Abstract
Polymerizable UV absorbing monomers (UVAMs) were copolymerized with bis(hydroxyethyl) terephthalate to yield copolymers of poly(ethylene terephthalate) (PET). PET copolymer films containing 3-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-3-hydroxyphenoxy]-1,2-propanediol (UVAM 12) and 6,6’-(6-phenyl-1,3,5-triazine-2,4-diyl)bis(3-(2-hydroxyethoxy)phenol) (UVAM 24) were exposed to UV radiation for 1082 hrs. in a QUV-A accelerated weathering instrument and analyzed periodically using FT-IR spectroscopy and GPC. It was found that PET films containing copolymerized UVAMs outperformed films containing admixed Tinuvin 1577 stabilizer, thereby offering even greater protection to polymer films against UV-induced crosslinking and chain scission.
Highlights
Poly(ethylene terephthalate) (PET) absorbs strongly in the ultraviolet (UV) region of the EM spectrum (Figure 1) and this leads to the photodegradation of polymer chains
The UV profile of UV absorbing monomers (UVAMs) 12 mirrored that of Tinuvin 1577 because the chromophore in UVAM 12 is identical to the chromophore present in the commercial UV additive
The presence of Tinuvin 1577, UVAM 12 and 24 resulted in a slow decrease in both the M̅̅wand number average molecular weight (M̅n) which showed that the UV absorbing stabilizers were effective in combating crosslinking and that chain scissions were the main product of degradation in the stabilized films
Summary
Poly(ethylene terephthalate) (PET) absorbs strongly in the ultraviolet (UV) region of the EM spectrum (Figure 1) and this leads to the photodegradation of polymer chains. The loss of additive over time leads to an increase in the rate of UV-induced degradation and deterioration of key polymer properties This is of particular concern for applications where polymers are exposed to high levels of UV radiation and/or conditions that allow leaching of additives from the polymers. It is of the utmost importance for polymer manufacturers to increase the lifetime of UV protection, and one way in which this can potentially be achieved is by exploiting polymerizable UVAs which are bonded covalently to the polymer chains. Kulia et al copolymerized BTs with phenolic moieties in a step-growth polymerization to yield polysulfone and polycarbonate copolymers.[15]
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