Preparation And Properties Of Rigid Polyurethane Foam/layered Silicate Composites

Polyurethane foams are versatile polymeric materials.They have desirable properties such as low density,high specific strength and low thermal conductivity,as structural material,Rigid Polyurethane(PU) Foam still have some disadvantages,It is short of the needs for using in many special conditions because of its inferior mechanical strength.It needs adding some reforcing fillers into polyurethane matrix in order to solve the problems.So it is a hot attention focused on the study of reinforced PU foam.Montmorillonite(MMT) is a layed silicate and consists of two external silica tetrahedral sheets and a central octahedral sheet of alumina.Isomorphic substitution of Al³⁺ for Mg²⁺or for Fe²⁺with the layers generate negative charges that are counterbalanced by cations such as Na⁺ and Ca²⁺ situated in the gallery.Rectorite(REC),with exchangeable hydrated cations between galleries and the d-space about 2nm,is a kind of natural clay and can be represented by regular (1:1)stacking of mica-like and montmorillonite-like layers.polymer-layered silicate nanocomposites have recently gained a great deal of attention.they used widely to prepare polymer-clay nano-composites.this paper used isocyanate and polyol as stuff to prepare PU foam via one-step process.this study added some different type of montmorillonite(MMT) and rectorite(REC) as reinforced materials to prepare different reinforced foams.the main conclusions list below:(1) Three kinds of MMT,alkyl quaternary ammonium salt treated MMT(CTAB-MMT),MMT with -OH(DK2) and MMT with -NH₂(DK5),as reinforced materials reinforced PU foams.The structure of composites are investigated on X-ray diffraction(XRD),it is founded that,CTAB-MMT are mainly intercalated in PU matrix,but DK2 and DK5 are mainly exfoliated in PU matrix.From SEM,it is founded that MMT can effectively reduce the cell size. the cell size of exfoliated PU composites is smaller than that of intercalated PU composites.General mechanical properties of composites achieved the optimal value as the MMT content at 2%based on the polyol.The mechanical properties of exfoliated PU composites are better than that of intercalated PU composites.In addition,the addition of OMMT gives an increase of the thermal stability. (2) the organic rectorite was synthesized through cation exchange reaction with two kinds of quaternary ammonium salt.REC/PU composites materials were prepared via in-situ polymerization.The structure of composites were investigated on X-ray diffraction(XRD),it is founded that,REC/PU are mainly exfoliated in PU matrix. The mechanical properties of REC/PU composites are much better than pure PU. the addition of REC gives an increase of the thermal stability of composites.