Study On Elastocaloric Effect Of Different Rubber Materials

Taking natural rubber,silicone rubber,cis-butadiene rubber,styrene-butadiene rubber and chlorosulfonated polyethylene as research objects,the thermal effect of rubber during stretch-retraction deformation was studied by using elastocaloric theory and constitutive equation of high elasticity based on statistical theory:Firstly,repeat cycle experiments were carried out at 500 mm/min loading-unloading rate corresponding to the maximum strain of each rubber to eliminate Mullins effect;secondly,at the rate of 500 mm/min,the stretch-retraction experiments were done on the specimens which have eliminated Mullins effect,and the deformation temperature rise of different rubber materials were compared.The specimen of minimum temperature rise was selected and loaded at different rates,respectively,to obtain the temperature-rate curve;the rate close to the adiabatic condition could be found depending on the curve,and all rubber materials were researched in different strain in the conditon of insulation.The main conclusions were as follows:1 For all materials,Mullins effect can be eliminated after 9 cycles of loading-unloading;2 The thermal effect of silicone rubber is the smallest,so its tensile tests at different rates are performed.It is found that the tensile process can be considered as insulation at 500 mm/min and above;3 Gauss fitting of stress-strain curves of rubber materials eliminated Mullins effect in tensile process are carried out,obtaining the number of net chains per unit volume of rubbers,which can be treated as crosslinking degree.The ranking list is chlorosulfonated polyethylene > styrene-butadiene rubber > cis-butadiene rubber > Natural Rubber > silicone rubber,among which the first three are much larger than the last two;4 By comparing the temperature rise of these five rubber materials with the strain,it can be concluded that in the process of stretch-retraction,crystallization and melt occurs in natural rubber,silicone rubber and cis-butadiene rubber,while styrene-butadiene rubber does not crystallize.The plastic deformation of chlorosulfonated polyethylene occurs in the process due to its nature property leading to a big irreversible loss;5 The main factors affecting the elastocaloric effect of rubber are crosslinking degree,crystallinity,elasticity and irreversibility;6 The elastocaloric coefficient is not the unique criterion for evaluating the material we are looking for,and the irreversibility and fatigue life should be taken into account,too.Natural rubber has excellent performance in these five materials,and can be used as an elastocaloric material in solid-state refrigeration.Silicone rubber,cis-butadiene rubber and styrene-butadiene rubber still have great potential to apply to elastocaloric refrigeration,as long as the crosslinking degree between molecules is well prepared(on the basis of this research,increasing the crosslinking degree of silicone rubber,reducing the crosslinking degree of cis-butadiene and styrene-butadiene rubber);7 Cycle analysis of natural rubber shows that the temperature rise of the system is 5.2? and the ideal refrigeration coefficient is about 20 times of that of the vapour compression refrigeration,which reveal the rubber materials,especially natural rubber,have great application potential,but the actual refrigeration coefficient is 1.648.In the future,heat transfer and system design should be strengthened.