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Oxygen Barrier Improvement of the BOPP Films in Food Industry

Shayanipour, Hamid Reza | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 52497 (57)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. One of the most popular methods in order to protect foods is to package using various materials. By this act, the shelf life of the packaged foods may range from a few days to more than a year. Multiple types of plastics are being used as materials for packaging food, including polyolefin, polyester, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, and ethylene vinyl alcohol. Although more than 30 types of plastics have been used as packaging materials, polyolefin and polyesters are the most common. Biaxially Oriented Polypropylene (BOPP) is a polypropylene film that has been stretched in both the machine and cross directions. BOPP film has become one of the most popular high growth films in the world. In this study, in order to optimize the properties of the BOPP film the parameters that may affect the final properties were recognized and then with the help of the modern methods of optimization, the best producing condition was found and introduced. For this purpose, three final important properties include transparency (or haze), film strength and oxygen permeability were considered as targets or responses and then, the effect of process variables on the three determined targets was evaluated. It is found that the lowest quenched temperature (12 °C) and stretch temperature in the longitudinal (120 °C) and transverse directions (135 °C) are required for obtaining the best film. Also the extruder temperature of about 135 °C and the draw ratio in the longitudinal of 5 and 8 for transverse (8) directions are required. Barrier properties of the biaxial oriented polypropylene (BOPP) films are the most important properties in food packaging industry. In this study different passive mechanisms (nanocomposites and blend polymers) were used to improve the barrier properties of the optimized BOPP film. In a novel action, both modified clay and PVA were used to produce a resistant composition. As each component was successfully improved the barrier properties of the BOPP film, it was tried to examine the synergistic effect of using both of them at the same time. The best oxygen permeability (220 cc 20 μm/m2 24 hrs atm) was found for the PP/gPP/PVA+Organoclay with the composition of 60/10/20+10 weigh %. Oxygen permeability of the optimized BOPP was 1630 (cc 20 μm/m2 24 hrs atm) as 87% reduction in oxygen permeability is considered a valuable achieve. In this regard, X-ray analysis and scanning electron microscope were used to identify the occurred event in the polymers. In addition to barrier studies, oxygen transition model through the BOPP film was studied and the best fitted model was found. Finally a modification on the obtained model was performed and a new model with less than 10 % error was introduced
  9. Keywords:
  10. Nanocomposite ; Permeability ; Oxygen Permeability ; Food Industries ; Biaxially Oriented Polypropylene (BOPP)

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