Sanjay K. Bhattacharyya, Sudip Jana, Giriraj Sharma, Rabindra Mukhopadhyay and Abhijit Bandyopadhyay 1 *

Transcription

1 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Sanjay K. Bhattacharyya, Sudip Jana, Giriraj Sharma, Rabindra Mukhopadhyay and Abhijit Bandyopadhyay 1 * Hari Shankar Singhania Elastomer and Tyre Research Institute (HASETRI), Jaykaygram, Dist. Rajsamand, Pin , Rajasthan, India 1 Department of Polymer Science and Technology, University of Calcutta, 92, A.P.C. Road, Calcutta , India Received: 14 March 2013, Accepted: 17 May 2013 Summary The latex of Euphorbia caducifolia Haines is a green renewable source of material which acts as the origin of Ash. Ash generated from toluene insoluble fraction of the coagulum at 750 C found to contain nearly 73% magnesium oxide (MgO). It was observed that the ash can act as a cure retarder in a model chlorobutyl rubber (CIIR) based truck inner tube compound and its action was comparable with the commercial MgO, though not exactly equivalent. Optimum cureretardation with ash was observed at 0.3 phr loading. Surprisingly, the ash also produced some cure activation effect due to presence of zinc oxide. Rate of cure in gum/ filled compositions at 0.3 phr loading of ash was found 125/48 min -1 against 106.4/29.6 min -1 of commercial MgO. Introduction Butyl rubber was discovered in 1937 and its commercialization started in 1940s [1-2]. It is a copolymer of isobutylene (98-99%) and a small amount of isoprene (1-2%) [1-3]. The principal characteristics feature to explore butyl *Corresponding Author: Tel: /6387/8386, Extn: abpoly@caluniv.ac.in Smithers Rapra Technology, 2013 Polymers from Renewable Resources, Vol. 4, No. 4,

2 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay rubber in tyre inner-tube application lies in its excellent air impermeability/ retention and good heat and ozone resistance properties. The chlorination of butyl rubber by Exxon researchers in 1950 s led to the development of CIIR with much higher curing rates enabling co-curing with general purpose rubbers [4-5]. Zinc oxide (ZnO) alone can vulcanize CIIR producing carbon-carbon bond involving an alkylation chemistry which increases thermal stability of the compound [5-7]. But a combination of curatives consisting of ZnO plus TMTD (tetramethylthiuram disulphide) plus MBTS (Mercaptobenzothiazole disulfide) is typical for a CIIR compound to be used in heavy-duty truck inner-tube application [8]. This curative package markedly improves state of cure, fatigue resistance, tensile strength and tear strength of the compound [8]. TMTD acts as a sulphur donor improving speed of reaction and degree of crosslinking [9-10]. MBTS plays dual roll during vulcanization. First it functions as a retarder and then as an accelerator. MBTS as an accelerator reacts with ZnO to form a sulfurating agent. This reactive intermediate then forms crosslinks with rubber [10]. It is well documented that CIIR contains nearly 2 mole% (on a monomer basis) chlorinated isoprenoid units having primarily the following structure [11-12] (Scheme 1). Scheme 1. Microstructure of CIIR Some of the combined chlorine, present in allylic form, are hyperactive [13-14]. Such a contention has been further supported by Hous [15]. The presence of reactive fraction of chlorine causes rapid vulcanization of CIIR compound and make it scorch-prone. Addition of a Lewis base such as MgO (Magnesium oxide) enhances scorch safety of a CIIR compound enabling safe processing [16-17]. Scheme 2 demonstrates the vulcanization of CIIR in presence of ZnO and MgO [7, 18]. Characterization of latex from Euphorbia caducifolia Haines and ash generated from toluene insoluble mass of its coagulum has been done and communicated. The key physicals of the latex and concentration of different metals present in the ash are reported in Table 1 for ready reference. Looking at very high concentration of magnesium metal present in ash we were tempted to explore 170 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

