Fabrication And Properties Of Epoxy Composites Reinforced Using Hierarchical PANI@NiPS Hybrids

Epoxy resin（EP）is a widely used thermosetting resin due to its excellent comprehensive properties.However,its high crosslinking density and tendency to crack and become brittle have limited its application in high-performance friction materials due to poor wear resistance.To address this issue,researchers both domestically and abroad have made significant efforts to enhance the anti-wear ability of EP.One particularly promising approach involves introducing stiff inorganic fillers,which typically requires additional surface treatment to improve filler-resin interfacial compatibility.Polyaniline（PANI）,an organic polymer characterized by rigid organic chains,is naturally compatible with EP due to the well-known like dissolves like principle.It is expected that PANI will be uniformly dispersed in the EP matrix,contributing significantly to the reinforcement effect.In addition,inorganic nanosheets of nickel phyllosilicate（NiPS）are introduced to in-situ decorate the surface of PANI,constructing an organic-inorganic hierarchical structure of PANI@NiPS hybrid.The effects of PANI@NiPS addition on the mechanical and tribological properties of EP composites are investigated,while careful attention is paid to the curing process and curing reaction kinetics.Some useful conclusions are obtained as follows:（1）To synthesize PANI nanorods for use in EP composites,a direct mixing route was employed using aniline and phytic acid as raw materials.The resulting nanorods had an average diameter of approximately 60 nm and a length-diameter ratio of 5～10.Various measurements were conducted to examine the phase structure,chemical composition,and morphology of the as-synthesized PANI nanorods,and good dispersibility in the EP matrix was confirmed.Mechanical analysis revealed that the introduction of PANI steadily increased the elastic modulus and hardness,while decreasing the elongation at break of EP composites.With increasing PANI content,the tensile strength first increased and then decreased,reaching a maximum value of 110.33MPa when PANI content was added up to 5%,which was approximately 43%higher than that of pure EP.The tribological performance of the EP composites showed that although the presence of PANI slightly increased the average friction coefficient throughout the friction process,it greatly enhanced the anti-wear ability of the material.When the PANI content reached 5%,the wear rate of the EP composite was found to be the lowest,at 2.12×10^-5 mm³/Nm,which was significantly decreased by about 70%compared to that of pure resin.（2）To furhter improve the wear resistance of EP composites,abundant inorganic NiPS nanosheets were introduced via a deposition-precipitation method to decorate the surface of PANI nanorods based on the idea of organic-inorganic integration.This resulted in the successful construction of a hierarchical PANI@NiPS hybrid with a Setaria-Viridis-like morphological structure.The research showed that PANI@NiPS had a very rough surface and could disperse uniformly in the matrix with good interface bonding between the EP and the hybrid.The introduction of PANI@NiPS effectively enhanced the strength and stiffness,including tensile strength,elastic modulus,and hardness,while the toughness,as evidenced by the elongation at break of EP composites,was reduced as expected.As the PANI@NiPS content increased from 1%up to 7%,the average friction coefficient of EP composites increased slightly.However,the wear rate showed an anti-parabolic curve,with the lowest value of 1.46×10^-5 mm³/Nm obtained at a PANI@NiPS content of 5%.This represented a remarkable reduction of up to 80%compared with pure EP,which was obviously better than the improvement on the anti-wear ability derived from the PANI with an equivalent mass fraction.These experimental results provided new ideas for the preparation of high-performance composite materials as well as a strong support for the application research of organic-inorganic hybrid nanomaterials.（3）To better understand the curing process of EP composites,differential scanning calorimetry was used to test the influence of added PANI@NiPS on the curing features of the amine-epoxy system.In addition,the kinetics of the curing reaction were analyzed in detail using several mathematical models,including Kissinger,Starink,and Friedman equations.The calculated results showed that PANI@NiPS had the ability to promote the curing process of the amine-epoxy system,decreasing the peak temperature and increasing the enthalpy of curing for all composite samples.As the PANI@NiPS content increased,the activation energy of the curing reaction decreased first and then increased slightly according to both Kissinger and Starink methods,reaching the lowest value of 49.1 k J/mol based on the Starink equation at a concentration of 5%PANI@NiPS.This represented a 5.6%reduction in activation energy compared to the pristine system,indicating that the energy barrier during the entire curing process of the amine-epoxy system could be suppressed to some extent.Further analysis confirmed that the reaction order for the cured amine-epoxy system remained unchanged,implying that the entire curing process for all investigated samples presented the same first-order reaction mode.Finally,the curing kinetic equations of pure EP and the composites were mathematically fitted using a self-catalytic Sesták-Berggren model.The fitting results were well validated by comparing them with the experimental values using the applied theoretical equation.These results deeply reveal the influence of PANI@NiPS on the curing process on the amine-epoxy system,providing a useful reference for optimizing the preparation of composite materials.Figure 38 Table 6 Reference 213...