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21Progress in Rubber, Plastics and Recycling Technology, Vol. 23, No. 1, 2007

Research on the Application of Recycled Waste RFL (Resorcinol-Formaldehyde-Latex) Dip Solid in Styrene Butadiene Rubber Based Compounds

*Corresponding author. Tel/fax: +91-2952 232019. E-mail [email protected]

©Rapra Technology, 2007


S. Bandyopadhyay*1, S.L. Agrawal1, P. Sajith1, N. Mandal1, S. Dasgupta1,

R. Mukhopadhyay1, A.S. Deuri2 and Suresh C. Ameta3

1Hari Shankar Singhania Elastomer and Tyre Research Institute (HASETRI), Jaykaygram, Kankroli, P.O. Tyre Factory, Rajsamand, Rajasthan-313 342, India2R&D Centre, J. K. Tyre, Jaykaygram, Kankroli, P.O. Tyre Factory, Rajsamand, Rajasthan-313 342, India3Department of Polymer Science, College of Science, Mohanlal Sukhadia University, Udaipur – 313 001, Rajasthan, India

Received: 11 January 2006 Accepted: 11 April 2006

ABSTRACT

Waste resorcinol-formaldehyde-latex (RFL) dip solid was collected from the

suction chamber of a typical tyre industry dip unit. The physico-chemical

characterization of the material was carried out, along with a fresh RFL dip

solid obtained by drying a fresh dip solution. The effect of the waste material

was studied in a styrene butadiene rubber (SBR) based compound in both gum

and fi lled state. The waste material was treated with boiled water and dilute

hydrochloric acid and the effect of the treated material was further studied in

the SBR based fi lled compound. The fi ller dispersion, polymer-fi ller interaction

and dynamic mechanical properties was also studied.

INTRODUCTION

The rapid rise in living standards has resulted in a fast growth of industrialization, which in turn has increased the demand for various resources, leading towards faster depletion of natural resources and also environmental pollution. Industrial waste disposal is one of the greatest problems, making a priority of either degradation or recycling, i.e. by utilizing the solid waste as a raw material in the same or another industry(1).

PRPRT 1 07.indb 21PRPRT 1 07.indb 21 14/2/07 8:01:42 am14/2/07 8:01:42 am

22 Progress in Rubber, Plastics and Recycling Technology, Vol. 23, No. 1, 2007

S. Bandyopadhyay, S.L. Agrawal, P. Sajith, N. Mandal, S. Dasgupta, R. Mukhopadhyay, A.S. Deuri and Suresh C. Ameta

Nylon, polyester, aramid, rayon, glass and steel are the major fi bers used as reinforcing element for tyres, belts and hoses. All of these fi bers, except steel, which is brass plated, require an adhesive coating for bonding to rubber. The manufacturers either treat these organic tyre cords at their plant or they purchase treated cord from the suppliers. Glass producers treat glass cord, since, in addition to adhesion, the adhesive also protects the fi laments from damage during processing.

In case of a tyre industry dip unit, the dip solution for dipping nylon 6 tyre cords is prepared using stoichiometric ratio of resorcinol and formaldehyde (2:1) prior to the addition of 2-vinyl pyridine-butadiene-styrene (VP) latex. The VP latex is primarily a terpolymer of butadiene (70%), vinyl pyridine (15%) and styrene (15%). The resorcinol formaldehyde resin is prepared under alkaline condition in the fi rst master stage. This resin is then added to VP latex under mild alkaline condition in the second stage (fi nal batch). The resin bonds to the fi bre and the latex primarily bonds (co-vulcanisation) to the rubber compound which is used as skim coating on the fi bre. The factors that affect adhesion are fi ber type, fi ber fi nish (spin fi nish), dip pick up, dip penetration, RF ratio, resin-latex ratio, pH of the dip solution and the rubber compound. The effect of all the above on rubber adhesion and the detail of RFL chemistry has been studied by several authors(2-13). The RFL adhesive system was developed in early 1940’s and is still in use throughout the rubber industry. No other resin has replaced RF resin and no other latex has replaced VP latex as components of dip recipes.