3 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Scheme 2. Vulcanization of CIIR in presence of MgO and ZnO its potential as a cure retarder and compared its action against commercial MgO in a truck inner-tube compound. MgO occurs naturally in the mineral form as Magnesite and Dolomite. There is report elucidating magnesium hydroxide (natural source, brucite) in place of MgO in halobutyls to achieve greater scorch safety, shelf life, and improved cure rates [19] but no report is available substituting commercial MgO with a source derived from plants and projecting its multifunctional behaviour. Moreover, magnesium oxide and magnesium hydroxide, derived from their naturally occurring deposits, require a controlled degree of purity, reactivity, and particle size for application in rubber compounds which can only be attained through synthetic route. The concept of multifunctional additive (MFA) in rubber compound is very important as it reduces number and complexity of compounding ingredients [20]. Previously many researchers have reported to use MFA in rubber compounds. For example, Guhathakurta has reported Bahera gum, extracted from the bark of Terminalic bellerica, to act as a MFA [21]. Bahera gum found to show accelerator-activator properties and was exploited as a replacement of stearic acid in natural rubber (NR)/brominated isobutyleneco-paramethylstyrene (BIMS) and as antioxidant in NR based compound. Bahera gum also reported to impart good tackiness and plasticization effect. Kuriakose et al. used rice bran oil as a natural MFA in SBR compound [22]. Nandanan and co-workers reported linseed oil to act as a MFA in NBR compounds [23]. A reduction in cure time along with improvement in Polymers from Renewable Resources, Vol. 4, No. 4,

4 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay mechanical properties and processibility was illustrated. Anandhan et al. demonstrated use of extract from the leaves of the oil palm species, Elaeis guineensis, as a MFA in NR [24]. The present article describes ash generated from toluene insoluble mass of coagulum at 750 C as a cure retarder-cumaccelerator in model CIIR compounds. Experimental Raw Materials and Suppliers Chlorobutyl rubber (38 ML 1+8 at 125 C, Chlorine content 1.26 (wt%)) used in model formulation was procured from Exxon Chemical, USA. Other compounding ingredients used were commercial grade zinc oxide (Zinc-O- India, India), stearic acid (Godrej Soap Limited, India), N660 carbon black (Hi-Tech Carbon, India), paraffinic oil (HPCL, Mumbai, India), sulphur (Jain Chemicals Ltd., India), MgO (98% active, Konoshima Chemical Co. Ltd, Japan), MBTS (mercaptobenzothiazole disulfide, NOCIL Ltd., Mumbai, India) and TMTD (tetramethylthiuram disulphide, Merchem Ltd., Cochin, India). Euphorbia caducifolia Haines, Rajsamand, Rajasthan, India was used as source of latex collection. After coagulation of latex, ash was generated from toluene insoluble mass of coagulum at 750 C. Collection of latex was done from species of same region to minimize variation. Chemical Characterization of the Ash Ash was generated from toluene insoluble portion of coagulum following ASTM D 297 in a muffle furnace at 750 C. The ash was dissolved in concentrated hydrochloric acid for metal content analysis in ICP (Inductively Coupled Plasma Optical Emission Spectrometer). The instrument used was icap 6300 from Thermo Scientific, UK. Surface area of the ash and conventional MgO was determined following ASTM The instrument used was Micromeritics, USA having model number Gemini Compound Mixing Mixing of the rubber compounds was carried out in a Brabender Plasticorder, PL 2000 of 80 cc capacity (Brabender OHG, Duisburg, Germany). 172 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

5 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II CIIR Gum Compound Mixing CIIR Gum compound mixing was done at a constant rotor speed of 40 rpm after setting the temperature control unit (TCU) at 90 C. First, raw rubber, stearic acid, magnesium oxide (wherever applicable), and ash (wherever applicable) were added and mixed for 4 min. Then zinc oxide and (MBTS and TMTD) were charged and mixed for another 3 min. After a total 7 min of mixing, the batches were discharged. The dump temperature of the batches was found to be in the range of 90 to 95 C. The batches were sheeted out using a laboratory two-roll mill. CIIR Filled Compound Mixing Master batch mixing was done at a constant rotor speed of 40 rpm with TCU set at 95 C. First, raw rubber was masticated for 10vs and then carbon black, oil, stearic acid, magnesium oxide (wherever applicable), and ash (wherever applicable) were added and mixed for 3.3 min. A ram sweeping was given at this point. After a total mixing time of 6 min, the batches were discharged. The dump temperatures of the batches were found to be within C. After a maturation time of 8 hours for the master batches, the final batches were mixed at a constant rotor speed of 30 rpm keeping the TCU at 90 C. Zinc oxide, MBTS and TMTD were mixed at that condition. A ram sweeping was done after 1.3 min of mixing. The batches were dumped after a total 3 min of mixing. The dump temperature of the batches was found to be within 95 to 100 C. Characterization of Mixes Cure Characteristics The cure characteristics of the rubber compounds were determined using a Rubber Process Analyzer (model, RPA 2000 from Alpha Technologies, USA). Curing was done at 166 C for 25 minutes using 0.5 arc following ASTM D The optimum cure time of the compounds (tc 90 ) obtained from the rheograph corresponding to an optimum torque (M 90 ) is given by Equation (1): M 90 = 0.9 (M H -M L ) +M L (1) where M H and M L represents the maximum and minimum torques, respectively. For gum compounds, the cure rate index (CRI) in those experiments were determined by using Equation (2): Polymers from Renewable Resources, Vol. 4, No. 4,

