Kaolin/Rubber Nanocomposites Prepared By Co-coagulating Of Rubber Latex And Kaolin Suspensions

There are three major propblems about traditional mechanical bleding methods:fly powder,unhomogeneously blending and high energy cost.However,filler suspension and rubber latex were mixed first,and floculants were used to obtain filler/rubber masterbatch in latex co-coagulating blending methods.A series of styrene butadiene rubber?SBR?and nature rubber?NR?were prepared in this paper by latex co-coagulating methods.The effect of coagulating,modification,synchronous coagulating-modification,aspect ratio of kaolinite,intercalation and delamination of kaolinite by long chain organic molecules on appearance,vulcanization,mechanical,crosslink density,dynamic mechanical,gas barrier properties were investigated.And the results reveal as follows:?1?A series of kaolin/SBR composites were prepared by mixing rubber latex with filler aqueous suspension and then co-coagulating by the addition of HCl solution as a flocculating agent.The impact of flocculation conditions on properties of composites was studied.The essentially reason of these factors effect properties of composites was the rate of co-coagulating.When co-coagulating happened fast,the adsorption of H⁺on kaolinite decrease.As result,the aging and delay of vulcanization were weaken,the crosslink net were optimized.Thus the vulcanization,mechanical,dynamic mechanical,gas barrier properties of kaolin/SBR nanocomposites were comprehensive improved.?2?HCl,H₂SO₄,ZnCl₂,ZnSO₄,CaCl₂,FeCl₃,Fe₂?SO₄?₃,P-FeSO₄,Al₂?SO₄?₃,KAl?SO₄?₂,TiSO₄ were used respectively as flocculants in preparing SBR and NR nanocomposites by co-coagulating methods.And the mixture of kaolin suspension and SBR latex was also directly dried in oven as comparison.The experiment results showed that:the rubber prepared by directly drying method aged seriously;salts with Zn and Fe could result to serious aging of rubber composites,the antiaging agent in NR recipe could prevent aging of rubber;based on comprehensive consideration,the rank of flocutants shall be HAC<HCl<H2SO4<sulphates,the best flocculant for kaolin/SBR co-coagulating were Al₂?SO₄?₃ and KAl?SO₄?₂.?3?Amine,sulfenyl and vinyl silane were used to modify kaolin by wet method first,then the modified kaolin were introduced into SBR and NR.The effect of modification agent spices of rubber nanocomposites were investigated,and the results showed:Amine silane possess the best modification due to its aqueous solubility.When amine silane was used as modification agent,the mechanical,dynamic mechanical of SBR nanocomposites were comprehensive improved,but the curing time were extended and gas barrier properties decreased;the tensile strength,dynamic mechanical,gas barrier properties were comprehensive improved,tear strength decreased but curing time decreased as well.?4?The mixture of kaolin suspensions/rubber latexes were co-coagulated first,then the masterbaches were modified by blending method.Amin,sulfenyl and vinyl siliane were used for modification and the effects of spices were investigated.The sulfenyl silane possessed the best modification in SBR,the mechanical and dynamic mechanical properties of SBR modified by sulfenyl were comprehensive improved,but the vulcanization was delayed.The amine possess the best modification in NR,the vulcanization,tensile strength,tensile modulus,dynamic mechanical were totally improved,but the tear strength decreased.?5?Other than flocculation,at the same time,amine siliane could be absorbed on kaolin surface,achieving modification and flocculation in one-step,thus making the preparation method simpler.Compared with composites co-coagulated by KAl?SO₄?₂,SBR composite co-coagulated by amine silane possessed better tensile strength,vulcanization properties,mechanical properties,but the tensile and tear strength were not improved much.And due to the large dosage of amine silane,the crosslink density of SBR increased sharply and elongation at break decreased sharply.?6?A small amount of amine silane were used associated with KAl?SO₄?₂ to achieve prepared kaolin/rubber composites by co-coagulating.The effects of KH-550,KH-792,KH-892 on properties of composites were investigated by modification and flocculation in one-step.Compared with composites co-coagulated by KAl?SO₄?