Preparation Of Polyacrylate/polyurethane/SiO₂ Nanocomposite Adhesives Through Miniemulsion Polymerization And Their Bonding Performance

Water-borne polyacrylate(PAcr)adhesive has the characteristics of environmental protection,low-cost and weather resistance.It is widely used in metal,ceramics,fabrics,wood,plastics and other materials in the field of bonding.But water-borne PAcr binders still have some problems,such as weak adhesive ability and poor strength of adhesive film.It is an important way to improve the comprehensive bonding properties of adhesives by the composite of polyurethane(PU)and nano-inorganic filler and PAcr with good film-forming and flexibility.However,the present research is based on simple blending and compounding.Although it can improve the properties of binder to some extent,there are still some problems such as uneven distribution of inorganic components,use of organic solvents and tedious steps.Therefore,there is an urgent need to develop a new preparation method based on water-based systems for the efficient synthesis of graft PAcr based multicomponent nano-adhesives with excellent adhesive properties.In this paper,SiO2 inorganic particles of 27�3 nm size were prepared by Stober method.And the vinyl modified SiO2(MPS-SiO2)was prepared by surface modification of Si02 with 3-(Trimethoxysilyl)propyl methacrylate(MPS).With MPS-SiO2 as inorganic particle,isooctyl acrylate(2-EHA),methacrylate(MAA)and methyl methacrylate(MMA)as vinyl monomer,isoflurone diisocyanate(IPDI),polycaprolactone diol(PCL diol)and 2-Hydroxyethyl acrylate(HEMA)were used as PU precursors to prepare PAcr/PU and PAcr/PU/SiO2 nanocomposite emulsions by one step method of fine emulsion polymerization.Dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FT-IR),mechanical properties test and differential scanning calorimetry(DSC)were used to characterize the composition,particle characteristics,adhesion and thermal properties of the adhesive.It was found that with the increase of PU content,the particle size of the binder latex increases,and the heat resistance and cross-linking degree of the film are improved in the PAcr/PU nanocomposite adhesive system.The sizing parameters such as the amount of thickener,the amount of adhesive,baking temperature and time were optimized,and the effect of polymer composition on the adhesive properties of PAcr/PU was studied under the optimum sizing conditions.The effect of polymer composition on the adhesive properties of PAcr/PU adhesive was studied.It was found that the polymer formed a cross-linking network structure and the adhesive property of the film was the best when the three components of IPDI,PCL diol and HEMA co-existed.With the content of PU precursor increasing,the density of polymer crosslinking network increased,the cohesion of adhesive film increased gradually,the shear strength and elongation at break increased first and then decreased.When the content of PU precursor is 3.96 wt%,the shear strength is 31.5 MPa,the elongation at break is 46.5%,which is 2.1 and 9.8 times of that of PAcr.And the peeling strength is 17.8 N m-1,the initial adhesion is 0.6 N.The adhesive film has both viscoelasticity and flexibility,the comprehensive bonding performance is the best.In PAcr/PU/SiO2 nano-composite adhesive system,with the increase of SiO2 content,the particle size of nano-composite adhesive increased gradually,the gel-rate gradually increased,and the storage stability of emulsion was good.The optimum sizing conditions of PAcr/PU/SiO2 nano-composite adhesive are as follows:the amount of glue is 3.0 g�m-2,the baking temperature is 100?,and the baking time is 2 min.The adhesive properties of the film were studied.The results showed that the surface active modified MPS-SiO2 could be connected to the hybrid polymer network by grafting reaction.The shear strength and elongation at break of the film were increased by 27.0%and 72.0%compared with the inert modified SiO2 system.With the increase of MPS-SiO2 content,the network structure of PAcr/PU/SiO2 polymer becomes more dense,and SiO2 is filled in the polymer chain as inorganic particles,which bears part of the stress and the cohesion of the film increases,the shear strength and elongation at break increase first and then decrease.When the content of MPS-SiO2 is 0.7wt%,the shear strength is 32.7 MPa.The elongation at break that increases 8.7%and 20.0%on the basic of PAcr/PU binder is 55.6%.The peel strength is 18.6 N�m-1,and the initial tack is 0.59 N.In this paper,a one-step method for the preparation of PAcr/PU and PAcr/PU/SiO2 nanocomposite adhesive latex by micro-emulsion polymerization was proposed.The method solves the problem of tedious synthesis of PU prepolymer and uneven dispersion of inorganic components.The corresponding relationship between the synthetic parameters and the adhesive properties of the film was clarified.On the basis of ensuring the adhesive property of the film,the cohesion of the film was improved,and the excellent comprehensive adhesive property was obtained.The results of this paper have important reference value for the design,preparation and improvement of properties of new nano-composite binders.