The tyre cord after dipping in the dip solution is heat treated in the drying, heat set and normalizing zones of the dip unit where, time, temperature and tension (3T) are very important parameters. The fabric material just after dipping is passed through a suction chamber, where excess dip material is deposited in the walls of the chamber. This excess material is subsequently dried in the chamber. The suction chamber is periodically cleaned and the excess dip solid material is scraped in a throw away price. The tentative production fi gure of the above material in a typical tyre industry is approximately 5 tons per annum.

Prior to this work the authors have reported the use of various recycled materials in tyre and rubber compounds(14-19). In the present work, the authors have studied the physico-chemical characterization of the waste dip material. The effect of the material was studied in a styrene butadiene rubber (SBR) based gum and fi lled compound. The material was treated with boiled water and dilute hydrochloric acid and the effect of the treated material was further studied in the SBR based fi lled compound. The fi ller dispersion, polymer-fi ller interaction and dynamic mechanical properties were reported.




EXPERIMENTAL

Material Used

The suppliers of all the materials used in this study are given in Table 1.

Table 1. Material and suppliers

Material SupplierStyrene butadiene rubber (SBR1502) BST Elastomers, Bangkok, Thailand

RFL dip solid waste Suction chamber of Tyre Cord Dip unit of JK Tyre, Kankroli, India

High abrasive furnace black (HAF, N330) Cabot India Ltd., Mumbai, India

Rubber seal zinc oxide Zinc – O – India, Ltd., Alwar, Rajasthan, India

Stearic acid Godrej Industries Ltd., Mumbai, India

Rubber makers sulfur (soluble sulfur) Jain Chemicals, Kanpur, India

Accelerator, tertiary butyl benzo thiazyl sulfenamide, TBBS, Pilcure NS

NOCIL, Thane, India

Scorch inhibitor, N-cyclo hexyl thio phthalimide, CTP, (pre-vulcanising inhibitor) PVI 100, ACCITARD RE

ICI, Rishra, India

Chemical Characterization of RFL Dip Material

In the case of chemical characterization, specifi c gravity (ASTM D297), ash content at 550 °C until constant weight (ASTM D297), solvent extractable (distilled water, acetone and toluene), pH (ASTM D1512) and percentage moisture using a Mettler IR Moisture Analyser of the sample was performed. Chemical characterization of dried fresh RFL dipped solution was also conducted.

The thermo gravimetric analysis of the un-extracted waste RFL dipped solid material as well as dried fresh RFL dipped solution was conducted through TGA 7 from Perkin Elmer, USA following ASTM D6370. The samples were heated at 40 °C per min in nitrogen atmosphere up to 600 °C and up to 850 °C in oxygen atmosphere and the weight loss over a specifi c temperature range were measured. The degradation temperature was also measured.

Fourier transform infrared (FTIR) spectroscopic study of the waste as well as dried fresh RFL dipped solid was performed in a 2000 FTIR System from Perkin Elmer, USA to characterize the various chemical groups present in the samples using pyrolysis method.




The glass transition temperature of the sample as well as dried fresh RFL dipped solution was determined using a Differential Scanning Calorimeter, DSC 7 from Perkin Elmer, USA. The samples were scanned from (–)140 ° to 50 °C at 20 °C per min heating rate.

The carbon and nitrogen content present in the waste material as well as dried fresh RFL dipped solution were determined with Elemental Analyser, NCS 2500 from Thermoquest, Italy.

The semi-quantitative ash analysis was done following ASTM D 297. The metal content present in the HCl soluble ash was determined using Atomic Absorption Spectrophotometer, AAS 3300 from Perkin Elmer, USA following ASTM D 4075.

