| Coordination crosslinking rubber is an alternative approach for comprehensive recovery of wasted rubber due to its reversible crosslinking feature.Unfortunately,the disadvantages of the coordination crosslinking rubber,such as large dosage and poor dispersion of metal salt in system,low ageing resistance,and poor restro-crosslinking ability,etc.,extremely limites its application.In this paper,based on our previous experimental,NBR was selected as a matrix,Al2(SO4)3·18H2O was employed as a coordination crosslinking agent,and organic acid or organic acid salt(O)was introduced to construct a microenvironment for dissociation of aluminum salt in the NBR/Al2(SO4)3·18H2O/O system.The influence of organic acid on the coordination crosslinking behavior of the NBR/Al2(SO4)3·18H2O/O system was discussed,the ageing resistance and dissociation coordination crosslinking of the constructed system were also studied.The results are given as follows:Firstly,methyl acrylic,stearic acid and stearic acid aluminum were selected to prepare NBR/Al2(SO4)3·18H2O/O system The roles of various organic moleculars for dissociation of Al2(SO4)3·18H2O in a limited space without desolving or melting techniques were investigated.The dynamics of coordination crosslinking reaction,the crosslinking net structure and the mechanic properties of the system were studied to conclude the relationship of structure and properties.The results show that,methyl acrylic plays the most significant role in NBR/Al2(SO4)3·18H2O/O system,which greatly enhances the reaction rate and torque values of coordination crosslinking reaction.Meanwhile the effect of stearic acid aluminmum proves to be the weakest followed by stearic acid.By adding an organic acid small molecule as a dispersant,on the one hand,the degree of dispersion of Al2(SO4)3·18H2O in NBR matrix is improved by the"coupling" effect of organic acids;on the other hand,The dissociation of Al2(SO4)3·18H2O in the microphase water is enhanced by the weak acid action of the organic acid.It is suggested that,the greater the acidity,the more favorable the ionization of Al2(SO4)3·18H2O in the confined space,which would further improve the coordination crosslinking efficiency and crosslinking density,and reduce the amount of A12(SO4)3·18H2O.Secondly,The ageing behavior of NBR/Al2(SO4)3·18H2O/O-SiO2 was investigated.The ageing behavior of the coordination crosslinking system was investigated.The results show that,the resultant system gives an excellent oil resistance,which meets the claims of the oil proof production standard.Reducing the dosage of Al2(SO4)3·18H2O cuases to enhancing the thermal ageing performance.It is also clear that the introduction of methacrylic acid and stearic acid in the system results in the enhancement of mechanical properties with decreasing of its ageing resistance property.Finally,mixed solvents were prepared with organic solvents and water to construct an environment for dissociation of the NBR/Al2(SO4)3·1842O system.The effects of organic solvent,temperature and the coordination crosslinking number on the dessociaton performance of the system were investigated.The results show that,the coordingtion crosslinking system desociates in buta none-water mixed solvent,partly crosslinks in heptyl ketone-water,whereas almost gives no change in ethylene glycol butyl ether-water mixed solution.It is suggested that,the coordination crosslinking system is firstly swelled by butanone.The widened gap between chains of polymer allows water molecular contacting with alumimum and taking the place of-C≡N group to forma new coordinate bond.As a result,the coordinate bond between alumimum ion and-C≡N is destroyed and the dissociation of the system occurs. |
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