| Poly (lactic acid)(PLA) is,a kind of high biodegradable polymer material withexcellent performance. However its poor crystallization, poor heat resistance andlarge brittleness seriously limits its application in industry. This study is trying toadopt quaternary ammonium salt modifier cetyl trimethyl ammonium bromide(CTAB), silane coupling agents KH550, KH560and chitosan (CTS) to modifyingmontmorillonite(MMT), then research the modification mechanism and preparePLA/organic MMT nanocomposites with PLA and modified montmorillonite as rawmaterials via melt intercalation. we compare the performance of several kinds ofnanocomposites, and discuss the intercalated structure formation mechanism, therelationship between inserted layer structure and the material properties which isexpected to guide the practical production.The main contents of the research are asfollows:1.The organic modification of MMT and intercalating mechanism researchWe adopted the cationic surfacant CTAB, silane coupling agent KH550, KH560and CTS to modified MMT. The results of FT-IR and XRD demonstated that CTABhas inserted MMT layers and increaed interlamellar spacing, playing a role ofintercalation modification.While KH550, KH560and CTS have only covered on thesurface of MMT, increasing the compatibility.(1)Firstly, CTAB worked separately with KH550, KH560, CTS and co-modifiedMMT to prepara second-modified MMR--TFC(KH550), TFC(KH560), TFC(CTS).Then the study researched the effect of CTAB content on modification. FT-IR andXRD showed that interlamellar spacing of TFC was lager than that of CMMT,indicating that second-modified agents have played a role of helping stretching andpart of KH550, KH560, CTS haved been into interlayer. The interlamellar spacing of1.0times CEC CTAB modifying MMT (1.0-CMMT) was larger than that of0.5timesCEC CTAB modifying MMT, and the corresponding TFC was larger as well(thesame TFC).2. Preparation and performance characterization of polylactic acid/organicmontmorillonite nanocomposites By melt intercalation, the MMT,1.0-CMMT, TFC were separately compsitedwith PLA to prepare PLA/MMT, PLA/1.0-CMMT, PLA/TFC(KH550),PLA/TFC(KH560), PLA/TFC(CTS) nanocomposites. Then we investigated theinfluence exerted by content and type on microstructure, crystallization properties andheat resistance of nanocomposites by XRD, DSC and TG.(1)XRD curves showed that PLA/1.0-CMMT, PLA/TFC nanocomposites wereall formed intercalated structure.When content of TFC increased, the intercalation gotworse.1wt%TFC(KH560)/PLA and TFC(CTS)/PLA nanicomposites were formedpartially exfoliated structure,while1wt%and3wt%TFC(KH550) were intercalatedstructure. In addation, XRD resulets sayed that the intercalation of1wt%TFC(CTS)/PLA was best in three1wt%TFC/PLA nanocomposites.(2)DSC datum indicated that Xcof TFC/PLA was higher than1.0-CMMT/PLAand Tclower under the same content of orgnaic MMT, which could control coldcrystallization better. Additionally, as the content of organic MMT increased, Xcofnanocomposites decreased gradually, and Xcmaximized when1wt%. Xcof1wt%TFC(KH550)/PLA was as high as39.23%, increasing proportion reaching6%. Thisstudy also compared crystallization performance of1wt%TFC/PLA nanocomposities,and got the conclusion that Xcall increased, but the crystallization behavior of1wt%TFC(KH550), TFC(KH560) was better in general.(3)From TG datum, we knew that unmodified MMT could promote thedegradation of PLA, while organic MMT could improve the heat resistance of PLA,declaying the degration.And the second modified MMT could enhance the heatresistance better.When the content of TFC(KH550) was3wt%, the heat resistance ofnanocomposites was best. |
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