Dr. Sateesh Peddini and August Krupp both presented recent works in Off-The-Road tire tread enhancements with Molecular Rebar at the most recent International Elastomer Conference in Louisville, KY. Significant interest in the use of Molecular Rebar to improve this tough & wear resistant application continues to be generated thru the presentation of new findings. Below are the abstracts of each paper, along with a link to purchase the full documents from the American Chemical Society.
Enhancements in Off-the-Road (OTR) Tire Formulations with Discrete Surface Functionalized Multiwall Carbon Nanotubes: Wear, Abrasion and Tear Resistance
Off-the-road tires (OTR) are an important segment of the tire market that heavy industry relies on to maintain continuous operation with low downtime. Lifetime of OTR tires relates to the cutting and chipping resistance of the tread and sidewall. The majority of OTR tire compounders have optimized OTR performance using natural rubber and small-size carbon black, and recently with some additional silica for reinforcement. Innovative new materials, such as carbon nanotubes, can provide benefits to those previously optimized formulations- surpassing current lifetime standards in OTR tread compounds. However, many rubber compounders have tried as-made bundles of carbon nanotubes and found them very difficult to disperse as individual tubes due to their inability to detangle during processing. This means the expected performance gains were not realized. MOLECULAR REBAR® (MR) are completely disentangled, cleaned of catalyst and carbon residues, surface functionalized multiwall carbon nanotubes. The surface functionalization is beneficial for good dispersion as well as bonding to the matrix for improved load transfer, especially under high strain. MR can be delivered via an oil based dry liquid concentrate, or rubber based masterbatches that fit within existing compounding process conditions. Wear resistant tests, such as tear, abrasion, and cut & chip resistance, show dramatic improvements – upwards of 100%, with the addition of MR as low as 1.25 parts per hundred rubbers in conventional OTR formulations. These improvements provide new, wider flexibility for the formulators to gain other properties, such as improved dynamic properties, though modification of the formulation.
Tear Testing of Nano-Reinforced Compounds & Their Relation to Macro-Abrasive Wear Tests
The improved tear initiation and propagation resistance in rubber materials with discrete, well bonded multi-wall carbon nanotubes (MWCNTs), known as MOLECULAR REBAR®, MR, has been well established in numerous materials. A challenge is to understand how laboratory tests with specific formulations relate to end-use applications requiring enhanced durability. Through careful analyses, the correlation between the nanotube enhanced compound’s tearing resistance and macro-abrasive wear tests will be addressed. One such macro-abrasive wear test that has showed good correlation and similar failure mechanisms of failure with off-road tire performance is the BF Goodrich cut and chip tester. The factors found for mitigation of tearing damage in a sample: namely higher tear initiation energies and increased energy consumption through higher tear propagation resistance, lead to improved tear arrest energy values. Through the use of discrete and functionalized MWCNTs, a dramatic improvement in tear resistant properties leads to an unsurpassed reduction in tread loss due to macro-abrasive wear conditions.
The full papers can be purchased thru ACS Rubber Division here.