Silica Modified Acrylic Miniemulsion And Its Membrane Properties

Acrylate miniemulsion contains no volatile organic compound,and hence has no contribution to environmental pollution.Its film exhibits excellent transparency,film-forming,and adhesion properties,etc.Therefore,it has been widely used in various industrial fields,such as construction,textile processing,leather industry,and so on.However,conventional acrylate miniemulsion cannot meet the strict requirements in some special fields because of its poor performance in water resistance,thermal stability,and abrasive resistance.Inorganic silica has lots of excellent properties including good thermal stability,good mechanical behavior,and good wear resistance,etc.Thus,silica is an ideal candidate as a reinforcement material for polymer.In this paper,hybrid silica-acrylate miniemulsion is synthesized by miniemulsion polymerization.The miniemulsion film is characterized by Scanning Electron Microscope(SEM).The results show that silica particles are uniformly dispersed in the matrix.The influence of silica on water resistance of the miniemulsion film is investigated by systematically changing silica amount in the miniemulsion.The experimental results show that the water resistance is improved with the increasing amount of silica.While the amount of silica in the miniemulsion reaches 3wt%,the water absorption is reduced by 40%.But the water absorption almost remains unchanged as the silica amount increases to 5wt%.The silica particles are further modified by 3-(trimethoxysilyl)propyl methacrylate(TMSPM),and then the modified silica particles are added into the acrylate miniemulsion.The C=C bonds on the surface of the modified silica particle reacted with C=C bonds of acrylate monomers in the miniemulsion.The modified-silica particles can act as crosslinking agents between polymers.As a result,the water resistance of film is improved after the addition of the modified silica.The mechanical property of miniemulsion film is tested by a series of tensile experiments.The results indicate that the tensile strength increases as the amount of silica increases.When silica amount reaches 5wt%,the tensile strength of the emulsion film is improved by 40%.Silica particles in the film can prevent craze propagation during tensile test.Meanwhile,silica particles can improve cross-linking degree of polymer and form an inorganic-organic hybrid film.As a consequence,the hybrid film has better mechanical property.Furthermore,two kinds of emulsion films are prepared to study the effect of organic-inorganic interactions on abrasive resistance.In the first kind of emulsion films,silica particles and polymers are linked by C-Si bonds,and the silica particles are homogeneously distributed in the films.These films have smooth surfaces,and external load can be efficiently transferred to polymer matrix.However,in the second kind of emulsion films,silica particles and organic matrix are only linked via intermolecular interactions either Van de Waals interaction or hydrogen bond.These films have rougher surfaces,and the silica particles within the films tend to aggregate.Wear tests shows that the silica particles in these filmsare easily abraded away,and pits are left on the surface as a result of the weak interactions between the inorganic particles and the polymer matrix.The results that the organic-inorganic interactions play a very important role in load transfer in films,and stronger interfacial interactions between inorganic particles and polymer matrix leads to a more homogeneous material and excellent mechanical properties.