Preparation of Composites

A) Study in Gum Compound (as an Additional Material)

Mixing of the compound was carried out using a four-wing rotor miniature laboratory mixer, Brabender Plasticorder PL 2000 of 80 cc capacity (Brabender OHG, Duisburg, Germany) in one stage and the formulation of the mix is given in Table 2.

Batch mixing was done keeping the temperature control unit (TCU) at 75 °C and rotor speed at 30 rpm. Initially, the rubber, zinc oxide (ZnO), stearic acid, soluble sulfur and RFL dip solid material (wherever applicable) was added and mixed for 2.0 min. The accelerator TBBS was charged and batch dumping was done after 3.0 min of mixing. The dump temperature of the batches was found to be nearly 95 - 105°C. The batches were sheeted off in a laboratory two-roll mill from Santosh Industries, New Delhi, India.

Table 2. Rubber compound formulation (as an additional material)

Ingredients Mix Id.

D1 D2 D3 D4 D5

RFL dip solid 0.00 2.50 5.00 7.50 10.00

Other ingredients used in the above formulation kept constant are: SBR 1502:100.0, zinc oxide – 3.0, stearic acid – 1.0, soluble sulfur – 1.75 and TBBS – 1.00

B) Study in Gum Compound (as Part Replacement of Polymer)

Mixing of compound was carried out in the conditions as mentioned earlier. The formulation of the mix is given in Table 3.




Table 3. Rubber compound formulation (part replacement of polymer)

Ingredients Mix Id.

D1 D6 D7 D8 D9

SBR 1502 100.0 97.5 95.0 92.5 90.0

RFL dip solid 0.00 2.50 5.00 7.50 10.00

Other ingredients used in the above formulation kept constant are: zinc oxide – 3.0, stearic acid – 1.0, soluble sulfur – 1.75 and TBBS – 1.00

C) Effect of Dipped Solid Material in Filled Compound

Mixing of compound was carried out using the same mixing equipment as mentioned earlier. In this case, the fi ller was added initially along with rubber, zinc oxide (ZnO), stearic acid, soluble sulfur and RFL dip solid material (wherever applicable) and mixed for 3.0 min. The accelerator TBBS was charged and batch dumping was done after 4.0 min of mixing. The dump temperature of the batches was found to be nearly 110 – 120 °C. The batches were sheeted off in a laboratory two-roll mill.

The formulation of the mix is given in Table 4.

Table 4. Rubber compound formulation (in fi lled compound)

Ingredients Mix Id.

D10 D11 D12

RFL Dip Solid 0.00 5.00 10.00

Other ingredients used in the above formulation kept constant are: SBR 1502: 100.0, HAF, N330: 50.0, zinc oxide – 3.0, stearic acid – 1.0, soluble sulfur – 1.75 and TBBS – 1.00

D) Effect of Treatment of Boiled Water and Acid on Waste RFL Dipped Solid

The waste RFL dipped material was taken in a beaker having boiled water, through stirring was done and the water was decanted. The process was repeated for two more times and the boiled water treated material was thoroughly dried. In a similar operation the material was treated with 0.1 N dilute hydrochloric acid. After acid treatment the material was washed with distilled water and dried well. Both the treated material was mixed in rubber compound.

Mixing of compound was carried out using the same mixing conditions as mentioned earlier for fi lled compound (mentioned in part C).




The formulation of the mix is given in Table 5.

Table 5. Rubber compound formulation (effect of treatment)

Ingredients Mix Id.

D13 (Untreated) D14 (Treated with boiled water)

D15 (Treated with dilute acid)

RFL dip solid 10.00 10.00 10.00

Other ingredients used in the above formulation kept constant are: SBR 1502: 100.0, HAF, N330: 50.0, zinc oxide – 3.0, stearic acid – 1.0, soluble sulfur – 1.75 and TBBS – 1.00

Characterisation of Composite

A) Study in Gum Compound (as an Additional Material)

Cure Characteristics

Rheometric properties were determined at 160 °C for 30 min using 0.5° arc in MDR 2000 E from Alpha Technologies, USA following ASTM D 5289. The onset temperature of curing of the compounds was also studied in DSC 7. The compounds were scanned from 50 °C to 300 °C at 20 °C per minute heating rate in nitrogen atmosphere.