6 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay CRI = [100/ (tc 90 -ts 1 )] min -1 (2) where ts 1 corresponds to the time to 1 unit rise in the torque above M L. For filled system, CRI was calculated as: CRI = [100/ (tc 90 -ts 2 )] min -1 (3) where ts 2 represents the time to increase 2 units torque from M L. Physical Properties The green rubber compounds were cured as per ASTM D3182 in an electrically heated hydraulic curing press from Hind Hydraulics, New Delhi, India using the compression molding technique at a 15 MPa molding pressure. Tensile slabs for the CIIR based compounds were molded at 166 C. Time for curing given was twice of the optimum curing time. The tensile properties were determined using dumb bell-shaped specimens punched from the vulcanized sheets according to ASTM D 412 using a Zwick UTM 1445 machine from Germany. Ageing of the compound was done at 120 C for 3 days according to ASTM D 573 in a Multicell Ageing Oven from Tempo Industries, New Delhi, India. After ageing, the samples were conditioned for 24 h at ambient temperature and tested for tensile properties. Retention of properties after ageing were calculated using the following equation (Equation (4)): (Aged property/unaged property) 100 (4) Measurement of Swelling Index Relative crosslink density was designated from swelling index studies. It was measured in cyclohexane in accordance with ASTM D3616 using the following equation: (Equation (5)) Swelling Index = Swollen weight/initial weight (5) Tension Set Measurement for CIIR Based Filled Samples Tension set measurement was carried out following ASTM D 412 at 105 C. 50% strain was used in the experiment. Tension set was calculated as: 174 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

7 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II (L f -L 0 )/(L 0 ) 100% (6) L f and L 0 represents final and initial length of the samples respectively. Results and Discussion Table 1 shows concentration of different metals present in the ash. During estimation of metal content from ash generated at 550 C, it was observed to be completely soluble in HCl with lot of effervescence indicating presence of metal carbonates/ bicarbonates in it and as expected, not found to exert any retarding influence when used in the compounds. To eliminate presence of any metal carbonates/bicarbonates, the ash was generated from toluene insoluble fraction at 750 C. Ash thus generated, found to be completely soluble in HCl without any effervescence indicating complete conversion of all metal carbonates/ bicarbonates to corresponding oxides. Table 2 shows concentration of different metals present in ash at 750 C. It clearly shows a dramatic improvement in metal concentration over the ash produced at 550 C; concentration of magnesium metal increases to nearly 44% from its initial 2%. This is due to complete decomposition of different magnesium carbonates/bicarbonates or some other inorganic metal salts, if any, at 750 C. Table 1. Key fetchers of Latex from Euphorbia caducifolia Haines and concentration of different metals in Ash derived from toluene insoluble mass of its coagulum Appearance of latex Milky white Total solid content (%) of latex 27 p H of latex Solubility of coagulum 70% soluble in toluene, rest 30% insoluble in toluene and other common organic solvent. Elemental analysis Checked for nitrogen and sulphur. Both are absent in toluene soluble and insoluble mass. Characterization of ash generated at 550 C Ash in coagulum (%) 5.4 Ash in toluene soluble portion (%) 0.6 Ash in toluene insoluble portion (%) 4.8 (from both material balance and experiments) Metal contents in the Ash (ppm) Zn Ca Mg Cu Mn Fe Al nil nil Solubility of Ash Completely soluble in HCl with effervescence. Polymers from Renewable Resources, Vol. 4, No. 4,

