Studies on the use of nano zinc oxide and modified silica in NR, CR ...

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Chapter 7 Ageing studies Thermal ageing 124 Thermal ageing was carried out at temperature of 100°C for 48 hrs and 96 hrs as per ASTM D 573-1999. Ozone resistance Ozone resistance was determined according to ASTM D 518 method B. Samples were exposed to ozonised air in an ozone chamber (Mast model 700-1) for 12 hrs. The concentration of ozone was maintained at 50 ppm at 20% strain and the inside temperature at 40°C. The ozone cracks developed on the samples were observed by a lens and the photographs were taken. 7.3 Results and discussion 7.3.1 Characterization Surface area studies Table 7.2 shows the surface area values of precipitated silica and modified silica. It is found that the surface area is lesser for modified silica compared to the unmodified precipitated silica. This shows that antioxidants are adsorbed on to the surface of silica under physical force of attraction. 7.3.2 Cure characteristics Table 7.2 Surface area of silica Samples Surface area (m 2 /g) Neat precipitated silica 178 Modified silica 127 Cure characteristics of the NR compounds with an optimum concentration of 50phr silica and 1phr antioxidant are shown in Table 7.3.
Mix Use of antioxidant modified precipitated silica in natural rubber, chloroprene rubber and styrene butadiene rubber Table 7.3 Cure characteristics of the mixes Min torque dNm Max torque dNm Scorch time (min) Optimum cure time (min) Cure rate index (%) E-1 0.481 9.88 1.39 4.77 29.58 E-2 0.559 9.69 1.06 5.07 24.93 F-1 0.251 8.52 1.15 5.11 25.20 F-2 0.392 8.01 1.10 5.18 24.50 G-1 0.643 9.64 1.55 6.37 20.72 G-2 0.457 8.23 1.39 6.49 19.60 From the Table, it is seen that the cure values of compounds filled with antioxidants modified silica exhibit higher cure rate and extent of cure over that of compounds with neat precipitated silica. Chemical surface groups on fillers play an important role in their effect on rate of cure, with many vulcanized systems. Physical adsorption activity of the filler surface is of greater importance than its chemical nature. The polar nature of silica surface adsorbs a part of the curatives and or silica- zinc ion interaction leads to slowing down of the curing reaction. 17 But in the case of antioxidant modified silica, the -OH groups on the surface are already hydrogen bonded with the NH group of the substituted phenylenediamine antioxidant. Cure graphs of the three types of antioxidants filled compounds are shown in the Figure 7.1(a-c). The maximum torque is a measure of crosslink density and stiffness in the rubber. 18 In general, for all the mixes, the torque initially decreases and then increases. The increase in torque is due to the cross linking of rubber. It is found that the antioxidant modified silica increases the torque compared to the neat precipitated silica. This increase is due to the presence of silica- rubber crosslink that imparts more restriction to deformation. 125
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Studies on the use
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WxvÄtÜtà|ÉÇ I hereby declare t
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My heartfelt thanks are also due to
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The use of prepared zinc oxides as
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2.2.10 Characterization techniques
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Part@ B 7.3.1 Characterization - su
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Introduction 1.1 Composites 1.1 Com
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Introduction of reinforcement and m
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Nanophase material: They are same a
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Introduction developed at Oxford Un
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Introduction Rubbers are broadly cl
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Introduction The polymers are prepa
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1.4.1 Zinc oxide Introduction Zinc
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Introduction and tinted rubber comp
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Pharmaceutical industry Introductio
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Introduction textiles contain ZnO,
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1.4.2a. Carbon blacks Introduction
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Introduction especially glass and c
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Introduction properties, filler cha
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Introduction coupling agent in sili
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Introduction amphiphilic di and tri
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Introduction It has been reported t
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Introduction The external manifesta
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Introduction concern for a clean en
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12. C.R.Martin, Chem. Mater, 1996,
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41. E.J.Stewart, J.Elastomers plast
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Introduction 69. J.B. Donnet (Ed),
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Introduction 100. C.T.Kresge, M.E.L
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Introduction 129. E.R.Ericsson, R.A
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Chapter 2 47 In a particular experi
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Chapter 2 Stearic acid (co-activato
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Chapter 2 roll with mill opening at
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Chapter 2 were carried out at a cro
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Chapter 2 2.2.4 Strain-sweep studie
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Chapter 2 2.2.6 Bound rubber conten
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Chapter 2 Surface area 59 Surface a
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Preparation and characterization of
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3.2.2 Method I- Precipitation metho
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Energy dispersive X-ray spectrometr
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3.4.9 Differential scanning calorim
Page 87 and 88: 3.6 References Preparation and char
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Page 101 and 102: Tear Strength (N/mm) 120 100 80 60
Page 103 and 104: 4.5 References Use of nano zinc oxi
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Page 107 and 108: Chapter 5 93 Ingredient phr Table 5
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Page 113 and 114: Chapter 5 99 Table 5.8 Reinforcing
Page 115 and 116: Chapter 5 101 Hours Table 5.11 Agei
Page 117 and 118: Chapter 5 5.5 References 103 1. D.C
Page 119 and 120: Chapter 6 105 Fatty acids as co-act
Page 121 and 122: Chapter 6 107 Physical properties s
Page 123 and 124: Chapter 6 The cure rate index of gu
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Page 127 and 128: Chapter 6 113 Table 6.6 Reinforcing
Page 129 and 130: Chapter 6 115 Tensile modulus (Mpa)
Page 131 and 132: Chapter 6 6.4 Conclusions 117 1. Gu
Page 133 and 134: Use of antioxidant modified precipi
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Page 143 and 144: Crosslink density Use of antioxidan
Page 151 and 152: Part@ B Use of antioxidant modified
Page 157 and 158: Thermal ageing studies Use of antio
Page 161 and 162: 7.9 References Use of antioxidant m
Page 163 and 164: Products from rice husk as filler i
Page 167 and 168: Rubber compounding Products from ri
Page 169 and 170: Soxhlet extraction Products from ri
Page 173 and 174: 8.3.4 Bound rubber content Products
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Page 185 and 186: 8.8 References 1. V.M.H. Govindaro
Page 187 and 188: Summary and Conclusions Polymers ar
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Summary and Conclusion compounds an
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ASTM : American Society for Testing
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A. International/National journals
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P.M.SABURA BEGUM Senior Scale Lectu
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