Study On The Preparation And Performance Of Mixed Polyurethane Tread Rubber

Millable polyurethane?MPU?is the ideal material to prepare the green tread rubber with excellent abrasion resistance,outstanding mechanical strength and good processability.MPU has broad prospects in tire manufacturing industry.However,MPU has the disadvantages of high dynamic heat generation and poor heat resistance.MPU tread rubber easily generates heat during driving and causes mechanical strength to decrease,which reduces the service life of the tire.This article chose the mixed polyurethane as the matrix,the first part is to improve the heat generation and heat resistance of the MPU.The effects of the cure system and the filler system on the fatigue heat generation and heat resistance of the MPU were studied.To overcome the weak mechanical properties of peroxide-cured MPU,the unsaturated carboxylic acid salt was used to enhance the properties of MPU.The reinforcement of the in-situ production of zinc methacrylate and magnesium methacrylate for MPU was studied under different prepared processes.The effect of blending ratio and fillers on the properties of MPU/NR blend was investigated.The results showed that:?1?Compared with sulfur curing system,the peroxide curing system resulted in the vulcanizated MPU with better thermal aging resistance,fatigue resistance and thermal performance.The MPU vulcanizates with 1.2 phr DBPH could be compressed 45,000times during dynamic compression without damage.Compared with carbon black,silica had better reinforcement effect on MPU.With the increase of the amount of silica,the tensile strength of MPU vulcanizates increased first and then decreased.When the amount of silica was 30 phr,the tensile strength and elongation at break of vulcanizates reached21 MPa and 420%,respectively.?2?By infrared spectroscopy characterization and crosslinking density test,it was confirmed that the unsaturated carboxylic acid metal salt particles could in-situ generate by oxides and MAA during the mixing process.In the subsequent peroxide curing process,the unsaturated carboxylic acid metal salt could self-polymerizate or graft in the MPU to form ion-crosslinking network,which had certain reinfored effect on peroxide-cured MPU.MgO and MAA became more active during the in situ reaction in MPU.MDMA filled rubber show good heat resistance.The MDMA present superior reinforcement for MPU than ZDMA.The ion crosslink density of MPU vulcanizate gradually increased when the molar ratio of MgO/MAA increased,resulting in the tensile strength increased first and then decreased.When the molar ratio of Mg O/MAA was 0.6,MgO could fully react with MAA to form MDMA,resulting in better mechanical properties of the vulcanizate.The T₉₀ gradually decreased,as well as M_L,?M and the crosslink density of ions increased,as the amount of MDMA increased.When the content of MDMA was 30 phr,the mechanical properties of MPU vulcanizate were the best,with the tensile strength being 35MPa,the elongation at break being 310%,the tear strength being 74N/mm,and the wear volume being 0.04cm³,respectively.When the molar ratio of MgO/MAA was 0.6 and the amount of MDMA was 30 phr,the ion crosslink density and the covalent bond crosslink density of the MPU vulcanizate increased with the increase of the amount of DBPH,and the temperature of sample gradually decreased during dynamical compress,and the compression life gradually increased.When the amount of DBPH was 1.2 phr,the self-polymerization and grafting reaction of MDMA in the vulcanizate tended to be stable,and the comprehensive properties of the vulcanizate were better.Through dynamic thermo-mechanical analysis,it was found that the ion-crosslinking network formed by the unsaturated carboxylate salt could greatly increase the storage modulus of the MPU vulcanizate.However,at high strains of high-filled vulcanizates,the ion-crosslinking network formed by the fillers was easily shear-damaged,and the degree of networking between the fillers is rapidly reduced.?3?Blending NR and MPU in combination could effectively improve fatigue property of MPU.With the increase of the amount of NR,the covalent bond cross-linking density of the rubber increased,which improved the heat aging resistance of the blend.When the proportion of NR is increased to 50%,the vulcanizates could be compressed 45,000 times during the dynamic compression process without being destroyed.The reinforcement effect for the MPU/NR blend by in-situ generation of MDMA was superior to carbon black or silica,which could effectively increase the tensile strength and tear strength to produce tread rubber with high mechanical strength,high wear resistance and low fatigue heat generation.When the amount of MDMA was 20 phr and the blending ratio of MPU/NR was 50/50,the tensile strength,tear strength and Akron abrasion volume of the blend were22.5 MPa,50 N/mm and 0.2 cm³,respectively.While the medium temperature of vulcanizates was reduced to 108°C when the sample was with compress dynamically45,000 times.