8 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay Table 2. Concentration of different metals present in ash generated at 750 C from toluene insoluble fraction of coagulum Metal content in Ash Zn Ca Mg Cu Mn Fe % of metal Nil Nil Excluding presence of any sulphur and nitrogen bearing magnesium salts in ash (Table 1), 43.86% magnesium metal may be considered to originate from its oxide only which is equivalent to ~73% MgO. Average surface area of the ash was found to be 2.8 m 2/ gm against 54 m 2/ gm for commercial MgO. It was also found to be free from any grit when sieved. The basic formulations used for the gum system are shown in Table 3. For gum compounds, retardation effect has been analyzed in terms of the induction time, ts 1. It is evident that ts 1 increases over control (G CIIR 0 ) on addition of ash displaying its cure-retardation characteristics. The increase in ts 1 is gradual up to a loading of 0.3 phr beyond which, it declines. Optimum cure time (tc 90 ) also follow the same trend. A comparative study was conducted using commercial MgO at this dose. The rheometric characteristics for ash, MgO, and control compositions at 0.3 phr loading are presented in Figure 1. The impact of ash on CRI is conspicuous. The rate of cure drops to 106 min -1 (G CIIR_MgO 0.30 ) from 125 min -1 (G CIIR_Ash 0.30 ) on substitution of ash by MgO with a very little sacrifice in induction time. Ash is not a pure compound but Figure 1. Rheometric characteristics of CIIR gum compounds at 166 C with 0.3 phr loading of MgO and ash along with control 176 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

9 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Table 3. Formulations of CIIR-Ash-MgO gum compounds and their impact on rheometric and swelling index properties Ingredients (phr*) G CIIR 0 G CIIR_Ash 0.1 G CIIR_Ash 0.2 G CIIR_Ash 0.3 G CIIR_Ash 0.5 G CIIR_MgO 0.3 CIIR Magnesium oxide ** Ash *** Stearic acid Zinc Oxide TMTD MBTS Cure characteristics ML (dn.m) MH (dn.m) t s1 (min) t c90 (min) CRI (min -1 ) Swelling index * Parts per hundred unit of rubber. ** 98% active. *** 73% MgO Polymers from Renewable Resources, Vol. 4, No. 4,

10 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay composed of several metal oxides. It shows presence of zinc oxide also at a low concentration. This complex combination of metal oxides may impart higher cure acceleration to CIIR-ash system. Excited from these observations, we next verified cure retardation-cumacceleration effect of the ash in a filled system at 0.3 phr loading. The formulation chosen is a typical heavy duty truck inner- tube compound (Table 4). The rheometric characteristics of the compounds are shown in Figure 2. Consistent with observation in the gum system, the retarding influence of MgO and ash is very eminent in the filled compositions. However, the difference in scorch safety between F CIIR 0 and F CIIR_MgO 0.3 was found much higher than those in the gum system. Ziarnik [17] also observed similar difference in retarding influence of MgO between a gum and a filled CIIR system and proposed an alteration of kinetics of crosslinking mechanism in presence of carbon black. With ash, alike gum system, the cure parameters exhibit cure-acceleration in the filled system as well. F CIIR_Ash 0.3 possesses a cure rate (48.0 min -1 ) much higher than F CIIR_MgO 0.3 (29.6 min -1 ). Figures 3 and 4 compare unaged physical properties of the compounds at 0.3 phr loading of ash and MgO along with control in gum and filled systems. It is clearly seen that the vulcanizates devoid of cure-retarder (G CIIR 0 and F CIIR 0 ) divulges moduli and tensile strength slightly higher than MgO and ash. A similar dependence is reported by Zapp [16] at 0.25 phr loading of MgO and increasing the dose further up to 0.5 phr. Higher MgO caused a sharp drop in tensile properties of filled CIIR MgO system. Ziarnik [17] observed Figure 2. Rheometric characteristics of filled CIIR system at 166 C 178 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

