تهیه و بررسی خصوصیات فیزیکی، مکانیکی و ضدمیکروبی فیلم‌های نانوکامپوزیتی پلی‌اتیلن/ پلی‌لاکتیک اسید تقویت ‌شده با نانواکسیدگرافن

در سال‌های اخیر به موضوع بسته‌بندی مواد غذایی از نظر حفظ ارزش غذایی محصول و افزایش ماندگاری محصولات توجه بیشتری شده است. فیلم‌های حاصل از ترکیب نانو مواد و پلیمرها/ پلیمرهای زیستی، خواص کاربردی مناسب‌تری نسبت به پلیمرهای پایه نشان می‌دهند. بهبود خصوصیات مکانیکی و ممانعت‌کنندگی و افزایش خاصیت ضدمیکروبی فیلم‌ها در صورت برخورداری نانو مواد از ویژگی ضدمیکروبی ازجمله این ویژگی‌ها می‌باشند. در این تحقیق، فیلم نانوکامپوزیتی پلی‌اتیلن سبک / پلی­لاکتیک اسید تقویت ‌شده با نانوذرات اکسیدگرافن توسط اکسترودر فیلم دمیده تهیه شد و خواص فیزیکی مکانیکی، ممانعت‌کنندگی و ضدمیکروبی آن مورد ارزیابی قرار گرفت. افزودن نانواکسیدگرافن در غلظت‌های یک، سه و پنج درصد وزنی باعث افزایش مقاومت کششی، مدول الاستیک، خاصیت ضدمیکروبی، خاصیت ضدقارچی و زیست‌تخریب‌پذیری فیلم و برعکس کاهش افزایش طول در نقطه پارگی، نرخ انتقال بخارآب، نرخ انتقال اکسیژن و انتقال نور مرئی و اشعه ماوراءبنفش آن شد. فیلم آمیزه پلی‌اتیلن سبک / پلی­لاکتیک اسید و فیلم آمیزه حاوی پنج درصد وزنی نانواکسید گرافن دارای مقاومت کششی 17.2 و 19.2 مگاپاسکال، مدول الاستیک 200 و 224 مگاپاسکال، قطر هاله عدم رشد باکتری استافیلوکوکوس اورئوس صفر و هشت میلی‌متر، زیست‌تخریب‌پذیری 10 و 11 درصد، افزایش طول در نقطه پارگی 198 و 170 درصد، نرخ انتقال بخارآب 18.8 و 16.4 گرم بر متر مربع ساعت، نرخ انتقال اکسیژن 425 و 380 سانتی­‌متر مکعب بر متر مربع روز، میزان انتقال نور مرئی 73.2 و 18.5 درصد و میزان انتقال اشعه ماوراءبنفش 53.5 و 23.5 درصد بودند.

preparation and study the physical, mechanical and antimicrobial properties of polyethylene/polylactic acid nanocomposite films reinforced with nano-graphene oxide

introductionpackaging is an intermediary between the produced food products and the customer, which maintains the quality of the product and provides the information required by the customer. the primary function of packaging is to preserve the nutritional quality of products and extend their shelf life. conventional packaging materials, such as polyethylene, polypropylene, and polystyrene, are derived from petroleum-based sources and are widely utilized in food packaging due to their advantageous properties, including high durability, lightweight nature, cost-effectiveness, ease of manufacturing, and low water vapor permeability. however, degradation of these synthetic materials is very slowly in the environment, leading to significant ecological pollution. in response to this issue, there has been growing interest in the use of biopolymer materials as a sustainable alternative to non-biodegradable, petroleum-derived packaging. biodegradable biopolymers offer several benefits, such as environmental degradability and lower production costs compared to synthetic polymers. additionally, in certain applications, biopolymers can enhance product shelf life and quality, making them a promising solution for sustainable packaging.materials and methodsin this study, a polylactic acid/polyethylene blend film reinforced with graphene oxide nanoparticles was produced and then its mechanical, physical, and antimicrobial properties were investigated in two phases.phase 1in this phase, three-component blends of blown film-type linear low-density polyethylene, general film-type low-density polyethylene, and extruded sheet-type polylactic acid were prepared. for this purpose, 80 wt% linear low-density polyethylene with 20 wt% low-density polyethylene and part 3, 6, and 9 part per hundred (phr) polylactic acid in the presence of 0.05 phr of maleic anhydride-linked polyethylene compatibilizer were melt-blended in a high-performance twin-screw extruder. before mixing and extruding, linear polyethylene, polyethylene, and polylactic acid granules were dried in a dryer at 80°c for 6 hours to remove moisture before the process. after mixing, a blown film was prepared from the mixture using a single-layer blown extrusion machine. in this stage, the optimal film was selected by performing various analyses.phase 2the optimal film selected from the first stage was used to investigate the effect of graphene nanooxide in the second stage. for this purpose, first, graphene nanooxide with phr concentrations of 0, 1, 3 and 5 relative to the three-component mixture was well dispersed in the polylactic acid solution by ultrasonication. after drying in a thermal oven, the solution was poured into a co-rotating twin-screw extruder along with linear low-density polyethylene, low-density polyethylene, and maleic anhydride-linked polyethylene compatibilizer for processing and granulation. after that, a nanocomposite film was prepared according to the first phase method. in order to investigate the effect of nano graphene oxide on the properties of the produced films, all relevant analyses were performed.results and discussionthe results showed that with the addition of pla to the polyethylene matrix, due to the immiscibility of these two materials, two peaks appeared at 122 and 165 °c in the thermogram of the blend, which was related to the melting temperatures of polyethylene and polylactic acid, respectively. the tensile strength and tensile modulus of the blends increased significantly with increasing pla and go content, so that the sample with 9  phrof polylactic acid and 5 phr of graphene oxide (ldp9-g5), had the highest tensile strength and tensile modulus, 19.2 and 224 mpa. the oxygen transfer rate decreased with increasing go content. so that the transmission rate for sample ldp9 was 425 cm3/m2.d and for samples ldp9-g1, ldp9-g3 and ldp9-g5 were 417, 402 and 380 cm3/m2.d, respectively. the ultraviolet light transmittance also showed that with increasing go content in the film, the ultraviolet light transmittance and transparency of the films decreased. the antimicrobial and antifungal test of nanocomposite films also showed a decrease in the microbial population with increasing go concentration. positively charged ions on the go surface react with negative charges on the bacterial membrane and inactivate the bacterial function. sample ldp9-g5 had the highest antifungal activity in the culture medium of candida albicans. also, the biodegradability of sample ldp9-g5 was 11% within 8 weeks.conclusionaccording to the results obtained, it can be said that the obtained nanocomposite film showed excellent mechanical and antimicrobial properties compared to the control film sample due to the presence of graphene oxide in its structure.