Preparation And Properties Of Silicone/Montmorillonite Nanocomposites By In-situ Intercalative

Silicone shows many excellent properties,such as high temperature resistance, weatherability,hydrophobic property and electrical insulation,but with poor solvent resistance and mechanical properties.Polymer/clay nanocomposites can solve these problems.In the present research,to improve the silicone properties of high temperature resistance,barrier performance and mechanical properties,silicone was modified with organo-montmorillonite(OMMT) by in-situ intercalative polymerization.Cetyltrimethylammonium bromide(CTBA) was firstly intercalated into layers of Na-MMT by cation exchange to prepare OMMT.Using Bragg's law,the d-placing of MMT and OMMT layers was calculated according to X-ray diffraction(XRD) analyses.The results show that CTBA was intercalated into MMT layers since the d-placing of MMT layers increased after CTBA intercalating.Using ultrasonic technology,phenylmethylsilicone/OMMT nanocomposites were prepared by in-situ intercalative polymeriztion.The internal structure and morphology of the nanocomposites were characterized by XRD,scan electron microscope(SEM) and transmission electron microscope(TEM).The effect of time for ultrasonic processing on the dispersing of MMT lamellar was also studied.The results show that the basal spacing of OMMT increased with the increasing of ultrasonic time.When the ultrasonic time is less than 20minutes,the OMMT lamellars exist orderly in nanocomposites,resulting in polymer/OMMT intercalated nanocomposites.However,when the ultrasonic time is over 30minutes,the OMMT lamellars exist disorderly in nanocomposites and most of layers were dispersed in nanosize,leading to the formation of polymer/OMMT exfoliated nanocomposites.The ultrasonic time,15min and 30min were selected to prepare intercalated and exfoliated phenylmethylsilicone/OMMT nanocomposites,respectively.The internal structure and morphology of the nanocomposites were characterized by XRD,TEM and SEM.Mechanical properties,high temperature resistance and barrier performance for gas and water were also studied.The results show that molecules of silicone chains inserted into the layer of montmorilonite(MMT),and successfully prepared the intercalation and exfoliation phenylmethylsilicone/OMMT nanocomposites.The barrier properties and mechanical properties of the composite are markedly improved by adding organo-montmoriUonite.The temperature resistance of pure silicone is poor since the thermal weight loss is more than 25%at 500℃.The silicone/OMMT nanocomposites which containing 8%OMMT have excellent high temperature resistance,the thermal weight losses of intercalated and exfoliated nanocomposites are 22.5%and 23.5%at 700℃,respectively.The barrier property for water decreases with the increasing of OMMT content.The water absorption rate of intercalated and exfoliated nanocomposites which containing 4wt%OMMT are 0.7687%and 2.802%, respectively,which is 10 and 3 times less than that of pure silicone.The barrier property of intercalated nanocomposite is better than that of exfoliated nanocomposite. The nanocomposite which containing 6wt%OMMT,has better mechanical performance.The impact strengthes of intercalated and exfoliated nanocomposites are 1.5932kJ/m~2 and 1.6957kJ/m~2,respectively,which is enhanced 7.45%and 14.4% more than that of pure silicone.The tension strengthes of intercalated and exfoliated nanocomposites are 7.021MPa and 6.264MPa,respectively,which is 5 times more than that of pure silicone.When the nanocomposites contain 4wt%OMMT,the compression strengthes of intercalated and exfoliated nanocomposites are 10.232 MPa and 11.503 MPa,respectively,which is 4 times more than that of pure silicone.When the nanocomposite contains 10wt%OMMT,the hardnesses of intercalated and exfoliated nanocomposites are 95.7 and 92.4,respectively,which is 1.5 times more than that of pure silicone.These results illuminare that the mechanical properties of exfoliated nanocomposites are better than those of intercalated nanocomposites, however,the barrier performance of intercalated nanocomposites is better than that of exfoliated nanocomposites.