Novol Methods For Modification Of MMT And Preparation Of Its Polymer NanoComposites

Montmorillonite (MMT) is a layered silicate mineral.With its crystal platelet being about a nanometer in thickness,MMT is a cheap natural nanomaterial.Along with the rapid development of nanomaterals, the research and application of MMT/polymer composites have become a hot topic in material science. At present, a widely used method for preparation of organic MMT is intercalation of MMT by organic alkylammonium cations, which is then used in the preparation of MMT/polymer nanocomposites.However,a great part of the domestic MMT can not meet the acquirement of this method, which limited the application of domestic MMT in field of polymer composites. Research on new methods of the modification of MMT and the preparation of MMT/polymer nanocomposites is not only theoretically meaningful but also practically valuable.In this thesis, high quality sodium MMT (Na-MMT) suspension was prepared from domestic natural MMT. Then by the monomer coordination and intercalation and the anionic surfactant precipitation-adsorption process, which were new methods proposed by us, Na-MMT was modified and MMT/polymer composites were prepared.These experimental results may provide a new approach for the development of MMT nanocomposites.The process of preparation of Na-MMT using cation exchange resin as sodium reagent, under microwave heating or water bathe heating was sysmatically studied. The optimum condition was determined by orthogonal experiment. For Na-MMT produced under microwave heating,the yield of MMT is about 80%; the cation exchange capacity(CEC) reaches 1.279 mmol/g; MMT content is 95.81%.The cation exchange resin can be recycled for more than 20 times.The crystalline structure and morphology was characterized by XRD and SEM. For the first time, using electron energy spectrum the chemical composition of the Na-MMT produced from Chaoyang, Liaoning province was determinted. It was calculated that the charge density of semi-crystal cell,ζ=0.44.the Na-MMT belongs to a transition type. The chemical formula of MMT crystal is:(Na,Ca,K)0.87 (Al,Mg,Fe,Mn)3.86 Si8.05 O20 (OH)4·nH2O.Urea was introduced into the interlayer of Ni-MMT by coordination effect. Then formaldehyde was added, and MMT/UF composites were prepared by condensation polymerization. The optimum reaction condition was determined and the properties of UF/MMT composite adhesive were examined. The XRD result of indicated that the MMT/UF composites is of a exfoliated type. Compared with that of pristine UF resin, the viscosity UF/MMT composites was increased by 2.24 times;the shelf life was increased about 30 days, the initial formaldehyde residue content is decreased and the shear strength was increased by more than 50%.Phenol was introduced into the interlayer of MMT by coordination effect of Ni2+ and phenol. Then, by in situ polymerization, phenolic resin/MMT composite was prepared. The optimum reaction condition was determined. The XRD results indicated that interlayer spacing of MMT was enlarged by the intercalation of phenolic resin. For composite containing 2% MMT, the interlayer spacing of MMT reached 2.075 run. Compared with that of pure phenolic resin, the soften point was basically unchange, adhesive strength and thermal stability of the phenolic resin/MMT composites were increasedWith an anionic surfactant precipitation-adsorption process, sodium dodecylbenzene sulfonate (SDBS) and sodium dodecylsulfate (SDS) were used as modification agents and CaCl2 as precipitation agent to modify the surface of Na-MMT layers by precipitation and adsorption. XRD results show that for SDBS modified MMT, the (001)characteristic peak of were disappeared,indicating that the layers of MMT are random dispersed,i.e. the MMT was exfoliated in the composites.For SDS modified MMT,the (001)characteristic peak was enlarged to 3.085nm, indicating that MMT was intercalated. The tensile strength of SDBS modified MMT/PP and SDS modified MMT/PP composite was increased 15.3% and 17.7%, respectively, compared with that of pristine PP.MMT was modified using transition metal cations as the precipitant agent,and anionic surfactants, sodium oleate and sodium stearate, as the modification agent. The effect of modification agent and precipitant was examined. The structure and properties of modified MMT was characterized by XRD,IR, SEM and TG. Results indicated that the modified MMT is in an intercalated state.MMT/polystyrene (PS) composite was prepared by in situ bulk polymerization with styrene monomer. Compared with that pure polystyrene, the compressive strength was increased 20.40% and 13.31%;elastic modulus was increased 11.67% and 6.24%, for 3% sodium oleate modified MMT/PS and 3% sodium stearate modified MMT/PS,respeactively.