This research has investigated nanocomposite based masterbatches as routes to improve the CO2 retention properties of PET bottles. Masterbatches of different types of polyamide/clay, PET/clay, PET/nano-silica flakes and PET/divalent layered metal phosphonates (DLMP) were produced by melt compounding and evaluated. In the case of polyamide based nanocomposites PA6 was found to produce the best dispersed nanocomposites followed by PA-MXD6, PA-6I/6T and PA-6-3-T. It was concluded from the results that surfactant/polymer compatibility and thermal stability play some role, but the most significant factor in effecting good dispersion was the polarity of the polymer and its ability to directly interact with the clay surface. The CO2 retention of PET/PA blends showed MXD6 to offer by far the greatest improvement (100% increase) but the use of PA-MXD6 nanocomposite did not result in further improvement. It was concluded that transfer of exfoliated clay platelets from the PA phase to the PET phase had not occurred. In order to address this issue and disperse the filler effectively through both polymer matrices several novel new processes were developed and the use of a catalyst was investigated. Overall, the novel PET/MXD6/clay blends had reduced CO2 retention compared to the direct PET/MXD6 blend due to significant degradation of the polymers in the extrusion stage prior to bottle manufacture. Nanocomposites produced by direct melt mixing of PET and organoclay were always intercalated in nature (with the exception of C30B and hexadecyl pyridinium surfactant where the layered structure collapsed due to degradation of the surfactant). A consistent interlayer spacing of ~3.15-3.25nm was observed for all these materials and it was concluded that a stable PET crystal structure had formed as the distance between layers corresponds to three repeats of the c dimension of the crystal unit cell. It is proposed that the stable equilibrium forms due to insufficient direct interaction between the polymer and the clay surface. Despite relatively poor dispersion modest improvements in CO2 barrier were achieved (up to 25%). The use of novel nano-silica flakes resulted in improved CO2 retention, particularly with the 100nm thickness grade (30% improvement) despite considerable breakage of the nano-silica flakes during melt compounding. In the case of DLMP the dispersion of the fillers was found to be poor and no improvement in CO2 barrier was obtained. It was also observed that all the fillers applied acted as nucleating agents for polymer crystallisation in the polymer systems to which they were applied.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:511434 |
| Date | January 2008 |
| Creators | Moloney, Steven John |
| Publisher | Nottingham Trent University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://irep.ntu.ac.uk/id/eprint/222/ |
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