Physical Properties

The green rubber compounds were cured following ASTM D3182 in an electrically heated hydraulic curing press, Hind Hydraulics, New Delhi, India using compression moulding technique. The moulding conditions followed to cure the compounds was at 160 °C for optimum cure time (tc90) plus fi ve minutes time for stress-strain properties.

The tensile properties were measured using Zwick UTM 1445 in accordance with ASTM D412. The hardness was measured with a Shore A Durometer, Prolifi c Engineers, New Delhi, India as per ASTM D2240.

The tensile specimen was air- aged in a Multicell Ageing Oven from Tempo Industries, New Delhi, India at 105 °C for 3 d.



Rheometric properties and DSC study was determined as per the conditions mentioned earlier.




Physical Properties

The green rubber compounds were cured, aged and tested as per the conditions mentioned earlier.



Rheometric properties were determined as per the conditions mentioned earlier.

Filler Dispersion Study

Dispersion of fi ller was determined using Rubber Process Analyser, RPA 2000 from Alpha Technologies, USA according to experiment as done by A.Y. Coran and J.B. Donnet(20). The confi guration of the experiment is given in Table 6.

Table 6. Test confi guration in RPA 2000 for fi ller dispersion study

Parameter Temperature (°C)

Strain (%)

Frequency (Hz)

Conditioning of the compound for 1.0 min

50 1.0 1.667

10 s static delay 50 0 0

High strain 50 50.0 1.667

10 s static delay 50 0 0

Low strain repeated until stable

50 1.0 1.667

Repeated last two steps until G’ reaches plateau

60 s delay 50 0 0

After 10 s G′ was measured

Polymer-Filler and Filler-Filler Interaction Study

The polymer-fi ller and fi ller-fi ller interaction was studied in RPA 2000. The conditions for the strain sweep are given in Table 7. All the mixed compounds were conditioned at 100 °C, 2 Hz, and 0.5% strain for 1 min before testing.




Table 7. Test confi guration used in RPA2000 for the strain sweep study

Test confi guration Test conditionTemp. (°C) Frequency (Hz) Strain (%)

Frequency sweep 100 0.05, 0.10, 0.21, 0.43, 0.88, 1.81,

3.71, 7.61, 15.61, 32

13.95

Strain sweep 100 0.10 0.98, 2.09, 4.58, 10.06, 21.55, 46.50, 100.04,

215.40, 464.13, 999.89

The elastic modulus G′ was measured in strain sweep.

Physical Properties

The green rubber compounds were cured, aged and tested as per the conditions mentioned earlier. In case of hardness testing, hardness in IRHD was also measured using a dead load IRHD tester, H.W. Wallace and Company Ltd., UK (ASTM D1415).

In dynamic mechanical property testing, the values of tan δ at 25° and 70 °C, at 5% strain level and at 11 Hz frequency were measured using a Metravib Dynamic Mechanical Analyser, VA4000 (ASTM D5992).



Rheometric properties were determined as per the conditions mentioned earlier.

RESULTS AND DISCUSSIONS

Physico-Chemical Characterization

The results of various chemical tests are given in Table 8.




Table 8. Chemical characterisation

Chemical properties Dried fresh RFL dip solution

Waste RFL dipped solid

Specifi c gravity @ 25 °C 0.962 0.966

Moisture (%) 0.05 2.00

Ash content (%) 1.90 2.04

pH 9.5 9.3

Water extractable (%) 7.9 8.1

Acetone extractable (%) 15.8 16.0

Toluene extractable (%) 28.5 29.1

Most of the chemical properties of the waste dipped material were found to be same as that of dried fresh RFL dip solution. The inherent moisture percentage of the waste material was higher. The material was also found to be basic in nature.

