Article pubs.acs.org/IECR
Exploring Microcrystalline Cellulose (MCC) as a Green Multifunctional Additive (MFA) in a Typical Solution-Grade Styrene Butadiene Rubber (S-SBR)-Based Tread Compound Sanjay Kumar Bhattacharyya,† Bhavani Shanker Parmar,† Abhijit Chakraborty,‡ Saikat Dasgupta,† Rabindra Mukhopadhyay,† and Abhijit Bandyopadhyay*,‡ †
Hari Shankar Singhania Elastomer and Tyre Research Institute, Jay Kay Gram, Dist: Rajsamand, Rajasthan 313342, India Department of Polymer Science and Technology, University of Calcutta 92, APC Road, Calcutta 700009, India
‡
S Supporting Information *
ABSTRACT: Multifunctional behavior of microcrystalline cellulose (MCC) was investigated in a typical solution-grade styrene butadiene rubber (S-SBR)-based tread compound in connection with its potential as reinforcing filler as well as processing aid. Optimum physical properties were obtained when the loading of MCC was at 10% of the precipitated silica amount by substituting silica. The presence of MCC in mixes had shown reduction in Mooney viscosity. Peak-power consumption during mixing was also found lower for such mixes. Because of enhanced plasticity, it was possible to reduce aromatic oil dosage by 3 phr (equivalent to 18% of the original oil amount) to get the Mooney viscosity and physicomechanical properties comparable to those of the control compound.
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viable solution7; however, to date, it has seldom been practiced industrially. But despite of this, the search for new and green MFAs continues and several researchers, at times, have reported such additives for different rubber recipes. For example, Nandanan et al. reported the use of linseed oil as MFA for nitrile rubber compounds.8 Guhathakurta et al. reported the use of naturally occurring bahera gum as MFA for both NR and brominated isobutylene-co-paramethyl styrene (BIMS) rubber compounds.9 Nando et al. investigated on cardanol and its phosphorylated derivatives grafted on natural and synthetic rubbers as MFA.10 Kuriakose et al. reported the use of rice bran oil as MFA in E-SBR compounds.11 Cellulose is the most abundant natural polymer, comprising up to 45% of the plant wood, and it plays an important role in the structural support of plant cell walls, because of its high mechanical strength. Chemically, it is a large and linear-chained polymer containing numerous hydroxyl groups. Its structural unit is anhydroglucopyranose (AGU), having three hydroxyl groups except the terminal ones (Figure 1).12 Native
INTRODUCTION Silica is extensively used to reduce rolling resistance of tires.1−3 However, silica compounds are difficult to mix, compared to carbon black compounds, because its polar surfaces do not interact with rubbers and thus chemical bonds are difficult to establish. Eventually, it is achieved through bifunctional coupling agents, called silane coupling agents, which, one the one hand, chemically reacts with active silanol groups and reduces surface polarity but on other hand reacts with rubber molecules during vulcanization to establish a strong chemical coupling. It is now established that sulfur radicals generated from split coupling agents are particularly reactive toward −CC− moieties.4 Based on this, S-SBR with 20%−70% vinyl content is more excavated than the conventional grade (emulsion-grade styrene butadiene rubber, E-SBR) in silica-rubber technology for achieving higher reactivity of coupling agents toward the rubber matrix. But, its lower cohesive strength than natural rubber (NR) (even lower than E-SBR) compels the use of easily dispersible silica (i.e., low mixing stress) for acceptable end-use properties.5 Precipitated silica used in rubber industries as reinforcing filler is exclusively manufactured from vitreous silicate through synthetic route and contributes toward huge ash generation when silica-filled tires are incinerated after completion of their life cycle.6 Apart from silica, several other ingredients are also added to gratify product quality without forfeiting occupational health and cost economy. But the use of a large number of ingredients finally creates a huge processing problem, since all of them have to be mixed within a minimum mixing cycle. Present environmental concerns have further worsened this situation, because it limits the addition of supplementary synthetic ingredients in the recipe. Multifunctional additive (MFA), especially from green resources, could be a © 2012 American Chemical Society
Figure 1. Molecular structure of cellulose.
Received: Revised: Accepted: Published: 10649
May 15, 2012 July 20, 2012 July 25, 2012 July 25, 2012 dx.doi.org/10.1021/ie301268e | Ind. Eng. Chem. Res. 2012, 51, 10649−10658
Industrial & Engineering Chemistry Research
Article
bromide (KBr) powder. The equipment used was a Model FTIR 2000 system from Perkin−Elmer (Norwalk, CT, USA) with a scan range of 400−4000 cm−1 at a resolution of 4 cm−1. An average of 4 scans was reported for analysis. Thermal stability of MCC was determined from thermogravimetric analysis (TGA) using Pyris-1 TG analyzer of Perkin−Elmer (Shelton, CT, USA). The sample was run three times using a heating rate of 10 °C/min and temperature was found to be reproducible up to ±3 °C. Initially, the heating was carried out under nitrogen from room temperature to 580 °C and then shifted to oxygen and further heated up to 850 °C. Preparation of Rubber Compounds. The basic formulations used are given in Table 1. A small amount of carbon
cellulose has both crystalline and amorphous domains. Both microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) are obtained after removing amorphous regions via acid hydrolysis.13−16 Since crystalline cellulose has high strength and high stiffness, it has great potential to be used as a reinforcing material in thermoplastic or rubber matrixes.17−19 MCC is commercially available in powder form and as a colloidal dispersion. Powder MCC is made by spraydrying aqueous MCC and has an average particle size within the range of 20−90 μm. Colloidal MCC has an average size of
