Microwave Absorbing Material Using Rubber & Carbon

Development of a new type of microwave absorbing material using rubber latex and carbon. for application in the interior lining of anechoic chambers, has been reported. Absorption coefficients of different combinations were estimated at X and S bands and the results were presented graphically. A combination of 50% rubber latex, 40% carbon and 10% graphite is found to form an ideal microwave absorbing material in the X and s bands

Environmental Impacts of Chromated Copper Arsenate (CCA) Treated Rubber Wood for Aquatic Applications

Faculty of Marine Sciences, Cochin University of Science and Technology

Dynamic mechanical analysis of binary and ternary polymer blends based on nylon copolymer/EPDM rubber and EPM grafted maleic anhydride compatibilizer

The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of nylon copolymer (PA6,66) with ethylene propylene diene (EPDM) rubber was investigated with special reference to the effect of blend ratio and compatibilisation over a temperature range –100°C to 150°C at different frequencies. The effect of change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass transition temperature (Tg) of individual components indicating incompatibility of the blend systems. The morphology of the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data with theoretical models.

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.

Chromated Copper Arsenate (CCA) Treatment for Rubber Wood Preservation and its Impact on the Aquatic Biota

Faculty of Marine Sciences, Cochin University of Science and Technology

Synthesis and Characterisation of Thermoplastic Ionomers based on Natural Rubber

Chemically modified novel thermo-reversible zinc sulphonated ionomers based on natural rubber (NR), radiation induced styrene grafted natural rubber (RI-SGNR), and chemically induced styrene grafted natural rubber (CI-SGNR) were synthesized using acetyl sulphate/zinc acetate reagent system. Evidence for the attachment of sulphonate groups has been furnished by FTIR spectra. which was supplanted by FTNMR results. Estimation of the zinc sulphonate group was done using spectroscopic techniques such as XRFS and ICPAES. The TGA results prove improvement in the therrno-oxidative stability of the modified natural rubber. Both DSC and DMTA studies show that the incorporation of the ionic groups affect the thermal transition of the base polymer. Retention of the improved physical properties of the novel ionomers even after three repeated cycles of mastication and molding at 120 degree C may be considered as the evidence for the reprocessabiJity of the ionomer. Effect of both particulate (carbon black. silica & zinc stearate) and fibrous fillers (nylon & glass) on the properties of the radiation induced styrene grafted natural rubber ionomer has been evaluated. Incorporation of HAF carbon black results in maximum improvement in physical properties. Silica reinforces the backbone chain and weakens the ionic associations. Zinc stearate plays the dual role of reinforcement and ptasticization. The nylon and glass filled lonorner compounds show good improvement in the physical properties in comparison with the neat ionomer. Dispersion and adhesion of the fillers in the ionomer matrix has been amply supported by their SEM micrographs. Microwave probing of the electrical behavior of the 26.5 ZnSRISGNR ionomer reveals that the maximum relative complex conductivity and the complex permittivity appear at the frequency of 2.6 GHz. The complex conductivity of the base polymer increases from 1.8x 10.12 S/cm to 3.3xlO·4 S/cm. Influence of fillers on the dielectric constant and conductivity of the new ionic thermoplastic elastomer has been studied. The ionomer I nylon compound shows the highest microwave conductivity. Use of the 26.5 ZnS-RISGNR ionomer as a compatibilizer for obtaining the technologically compatible blends from the immiscible SBR/NBR system has been verified. The heat fugitive ionic cross-linked natural rubber may be, therefore, useful as an alternative to vulcanized rubber and thermoplastic elastomer

Studies on short nylon fiber - reclaimed rubber/elastomer composites

The thesis deals with the development of short nylon fiber-reclaimed rubber/elastomer composites. Three rubbers viz, natural rubber, acrylonitrile butadiene rubber and styrene butadiene rubber were selected and were partially replaced with reclaimed rubber. The blend ratio was optimized with respect to cure characteristics and mechanical properties. Reclaimed rubber replaced 40 parts of NR and SBR and 20 parts of NBR without much affecting the properties. These blends were then reinforced with short nylon fibers. The mechanical properties of the composites were studied in detail. In all the cases the tensile strength, tear strength and the abrasion resistance increased with increase in fiber content. In the case of NRlreclaimed rubber blends, the tensile strength-fiberloading relationship was non-linear where as in the case of NBRlreclaimed rubber blends and SBRlreclaimed rubber blends the tensile strength-fiber loading relationship was linear. All the composites showed anisotropy in mechanical properties. The effect of bonding system on the composite properties was also studied with respect to cure characteristics and mechanical properties. For this, a 20 phr fiber loaded reclaimed rubber/elastomer composites were selected and the effect of MDI/PEG resin system was studied. The resin used was 5 phr and the resin ratios used were 0.67: I, 1:1, 1.5:1 and 2:1. The bonding system improved the tensile strength, tear strength and abrasion resistance. The best results are with SBRlreclaimed rubber-short nylon fiber composites. The optimized resin ratio was 1:1 MDI/PEG for all the composites.

