Effect of Urethane Based Bonding Agent on the Cure Characteristics and Mechanical Properties of Styrene Butadiene Rubber - Whole Tyre Reclaim - Short Nylon Fiber Composite

The cure characteristics and mechanical properties of short nylon fiber- styrene /whole tyre reclaim (SBR/WTR) composites with and without an interfacial bonding agent based on 4,4 diphenyl methane diisocyanate and polyethylene glycol (MDI/PEG) have been studied. An 80:40 blend of SBR/ WTR reinforced with 20 phr of short nylon fiber has been selected and the MDI/ PEG ratio has been changed from 0.67:1 to 2:1. The minimum and maximum torques increased with isocyanate concentration. The scorch time and cure time showed an initial reduction. The cure rate showed an initial improvement. Tensile strength, tear strength and abrasion resistance increased with MDI/PEG ratio, these values were higher in longitudinal direction. Resilience and compression set increased with isocyanate concentration.

Preparation of Low-Protein Natural Rubber Latex: Effect of Polyethylene Glycol

Low-protein content natural rubber latex was produced by using a nonionic surfactant-polyethylene glycol (PEG). Extractable protein content of natural rubber latex was found to decrease with PEG treatment and reduction increased with increase in the molecular weight of PEG. The low-protein latex samples were characterized by tensile testing, Fourier transform infrared and thermogravimetric analysis. The results have shown 35% reduction in the extractable protein content, without any compromise on the mechanical properties of the latex; however, thermal stability of low-protein latex was found to be reduced marginally with PEG treatment.

Studies on the Utilisation of Rubber Reclaim in Elastomers

The thesis describes utilisation of reclaimed rubber, Whole Tyre Reclaim (WTR) produced from bio non- degradable solid pollutant scrap and used tyres. In this study an attempt has made to optimize the substitution of virgin rubber with WTR in both natural and synthetic rubber compounds without seriously compromising the important mechanical properties. The WTR is used as potent source of rubber hydrocarbon and carbon black filler. Apart from natural rubber (NR), Butadiene rubber (BR), Styrene butadiene rubber (SBR), Acrylonitrile butadiene rubber (NBR) and Chloroprene rubber (CR) were selected for study, being the most widely used general purpose and specialty rubbers. The compatibility problem was addressed by functionalisation of WTR with maleic anhydride and by using a coupling agent Si69.The blends were systematically evaluated with respect to various mechanical properties. The thermogravimetric analyses were also carried out to evaluate the thermal stability of the blends.Mechanical properties of the blends were property and matrix dependant. Presence of reinforcing carbon black filler and curatives in the reclaimed rubber improved the mechanical properties with the exception of some of the elastic properties like heat build up, resilience, compression set. When WTR was blended with natural rubber and synthetic rubbers, as the concentration of the low molecular weight, depolymerised WfR was increased above 46-weight percent, the properties deteriorates.When WTR was blended with crystallizing rubbers such as natural rubber and chloroprene rubber, properties like tensile strength, ultimate elongation were decreased in presence of WTR. Where as in the case of blends of WTR with non-crystallizing rubbers reinforcement effect was more prominent.The effect of functionalisation and coupling agent was studied in three matrices having different levels of polarity(NBR, CR and SBR).The grafting of maleic anhydride on to WTR definitely improved the properties of its blends with NBR, CR and SBR, the effect being prominent in Chloroprene rubber.Improvement in properties of these blends could also achieved by using a coupling agent Si69. With this there is apparent plasticizing effect at higher loading of the coupling agent. The optimum concentration of Si69 was 1 phr for improved properties, though the improvements are not as significant as in the case of maleic anhydride grafting.Thermal stability of the blend was increased by using silane-coupling agent.

Design and Development of Instrumentation Systems to determine the Dry Rubber Content in Natural Rubber Latex

Hevea latex is a natural biological liquid of very complex composition .Besides rubber hydrocarbons,it contains many proteinous and resinous substances,carbohydrates,inorganic matter,water,and others.The Dry Rubber Content (DRC) of latex varies according to season, tapping system,weather,soil conditions ,clone,age of the tree etc. The true DRC of the latex must be determined to ensure fair prices for the latex during commercial exchange.The DRC of Hevea latex is a very familiar term to all in the rubber industry.It has been the basis for incentive payments to tappers who bring in more than the daily agreed poundage of latex.It is an important parameter for rubber and latex processing industries for automation and verious decesion making processes.This thesis embodies the efforts made by me to determine the DRC of rubber latex following different analytical tools such as MIR absorption,thermal analysis.dielectric spectroscopy and NIR reflectance.The rubber industry is still Looking for a compact instrument that is accurate economical,easy to use and environment friendly.I hope the results presented in this thesis will help to realise this goal in the near future.