The FTIR spectra of the sample are shown in Figure 1.

In case of the waste material, as well as the dried fresh dip solid material, the strong stretching frequency at 650 – 800 cm-1 indicates the presence of styrene as well as resorcinol (aromatic –CH stretching frequency). The presence of weak stretching frequency at 1500 – 1600 cm-1 also characterizes the presence of aromatic group.

Figure 1. FTIR spectra of fresh RFL dip and waste RFL dip




The stretching frequency at 909 cm-1 supports the presence of butadiene. The stretching frequency at around 2200 cm-1 indicates the presence of pyridine (due to C=N stretching). Therefore, from the FTIR spectra it can be inferred that similar type of characteristic functional group was observed in both the samples.

The degradation and glass transition temperature of the samples are shown in Table 9. The TGA diagram of the fresh dip solid material and the waste material is shown in Figure 2.

From the TGA diagram it was clear that the decomposition temperature of both the samples was very close. The decomposition pattern of both the sample was also very much similar. The presence of the volatile material, polymeric substances as well as the ash material in both the samples was also almost same.

Table 9. TGA and DSC study

Test parameters Dried fresh dip solution

Waste RFL dipped solid

Degradation temperature (°C) 506.9 500.7

Tg (°C) – 41.9 – 43.9

Figure 2. TGA thermogram of fresh RFL dip solid material and waste RFL dip material




The DSC thermogram for determination of glass transition temperature (Tg) of the fresh RFL dip material is shown in Figure 3(a) and that of the waste RFL dip material in Figure 3(b).

Figure 3a. DSC thermogram of fresh RFL dip solid material

Figure 3b. DSC thermogram of waste RFL dip material




From the DSC thermogram it was clear that the glass transition temperature of the fresh sample was almost similar as that of the waste material.

The elemental analysis (carbon and nitrogen content) data of the samples are shown in Table 10.

Table 10. Elemental analysis (by NCS)

Test parameters Nitrogen (%) Carbon (%)Dried fresh RFL dip solution 2.4 85.6

Waste RFL dip solid 2.6 81.7

The test data related to percentage nitrogen and carbon content of both the samples were found to be comparable.

The test data obtained from AAS 3300 is shown in Table 11.

Table 11. Metal analysis (by AAS)

Test parameters Dried fresh RFL dip solution Waste RFL dip solidCopper (ppm) 0.17 2.8

Manganese (ppm) 0.63 0.8

Iron (ppm) 10.5 49.5

The poisonous metals (copper, manganese and iron) were found to be higher in case of the waste material; however, the levels of the poisonous metals were not much alarming.

Characterization of Composite

A) Study in Gum Compound (as Additional Material)


The rheometric curves obtained in the experiment are shown in Figure 4. Faster cure behavior was observed in case of experimental batches with waste RFL dip solid due to its basic nature. With increase in dosage level of the waste RFL dip solid, the cure rate was further increasing.

The rheometric as well onset temperature of curing data is shown in Table 12.




Table 12. Cure characteristics

Sample Id.

Test Parameter

Scorch safety time, ts2

(min)

Optimum cure time, tc90

(min)

Cure rate index, CRI

(min-1)

Onset temperature

(°C)D1 8.81 16.30 13.35 197.2

D2 8.40 13.63 19.12 198.4

D3 7.41 12.25 20.66 194.6

D4 6.93 11.39 22.42 192.6

D5 6.04 10.42 22.83 192.8

The faster cure behavior of the experimental was further confi rmed through the lower onset temperature of curing observed in DSC study.

Physical Properties

The results of unaged and air aged physical properties are given in Table 13.

Figure 4. Rheometric properties in gum compound (as an additional material)




Table 13. Physical properties

Sample Id.