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.

Studies on New Binary Accelerator Systems in Rubber Vulcanisation

Department of Polymer Science and Rubber Technology, Cochin University of Science and Technology

Studies on adhesives for bonding rubber to rubber and rubber to textiles

The primary objective of this investigation has been to develop more efficient and low cost adhesives for bonding various elastomer combinations particularly NR to NR, NR/PB to NR/PB, CR to CR,NR to CR and NR to NBR.A significant achievement of the investigation was the development of solventless and environment friendly solid adhesives for NR to NR and NR/PB to NR/PB particularly for precured retreading. Conventionally used adhesives in this area are mostly NR based adhesive strips in the presence of a dough. The study has shown that an ultra accelerator could be added to the dough just before applying it on the tire which can significantly bring down the retreading time resulting in prolonged tire service and lower energy consumption. Further latex reclaim has been used for the preparation of the solid strip which can reduce the cost considerably.Another significant finding was that by making proper selection of the RF resin, the efficiency and shelflife of the RFL adhesive used for nylon and rayon tire cord dipping can be improved. In the conventionally used RFL adhesive, the resin once prepared has to be added to the latex within 30 minutes and the RFL has to be used after 4 hours maturation time maximum shelf life of the RFL dip solution being 72 hours. In this study a formaldehyde deficient resin was used and hence more flexibility was available for mixing with latex and maturing. It also has a much longer shelf life. In the method suggested in this study, formaldehyde donors were added only in the rubber compound to make up the formaldehyde deficiency in the RFL. The results of this investigation show that the pull through load by employing this method and the conventional method are comparable. This study has also shown that the amount of RF resin with RFL adhesive can be partially replaced by other modifying agents for cost reduction.Cashew nut shell liquid (CNSL) resin can be employed for improving the bonding of dipped nylon and rayon cord with NR.Since CNSL resin cannot be added in the dip solution since it is not soluble in water, it was added in the rubber compound. The amount of wood rosin in the rubber compound can be reduced by using CNSL resin.Another interesting result of the investigation was the use of CR based adhesive modified with chlorinated natural rubber for CR to CR bonding. Addition of chlorinated natural rubber was found to improve sea water resistance of CR based adhesive. In the bonding of a polar rubber like nitrile rubber or polychloroprene rubber to a non polar rubber like natural rubber, an adhesive based on polychloroprene rubber was found to be effective.

Investigations on The Finite Size Effects of Some Inverse Spinels and Studies on Their Composites Based on Nitrile Rubber

Magnetism and magnetic materials have been an ever-attractive subject area for engineers and scientists alike because of its versatility in finding applications in useful devices. They find applications in a host of devices ranging from rudimentary devices like loud speakers to sophisticated gadgets like waveguides and Magnetic Random Access Memories (MRAM).The one and only material in the realm of magnetism that has been at the centre stage of applications is ferrites and in that spinel ferrites received the lions share as far as practical applications are concerned.It has been the endeavour of scientists and engineers to remove obsolescence and improve upon the existing so as to save energy and integrate in to various other systems. This has been the hallmark of material scientists and this has led to new materials and new technologies.In the field of ferrites too there has been considerable interest to devise new materials based on iron oxides and other compounds. This means synthesising ultra fine particles and tuning its properties to device new materials. There are various preparation techniques ranging from top- down to bottom-up approaches. This includes synthesising at molecular level, self assembling,gas based condensation. Iow temperature eo-precipitation, solgel process and high energy ball milling. Among these methods sol-gel process allows good control of the properties of ceramic materials. The advantage of this method includes processing at low temperature. mixing at the molecular level and fabrication of novel materials for various devices.Composites are materials. which combine the good qualities of one or more components. They can be prepared in situ or by mechanical means by the incorporation of fine particles in appropriate matrixes. The size of the magnetic powders as well as the nature of matrix affect the processability and other physical properties of the final product. These plastic/rubber magnets can in turn be useful for various applications in different devices. In applications involving ferrites at high frequencies, it is essential that the material possesses an appropriate dielectric permittivity and suitable magnetic permeability. This can be achieved by synthesizing rubber ferrite composites (RFC's). RFCs are very useful materials for microwave absorptions. Hence the synthesis of ferrites in the nanoregirne.investigations on their size effects on the structural, magnetic, and electrical properties and the incorporation of these ferrites into polymer matrixes assume significance.In the present study, nano particles of NiFe204, Li(!5Fe2S04 and Col-e-O, are prepared by sol gel method. By appropriate heat treatments, particles of different grain sizes are obtained. The structural, magnetic and electrical measurements are evaluated as a function of grain size and temperature. NiFel04 prepared in the ultrafine regime are then incorporated in nitrile rubber matrix. The incorporation was carried out according to a specific recipe and for various loadings of magnetic fillers. The cure characteristics, magnetic properties, electrical properties and mechanical properties of these elastomer blends are carried out. The electrical permittivity of all the rubber samples in the X - band are also conducted.

