Preparation And Properties Of Organ-modified Layered Double Hydroxides/Polyolefin Nanocomposites

Layered double hydroxides(LDHs),as a new kind of inorganic layered material,can be used as adsorbents,insulators because of the controllability of layers and anionic exchanging.Polymer/LDHs nanocomposites have attracted widely research attention owing to the superior properties compared to conventional composites.Polyolefin materials have been widely used in many fields,like agricultural,packaging,medical,appliances due to their low cost,excellent mechanical properties,and insulation properties.In our work,polyolefin/OM-LDH nanocomposites were synthesized by adding different loadings of OM-LDH.The MgAl-LDH was organically modified by using potassium monolauryl phosphate(MAPK)as an intercalator to improve the compatibility between the matrix and filler.The structure and property of organo-modified layered double hydroxide(OM-LDH)were characterized through Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction techniques(XRD),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA).Then the HDPE/OM-LDH,HDPE/EVA/OM-LDH,LDPE/EVA/OM-LDH nanocomposites were prepared by melt mixing of polyethylene and OM-LDH where EVA was used as compatibilizer.The structure and micro-morphology of the nanocomposites were studied using FTIR,XRD and SEM.The thermal properties and mechanical properties were investigated using TGA,differential scanning calorimetry(DSC)and tensile testing.The main conclusions are as follows:(1)After organo-modified by MAPK,the basal space was increased from 0.74 nm to 1.64 nm and the OM-LDH had a good crystalline-layered structure.The interlayer spacing was enlarged so that polymer segments could intercalate into the interlayer galleries.The OM-LDH presented a rough surface and irregular crystal size compared to LDH.The results of FTIR,XRD and SEM confirmed that the organo-modified LDH has been prepared successfully.The TGA results suggested that the OM-LDH was hydrophobic and the organic groups reduced the thermal stability of hydrotalcite.(2)The HDPE/OM-LDH nanocomposites were prepared via direct melt intercalation.XRD results indicated that the OM-LDH was delaminated when the addition of OM-LDH was lower than 6 wt%.While the intercalated structure was formed when 8 wt%OM-LDH was added.SEM results confirmed that the organo-modification enhanced the binding force between OM-LDH and matrix.The DSC revealed that OM-LDH played a better heterogeneous nucleation effect and the crystallinity increased obviously compared with LDH.But the addition of OM-LDH catalyzed the thermal degradation of HDPE.(3)In order to improve the miscibility of HDPE and OM-LDH,the HDPE/EVA/OM-LDH nanocomposites were prepared using EVA as a compatibilizer.The exfoliated structure was formed when OM-LDH content is low.The SEM results reflected that the compatibility between HDPE and OM-LDH was improved with the addition of EVA which would be helpful to enhance the properties of HDPE.The crystallization behavior of HDPE was facilitated by OM-LDH and HDPE/EVA/OM-LDH nanocomposite showed a better thermal stability than that of LDPE/EVA and HDPE/EVA/LDH at high temperatures.HDPE/EVA/OM-LDH nanocomposite with 4 wt%OM-LDH formed exfoliated structure and acquired the most optimul thermal stability.(4)In order to research the influence of OM-LDH on different kinds of polyolefin,LDPE/EVA/OM-LDH nanocomposites were prepared where EVA was used as a compatibilizer.The intercalated structure was formed due to the branched chain of LDPE which hindered the movement of polymer chain.The organic modification enhanced the compatibility between substrate and filler.The incorporation of OM-LDH increased the crystallinity of LDPE.However,only LDPE/EVA/OM-LDH(6wt%)showed a better thermal stability than LDPE/EVA at a higher temperature.All in all,LDPE/EVA/OM-LDH(6wt%)obtained the optimal crystallinity and thermal stability.