دانلود رایگان مقاله انگلیسی مطالعه جامع در مورد پلی استرهای عقب مانده شعله ای از افزودنی های فسفر - الزویر 2018

abstract

In this work we have performed a comprehensive study on synthesis, processing, detailed material characterization and preliminary assessment of toxicity of relatively new flame retardant (FR) additives as a key for developing environmentally friendly fire safe polyesters. Two 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO) based FR additives were synthesized using principles of green chemistry and incorporated via thermal processing in high temperature polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The green synthesis strategies included (i) the use of N-chlorosuccinimide as a sustainable chlorinating agent for DOPO and (ii) a solvent and catalyst free microwave-assisted synthesis. Atomistic molecular dynamics (MD) simulations were employed in order to calculate the solubility parameters of these additives so as to estimate their compatibility in the polyesters. Detailed rheological measurements of the polyester/FR blends were carried out and the results indicated a clear difference in all three additives tested. Based on these analyses, 6H-dibenz[c,e][1,2] oxaphosphorin,6-[(1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]oct-4-yl)methoxy]-, 6-oxide (DOPOPEPA) exhibited the highest compatibility with both polyesters and their blends and showed the highest thermal-oxidative stability guaranteeing stable and steady processing at high temperatures. All polyester/FR formulations exhibited higher flame retardancy compared to the virgin polyesters in the small scale fire tests. The FR additives were evaluated for their potential toxicity using a well-established in vitro platform. Our results indicate no acute cytotoxic potential for all FRs analyzed in two different cell types (the human lung epithelial cell line A549 and macrophages derived from the monocytic cell line THP-1) and under the chosen experimental conditions.

4. Conclusions

In this work comprehensive strategies i.e. green synthesis methodology, detailed material characterization and first toxicity evaluation of the FR additives as a way to develop fire safe sustainable polyesters were presented with an eventual goal for future commercialization. Both DOPO-based additives (DOPO-PEPA and AAM-DOPO) were synthesized using green chemistry principles and compared with the commercial FR additive Aflammit PCO 960. The DOPO derivatives could be processed with high temperature polyesters like PET and PBT due to their high thermal stability. Theoretical data obtained via atomistic simulations and experimental data obtained via rheological measurements indicate that DOPO-PEPA offers the most steady and sustainable melt processing conditions with polyesters compared to the other two FR additives. The polyester films containing all FR additives passed the vertical fire tests and exhibited higher LOI values compared to the virgin polyester films. TGA data and elemental analysis of char obtained for FR formulations indicates possible limited condensed phase activity of the FR additives. We could identify phosphorus based volatile species in the evolved gas analysis performed using DIPMS. Such phosphorus species could be responsible for the gas phase flame inhibition and thus improving the flame retardancy of the polymer in this study. Based on the DIP-MS data we have also proposed simplified decomposition pathways of the FR additives. In case of DOPO derivatives DOPO radical was clearly observed as one of the volatile species. Methyl phosphonic acid was observed as the primary volatile spices in case of Aflammit PCO 960. All FR additives were shown to be non-toxic in the in vitro assays and conditions chosen. Thus in this study, detailed multi-dimensional analyses of these relatively new FR molecules were provided with focus on the green chemistry principles at the synthesis level, the thermooxidative stability at the processing stage, fire and environmental safety during the product consumption, and the prospect of sustainability at the recycling stage.