The　effect　of　aluminium　nitrate　hydrate　(Al(NO3)3·9H2O)　on　the　crystalline,　thermal　and　mechanical　properties　of　PVA　was　studied　in　this　paper.　The　interaction　between　Al(NO3)3·9H2O　and　PVA　was　investigated　by　Fourier　transform　infrared　(FT-IR)　spectroscopy.　The　influence　of　Al(NO3)3·9H2O　on　the　crystalline,　thermal,　and　mechanical　properties　of　PVA　was　studied　by　X-ray　diffraction　(XRD),　differential　scanning　calorimetry　(DSC),　thermogravimetric　analysis　(TGA),　and　tensile　testing,　respectively.　The　results　indicated　that　Al(NO3)3·9H2O　could　form　interaction　with　the　hydroxyl　group　on　PVA　chain.　The　XRD　studies　revealed　that　the　crystallites　of　PVA　were　destroyed　by　Al(NO3)3·9H2O.　DSC　studies　showed　that　Al(NO3)3·9H2O　could　increase　the　flexibility　of　PVA　chains　and　decrease　the　Tg　of　PVA.　Tensile　testing　showed　that　after　the　addition　of　Al(NO3)3·9H2O　the　tensile　strength　of　PVA　film　decreased　and　elongation　at　break　increased.　All　these　results　show　that　Al(NO3)3·9H2O　has　a　high　plasticizing　efficiency　for　PVA.　However,　Al(NO3)3·9H2O　is　a　Lewis　acid　and　the　acidic　property　of　Al(NO3)3·9H2O　would　cause　the　significant　decrease　of　the　thermal　stability　of　PVA.　©　Smithers　Information　Ltd.,　2015.