11 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Figure 3. Impact of MgO and ash on unaged physical properties of gum CIIR compounds Figure 4. Influence of MgO and Ash on unaged tensile properties of filled CIIR compositions a sharp rise in scorch safety using 1 phr MgO at the expense of tensile properties and explained it in terms of retardation exerted by MgO towards development of polymer-pigment interaction. We also had observed similar effect and demonstrated that by studying swelling index of the compounds. It Polymers from Renewable Resources, Vol. 4, No. 4,

12 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay Table 4. Formulations of CIIR-Ash-MgO filled compounds and their impact on rheometric properties and swelling index Ingredients (phr) F CIIR 0 F CIIR_MgO 0.3 F CIIR_Ash 0.3 CIIR Stearic acid N Paraffinic oil Magnesium oxide Ash Zinc oxide TMTD MBTS Cure characteristics ML (dn.m) MH (dn.m) t s2 (min) t c90 (min) Cure rate (min- 1 ) Swelling index was slightly lower for G CIIR 0 and F CIIR 0 than the corresponding compounds with retarder (Tables 3 and 4). The overall unaged tensile properties of the vulcanizates with MgO and Ash found comparable. G CIIR_Ash 0.3 shows higher 300% modulus but tensile strength found slightly lower than MgO. This is because of higher ultimate elongation at break in G CIIR_ MgO 0.3. In filled composition, Ash exhibits slightly higher elongation at break than MgO; tensile strength found comparable with a slight reduction in 300% modulus. The raw data generated from the tensile machine during testing of physical properties has been uploaded as Supporting Information, furnishing detail about the experimental data scattering. Figure 5 depicts retention of physical properties for filled compounds at 0.3 phr loading of Ash and MgO along with control. It shows an overall increase in modulus and tensile strength of the compounds upon ageing. It is well known that heat treatment increases polymer-pigment interaction for butyls improving stress-strain behaviour [16]. Of further interest is the observation that the increase in 300% modulus is steep for the compositions containing retarders than control. Ziarnik demonstrated that heat treatment of CIIR- HAF black-mgo master batches reduces retarding influence of MgO on polymerpigment interaction improving stress-strain properties of the vulcanizates [17]. 180 Polymers from Renewable Resources, Vol. 4, No. 4, 2013

13 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II Ageing of F Ash and MgO 0.3 was conducted at 120 C for 3 days. The sharp rise in modulus, as indicated by data, may be attributed towards diminishing influence of retarders during ageing which helped to develop a more elastic network through better polymer-filler interaction. Tension set is an inverse measure of elastic recovery of the rubber vulcanizates [25] and is an important property for a CIIR compound to be used in truck inner-tube application. The parameter measured at high temperature for the butyl compounds generally acts as a good predictor for growth of inner-tubes which are subjected to tensile stress either continuously or intermittently during application. Tension set measured at 105 C for compounds F CIIR 0 and F Ash_0.3 found comparable and it s slightly better than F MgO_0.3 (Table 5). This indicates absence of any adverse influence of Ash on stability of crosslinks even when exposed to a severe environment as that of tension set measurement. This is significant from the application standpoint of Ash in CIIR compounds for heavy duty truck inner-tubes. Figure 5. Retention of physical properties for filled CIIR compounds after ageing at 120 C for 3 days Table 5. Influence of ash and MgO on tension set properties of CIIR based filled compounds Compound F CIIR 0 F CIIR_MgO 0.3 F_ CIIR Ash 0.30 Tension set (%) Polymers from Renewable Resources, Vol. 4, No. 4,

