Study On The Preparation, Struction And Properties Of PET/Montmorillonte Nanocomposites

Poly(ethylene terephthalate)(PET) is a thermoplastic with many excellent physical. However, the disadvantages such as low rate of crystallization, low thermal distortion temperature and low modulus have limited its application as an engineering plastic. PET/MMT nanocomposites with intercalated/exfoliated nano-structure can be prepared by adding a small amount montmorillonite (MMT) to PET matrix. Compared with the pristine PET, PET/MMT nanocomposites have remarkable improvements in crystallization rate, mechanical property, thermal stability, gas barrier property and flame retardancy. Therefore, more and more attentions are focus on this field.Three organo-modified MMT(OMMT) were prepared, and the impact of the intercalation agents and preparation processing on OMMT was studied. PET/MMT nanocomposites with intercalated and exfoliated nano-structure are prepared by melt intercalation. And the impact of the types and contents of modified MMT on the structure and properties of composite materials was studied. The main work is as follow:1,OMMT were organo-modified by intercalation agents of hexadecyltrimethyl ammonium bromide (CTAB), polyethylene glycol(PEG)and both of them; FT-IR showed OMMT included the intercalation agent; Wide-angle X-ray diffraction showed the interlayer spacing of MMT increased from 1.5nm to 2.22nm; TG showed CTAB-PEG-MMT had the best thermal stability all of OMMT.2,Study on the optimization process of CTAB-MMT showed that the biggest affect factor of the layer spacing of MMT was the ratio between the molar mass of CTAB and the exchange capacity ratio(CEC) of MMT, but stirring rate and temperature range in my study had little effect on it.3,A series of PET/MMT nanocomposites were prepared by melt intercalation. Wide-angle X-ray diffraction showed PET/OMMT obtained intercalated'and agglomerate nano-structure, PET-MMT compounding MMT and PET obtained exfoliated nano-structure. 4,Study on flow property of PET/MMT showed flow property of PET-MMT was worst all of PET/MMT, because of its exfoliated nano-structure.As the content of MMT increased, the exfoliated nano-structure of PET-MMT gradually blocked flow of PET, and the plasticization of CTAB in PET-CTAB-MMT system gradually made the flow property better, but the flow property of PET-MMT and PET-CTAB-MMT was poor than pristine PET.Only PET/MMT containing 8%of CTAB-PEG-MMT had a good flow property than pristine PET, because of the good compatibility between PEG and PET.5,TGA showed that all of composite materials, only PET/MMT contenting 4% CTAB-PEG-MMT had better thermal stability than pure PET, because of a strong hydrogen bonding between PEG and PET.6,PET/MMT of crystallinity property was studied by DSC and POM. The result showed PET/MMT nanocomposites had a higher level of crystallization rate than pristine PET,because MMT behaved as a nucleating agent and nucleated the PET crystallization process. PET-MMT had a highest level of crystallization property because of its exfoliated nano-structure. As the content of MMT increased, the crystallinity rate of PET-CTAB-PEG-MMT became quick, while that of the others became slow. This related to the compatibility between PEG and PET.