Investigations of Highly Dispersible Silica Types and Silane Types in an OTR Cut Resistant Tire Tread Application

Rolling resistance has an analog in the OTR market referred to as Ton Mile Per Hour (TMPH).  This is an index of the heat generation as measured by tread temperature with respect to the load carried by the tire.  Improving the TPMH can increase the durability of the tire by reducing the tire operating temperature.  The application of silica as employed in the green tire has been tried but has had some limitations in “tearing, cut and chip” resistance.  The largest cause for tire removal in mining operations is related to tread damage from low tear, cut and chip resistance.  It is estimated that this failure mode may be the cause for as high as 60 to 70% of tire removals.  This work looks to optimize the use of silica by studying, in a partial factorial DOE, the effects of silica surface area and silane types to improve the cut resistance while producing a high TMPH “greener” OTR tire tread compound.

This work will study a highly dispersible green tire silica: ULTRASIL^® 7000 GR silica at a specific CTAB surface area of 160 m²/g to a higher CTAB surface area highly dispersible silica: ULTRASIL^® 9000 GR silica at 200 m²/g.  Both silicas will be evaluated to the typical OTR loading of higher carbon black to silica ratio and at an inverted ratio of higher silica to carbon black.  Silane will also be varied as DOE factors to maintain or improve fracture resistance.  The silane DOE factors will be: type of silane being sulfur crosslinking Si 69^® silane or silanes providing lipophilic modification; the character of the lipophilic silane (alkyl chain length) provided by Dynasylan^® PTEO or Dynasylan^®OCTEO silanes; the total dosage of both silane types; and finally, the ratio of the crosslinking versus lipophilic silane types.

It is the objective of this work to find an optimum formulation having low heat generation while providing high elongation and facture strength while at the same time having comparable or higher modulus.  The fracture improvement goal is to increase the elastic limit while increasing the stress storage capacity of the material.  The analysis will summarize the relative strength of each of these factors for these objectives of rubber viscoelastic and physical properties.