Short Nylon-6 Fibre/Rubber-Toughened Polystyrene Composites

The thesis describes studies on development of short Nylon-6 fibre composites based on rubber-toughened polystyrene (PS). Toughening was done using natural rubber (NR), styrene-butadiene rubber (SBR) and whole tyre reclaim (WTR). The composites were prepared by melt mixing in an internal mixer at 170 oC. It was found that the optimum blend ratio was 85/15 for PS/NR, 90/10 for PS/SBR and 90/22 for PS/WTR blends. The effect of dynamic vulcanisation on 85/15 PS/NR and 90/10 PS/SBR blends using dicumyl peroxide (DCP) at various concentrations were also studied. The dynamic crosslinking improved the tensile properties, flexural properties, impact strength and dynamic mechanical properties of both the blends. The effect of unmodified and resorcinol formaldehyde latex (RFL)-coated short Nylon-6 fibres on the mechanical properties, morphology and dynamic mechanical properties of 85/15 PS/NR, 90/10 PS/SBR and 90/22 PS/WTR blends were studied. Fibre loading was varied from 0 to 3 wt.%. For 85/15 PS/NR blend, there was a significant enhancement in tensile properties, flexural properties and impact strength with 1 wt.% of both unmodified and RFL-coated fibres. Dynamic mechanical analysis revealed that the storage modulus at room temperature was maximum at 1 wt.% fiber loading for both composites. The surface functionality of the fiber was improved by giving alkali treatment. Maleic anhydride-grafted-polystyrene (MA-g-PS) was prepared and used as a compatibiliser. The effect of MA-g-PS on the composites was investigated with respect to mechanical properties, morphology and dynamic mechanical properties. The compatibiliser loading was varied from 0 to 2 wt.%. The properties were enhanced significantly in the case of treated and untreated fibre composites at a compatibiliser loading of 0.75 wt.%. SEM analysis confirmed better bonding between the fibre and the matrix. Dynamic mechanical studies showed that the storage modulus at room temperature improved for treated fibre composites in the presence of compatibiliser. In the case of 90/10 PS/SBR composites, the addition of short Nylon-6 fibres at 1 wt.% loading improved the tensile modulus, flexural properties and impact strength while the tensile strength was marginally reduced. The surface treated fibers along with compatibiliser at 0.5 wt.% improved the tensile properties, flexural properties and impact strength. DMA reveale that the storage modulus at room temperature was better for composites containing untreated fibre and the compatibiliser. In the case of 90/22 PS/WTR blends, 1 wt.% unmodified fibre and 0.5 wt.% RFL-coated fibres improved tensile modulus, flexural properties and impact strength. Tensile strength was improved marginally. The surface treatment of Nylon fibre and the addition of compatibiliser at 0.5 wt.% enhanced the tensile properties, flexural properties and impact strength. The dynamic mechanical analysis showed that the storage modulus at room temperature was better for untreated fibre composites in conjunction with the compatibiliser. The thermal stability of PS/NR was studied by TGA. Thermal stability of the blends improved with dynamic vulcanisation and with the incorporation of RFL-coated Nylon fibres. The untreated and partially hydrolyzed fibre composites in conjunction with the compatibiliser enhanced the thermal stability. Kinetic studies showed that the degradation of the blends and the composites followed first order kinetics.

