Study On The Preparation Of Flame-retardant Nanocomposite Copolyester And Its Fiber

Poly?ethylene terephthalate??PET? is one kind of polymer material with high strength, high modulus, good heat resistance and shape preservation, etc. It is used widely in the fields of fibers and plastics. Polyester fiber is also a kind of synthetic fiber with the biggest yield and widest use among all the synthetic fibers now. However, due to its low LOI, its widespread application has brought a big hidden trouble to the safety of people's lives and property. Therefore, PET modified with fire-retardant has been the topic for recent years, and it is very important to the development of polyester industry. In this article, a series of phosphorus-containing copolyester?PET-co-CEPPA? were prepared by copolymerization method with the raw materials of terephthalic acid?PTA?, ethylene glycol?EG? and CEPPA-EG which had been pre-synthesized from 2-carboxyl ethyl?phenyl? phosphinic acid?CEPPA? and ethylene glycol?EG?. A series of phosphorus-containing copolyester/organic montmorillonite?PET-co-CEPPA/MMT? nanocomposites, a series of phosphorus-containing copolyester/modified zinc borate?PET-co-CEPPA/ZB@SiO₂? composites were prepared by in-situ polymerization. And the thermal properties, thermal stability and combustion performances of the synthetic materials were studied by Differential scanning calorimeter?DSC?, Thermogravimetric analysis?TGA?, Limit oxygen index?LOI? and Vertical combustion experiment?UL-94?. The corresponding flame resistant polyester fibers were prepared by melt-spinning and their mechanical properties and combustion performances were studied. The results were as follows:?1? The PET polymerization process was strongly catalyed by unmodified ZB, which caused substantial decrease in viscosity characteristics. After the ZB coated by nano-meter silicon dioxide through sol-gel method, a dense outer protective layer was formed on the surface of it, which effectively restrained the influence of ZB in PET polymerization process. When the ratio of H2O/NH3/TEOS is 7.1:3.4:1, a good coating effect could be achieved.?2? The intrinsic viscosities were not affected by adding CEPPA-EG. With increasing of phosphorus, the LOI of PET-co-CEPPA increased, Tg and Tm of PET-co-CEPPA dropped. With increasing of OMMT, the intrinsic viscosity of PET-co-CEPPA/MMT decreased, the Tg, Tcc and Tmc generally showed increased tendencies while Tm showed little changes, ?Tmc generally showed decreased tendencies. When 1.5wt% OMMT of terephthalic acid?PTA? was added, the crystallization property of PET-co-CEPPA/MMT was best. With increasing of ZB@SiO₂, the intrinsic viscosity of PET-co-CEPPA/ZB@SiO₂ had no obvious change, the change of Tm was irregular, the Tg and Tmc increased, the ?Tcc and ?Tmc decreased.?3? Compared with PET, PET-co-CEPPA had higher LOI and better self-extinguishing effect. With increasing of OMMT and ZB@SiO₂, the flame retardant performances of the copolyesters and their nanocomposites had been improved obviously, the LOI values were further improved and the UL-94 level were raised from V-2 to V-0. The TGA tests in nitrogen showed that the initial decomposition temperature of PET-co-CEPPA was lower than that of pure PET. After adding OMMT and ZB@SiO₂, the charing amount, char layers' density and thermal stability of the composite materials were considerably improved.?4? There were no obvious differences of mechanical properties between PET fibers and PET-co-CEPPA fibers, and the LOI values of PET-co-CEPPA fibers could reach to 29%. When OMMT and ZB@SiO₂ were added, the mechanical properties of the two fibers decreased in some extent, while the flame retardant properties of them were improved significantly, and the LOI values were 30.5% and 31.7%, respectively.