Evaluation of Magnetic,Dielectric and Mechanical Properties of Rubber Ferrite Composites

In the present study the preparation and characterisation of rubber ferrite composites (RFC) containing barium ferrite (BaF) and strontium ferrite (SrF) have been dealt with. The incorporation of the hard ferrites into natural and nitrile rubber was carried out according to a specific recipe for various loadings of magnetic fillers. For this, the ferrite materials namely barium ferrite and strontium ferrite having the general formula MO6Fe2O3 have been prepared by the conventional ceramic techniques. After characterisation they were incorporated into the natural and nitrile rubber matrix by mechanical method. Carbon black was also incorporated at different loading into the rubber ferrite composites to study its effect on various properties. The cure characteristics, mechanical, dielectric and magnetic properties of these composites were evaluated. The ac electrical conductivity of both the ceramic ferrites and rubber ferrite composites were also calculated using a simple relation. The investigations revealed that the rubber ferrite composites with the required dielectric and magnetic properties can be obtained by the incorporation of ferrite fillers into the rubber matrix, without compromising much on the processability and mechanical properties.

Investigations on Dezincification of Brass and Epoxy Coated Brass

Brasses are widely used as constructional materials in marine environment due to their anticorrosive,antifouling and mechanical properties.However, its resistance to corrosion and fouling may vary according to local marine environmental condition and the seasons.The dezincification of brass is one of the forms of selective corrosion which has attracted the attention of researchers for the last two decades.Many of the dezincification mechanistic studies have been performed in noncomplex media and hence their conclusions cannot be extended to esturine water,which is of great significance since brass is extensively used in marine environment.Inhibited α brasses are largely immune to dezincication and the effect of tin and arsenic addition to α/beta brasses is not so reliable in controlling the dezincification. There have been many cases of dezincification in duplex brasses in both freshwater and seawater.Though there is some protection methods such as inhibitors,electro deposition and electro polymerization,there is no reliable method of inhibiting the dezincification of two-phase brass.Organic coatings are effectively used for the protection metals due to their capacity to act a physical barrieer between the metal surface and corrosive environment.Hence,pure epoxy coating is selected for this as it has antocorrosiion effect on brass.The dezincification behaviour of brass of the present study has been highlighted in terms of corrosion rate,weight gain/loss,corrosion current and polarization resistence,open circuit potential,dezincification factor. The marine fouling as biomass on brass was assessed and presented in this thesis, The physicochemical properties of estuarine water were correlated with corrosion behaviour of brass.The deterioration of the brass subjected to the effect of estuarine water was also investigated as a measure of loss in mechanical properties such as tensile strength,yield strength,percntage elongation and percentage reduction in area.To validate dezincification data,visual observation,spot analysis,surface morphology before and after removal of corrosion products and corrosion product analysis were performed.The dezincification behavior of epoxy coated brass of the present study has beenhighlighted in terms of corrosion rate ,weight gain/loss,corrosion current and polarization resistance,open circuit potential.dezincification factor.The marine fouling as biomass on epoxy coated brass subjeted to the effect of estuarine water was also investigated as ameasure of loss in mechanical properties such as tensile strength,percentage elongation and percentage reduction in area.The results of dezincification behavior of brass and epoxy coated brass in Cochin estuary water has been presented and discussed.Attempt has been made to correlate the dezincification behavior of brass with epoxy coated brass.