The work presents the synthesis and characterization of a biowaste-based tackifying phenolic resin and its application in rubber. Biophenol−furfural resin was successfully synthesized from monosaccharides and their derivatives prepared from naturally occurring Moringa oleifera gum. Different resins synthesized by varying the biophenol to monosaccharide ratio exhibited the glass transition temperature in the range of 16−31 °C. Characterization of the resin was done by Fourier transform infrared spectroscopy, 1 H NMR, thermogravimetric analysis, and differential scanning calorimetry. The molecular weight of the resins was in the range of 652−1291 m/z. The effect of the synthesized resin on the mechanical, dynamic mechanical, tack, and rheological properties of the styrene butadiene rubber (SBR) was investigated. Synthesized resin improved the tack and the rheological properties of the rubber. Tensile strength of the SBR compound with resin having 2:1 biophenol to carbohydrate ratio was the same as or higher than that of the mixture of commercial resin and SBR.

The current focus in the elastomer industry is to look for biobased or natural filler for various compounds. The reinforcing effect of waste drumstick-derived cellulose micro and nanofiber in styrene butadiene rubber (SBR) was investigated for the very first time. Cellulose microfibers and nanofibers were isolated from the drumstick fruit peel and characterized using different techniques such as x-ray diffraction, scanning and transmission electron microscopy, and x-ray photoelectron spectroscopy. The filler-polymer interaction in the composites was studied using the bound rubber measurements, which showed that the bound rubber content of the composite increased from 0.5% to 8.1% at 5 phr cellulose nanofiber loading. The tensile strength and modulus of the modified cellulose microfiber-containing composite were higher than both the unfilled SBR and the raw fiber-SBR composites. The addition of 5 phr nanofiber to SBR showed a 46% increment of the tensile strength than the control compound. The die swell index of the cellulose fiber reinforced composites came down attesting the better processability of the extrudates. The addition of cellulose fiber also improved the wet skid resistance of the composites as seen from dynamic mechanical thermal analysis. Hence, this work confirms the application of modified drumstick microfibers and nanofibers as sustainable fillers for high-performance elastomers composites.

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Low cost and environment‐friendly bio‐oils are gaining market value as a plasticizer for elastomeric compounds. Unsaturated triglycerides of bio‐oils can be easily modified in various ways, like epoxidation, esterification, and so on. In the present work, 15 mole percentage of the total double bond content of the neem oil (NO) was epoxidized by acetic acid‐hydrogen peroxide system to synthesize epoxidized neem oil (ENO). NO and ENO were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry. The effect of ENO on the properties of nonpolar styrene butadiene rubber (SBR) and polar nitrile rubber (NBR) was investigated. Tear strength (69.9 N/mm), abrasion resistance index (ARI) (68.2) and hardness (64 shore A) of the SBR/ENO compound were comparable to the compound containing total distillate aromatic extract (TDAE) (values: 70.8 N/mm, 68.0 and 64 shore A respectively). Tensile strength and ARI of conventional NBR/dioctyl phthalate (DOP) compound were 24.9 MPa and 107 respectively, whereas NBR/ENO compound showed improved tensile strength (26.9 MPa), and ARI (138). Tear strength (83.4 N/mm) and hardness (74 shore A) of NBR/ENO were comparable to the tear strength (83.5 N/mm) and hardness (74 shore A) of NBR/DOP compound. Hence, the multifunctional additive property of ENO makes it a cheap and sustainable replacement of TDAE and DOP.

A natural waste (gum) of the drumstick tree, Moringa oleifera, was used for the first time as a sustainable multifunctional additive in an SBR compound. Improved cure rate with lower optimum cure time was obtained by using the gum as an accelerator activator. Tack strength of the M. oleifera gum–SBR compound was superior to both the control and the compound containing commercial phenol–formaldehyde resin at 5 parts per hundred of rubber loading. At different loadings, the gum acted as a plasticizer for the rubber and augmented processing by reducing the viscosity of the compound. The glass transition temperature of the compounds decreased by 2 °C compared with the pristine SBR. Moringa oleifera gum at any loading reduced the die swell of SBR. This study has relevance because the rubber industry is looking for feasible sustainable additives as alternatives to existing petroleum-based compounding ingredients.