تهيه و مشخصه يابي بيوفوم هاي كامپوزيتي بر پايه نشاسته تقويت شده با نانو الياف سلولزي استخراج شده از ساقه گندم

چكيده انگليسي :

Preparation and Characterization of Bio Foam Composites Based on Starch Reinforced by Cellulose Nanofibers Extracted from Wheat Straw Amin Karimi amin karimi@ce iut ac ir 9 June 2014 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Tayebe Behzad tbehzad@cc iut ac irAbstract Due to environmental issues starch could be an appropriate alternative for film and foam Starch is obtained fromrenewable resources inexpensive and can be found in abundance Unfortunately starch has some disadvantages It is highly hydrophilic it has brittle behavior without plasticizer and its mechanical properties are very sensitiveto moisture Few approaches for overcoming these disadvantages have been proposed Blending starch withsuitable biodegradable polymers and addition of nanofibers to starch can be considered High specific surfacearea aspect ratio and strength and flexibility are characteristics of microcrystalline cellulose fibrils In this study the cellulose nanofibers were extracted from wheat straw and used as reinforcing materials in foam production Combination of chemical and mechanical methods were used to extract cellulose nanofibers In order to removelignin and hemicellulose chemical steps were designed A supergrinder was used to isolate nanofibers In thisprocess a slurry of microfibers was passed through a gap between fixed and rotate grinder stones Freeze dryingmethod was employed for foam production First suspension of starch in water was prepared and then differentpercentages of nanofibers 0 10 20 30 wt with 3 glycerol as plasticizer were added to the mixture In order togel starch this suspension was stirred at a temperature of 90 C for 30 min by a mechanical stirrer To completethe gelatinization process the mixture is poured into a Petri dish for 24 h at a temperature 4 C is placed This gelwas frozen at a temperature 80 C and then placed into the freeze dryer for 48 hours To determine the chemicalcomposition of the fiber constituents cellulose hemicellulose and lignin NREL TP 510 42618 was used Theresults showed that amount of cellulose after chemical processing has increased from 40 to 90 Morphological changes during the process of chemical fibers was showed that the fiber diameters was reduced Fibers diameter distribution from SEM images was determined to be 70 90 nm Peaks observed in the FTIRspectroscopy confirmed the removal of lignin and hemicellulose Adding nanofibers leading to the formation ofuniform cells with small diameters Adding nanofibers by 20 wt increased the composite modulus andcompressive strength of the foam Water absorption and diffusion coefficient of foams decreased with increasingcellulose nanofibers Key words Wheat straw nano fibers cellulose starch foam

كريمي، امين

تهيه و مشخصه يابي بيوفوم هاي كامپوزيتي بر پايه نشاسته تقويت شده با نانو الياف سلولزي استخراج شده از ساقه گندم