Test Parameter

Modulus at 100%

elongation(MPa)

Modulus at 300%

elongation(MPa)

TS(MPa)

EB(%)

Hardness(Shore A)

D1 0.9 (233) 2.7 (-) 3.1 (71) 346 (30) 44 (+10)

D2 0.9 (178) 2.8 (-) 3.2 (56) 338 (34) 46 (+6)

D3 0.8 (163) 2.5 (-) 3.4 (62) 351 (46) 45 (+5)

D4 0.9 (133) 2.3 (-) 3.1 (58) 376 (38) 45 (+4)

D5 0.9 (144) 2.2 (-) 3.6 (50) 384 (34) 47 (+2)

Note: Results in the parenthesis ( ) are the percentage retention of physical properties after air aging at 105 °C for three days. In case of hardness, the + values indicate increase in hardness after aging

A slight drop in modulus at 300% elongation was observed in case of experimental batches and the drop was increasing with increase dosage level of waste RFL dip solid. Better retention of hardness, modulus and elongation at break was observed in case of the experimental samples after aerobic aging. In case of tensile strength retention was marginally lower for the experimental batches.



The rheometric curves obtained in the experiment are shown in Figure 5. The rheometric as well as onset temperature of curing data is shown in Table 14.

Table 14. Cure characteristics

Sample Id.

Test Parameter Scorch safety

time, ts2 (min)

Optimum cure time, tc90

(min)

Cure rate index, CRI

(min-1)

Onset temperature

(°C)D1 8.81 16.30 13.35 197.2

D6 6.05 10.87 9.20 195.9

D7 7.04 11.48 8.71 194.9

D8 6.31 10.52 9.51 192.5

D9 5.68 9.61 10.41 191.0




Similar type of cure behavior (faster cure) as observed in the case of earlier study was found.

Physical Properties



Sample Id.

Test Parameter Modulus at 100%

elongation(MPa)

Modulus at 300%

elongation(MPa)

TS(MPa)

EB(%)

Hardness(Shore A)

D1 0.9 (233) 2.7 (-) 3.1 (71) 346 (30) 44 (+10)

D6 1.0 (160) 2.5 (-) 3.1 (52) 356 (30) 45 (+7)

D7 0.9 (-) 2.2 (-) 2.9 (48) 356 (26) 46 (+6)

D8 1.0 (140) 2.4 (-) 3.6 (47) 389 (32) 46 (+5)

D9 0.9 (-) 2.3 (-) 3.9 (31) 414 (21) 47 (+3)


A slight drop in modulus at 300% elongation was observed in case of experimental batches. Better retention of hardness and modulus at 100% elongation was observed in case of the experimental samples after aerobic

Figure 5. Rheometric properties in gum compound (as part replacement of polymer)




aging. In case of tensile strength, original values were found to be higher for experimental batches with lower retention after aging.



The rheometric curves obtained in the experiment are shown in Figure 6. Similar type of cure behavior (faster cure) as observed earlier was noticed.

Filler Dispersion Study

The results are given in Table 16.

Table 16. Filler dispersion study

Parameter D10 D11 D12G’ (MPa) at 1% strain 0.525 0.508 0.566

G’ (MPa) at 50% strain 0.203 0.208 0.225

G’ (MPa) at 1% strain 0.459 0.469 0.520

G’ (MPa) at plateau level 0.574 0.608 0.662

Fraction recovery of G’(G’ at plateau / G’ initial)

1.09 1.30 1.27

Higher the fraction recovery of G’, better is the quality of fi ller dispersion. Therefore, in case of experimental compounds the dispersion of the fi ller was found to be better.

