Study On Formula Design And Friction And Wear Behavior Of The Nitrile Rubber Based On The Screw Pump

The outstanding advantages of convenient maintenance,constant flow rate,high efficiency and energy saving of progressing cavity pumps（PCPs）have made them among the most promising equipment in a wide range of oil extracting applications.Compared with the traditional oil recovery equipment,PCPs as a rod less oil equipment can be especially applied for oil production in high temperature,pressure,sand volume and viscosity of oil et al.conditions.PCPs is mainly composed of the stator and rotor.The material of rotor is usually made of high quality carbon structure steel.Acrylonitrile-butadiene rubber（NBR）is widely applied as the stator due to its excellent properties of viscoelasticity,oil and wear resistance.However,during operations in bad work conditions,tear and degumming failure phenomenon of the stator could be formed due to the blending of the crude oil and sand,gas,corrosive medium et al.leading to reductions of the service life of the PCPs.In this thesis,in order to improve the service life of PCPs stator,the mechanical and tribological properties of different kinds of NBR are mainly forced.The effects of the content of reinforcements on the glass transition temperature of NBR under different pressure are examined using molecular dynamics（MD）simulations.Mechanical and tribological properties of NBR are also experimentally tested.The optimal recipe of NBR is determined based on orthogonal optimization method by comparing and analyzing different content effects of plasticizing and reinforcing system.Comparison studies on the intrinsic and tribological properties of LNBR/CBN330/CBN550/SiO₂·nH₂O reinforced NBR materials are experimentally dedicated respectively.The inherent mechanisms of wear behavior of NBR under dry and different media friction conditions are explored and discussed accordingly.By comparison of effects on the intrinsic properties of NBR by blending different reinforcements and plasticizing system,the results showed that the vulcanization degree and crosslink density of the NBR can be improved by decrease the size of carbon black reinforcements leading to the enhancements of swelling resistance,heat resistance and reduction of curing time of NBR rubber.The mechanical properties of NBR with same SiO2 contents can be enhanced when introductions of smaller size of carbon black.It is indicated that smaller size of carbon black can be easily interacted with the rubber chains leading to greater bulk modulus and better reinforcing effects than that of the larger size of carbon black.It is also pointed that with the increase of the amount of plasticizer,the crosslinking degree of the rubber shows a decreasing trend.In contrast,LNBR plasticizer was performed worse effects on enhancing the crosslink density of NBR than that of the DOP plasticizer.In addition,with the increase of plasticizer content,the mechanical properties of NBR with all different plasticizers,such as tensile stress and fracture strength were behaved first increased and then decreased trend.It can be concluded that the optimal reinforcing effects of the plasticizer are existed,the mechanical properties of NBR tended to decrease when the content of the plasticizer beyond the critical values.Molecular models of pure NBR and SiO₂ reinforced NBR composites are built respectively.The glass transition temperature of the two models are predicted using MD simulations.The results showed that the glass transition temperature of NBR matrix can be enhanced by incorporation of SiO₂ as reinforcements.By examining the mean square displacements of NBR chains,it was indicated that the mobility of the molecular chains of SiO₂/NBR composites were restricted by the van der Wall interactions provided by the surfaces of SiO₂ leading to higher glass transition temperature of the NBR rubber.It was also pointed that with increasing of the mass fractions of the SiO₂ reinforcements,the molecular chain of NBR are subjected more and more adsorption and behave less active states leading to higher and higher glass transition temperature.The effects of different pressure on the glass transition temperature of NBR matrix were also calculated and discussed respectively.Based on the MD simulation results,it was hence understand as followings:With the increase of the pressure,the NBR matrix were continuously compressed leading to less and less free volume inside the whole system.Less and less active space were left for the thermal motion of the NBR chains.The activity of the NBR chains were reduced and the glass transition temperature of NBR matrix tend to be increased.Orthogonal tests were conducted to examine the mechanical and tribological properties of NBR rubber introduced by different reinforcing and plasticizer system.Two kinds of optimization recipe were obtained by comparing and analyzing the performance of the glass transition temperature,tensile strength and swelling resistance volume change rate of the NBR rubber.By further examining the tribological properties of the NBR rubber,the optimal recipe was obtained for the stator materials of PCPs.For the NBR rubber made by the optimal recipe,tribological properties were tested under KCL solution medium included 3.5%concentrations of sands.The experimental results showed that the friction coefficient decreases with the increase of the normal loadings and decrease of the wear rates which were greater than that in the distilled water medium.The wear mechanism was contributed to the wet abrasive wear and sliding erosion under the action of free abrasive particles.It was also found that the molecular chains in the surface and subsurface of the NBR rubber were proven to be break and creak due to the existence of the K⁺.The products with low molecular weight and low dispersion and small molecular monomers and a new branched network have been formed.