| The molecular structure of nitrile rubber(NBR)contains polar nitrile(-CN),which makes it has a series of excellent properties,especially oil resistance.It(NBR)is widely used in oil well sealing materials.However,like other diene materials,because of the existence of unsaturated double bonds(C=C),the aging phenomenon of NBR products during processing,storage and use is serious,which is difficult to meet the application requirements under high load and extreme conditions.Therefore,it becomes a research hotspot to develop effective anti-aging methods of NBR,to improve its aging resistance and to expand the application field of its products.Several typical layered fillers(graphene oxide,Layered Double Hydroxides and zirconium phosphate)are used in functional modification of NBR.Loading groups with anti-aging effect to make NBR has both anti-aging barrier function of layered fillers and chemical anti-aging effect of functional groups so that to prepare NBR or(modified)layered fillers composites with good aging resistance.NG,LDH-GO-KH560-RT and ZrP-RT were prepared respectively by means of surface grafting,in situ deposition and organic intercalation.Their structures were characterized by FITR,XRD,SEM,TGA,and Raman.Mechanical blending of NBR and layered fillers were used to prepare composites,which investigates the effects of each layered packing on heat-resistant oxygen aging properties and mechanical properties of NBR.The results of mechanical tensile test show that the fracture strength of the composites increases first and then decreases as the content of layered fillers increases.When the content of NG,LDH-GO-KH560-RT and ZrP-RT reaches 3phr,7phr and 10phr respectively,the mechanical properties and heat-resistant oxygen aging properties of the composites are optimal,and the fracture strength increases by 131%,102%and 108%respectively.The retention rate of fracture strength after aging is 90%,141%and 114%respectively,which are higher than the retention rate 83%of the blank sample(KB-1)and the retention rate 89%of the contrast sample(KB-2)with adding commercial small molecule antioxidant.The SEM analysis of the composites shows that NG,LDH-GO-KH560-RT and ZrP-RT are all well dispersed in NBR matrix,and there is no obvious phase separation between each layered filler and NBR matrix after thermo-oxidative aging.In addition,according to the mechanical performance data,the Moony-Rivlin model is also indirectly proved that there is a strong force between each layered filler and NBR matrix,and the layered fillers are well dispersed.The results of TGA-DSC test in the oxygen atmosphere of the composites indicate that the thermal oxidative degradation of NBR mainly consists of two stages:chain segment oxidation and chain segment decomposition.NG,LDH-GO-KH560-RT and ZrP-RT can effectively inhibit the oxidation reaction in the early stage of aging.The ATR-FTIR results of NG,LDH-GO-KH560-RT and ZrP-RT can inhibit oxidation and chain scission of NBR.The results of crosslinking density test and DMA test show that there are crosslinking reaction and chain scission in the thermo-oxidative aging process of NBR,while molecular chain crosslinking reaction is the main chain reaction and chain scission is supplemented in the aging stage of 0-96h.NG,LDH-GO-KH560-RT and ZrP-RT can inhibit the crosslinking reaction of NBR molecular chain.NG,LDH-GO-KH560-RT and ZrP-RT are well dispersed in NBR matrix and have good interaction with the matrix.They have good enhancement effect on NBR.Moreover,they can effectively inhibit the crosslinking,fracture and oxidation of NBR molecular chain in the process of thermo-oxidative aging and improve the service life of NBR products in thermo-oxidative environment. |
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