| Polymer/layered double hydroxides nanocomposites,as a new kind of nano-composites,can combine the physicochemical properties of polymers and inorganic materials.Layered double hydroxides is difficult to disperse in polymer matrix due to it belong to anionic clay of small gallery height,high charge density and strong hydro-philicity.At present,the solution to improve the dispersion of layered double hydroxides in polymer matrix,and even the preparation of composite materials that can exert nano-effects in polymers or chemical bonding are the key to the development of polymer materials.In general,the pristine LDHs have to modified with organic anions to obtain good dispersion of LDHs in a hydrophobic polymer matrix.In this work,the organic LDHs with different modification methods was prepared by the T-type microreactors,such as modified with SDS,modified with WPU,and modified with SDS and WPU.The influence of modification modes and content of LDHs on the structure of LDHs and the mechanical properties and thermal stability of the nanocomposites were discussed,which to provide basis information for the development of polyurethane materials.The main contents and conclusions are as follows:(1)LDHs modified with sodium dodecyl sulfate were successfully prepared by co-precipitation method in aqueous using T-type microreactor.The results showed that the space of organic LDHs was increase,and its hydrophobicity also arised,and the crystal form was intact.This has great guiding significance for preparing hydrophobic hydrotalcite-like materials.The PU/SD-LDHs nanocomposites was synthesized by SD-LDHs and polyurethanes,and was mainly intercalated.The mechanical propertiesand thermal stability of the nanocomposites showed that the flexibility of the nancomposites is significantly improved by the incorporation of SD-LDHs,especially for the SD-LDHs content of 3wt%.Compared with the pure PU,the tensile strength of PU/SD-LDHs nanocomposites was increase from 38.6MPa to 43.9MPa,the growth rate was 13.7%.And the elongation at break was increase from 421% to 507%,the increase was 20.4%.Meanwhile,the thermal stability of PU/SD-LDHs nanocomposites was also improved,Td(10)increased by 16.2℃,Td(60)increased nearly12.9℃.(2)P-LDHs were successfully prepared by co-assembling between anionic aqueous polyurethane and Zn Al-LDHs using a microreactor.The PU/P-LDHs nanocomposites with different P-LDHs content were prepared by prepolymer method.The results showed that the hydrophobic properties of the surface modified P-LDHs was obviously improved,and its water contact angle can reach 100°.P-LDHs layer was exfoliated partical in the range of 1wt%-2wt%,which could play an excellent strengthening and toughening effect on the PU/P-LDHs nanocomposites.The tensile strength of PU/P-LDHs nanocomposites was increase by 33.6%.The elongation at break was increase by 20.5%.In addition,the thermal stability of the composites was also improved,Td(10)increased by 26.1℃,Td(60)increased nearly 22.2℃.(3)P@LDHs-SD were prepared by modified intercalation-surface method.Firstly,anionic waterborne polyurethane was prepared,and then co-assembled with the SD-LDHs prepared by the microreactor.The water contact angle of P@LDHs-SD can reach 105°,it was higher than that of SD-LDHs and P-LDHs.P@LDHs-SD was compounded with polyurethane in a certain proportion to obtain PU/P@LDHs-SD nanocomposites.Hydrogen bonding and the nano-effect of the layer have a positive effect on the improvement of the properties of the composite material.Mechanical properties of the nanocomposite with 3wt% of P@LDHs-SD content showed the maximal values.The tensile strength of PU/ P@LDHs-SD nanocomposites was increase from 38.6MPa to 54.72 MPa,the growth rate was 41.80%.The elongation at break was increase from 421% to 504.0%,with an increase of 19.80%.The thermal stability was improved significantly with 2wt% P@LDHs-SD content,Td(10)and Td(60)increased by 21.3℃ and 14.7℃. |