Figure 6. Rheometric properties in fi lled compound




Polymer-Filler and Filler-Filler Interaction Study

The addition of fi llers to rubber compounds has a strong impact on the static and dynamic behavior of rubber. Besides the strain-independent contribution of the hydrodynamic effect, the fi ller-to-rubber interaction and the crosslinking of the matrix, the complex modulus, G* shows also a strong dependency at low strains i.e. modulus decreases with increasing strain. This stress softening at small deformations, also known as the Payne effect, plays an important role in understanding reinforcement mechanisms in fi lled rubber samples, and can be attributed to the breakdown of the fi ller-fi ller networks, an indication of the interactions between fi ller particles(21).

The fi ller networking or agglomeration of fi ller particles, which is controlled mainly by fi ller-fi ller interactions in a rubber compound, was quantifi ed from the strain dependence of the elastic modulus G′. The fi ller network was gradually destroyed on increasing the strain (at strains well below 100%). This resulted in a decrease in elastic modulus G′ with strain amplitude. The ratio of the elastic modulus G′ at low and high strain levels related to the fi ller-fi ller interactions(22-25).

More recently, an interaction parameter defi ned by (σ/η) has been proposed for the measurement of interaction between polymer and fi ller(23). The term σ is the slope of stress-strain curve in linear region and at typical extension ratios varying from 1 - 3. The moduli in this deformation relate the polymer-fi ller interaction. The non-dimensional term η is the ratio of the dynamic modulus G′ at 1% and 25% strain. This is related to fi ller-fi ller interaction.

The elastic modulus G′ in strain sweep are shown in Figure 7 and the data related to polymer-fi ller interaction (σ/η) are given in Table 17.

Figure 7. Strain sweep in RPA2000




Table 17. Polymer-fi ller interaction

Parameter D10 D11 D12σ 0.07 0.06 0.06η 1.53 1.55 1.58

σ/η 4.36 3.91 3.79

The compounds containing the experimental material had shown lower (σ/η) value, which is an indication of lower polymer-fi ller interaction.

Physical Properties



Test Parameter

Sample Id.

Modulus at 100%

elongation(MPa)

Modulus at 300%

elongation(MPa)

TS(MPa)

EB(%)

Hardness Tan δ

(IRHD) (Sh-A) At 25 °C

At 70 °C

D10 3.1(130)

16.4(135)

25.1(70)

431(75)

70(+5)

70(+5)

0.210 0.157

D11 3.1(126)

15.2(132)

25.5(69)

461(73)

71(+3)

71(+2)

0.208 0.168

D12 3.0(120)

15.0(129)

24.8(71)

464(75)

72(+2)

71(+3)

0.201 0.171


Stress- strain properties of all the compounds were found to be comparable both in original as well as after heat ageing. Marginal inferior dynamic mechanical properties of the experimental compounds may be due to the lower polymer-fi ller interaction.



The rheometric curves obtained in the experiment are shown in Figure 8. The faster cure characteristic of the material was offset and the effect was more prominent in case of the compound with boiled water treated material.




CONCLUSIONS

The waste dipped RFL material was thoroughly characterized by different chemical and analytical techniques. The basic nature of the material was found. It was characterized in a SBR based gum compound as an additional material and also as a part replacement of SBR polymer. In both cases, faster cure characteristics of the experimental compounds were observed. The faster cure characteristics were further confi rmed through onset temperature of curing by DSC study. In case of fi lled compounds, stress- strain properties of all the compounds were found to be comparable both in original as well as after heat ageing. Treatment of the material with boiled water and dilute acid minimized its basic nature. It can be concluded that the waste RFL dipped material can be used in a styrene butadiene rubber based compound at 5 to 10 phr usage level with minor adjustment in cure package and also the material being a waste one, any effort of using the same will give rise to benefi t of cost as well as environment protection.

ACKNOWLEDGEMENT

The authors would like to thank Mr. B. B. Singh of JK Tyre for his kind assistance in material collection and discussions during the project. The authors would also like to thank HASETRI and JK Tyre Management for their kind permission to publish this work.

Figure 8. Rheometric properties in fi lled compound (surface treatment)




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