Plasticizer reducing dynamic fatigue in fiber reinforced elastomers

Abstract

The dynamic fatigue and hysteresis performances of fiber reinforced rubber compounds are compared using different plasticizers. Polymer-based fiber reinforced rubber compounds including a non-linear functionalized fatty acid ester, preferably a trimellitate, and more preferably Tris (2-Ethylhexyl) Trimellitate (TOTM) are shown to demonstrate greatly improved dynamic fatigue and hysteretic performance as compared to reference fiber reinforced rubber compounds including conventional reference plasticizers such as Di-isodecyl phthalate (DIDP).

I claim: 
     
         1 . A stator for use in a positive displacement motor or a progressing cavity pump, the stator comprising:
 a stator tube having interior helical pathways therein, the helical pathways extending in a longitudinal direction along the stator tube, the stator tube further including a first rubber compound;   the first rubber compound including polymer-based fiber reinforcement;   the first rubber compound further including a trimellitate acting as a plasticizer;   wherein, when the stator tube receives a rotor to form a positive displacement motor or a progressing cavity pump, rotation of the rotor within the stator tube places a cyclic compressive load on the first rubber compound.   
     
     
         2 . The stator of  claim 1 , in which, for strains on the first rubber compound in a range between about 5.6% and about 19.4%, the first rubber compound has a tan delta at least 10% lower than a reference tan delta,
 herein the reference tan delta is for corresponding strains on a reference rubber compound between about 5.6% and about 19.4%, wherein the reference rubber compound is the first rubber compound modified to include, in place of trimellitate, a reference plasticizer selected from the group consisting of Di-isodecyl phthalate (DIDP), linear fatty acid esters, adipates, sebacates, maleates and phthalates.   
     
     
         3 . The stator of  claim 1 , in which, for strains on the first rubber compound in a range between about 5.6% and about 19.4%, the first rubber compound has a lower tan delta than a reference tan delta,
 wherein the reference tan delta is for corresponding strains on a reference rubber compound between about 5.6% and about 19.4%;   wherein the reference rubber compound is the first rubber compound modified to include, in place of trimellitate, a reference plasticizer selected from the group consisting of Di-isodecyl phthalate (DIDP), linear fatty acid esters, adipates, sebacates, maleates and phthalates; and   wherein the polymer-based fiber reinforcement in the first rubber compound has a higher polymer-based fiber content than the polymer-based fiber reinforcement in the reference rubber compound.   
     
     
         4 . The stator of  claim 1 , in which the trimellitate has a molecular weight of at least 500 g/mol. 
     
     
         5 . The stator of  claim 1 , in which the first rubber compound includes at least one rubber selected from the group consisting of NBR, HNBR and NBR-isoprene terpolymer. 
     
     
         6 . The stator of  claim 1 , in which the first rubber compound includes a carbon nanostructure, wherein the carbon nanostructure is in a range from about 50 phr to about 110 phr based on weight. 
     
     
         7 . The stator of  claim 1 , in which the polymer-based fiber reinforcement includes fibrillated fibers. 
     
     
         8 . The stator of  claim 7 , in which the polymer-based fiber reinforcement further includes chopped fibers. 
     
     
         9 . The stator of  claim 8 , in which the fibrillated fibers and chopped fibers are in a ratio of between about 50:1 to about 3:1 of fibrillated fibers to chopped fibers. 
     
     
         10 . A stator for use in a positive displacement motor or a progressing cavity pump, the stator comprising:
 a stator tube having interior helical pathways therein, the helical pathways extending in a longitudinal direction along the stator tube, the stator tube further including a first rubber compound;   the first rubber compound including polymer-based fiber reinforcement;   the first rubber compound further including Tris (2-Ethylhexyl) Trimellitate (TOTM) acting as a plasticizer;   wherein, when the stator tube receives a rotor to form a positive displacement motor or a progressing cavity pump, rotation of the rotor within the stator tube places a cyclic compressive load on the first rubber compound.   
     
     
         11 . The stator of  claim 10 , in which the first rubber compound includes TOTM in a range from about 1 phr to about 25 phr. 
     
     
         12 . The stator of  claim 10 , in which, for strains on the first rubber compound in a range between about 5.6% and about 19.4%, the first rubber compound has a tan delta at least 10% lower than a reference tan delta,
 wherein the reference tan delta is for corresponding strains on a reference rubber compound between about 5.6% and 19.4%, wherein the reference rubber compound is the first rubber compound modified to include, in place of TOTM, a reference plasticizer selected from the group consisting of Di-isodecyl phthalate (DIDP), linear fatty acid esters, adipates, sebacates, maleates and phthalates.   
     
     
         13 . The stator of  claim 10 , in which, for strains on the first rubber compound in a range between about 5.6% and about 19.4%, the first rubber compound has a lower tan delta than a reference tan delta,
 wherein the reference tan delta is for corresponding strains on a reference rubber compound between about 5.6% and about 19.4%;   wherein the reference rubber compound is the first rubber compound modified to include, in place of TOTM, a reference plasticizer selected from the group consisting of Di-isodecyl phthalate (DIDP), linear fatty acid esters, adipates, sebacates, maleates and phthalates; and   wherein the polymer-based fiber reinforcement in the first rubber compound has a higher polymer-based fiber content than the polymer-based fiber reinforcement in the reference rubber compound.   
     
     
         14 . The stator of  claim 10 , in which the TOTM has a molecular weight of at least 500 g/mol. 
     
     
         15 . The stator of  claim 10 , in which the first rubber compound includes at least one rubber selected from the group consisting of NBR, HNBR and NBR-isoprene terpolymer. 
     
     
         16 . The stator of  claim 10 , in which the first rubber compound includes a carbon nanostructure, wherein the carbon nanostructure is in a range from about 50 phr to about 110 phr based on weight. 
     
     
         17 . The stator of  claim 10 , in which the polymer-based fiber reinforcement includes fibrillated fibers. 
     
     
         18 . The stator of  claim 17 , in which the polymer-based fiber reinforcement further includes chopped fibers. 
     
     
         19 . The stator of  claim 18 , in which the fibrillated fibers and chopped fibers are in a ratio of between about 50:1 to about 3:1 of fibrillated fibers to chopped fibers. 
     
     
         20 . A stator, comprising:
 a stator tube, the stator tube including a first rubber compound, wherein the first rubber compound is deployed on the stator tube to receive a cyclic compressive load;   wherein the first rubber compound includes polymer-based fiber reinforcement; and   wherein the first rubber compound further includes a trimellitate acting as a plasticizer.