Study Of UV Screening Ability And Photo Stabilization Of Poly(Ethylene Terephthalate)/ Carbon Black Grafted By Organic UV Absorber Composites

Poly(ethylene terephthalate) (PET) is a material with good weatherability and optical transparency can be applied in packaging, film and engineering plastics. Compared with PET, Poly(ethylene terephthalate) glycol (PETG) is a copolymer of PET performing less crystallization and better optical transparency to be applied in transparent plastic products. Thus the research of the crystallization behavior of PETG is meaningful for not only theory study but also practical production. PET is transparency for UV light which wavelength is over 280 nm. Therefore UV absorber has to be added into PET to improver its UV resistance.Carbon black (CB) is an important additive acted as reinforcing agent, colorant and conductive filler. But there are few studies about its UV stabilization property. In this paper, UV stabilization property of polymer/CB composite is investigated. CB is usually modified to improve its dispersibility in polymers. This helps to decrease the aggregate size of CB and improve certain properties of polymers.CB was modified with a commercial UV absorber to prepare an organic and inorganic compound UV stabilizer through in-situ reaction in solid phase. Modified CB (m-CB) was added into PET films or plates and the crystallization behavior, transparency and UV resistance of PET/CB composites were discussed.Firstly, transparency influenced by the crystallization of homopolymerized PET (homo-PET) and PETG was investigated. It is proved that the haze of PET films is strongly influenced by the crystallizing ability. PETG whose crystallizating ability is lower performs better transparency than homo-PET. Different type of CB or benzotriazol UV absorbers (UV-P and UV327) was added into PET to improve its UV resistance. The results showed that pigment CB Mogul-L with small aggregate size is more efficient in enhancing UV resistance and bezotrazol UV absorbers can increase UV absorbance and keep high transparency of PET film. The research on the synergistic effect for the combination of organic UV absorber and in organic UV stabilizer CB showed that Beer-Lambert law is suitable to both organic UV absorber and CB in PET. The synergistic effect for bezotrazol UV absorber and CB behaves as the addition of their absorbence index.CB was modified with UV-P and UV327 to improves its dispersibility and the synergistic effect between them. Haake rheometer and thermogravimetric analysis (TGA) characterization showed the reaction between UV-P and CB was more obvious than between UV327 and CB. Fourier transform infrared (FTIR) and Energy Dispersive Spectrometry (EDS) characterizations showed that the chemical reaction happened between the oxygen-containing groups on the surface of UV-P and CB. But the strong steric hindrance of UV327 weakened the reaction between UV327 and CB. After the modification, the aggregate size of UV-PCB decreased to below 100 nm and the specific surface area increased.PET/UV-PCB composite films were prepared and exhibited higher UV absorbing ability than PET/CB, PET/UV-P systems and PET/UV-P/CB systems. The absorbance index of UV-PCB is larger than UV-P/CB indicated that UV-PCB obtained nano-effect.Both UV-PCB and UV-P/CB acted as good nuclear agent in PET. The non-isothermal kinetics of PETG/UV-P/CB and PETG/UV-PCB were investigated. The results showed that pure PETG can hardly crystallization under a relative high cooling rate and can be described by Jeziorny and Ozawa methods. The spherulite growth of PETG is between two dimension and three dimension through heterogeneous nucleation. After the addition of UV-P/CB or UV-PCB, the spherulite growth of PETG changed to three dimension and contained second step crystallization. The nucleating ability of UV-PCB is better than UV-P/CB because of the aggregate size decreasing and the surface area increasing of UV-PCB. The increase crystallizing ability of UV-PCB and UV-P/CB did not increase the haze of PETG very much.UV degradation kinetics of PET/CB composites were investigated. The results showed that the weak links in PET brake much more easily than normal links. The protection of UV-PCB for PET exhibited on the decreasing of the UV degradation rate constants and the fraction of weak links. The melt temperature, glass transition temperature and heat-deformation temperature were slightly influenced by UV radiation. But UV radiation caused the decreasing of storage modulus, impact strength and tensile strength for PET. PET with UV-PCB performs more stabilized than with CB or UV-P individually. UV-PCB in proved as an efficient UV stabilizer to improve the UV absorbing ability and stability of PET.