Research On Coordination Vulcanization And Foaming Materials Of Nitrile Rubber

Nitrile rubber?NBR?and its foamed materials exhibits excellent oil and heat resistance due to its high polarity of acrylonitrile,which play an irreplaceable role in the national economy and military fields.However,the irrecyclability has limited its application.In this paper,the high strength with excellent reproducible processability of NBR is designed and the foaming properties under different sulfur methods are compared.This paper not only provides ideas for the development of new vulcanization methods but also lays the foundation for the research of NBR foaming.In this paper,NBR with high strength and recycling ability was designed based on the interaction between metal ions and ligands.Herein,we firstly epoxidized the nitrile rubber latex through the peroxyformic acid method,and then dopamine was grafted onto the epoxidized nitrile rubber via the ring-opening reaction followed by acted as dynamic cross-linking points to connect separate NBR molecules.The NBR exhibited valuable mechanical properties due to the formation of the Fe³⁺-catechol groups coordination bonds,for example,the tensile strength of modified NBR with 2.5 phr Fe³⁺reached 8.93 MPa,which was far higher than most reported noncovalent supramolecular rubbers.Meanwhile,the reversible association-dissociation behavior of the Fe³⁺-catechol groups coordination bonds endow NBR with excellent recycling ability?about 90%performance retention rate?,which is considerably distinguished from the conventional vulcanized rubber.In this paper,the effects of pre-curing time and foaming conditions on the supercritical CO₂ foaming properties of NBR were studied,and the differences in coordination crosslinked,sulfur vulcanized,and DCP vulcanized NBR were compared.Firstly,it was found that a suitable pre-curing time was the key to supercritical foaming NBR through the study of supercritical foaming performance.In addition,the effects of foaming temperature and pressure on the nitrile rubber foaming performance were studied,We can easily see that the increase of foaming pressure is beneficial to NBR foaming;and the impact of temperature on the foaming behavior is more complicated.Finally,the foaming behavior of three different vulcanized NBR was compared.The conclusion is that the density of the coordinated vulcanized foamed NBR was the smallest,and the sulfur vulcanized foamed NBR exhibited the worst overall performance.This paper also studies the effects of foaming agent decomposition characteristics,the amount of foaming agent on the chemical foaming properties of NBR and compares the differences in foaming properties of coordination crosslinked,sulfur vulcanized,and DCP vulcanized NBR.Firstly,the decomposition characteristics of different foaming agents and how were the foaming auxiliary agent and blending effect on the decomposition temperature of the AC was studied.Then,the optimal foaming agent was applied to NBR and studied the effects of amount on chemical foaming of NBR.Finally,the foaming behavior of three different vulcanization systems of NBR was compared.It was found that the density of coordinated vulcanized foamed NBR was the smallest,but DCP vulcanized foamed NBR obtained the best overall performance.