Interfacial Manipulation And Performance Of Rubber Composites Filled With Boehmite Or Silica

Motivated by the development of technology and science,and the increasing concern on environmental protection and energy saving,higher requirements are put forward to rubber materials.Due to the high reinforcing efficiency and functions possessed by nanofillers,rubber nanocomposites have drawn extensive interests in both industrial and academic communities.The reinforcement and functionality of rubber nanocomposites are closely related to the interface property.However,the interfacial strength of rubber composites is supposed to be weak due to the incompatibility between diene-based rubber matrix and inorganic filler.The preparation of rubber composites with high performance and functions by interface manipulation is fundementally significant as well as practically feasible.Strong interface in rubber composites facilitates the dispersion of fillers with high aspect ratio,and simultaneously reduces the permeability of interfacial region,resulting in improved gas barrier performance of rubber composites.Manipulating the interface property between rubber matrix and silica,the main fillers used in “Green Tire”,is one of important technical approachs to improve the dynamic performance of “Green Tire”(the combination of reduced rolling resistance and improved wet-traction).Based on the above-mentioned background,in the present dissertation,the research was carried out on two typical systems,the rubber/boehmite nanoplates(BM)composite and rubber/silica composite.The interfacial crosslinking in rubber/BM composite is achieved by in-situ interface modification,leading to improved gas barrier property.In rubber/silica composite,the manipulation and optimization of interface is realized by controlling the surface chemistry of silica,which offering new avenue for achieving trade-off between wet-traction and rolling-resistance in tread rubbers.The main contents of the present dissertation are as follows:(1)Based on the reactivity of the surface aluminol groups of BM,tannic acid(TA)and phosphate esters are investigated as in-situ interfacial modifiers for styrene-butadiene rubber(SBR)/BM nanocomposites.TA can be chemisorbed onto BM surface through the coordination interaction between them,and the ortho-quinone groups of adsorbed TA can further react with polythiyl radicals during vulcanization,thus constructing strengthened interface between BM and rubber;phosphate esters with unsaturated alkyl groups can modify BM through the condensation between the P-OH groups and the aluminol groups on BM,and simultaneously take part in rubber vulcanization to promote interfacial crosslinking.The effects of the interfacial strengths on the ultimate performance of rubber composites were fully studied.The interfacial strength of rubber/BM composites could be optimized through molecular design of phosphate esters,which contributes to the preparation of rubber composites with improved gas barrier performance.(2)A series of modified silica with controlled surface property were prepared by the modification of methyl trimethoxy silane(MTMS),and the effects of the subtle change of surface property on the dispersivity,the interfacial interactions and the ultimate performance of rubber composites were fully investigated.It is verified that the decreased surface energy of silica significantly improves the dispersion of silica in rubber matrix,which is in accordance with the prediction of thermodynamic equation.The improved dispersion of silica contributes to increasing the fraction of interphase in presence of the silane,which is interpreted by the improved accessible surfaces for silanization.Due to the improved dispersion and interfacial interaction,improved mechanical property and balanced dynamic performacne are concurrently observed in modified composites.(3)The modification of silica by polymethyl hydrosiloxane(PMHS)was conducted via an efficient and fast tris(pentafluorophenyl)borane-catalyzed functionalization.A highly hydrophobic surface with uncompromised reactivity is observed in the modified silica.It is revealed that such PMHS modification can not only improve the dispersibility of silica by lowering the surface energy,but also enhance the interfacial interaction in virtue of the reactivity of the residual Si-H bonds.With a PMHS grafting content as low as 1.5 wt%,the modified composite exhibits tremendous improvements in mechanical properties(116% increase in modulus)and dynamic performances(116% increase in wet-skid resistance and 26% reduction in rolling resistance).Considering the superior overall performance of the modified rubber composites,together with the simplicity and rapidity of the modification process,we envision that the hydrosilane-modified silica has great potential in the fabrication of high-performance polymer composites such as energy-saving tire treads.