₂,composites prepared by KH-892 asocial possessed better properties except gas barrier properties.When KH-892 was used as modification agent,NR composites possessed best vulcanization,mechanical,and gas barrier properties.Best dynamic mechanical was achieved when KH-550 was used in NR composites.?7?The dosage of KH-550 in wet-modification and asocial co-coagulating,the conclusion could be made by comparing the rubber nanocomposites prepared by two methods:the modification was poor in asocial co-coagulating because of short contact time between amine silane and kaolin.There were no big difference between two kinds of SBR composites.The properties of NR prepared by associatly co-coagulating were weaker than wet-method modification.?8?A series of four kaolinite?Kaol?samples with various aspect ratios were prepared via a multi-step treatment consisting of intercalating Kaol by potassium acetate,ball-milling,de-intercalation,and classification.This method offers a facile and scalable production of Kaol with various aspect ratios for different applications.The morphology and structure of the samples were characterized by particle size analysis,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,and X-Ray diffraction?XRD?.Compared with intercalation by potassium acetate only or ball-milling only,intercalation followed by ball-milling was proved to be a much more effective method to delaminate Kaol to generate high aspect ratio samples.The results showed that the structural defects decreased with an increase of Kaol aspect ratio,which was supported by an increase of Hinckley index calculated from their XRD patterns.?9?Kaolinite with different aspect ratios were introduced into SBR nanocomposites by latex co-coagulating methods,and the effect of aspect ratio on the properties of composites were investigated.The results showed that:the key factor was the width of kaolinite platy particles.Compared with decreasing particle thickness,decreasing width could remarkable increase the amount of particles.Therefore,form Kaol-1 to Kaol-4,the tensile strength and storage module of composites decreased with the increasing width.And kaolinite particles with large width could contact each other in matrix,forming cards-houses net-work.And the resulting filler-filler rubbing could furthermore increase the loss module.?10?Organic acid?Formic acid and acetic acid?,inorganic acid?sulfuric acid?,Lewis acid?ferric chloride and aluminum chloride?were used in this paper as catalyst,to accelerate the react even without refreshing the methanol.The experiments showed that:the DLVO resulted from metal ion absorbed on the surface of kaolinite could be destroyed in acid environment,methanol molecule could get through and enter the kaolinite inner space,thus shorten the time cost.And due to the complexation between aluminum chloride and methanol,the grafting time decrease from 384 h to 0.5 h as aluminum chloride was used.?11?The XRF reveals that large amount of metal iron were adsorbed on compound surface when it was prepared by catalysis method,preventing the CTAB molecules going through the DLVO resulted from metal iron.Thus after the compounds were wash by HCl solution,the metal iron desorbed,the CTAB could be easily intercalated into methanol/kaolinite compounds prepared by catalysis method.And the catalysis intercalation method were further improved,raw kaolinite was washed by HCl first to achieve desorption of metal iron,and merged methanol grafting and CTAB intercalation into one step.CTAB was successfully intercalated into kaolinite inner space,the basal space was extended to 4.50 nm and the platy kaolinite curling into nanotube due to well delamination.?12??-aminopropyltriethoxysilane?APTES?was intercalated into the kaolinite layers basing on the wet kaolinite/methanol grafting compound as an intermediate.The APTES molecules linked to Al-O-CH₃ by hydrogen bond.The rolling from platy kaolinite into nanotube along the b-axis was observed.High dosage of APTES was found advantageous to the formation of larger basal space and the transformation of the kaolinite plate into nanotube.The basal spacing was observed in the ranges of2.36².66 nm when kaolinite/APTES intercalated compounds in toluene-wet state,and2.01².10 nm when dried into powder,indicating inhomogeneous intercalation.The XRD patterns for kaolinite/APTES intercalated compound,in which APTES was 80times of the mass of methanol in the wet kaolinite/methanol grafted compound,suggested that the molecular axis of the amine chains arranged in a bilayer was titled with respect to the methanol layers at an angle of 64°in toluene-wet state and in a monolayer angle at angle of 90°in dry-powder state.The approximate model of the new intercalate was proposed on the basis of XRD and IR data.The results confirmed the possibility of modification of the kaolinite interlayer surface with APTES at low temperatures with methanol-grafted kaolinite as intermediate.?13?Kaolinite intercalated and delaminated by CTAB and APTES were introduced into SBR by latex co-coagulating respectively,and the effect of nanotube and platy particle on the properties of composites was investigated.The experiments data showed that:compared with platy kaolinite,nanotube kaolinite processed bigger amount of particles and special areas,resulting better restricting of rubber molecule chains.Thus,composites filled with nanotube processed better mechanical properties and DMA.But due to the outside Si-O surface,of which reactive was low,the bonding of nanotube and matrix was weak.Therefore the tensile strength of composite filled by nanotube was low,and the improvement of DMA was limited.