| The polylactide is a sort of green,biodegradable,environmental friendly materials.As its poor thermal stability and gas barrier properties,the thermal performance,the gas barrier properties and mechanical properties of PLA can be significantly improved by adding layered silicate additives.Therefore,for industrial application of PLA,it is vital to organically modify layered silicate in order to enhance the compatibility between the layered silicates and polyactide to produce the PLA/layered silicate nanocomposites.The unique double quaternary ammonium cations of Gemini quaternary ammonium salt surfactant may make it process stronger interaction force with the negatively charged silicate laminates,at the same time,double hydrophobic tail chain could be more compatible with the hydrophobic polymer,hence,it is quite a kind of potential organic modifier for PLA/layered silicate composites.In this paper,firstly the four alkyl amine and five brominated hydrocarbon are selected for substitution reactions,9 bifunctional Gemini quaternary ammonium surfactant were synthesized containing a coupling group with a carbon number of 2,6 and 12,the hydrophobic chain length of 8,12 and 16 carbon,followed by multi-step recrystallization purification and nuclear magnetic resonance detection.Finally it is confirmed the synthesis of the pure 9 kinds of Gemini target surface active agent.Secondly in this paper,purified Na-montmorillonite organic was modified by utilizing 9 kinds of Gemini surfactant and a series of PLA/montmorillonite nanocomposites was prepared by solution intercalation method.XRD,TG,TEM test and characterization was carried out to contrapose Gemini surfactants modified montmorillonite and PLA/montmorillonite nanocomposites,focusing on the arrangement of structure,decentralized state of different linkage groups and the hydrophobic chain Gemini surfactants to the modified montmorillonite and its PLA matrix,and thermal properties of PLA/montmorillonite nanocomposites.Studies have shown that montmorillonite interlayer spacing has increased after modified by 9 kinds of Gemini surfactant,thermal stability of PLA/montmorillonite nanocomposites is also improved comparing with pure PLA.The modified montmorillonite interlayer spacing and the thermal stability differ as Gemini surfactants of the nanocomposites are different,besides,different rules occurs according to the different spacer group and hydrophobic chain length,among which,Gemini 16-2-16-modified montmorillonite and its nanocomposites perform best.Finally,organic modification was carried out on the activated sericite by using 9 kinds of Gemini surfactant and preparation of PLA/sericite nanocomposites was also carried out by using solution intercalation method.By XRD,TG testing,interlayer spacing has increased of different Gemini surfactants modified sericite,the thermal stability of PLA/sericite nanocomposites has improved and it seems related to spacer group and hydrophobic chain length of Gemini surfactant.Among them,the PLA/Gemini 12-6-12 modified sericite and its nanocomposites show best performance. |
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