Preparation And Characterization Of Polymer/SiO₂ Composites Based On The Theory Of IPN

Organic/inorganic interpenetrating network(IPN) materials have extracted extensive research interests due to their unique properties.The materials combine the advantages of the inorganic materials(rigidity,high thermal stability and unique optical) and the organic polymers(flexibility,dielectric,ductility and processability), which is different with the single material and conventional composite materials. Moreover,those materials have more capability because of special IPN structure.In the thesis,several types of organic/inorganic composites were prepared using sodium silicate,TEOS as the inorganic components and cellulose,PVA and alginate as organic compounds for different purposes.The correlation between structure and the propertied for those materials was studied.1) PVA/SiO₂ Organic-inorganic Composite materials were prepared by hydrolysis and condensation of tetraethoxysilane(TEOS) in poly(vinyl alcohol)(PVA) solution. The organic phase and inorganic phase were all continouse in the IPN.The structure and morphology of the materials were investigated by infrared spectroscopy (FTIR),²⁹SiNMR and transmission electron microscopy(TEM).The thermal properties were examined by thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC).FTIR spectroscopy showed the formation of Si-O-Si bonds in the system.TEM demonstrated a homogeneous dispersion of silica in the PVA matrix when the amount of TEOS added was appropriate.DSC and TGA revealed that,compared with pure PVA materials,the composite materials exhibited a higher glass transition temperature(Tg) and high thermal stability.It showed that the adding of silica reinforced thermal stability of PVA/SiO₂ composite fibers.The SiO₂ particles changed the thermal and reduced thermal degradation behaviors.The Flammability Property of fibers were exanimed by LOI and CONE.It showed that SiO₂ can improve the flame-retardant property of fibers.2) Cellulose/SiO₂ Organic/inorganic Composite fibers were prepared by an in sol-gel method.Poly(silicic-acid) extracted from sodium silicate was used as the inorganic component and cellulose was used as an organic compound.The cellutated IPN was formed.The obtained membranes were characterized by Fourier-transform infrared spectroscopy(FTIR),Transmission electron micrograph(TEM).The results revealed that the inorganic content in the membranes varied with the amount of sodium silicate,temperature and pH of regeneration solution.The Combustion Mechanism of Cellulose/SiO₂ Composite fibers were characterized by PY-GC-MS.It showed that the inorganic in fibers decrease the levoglucosan and hydroxyacetaldehyde, accordingly decreased small flammable molecular compounds.The SiO₂ out of fibers could prevent O₂ and flammable molecular compounds.3) Alginate/SiO₂ Organic-inorganic composite fibers were prepared by an in sol-gel method using sodium silicate and TEOS as inorganic components.The cellutated IPN was formed.The structure and morphology of the fibers were investigated by FTIR and TEM.The crystallinity was examined by XRD.The FTIR spectroscopy showed the formation of Si-O-Si bonds in the system.TEM demonstrated a homogeneous dispersion of silica in the alginate matrix.The crystallinity was higher than alginate materials.The Flammability Property of fibers were exanimed by CONE.It showed that SiO2 can improve the flame-retardant property of fibers.