14 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay Conclusions A new class of MFA of natural origin was been found. The latex exuding shrub, Euphorbia Caducifolia Haines (local name Thor), grows abundantly in the deserted area of Rajasthan, India acts as the green source of this MFA. The conclusions drawn from the study are summarized as follows: ash generated from the toluene insoluble fraction of coagulum can act as cure retarder in CIIR based gum and filled compounds and the action is comparable with commercial MgO, though not exactly equivalent. Usage of ash shows cure-acceleration; rate of cure observed much higher than commercial MgO. Unaged and retention of physical properties of the vulcanizates with Ash was comparable with MgO and thus recommended for scaled up trials for commercialization. Acknowledgements The authors would like to thank HASETRI and JK Tyre management for their kind permission to publish this work. References 1. Edwards D.C., Progress in butyl/halobutyl vulcanization chemistry, Bayer Inc. internal report, Wilson G.Y., Polysar s World of Technology: butyl and halobutyl elastomers, Bayer Inc. internal report, Chu C.Y. and Vukov, R. Determination of butyl rubber by NMR spectroscopy. Macromolecules, 18 (1985) Baldwin F.P., Modifications of low functionality elastomers. Rubber Chem. Technol., 52 (1979) Baldwin F.P., et al. Process of chlorinating butyl rubber and vulcanizing the chlorinated product, US Patent , Dec. 13, Vukov R., Zinc oxide crosslinking chemistry of halobutyl elastomers- a model compound approach. Rubber Chem. Technol., 57 (1984) Kuntz I., Zapp R.L., and Panchrov R.J., The chemistry of the zinc oxide cure of halobutyl. Rubber Chem. Technol., 57 (1984) Model vulcanization systems for butyl rubber and halobutyl rubber, Exxon Mobil Chemical, Ref. B E Eby L.T. and Fusco J.V., A new Chlorine-containing elastomer. J. Chem. Eng. Data, 4 (1959) Polymers from Renewable Resources, Vol. 4, No. 4, 2013

15 Unique Multifunctional Behaviour of Ash From the Latex of Euphorbia Caducifolia Haines in Chlorobutyl Rubber (CIIR) Compound for a Truck Inner-Tube Application - Part II 10. Batman L., Moore C.G., Porter M., and Saville B., Chemistry and physics of rubber like substances; Maclaren Press: London, Zapp R.L. and Oswald A.A., Radiation-induced crosslinking of chlorobutyl and polydiene elastomers. Promotion by polythiols. Rubber Chem. Technol., 48 (1975) Vukov R., Halogenation of butyl rubber- a model compound approach. Rubber Chem. Technol., 57 (1984) Blackley D.C., Synthetic Rubbers: Their Chemistry and Technology; Applied Science Publishers: New York, 1983; p Ivˈan B., Kennedy J.P., Kelen T., and Tüdös F., Determination of labile chlorine content in polychloroprene, chlorobutyl rubber and chlorinated ethylenepropylene copolymer by thermal dehydrochlorination combined with Me 3 Al treatment. Polymer Bulletin, 2 (1980) Pierre House. Stabilized halobutyl rubber, US Patent , 08/01/ Zapp R.L. and Hous P., Rubber Technology, Second Edition, Van Nostrand Reinhold: New York, 1973; p , Ziarnik G.J., Chlorobutyl rubber- optimum processing procedures. Rubber Chem. Technol., 35 (1962) Coran A.Y., The Science and Technology of Rubber, Third Edition, Academic press: New York, 2005; p Hastbacka M.A., Magnesium hydroxide: a new and versatile rubber chemical. Rubber World, 1989, Aug Hepburn C., Halim M.H., and Madhi M.S., Multifunctional additives (MFA s) as optimisers in rubber formulation design. Kautschuk Gummi Kunstoffe, 43 (1990) Guhathakurta S., Anandhan S., Singha N.K., Chattopadhyay R.N., and Bhowmick A.K., Waste natural gum as a multifunctional additive in rubber. J. Appl. Polym. Sci., 102 (2006) Kuriakose A.P. and Rajendran G., Use of rice-bran oil in the compounding of styrene butadiene rubber. J. Mater. Sci., 30 (1995) Nandanan V., Joseph R., and Francis D.J., Linseed oil as a multipurpose ingredient in NBR vulcanizate. J. Elast. Plast., 28 (1996) Anandhan S., Viknesh C.J., Othman N., and Sasidharan S.A., new processing additive for natural rubber from agricultural waste. Kautschuk Gummi Kunstaffe, 64 (2011) Coran A.Y. and Patel R., Rubber-thermoplastic compositions. Part IV. Thermoplastic vulcanizates from various rubber-plastic combinations. Rubber Chem. Technol., 54 (1981) 892. Polymers from Renewable Resources, Vol. 4, No. 4,

16 S.K. Bhattacharyya, S. Jana, G. Sharma, R. Mukhopadhyay and A. Bandyopadhyay 184 Polymers from Renewable Resources, Vol. 4, No. 4, 2013