Studies on the Production, Properties and Processability of Low Protein Latex

Latex protein allergy is a serious problem faced by users of natural rubber latex products. This is severe in health care workers, who are constantly using latex products like examination gloves, surgical gloves etc. Out of the total proteins only a small fraction is extractable and only these proteins cause allergic reactions in sensitized people. Enzymic deproteinisation of latex and leaching and chlorination of latex products are the common methods used to reduce the severity of the problem.Enzyme deproteinisation is a cubersome process involving high cost and process loss.Physical properties of such films are poor. Leaching is a lengthy process and in leached latex products presence of extractable proteins is observed on further storing. Chlorination causes yellowing of latex products and reduction in tensile properties.In this context a more simple process of removal of extractable proteins from latex itself was investigated. This thesis reports the application of poly propylene glycol (PPG) to displace extractable proteins from natural latex. PPG is added to 60 % centrifuged natural latex to the extent of 0.2 % m/rn, subssequently diluted to 30 % dry rubber content and again concentrated to obtain a low protein latex.Dilution of concentrated latex and subsequent concentration lead to a total reduction in non - rubber solids in the concentrate, especially proteins and reduction in the ionic concentration in the aqueous phase of the latex. It has been reported that proteins in natural rubber / latex affect its behaviour in the vulcanisation process. Ionic concentration in the aqueous phase of latex influence the stability, viscosity and flow behaviour of natural latex. Hence, a detailed technological evaluation was carried out on this low protein latex. In this study, low protein latex was compared with single centrifuged latex ( the raw material to almost every latex product), double centrifuged latex ( because dilution and second concentration of latex is accompanied by protein removal to some extent and reduction in the ionic concentration of the aqueous phase of latex.). Studies were conducted on Sulphur cure in conventional and EV systems under conditions of post ~ cure and prevulcanisation of latex. Studies were conducted on radiation cure in latex stage. Extractable protein content in vulcanised low protein latex films are observed to be very low. lt is observed that this low protein latex is some what slower curing than single centrifuged latex, but faster than double centrifuged latex. Modulus of low protein latex films were slightly low. In general physical properties of vulcanised low protein latex films are only siightly lower than single centrifuged latex. Ageing properties of the low protein latex films were satisfactory. Viscosity and flow behaviour of low protein latex is much better than double centrifuged latex and almost comparable to single centrifuged latex. On observing that the physical properties and flow behaviour of low protein latex was satisfactory, it was used for the preparation of examination gloves and the gloves were evaluated. It is observed that the properties are conforming to the Indian Standard Specifications. It is thus observed that PPG treatment of natural latex is a simple process of preparing low protein latex. Extractable protein content in these films are very low.The physical properties of the films are comparable to ordinary centrifuged latex and better than conventionally deprotenized latex films. This latex can be used for the production of examination gloves.

Influence of compounding and process variables on quality of condams made from natural rubber latex

Condoms are widely accepted as a contraceptive for family planning and population control. It is also accepted as the most effective barrier against sexually transmitted diseases, especially AIDS, the incurable disease. But presence of pinholes and low film strength of condoms make it unsuitable for the purpose. Quality improvement of condoms by reducing the pinhole formation and increasing the film strength is thus an essential requirement for population control as well as for preventing the spread of sexually transmitted diseases. Strict implementation of WHO specification of condoms further increases the rejection percentage. This causes higher rejection loss to condom manufacturers because the defects could be identified only at the final stage of processing. If the influence of various factors which cause these defects is known, manufacturers can take remedial measures to reduce the defectives so that rejection loss can be decreased and quality of condoms increased. In the present study, it was proposed to conduct experiments to improve the quality of condoms by reducing the pinhole rejection percentage and increasing the tensile properties, burst volume, and burst pressure. Ageing property improvement also was an important target among other parameters. Until a cure for AIDS is found, a high quality latex condom is the only effective device in the prevention of the spread of HIV, AIDS and STD's. Hence it is all the more necessary to have high quality condoms.

Studies on prevulcanization of rubber latex with special reference to influence of storage and after treatments on properties of films

Systematic investigations on prevulcanization of NR latex with special reference to the influence of storage of latex and after-treatments of films, have been carried out. The other aspects studied include the effect of temperature on sulphur prevulcanization, the extent of crosslinking, tensile properties, stress relaxation characteristics, water absorption and leaching characteristics of prevulcanizcd latex films

Studies on Latex Compounding

The main objective of the present study was to explore ways of making latex products more cost effective and versatile. Polyethylene glycol was identified as a surface active agent in latex compounds which improves the filler-polymer interaction and also distributes the filler more uniformly. The use of such surface active agents can develop filled latex products with improved mechanical properties at a lower cost. In this study dispersions of carbon black and silica were successfully added to NR latex under high speed stirring without destabilizing latex.

Studies On Vulcanization, Rheology And Reinforcement Of Natural Rubber Latex With Special Reference To Accelerator Combinations, Surface Active Agents And Gamma Irradiation

In the present work, studies on vulcanization, rheology and reinforcement of natural rubber latex with special reference to accelerator combinations, surface active agents and gamma irradiation have been undertaken. In vulcanization, the choice of vulcanization system, the extent and mc-zie of vulcanization and network structure of the vulcanizate are important factors contributing to the overall quality of the product. The vulcanization system may be conventional type using elemental sulfur or a system involving sulfur donors. The latter type is used mainly in the manufacture of heat resistant products. For improving the technical properties of the products such as modulus and tensile strength, different accelerator combinations are used. It is known that accelerators have a strong effect on the physical properties of rubber vulcanizates. A perusal of the literature indicates that fundamental studies on the above aspects of latex technology are very limited. Thereforea systematic study on vulcanization, rheology and reinforcement of natural rubber latex with reference to the effect of accelerator combinations, surface active agents and gamma irradiation has been undertaken. The preparation and evaluation of some products like latex thread was also undertaken as a part of the study. The thesis consists of six chapter

