Synthesis And Properties Of WPU/Montmorillonite Nanocomposite Dispersion

Waterborne polyurethane(WPU)are used in various fields,such as coatings,inks and adhesives,and so forth,due to many excellent features with non-pollution,high molecular weight and low viscosity of it.Mechanical,water resistance and gas barrier properties of WPU,however,are generally inferior to those of conventional solvent-borne polyurethanes,which limit the application of WPU in the field of high performance materials.For addressing the above issues with the WPU,this paper combined the surface and interlayer chemical properties of montmorillonite(MMT)with the synthetic chemistry of WPU,to preparation of WPU/montmorillonite nanocomposite dispersion.The main research work is as follows:1.Waterborne polyurethane(WPU)dispersion,based on isophorone diisocyanate(IPDI)or 4,4'-dicyclohexylmethane diisocyanate(HMDI)as hard segment,Polycarbonate diol(PCD)or tetrahydrofuran diol(PTMG)as soft segment,dimethylolpropionic acid(DMPA)as ionic center,and 1,4-butandiol as chain extender,were synthesized with different soft and hard segment structures.The effects of different soft and hard segment structures on WPU performance were discussed.The results showed that WPU with HMDI as the hard segment and PTMG as the soft segment has high performancewith a tensile strength of 54.6 MPa and a water absorption of 14.6%.2.WPU/PEA-MMT nanocomposite dispersions were synthesized by combined WPU with MMT organically modified with polyetheramine(PEA).The effects of different PEA-MMT additions on the particle size and dispersibility of WPU/PEA-MMT nanocomposite dispersions,as well as the effects on the morphology,mechanical properties,water resistance,thermal stability and moisture barrier properties of nanocomposite films were investigated.Particle size analysis showed PEA-MMT could be stably dispersed in WPU.SEM analysis confirmed that PEA-MMT was homogeneously dispersed in the nanocomposite film and had an intercalation structure.Compared with pure WPU,tensile testing displayed that tensile strength and Young's modulus of WPU/PEA-MMT reached to 81.0 MPa and 689.3 MPa,respectively,with the addition of 3 wt% PEA-MMT.Water resistance and water vapor barrier of composite were greatly improved by a synergistic effect of layering structure of montmorillonite and the excellent interfacial interaction between PEA-MMTA nanosheets and WPU.When the mass fraction of PEA-MMT rose up to 5 wt%,water absorption decreased to 2.8% and water vapor transmission rate decreased by 39.3%.3.Aliphatic diamine sulphonate(A95)as a modifier to modify montmorillonite.The WPU/A95-MMT nanocomposite dispersions were prepared by combining A95-MMT with WPU.Compared with PEA-MMT,A95 modified MMT can be used to prepare WPU/montmorillonite nanocomposite dispersions with montmorillonite content up to 30 wt% and good dispersion stability.TEM,DLS,XRD,FT-IR,TGA,AFM,SEM,DMA,tensile test,water absorption,water vapor transmission rate,and oxygen barrier tests were used to analysis the structure and performance of nanocomposite emulsions,films and coatings.Research indicated that the addition of 5 wt% A95-MMT gived nanocomposite film the best overall performance.The tensile strength,Young's modulus and water absorption of WPU/A95-MMT-5 wt% nanocomposite film were 80.6 MPa,612.3 MPa and 3.1%,respectively.The nanocomposite dispersion with 30 wt% A95-MMT content still maintained good stability,while the MMT sheet was arranged in a regular layer in the nanocomposite film,and the water vapor transmission rate and oxygen transmission rate of WPU were respectively reduced 92.8% and 64.7%,as a significant property,high optical transparency was also observed.This study provides a new way to solve the dispersion,stripping and compatibility of MMT in WPU.WPU/montmorillonite nanocomposite were synthesized by combined WPU with MMT which was organically modified with PEA or A95.The prepared WPU/montmorillonite nanocomposite dispersion can be used as an environmentally-friendly adhesive and coating product in high-end markets such as food,medicine and solar battery backplane composite film packaging,which have high requirements on mechanics,water resistance and barrier properties.