Study On High Temperature Formula System Of EPDM And Its Dynamic Rheological Properties

Two aspects,vulcanization system and reinforcing system of the rubber,were studied as the objects with two peroxides?Luperox F40S and Luperox DC40?and sulfur as an auxiliary vulcanizing agent with the addition of four reinforcing fillers?N550,N330,silica and CNTs?,respectively.Accordingly,the vulcanization characteristics,basic mechanical properties and dynamic mechanical properties of Ethylene Propylene Diene Monomer?EPDM?were further investigated.Firstly,the effect of vulcanization system on properties of EPDM was studied with the change of Luperox F40S,Luperox DC40 and sulfur contents.The results showed that the basic mechanical properties of EPDM vulcanizates decreased with the increase of temperature.The increase of peroxides dosage lead to an increase of torque,shortening of the curing time t₉₀,decrease of the elongation at break and tear strength.The addition of sulfur in the system had little effect on the torque and tensile strength,but the elongation at break and tear strength of EPDM were improved,it was significant at high temperature,and the Luperox DC40 system was superior to the Luperox F40S system.The tear strength at high temperature was best when the content of sulfur is 0.6 phr.Besides,the crosslink density of EPDM increased with increasing of peroxide and sulfur contents.With the respect of dynamic mechanical properties of EPDM,the G'decreased with the addition of sulfur to the system.And the G'under the strain sweep and frequency sweep at 100°C increased with increasing vulcanizing system content.The?tan?of the two vulcanizing systems were all positive under the strain sweep,but decreased with the increase of the strain.While,the?tan?was negative under the frequency sweep.Comprehensively consideration,Luperox DC40 as the peroxide curing agent and sulfur with the content of 0.6 phr were selected as the composition of the basic formulation for the further study.After determining the basic formulation,the effect of reinforcing system on properties of EPDM was studied with the change of N550,N330,silica and CNTs contents.The results showed that the increase of fillers dosage lead to an increase of torque and shortening of the curing time t₉₀.Taken together,When the content of carbon black?N550,N330?is 60 phr,the tear strength at high temperature is best;overall,the silica/N550 combination system shows the best high temperature tear strength,when the ratio of silica/N550 is 20/40.Besides,the crosslink density of EPDM increased with increasing of N550,N330 and CNTs contents,on the contrary,the crosslink density decreased with increasing of silica content.All the reinforcing fillers exhibited different degrees of Payne effect with the respect of dynamic mechanical properties of EPDM,but the N330 system was the most obvious and the silica/N550 system was the weakest.G'under the strain sweep and frequency sweep at 100°C were lower than those at 25°C,which was contrary to the change rule of the vulcanization system.The?tan?of the N550,N330 and silica/N550 systems were all positive under the strain sweep,and decreased with the increase of the strain.While,there is no change in?tan?under frequency sweep.The?tan?of the CNTs system was positive under the strain sweep,but the curves had no intersection.The?tan?was negative under the frequency sweep.