توليد و ارزيابي پلي مر تجزيه پذير پلي اسيد لاكتيك از طريق شاخه دار كردن اسيد لاكتيك تخميري حاصل از پنير فراپالايش

چكيده انگليسي :

75 Synthesis and Characterization of Biodegradable Lactic Acid Based Polymers Through the Chain Extension of Fermented Lactic Acid Produced With Whey Permeate Seyede Zahra Ghafari Zahra ghafari64@gmail com November 1 2010 College of Agriculture Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language Farsi Supervisor s S Solemanian zad E mail address Soleimam@cc iut ac irAbstract Environmental pollution is one of the problems that attracts every body s attention to itself The maincause of this problem is disposal of plastic materials in nature which almost are not degradable To solvethe problem various methods such as production of biodegradable polymers have been proposed Suchpolymers might be produced from plant or microbial sources Poly Lactic acid is a high strengththermoplastic polymer that its monomer can produce either synthetically or through fermentation usingagricultural waste materials In the present study producing poly lactic acid via chain extending reaction with three different chain extenders called Hexa methylene diisocyanate Isophoren diisocyanate and 4 4 diphenylmethane diisocyanat using whey permeate as the microbial culture medium was investigated Atfirst lactic acid was produced through fermentation by two different homo fermentative microorganisms which produce only the L isomer of lactic acid the obtained results showed that Lactobacillus casei canproduce 15 47 g L lactic acid while Lc lactis only produce 9 72 g L of that which lead to the selection of L casei as the producer microorganism in this project In the next step the produced lactic acid was purifiedwith anion and cation exchange resins and the identity of the product was determined with HPLC Thepurity of this product was about 84 69 percent Chain linked lactic acid polymers were synthesized throughthree sequential steps in the first purified lactic acid was dehydrated and then hydroxylated and in thethird the chain extending reaction was took place with 3 different chain extenders They were hexamethylene diisocyanate with a linear structure isophoren diisocyanate with a single loop in its structure and4 4 diphenyl methane diisocyanate with two loops in its structure FT IR analysis was used to monitor theformation of chain extended polymers The FT IR spectra confirmed the molecular structure of thepolymers produced Morphological properties of the produced polymer was investigated with SEM andthe result showed that the polymer manufactured with mediatory of 4 4 diphenyl methane diisocyanateamong the other polymers has the most soften structure Results of the molecular weight and thermalstability measurements of the manufactured polymers showed that the polymer made with 4 4 diphenylmethane diisocyanate had the largest molecular weight and the highest thermal stability among the otherpolymers According to the results by altering the chain extender structure from having two loops to havingone loop in their structures or having linear structure these polymers specifications are lowered consequently As conclusion it could be said that 4 4 diphenyl methane diisocyanate is the best chainextender for lactic acid polymerization purposes amongst the chain extender tested Comparison of theresults of this project with the results of the other researchers working on the production of poly lactic acidusing chain extenders it seems that 4 4 diphenyl methane diisocyanate act better than that the ones used intheir researches because it produces a polymer with the higher molecular weight higher thermal stabilityand soft surfaces so more convenient for food packaging industries Key words Poly lactic acid Fermentation Chain extending reaction Lactic acid and whey permeate

غفاري، زهرا

توليد و ارزيابي پلي مر تجزيه پذير پلي اسيد لاكتيك از طريق شاخه دار كردن اسيد لاكتيك تخميري حاصل از پنير فراپالايش

واكنش شاخه دارشدن , آب پنير حاصل از پنير , فراپالايش