Poly(Lactic Acid)-based UV-blocking Materials Based On Rare Earth Complex Transmutants And Their Effects On The Storage Quality Of Linseed Oil

Flaxseed oil with rich unsaturated fatty acids is highly susceptible by UV irradiation and oxidation in the process of storage,transportation and marketing,therefore,it is necessary to prepare UV-blocking packaging to prevent the oxidation of flaxseed oil.In response to the problems that organic UV absorbers easily migrate and inorganic UV masking agents reduce the transparency of the packaging,this study synthesized rare earth complex trans-optics with UV absorbing function,doped them into PLA matrix,to develop a green degradable PLA-based UV-blocking packaging material.Finally,the effect of UV light on the storage quality of linseed was investigated,as well as the protective effect of the material on linseed oil.（1）The PLA/Eu（DBM）₃phen（P/E）composite films were prepared by melt blending and hot pressing method using Eu（DBM）₃phen as a functional additive.The results showed that the UV-blocking performance of the P/E hot-pressed films improved significantly with the increase of Eu（DBM）₃phen addition.The P/E1 hot-pressed film with a mass fraction of 1%showed the best overall performance with a UV transmittance of 12.39%in the 280～400 nm region,much lower than that of PLA at 82.05%.And The P/E1 film still possessed good mechanical properties and transparency.However,the average UV transmittance of the P/E1 hot-pressed film increased to 27.64%after a continuous 2 d UV aging acceleration experiment,indicating that its ability to provide long-lasting UV protection for food products was limited.（2）Introduced BP-2 ligand to synthesize long-lasting rare-earth translucent Eu（DBM）₂（BP-2）phen,blended it into PLA by twin-screw extrusion pelletizing,and prepared PLA/Eu（DBM）₂（BP-2）phen cast film（C-P/E2）with thickness of 200μm by extrusion calendering.The test results show that C-P/E25 cast film with 0.5%mass fraction has long-lasting UV shielding performance,and its average UV transmission only increases from 7.7%to 11.6%after 12 d of UV aging,which can provide long-lasting protection for fatty foods.（3）A UV aging chamber was used to simulate daylight exposure to investigate the protective effect of C-P/E2 cast film on linseed oil.The results showed that the protective effect of C-P/E25 cast film on linseed oil was similar to that of the dark environment.After 12 d of storage,the flaxseed oil in the C-PE25 group still had the characteristic flavor of flaxseed oil.In contrast,the flaxseed oil packed with unmodified PLA showed a strong odor at the 4th day.In addition,the results of HS-SPME-GC-MS analysis showed that the unprotected flaxseed oil generated a large amount of olefins and ketones under UV irradiation,while only aldehydes were dirived in the C-P/E25 and Control groups（dark environment）.This indicates that the UV barrier packaging can significantly slow down the deterioration process of flaxseed oil.