استخراج و مشخصه يابي نانو الياف سلولز از ساقه ي برنج و استفاده از آن در تهيه ي نانو كامپوزيت بر پايه ي نشاسته ي ترموپلاستيك

چكيده انگليسي :

61 Extraction and Characterization of Cellulose Nanofibers from Rice Straw and Manufacturing the Nanocomposites based on Thermoplastic Starch Bijan Nasri Nasrabadi Bijan nasr84@yahoo com January 22 2013 Departemant of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Superviser Tayebeh Behzad tbehzad@cc iut ac ir Abstract In the last decade due to environmental challenges and non renewability of fossil sources synthetic polymers in many applications have been replaced by biopolymers where the long term durability is not needed The thermoplastic starch is wildly used in various domains such as food containers and packing industries Within the wide family of biopolymers the starch has the high usage because of its availability biodegradability biocompatibility and ease of chemical modification Starch is extensively found in seeds stems leaves tubers and fruits of plants Starch is a hydrophilic polymer that consist of anhydro glucose unites linked by D 1 4 glycosidic bonds Starch contains of two different main phases of amylose linear and amylopectin non linear Biological interactions post modification and processing conditions are the most effective parameters in arrangement of these distinct phases Starch can be converted to thermoplastic starch via incorporation of plasticizers such as water and or polyalcohols Compare to synthetic polymers starch has some disadvantages such as high water sensitivity brittleness low mechanical properties and poor barrier properties To overcome these problems some solutions such as blending with other biopolymers chemical modifications and also reinforceing with nanofillers such as nanoclay and cellulose nanofibers CNF have been suggested Cellulose nanofibers in addition to biodegradability biocompatibility have high crystallinity high aspect ratio and low density compared to glass fibers that cause noticeable increase in stiffness of matrix In the present study bio nanocomposite films were manufactured using thermoplastic starch and cellulose nanofibers Nanofibers were extracted from rice straw employing a chemo mechanical method Chemo mechanical treatment included swelling acid hydrolysis alkali treatment bleaching and sonication A design of experiment was used for acid hydrolysis step to optimize the concentration of acid ratio of acid to pulp and time of treatment to achieve the highest total crystallinity index The dimensions and morphology of chemically treated fibers and extracted nanofibers were investigated by scanning electron microscopy and field emission scanning electron microscopy respectively The chemical compositions of fibers including cellulose hemicelluloses lignin and silica were determined by different tests The achieved results showed that the cellulose content was increased around 71 for alkali treated fibers compare to raw materials Also it can be noticed that almost all of the silica content of fibers was solubilized in the swelling step The thermal gravimetric analyses were performed on untreated and bleached fibers It was demonstrated that the degradation temperature was increased around 19 for purified fibers compare to raw materials Afterward bio nanocomposites were manufactured employing cellulose nanofibers and thermoplastic starch via film casting In order to study the effect of nanofibers reinforcement on composite properties mechanical and dynamic mechanical properties morphology humidity absorption and transparency of films were investigated at various nanofibers contents The yield strength and young modulus of nanocomposites were satisfactorily enhanced compare to pure starch film The glass transition temperature of films was shifted to higher temperatures by increasing nanofiber contents The SEM images illustrated that nanofibers were dispersed uniformly in the matrix The humidity absorption resistance of films revealed significant enhancement until 10 wt cellulose nanofibers The transparency of nanoco

نصري نصرآبادي، بيژن

استخراج و مشخصه يابي نانو الياف سلولز از ساقه ي برنج و استفاده از آن در تهيه ي نانو كامپوزيت بر پايه ي نشاسته ي ترموپلاستيك

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