Preparation and characterization of micro and nano fiber reinforced natural rubber composites by latex stage processing

Use of short fibers as reinforcing fillers in rubber composites is on an increasing trend. They are popular due to the possibility of obtaining anisotropic properties, ease of processing and economy. In the preparation of these composites short fibers are incorporated on two roll mixing mills or in internal mixers. This is a high energy intensive time consuming process. This calls for developing less energy intensive and less time consuming processes for incorporation and distribution of short fibers in the rubber matrix. One method for this is to incorporate fibers in the latex stage. The present study is primarily to optimize the preparation of short fiber- natural rubber composite by latex stage compounding and to evaluate the resulting composites in terms of mechanical, dynamic mechanical and thermal properties. A synthetic fiber (Nylon) and a natural fiber (Coir) are used to evaluate the advantages of the processing through latex stage. To extract the full reinforcing potential of the coir fibers the macro fibers are converted to micro fibers through chemical and mechanical means. The thesis is presented in 7 chapters

Microbial Treatment Of Rubber Latex Centrifugation Effluent

Many of the existing methods for the treatment of rubber latex centrifugation eflluent are not only unsatisfactory in their efliciency to effect near perfect treatment in bringing down the COD to optimum level, but also time consuming and need a large landspace. As the rate of effluent generation is extremely high (20 litres for kilogram of rubber) there is a need for development of efficient system,capable of rapid reduction of COD and BOD. Though the organic load of the rubber efiluent is very high, it does not contain much processed chemicals and therefore it can be considered as a ‘biological eflluent’. Further, the ratio of the Chemical Oxygen Demand to Biological Oxygen Demand (COD/BOD) of this effluent remain almost as a constant value. According to Montgomery (1967), estimation of BOD is not ideally suited for studies on process design, treatability, control of treatment plants, setting standards for treated effluents and assessing the effect of polluting discharges on the oxygen resources of receiving waters. Hence in the present study COD was measured to determine the impact of treatment system on the effluent. In the present study, attempts were made to evaluate the efficiencies of certain methods such as packed bed reactor using immobilized microbial cells, rotating biological contactor (RBC) and activated sludge process, for rapid and efficient treatment of natural rubber latex centrifugation effluent. In addition, studies were also carn'ed out to develop a suitable bioprocess for the coagulation of skim latex, as an alternative to the presently used acid coagulation process towards reducing the pollution load, besides recovering quality rubber

Biological coagulation of skim latex using Acinetobacter sp. isolated from natural rubber latex centrifugation effluent

An Acinetobacter sp, isolated from latex centrifugation effluent, effectively coagulated skim rubber from skim latex. After coagulation for 48 h without the addition of any nutrients, at an optimum dilution of 1:10(v/v) and with an inoculum concentration of 6.4 mg dry cell /ml, the yield of the skim rubber was 8 % (w/v) and the COD of the residual solution was only 0.4 g/l. chemical coagulation at the same dilution resulted in 7 % (w/v) yield of dry rubber content and 2.2 g COD /l.

A Novel Acinetobacter Sp. For 'Treating Highly Acidic Rubber Latex Cen'trifugation Effluent

A novel Acinetobacter sp. BTJR-IO isolated from highly acidic (pH 2.5-4.5) rubber latex centrifugation effluent with high COD (22000 rng/L) and BOD (5000 rng/L). This strain could effect 39.5% COD reduction on free cell inoculation of effluent without incorporation of additional nutrients after 8 days. CalciLnn alginate irrmobilized cells showed 16.4% and 25% COD reduction after 6 hra, without aeration and after 1 hr. with mild aeration under batch process respectively. Whereas 44.0% COD reduction could be achieved after 6 hrs. on continuous treatment in a packed bed reactor with mild aeration. Further, even after 3 cycles 37% COD reduction was recorded with continuous treatment

Marine bacterial prodigiosin as dye for rubber latex, polymethyl methacrylate sheets and paper

Prodigiosin is known for its immunomodulatory, antibacterial, antimycotic, antimalarial, algicidal and anticancer activities. Here, we reported the evaluation of prodigiosin pigment as a dyeing agent in rubber latex, paper and polymethyl methacrylate (PMMA) so that it can be considered as an alternative to synthetic pigments. Maximum color shade was obtained in rubber sheet prepared with 0.5 parts per hundred gram of rubber (phr) pigment and PMMA sheet incorporated with 0.08 μg pigment. Results indicate scope for utilization of prodigiosin as dye for PMMA and rubber and also prodigiosin dyed paper as a pH indicator. Further, being a natural and water insoluble pigment, it is ecofriendly