In-situ Preparation And Film Formation Mechanism Of Guava-like PA/SiO₂Grafted Composite Latex

At presence of inorganic functional particles, the film formation of water-based compositelatex on fabric surface is a typical process in textiles functional finishing. Generally, acontrollable dispersion and arrangement of inorganic particles in its film is regarded as aneffective way to give film better functionality and fastness. However, in the traditionalwater-based composite latex film formation system which based on simple physical blending, thedispersion of inorganic particles in the resulted film always poor. It has serious impact on thequality improving of the film. In recent20years, based on the great development of in-situpolymerization technology, a series of composite particles with controllable structures andgrafted state have been successfully prepared. The application of these grafted compositeslatexes onto functional finishing has been proven to be one of the most promising ways to solvethe above problems. However, the structure formation mechanism of the composite latex film,especially the relationship between the morphology of composite latex particles and the structureof the film is still lack of systematic understanding.As a representative inorganic functional particle, nano-silica (SiO2) was modified by silanecoupling agent MPS. And then a series of aqueous dispersion and acrylate monomer dispersioncontaining SiO2with different modified degree were prepared. It was found that the MPScoupling density can effectively change the surface properties of SiO2. Under the highermodification degree, SiO2can be completely mono-dispersed in monomer phase and then in thesub-micrometer latex particles after in-situ micro-suspension polymerization. Under a moderatedegree, SiO2can play an emulsification role in the monomer/water interface layer. Thus, SiO2would be pulled into the inner of the nanometer latex particles with the graft reaction ofmonomer from SiO2surface during in-situ emulsion polymerization. Thus, a series of guava-likePA/SiO2composite latex particles with different graft states and particles size can be successfullyprepared.Then, these guava-like PA/SiO2composite latexes were used to prepare the correspondinglatex films. The film formation process and film morphology of these films were compared withthose of the traditional physical blended system. It was found that, because of a huge differencebetween SiO2and adhesive latex particles in the compatibility, polarity and infiltration, as well as the lack of an effective binding force between latex and silica, the silica tends to aggregationin a large scale during water volatilization process in the film formation system of the blendinglatex. This is one of the reasons to deteriorate the latexes films quality in the traditionalfunctional finishing. However, as far as the guava-like composite latex, the silica waspre-encapsulated inside the adhesive latex particles efficiently. The adhesive wall layer caninhibit the aggregation of silica particles and simultaneously form a continuous adhesive film.And as for the silica was modified by the coupling agent MPS, many large molecular chainscould be grafted from the silica surface. An extensive crosslinked network structure can beformed in the latex particles, taking silica as crosslinking point. Thus, even the latex particlesbeing dissolved in THF solution, its guava-like cluster structure can be still remained in such ahigh mobility system. It convincingly demonstrates that this guava-like cluster structure is athermodynamics steady system, and the efficient pre-encapsulation of functional particles byadhesive layer is an effective way to improve the dispersibility of functional particles in latexfilm.In this study, a series of guava-like PA/SiO2grafted composite latex were prepared viain-situ polymerization, and then were used to film formation. The effects of grafting state andsizes of latexes particles on the silica dispersion-aggregation state in latexes film were focused.Above that, a structure formation mechanism of the guava-like composite latexes film wasrevealed, which can be used to guide the preparation and application of composite latex intextiles functional finishing.