 and 5 can protect SBR vulcanizates against oxidative deterioration.

The solubility of the prepared compounds 3 and 5 is very poor and they are only soluble in dimethyl formamide (DMF) or dimethyl sulphoxide (DMSO) which have high boiling points. Also, new compounds 3 and 5 have melting points (above 300°C).

Triazine and antipyrine derivatives have many medical and industrial applications.

The new synthesized compounds revealed excellent antioxidant behaviour in comparison with the commercial antioxidant phenyl‐β‐naphthyl amine (PβN) which is used in industry.

Calcium and Zinc lignates were proven to be good antioxidants for rubber composites. The purpose of this paper is to evaluate the copper lignate antioxidant activity along with evaluating its electrical conductivity in rubber composites.

The antioxidant activity of the Cu-LSF complex was compared with that of standard commercial antioxidant additives as a green alternative. The rheological characteristics, thermal aging and mechanical and electrical properties were evaluated for the NBR vulcanizates containing the different antioxidants in the presence or absence of coupling agents.

Results revealed that the Cu-LSF complex (5 phr) can function as a compatibilizing, antioxidant and electrical conductivity agent.

The new copper complex prepared from paper-pulping black liquor of wastes could be used as a green antioxidant and electrical conductivity agent in rubber composites.

Polyoxyethylated hydroxy benzyl oleamide has found use in lubricants to prevent adhesion in moulds during the production of vulcanizates of natural and of synthetic rubbers. Polyoxyethylated oleamide acts as a mould lubricant for synthetic rubbers, whilst polyglycol 400 dilaurate can be used to reduce the time and temperature necessary for the recovery of old vulcanizates using paraffin oil and bitumen. Anti‐fogging properties can be sustained in rubber hydrochloride films by the use of polyglycol 1500 dilaurate, and improved percentage elongation can be promoted in intimate blends of polystyrene and SBR rubbers by the inclusion of polyglycol 4000 monostearate. Polyoxyethylated sorbitan monostearate acts as an emulsifer in the emulsion polymerisation of styrene, butadiene and styrene/ butadiene copolymer rubbers, and it can perform as an anti‐static for the latter. Polyoxyethylated stearylamine can be incorporated into lubricants designed to prevent adhesion in moulds during production of vulcanizates of synthetic and of natural rubber, and rubber latexes and other aqueous dispersions of rubber can be rendered more stable by the employment of polyoxyethylated stearyl alcohol, and thus allow storage in untreated containers for long periods of time. Polyoxypropylated sorbitan monopalmitate will serve as a parting agent, releasing aid, for unvulcanized rubber and vulcanized rubber, without interfering with further bonding and coating of rubber.