5498
Heba Salah El–Din Abd El- Sadek Kandil
Utilizing Agricultural Wastes Such As Rice Husks To Prepare Some Polymeric Nanocomposites For Industrial Application
EPDM rubber, rice husk powder, nanocomposites, mechanical properties, dielectric properties, cytotoxicity
Over the past two decades, there has been a growing interest on using agricultural waste fibers (biofibers) as reinforcement in manufacturing the polymer composites. This interest was attributed to their outstanding advantages such as their environmentally-friendly, renewable, biodegradable character with low cost, remarkable physical and mechanical properties such as low density, lightweight, good strength, processing flexibility, high specific stiffness. Rice husk appeared among various biofibers as a promising material which could be used in several applications as it is relatively inexpensive, commercially available and possessing an unusual high percentage of silica. Therefore, this thesis was designed to use rice husk (RH) as filler in synthetic rubbers, especially EPDM rubber, to produce beneficial composites could be used in industrial applications instead of disposing it either by burning or dumping as wastes in open fields causing serious environmental problems. The major problem in developing this composite was the incompatibility between RH and EPDM rubber which was overcome by surface modification for RH to decrease its' hydrophilicity and increase its' dispersion in EPDM matrix. Two types of surface modifications for RH was used as mechanical and chemical modifications. In mechanical modification, RH was milled and sieved by using high ball mill energy to nanosized rice husk powder (nRHP) where its' nano scale was confirmed by scanning electron microscopy (SEM). After that, the resulting nRHP was incorporated into EPDM matrix by using a laboratory two roll mill whether in the presence or absence of using chemical modifications for nRHP surface to prepare chemically modified and unmodified nRHP- EPDM nanocomposites. The used chemical modifications for nRHP treatment included usage of maleated EPDM whether as a coupling agent (M-EP) linking between nRHP and EPDM matrix or as a grafting agent to be tethered onto nRHP surface; usage of a dry bonding agent from hydrated silica, resorcinol and hexamethylene tetramine (HRH system); and usage of polyols such as glycerol, polyethylene glycol 400 and tween 20 to act as filler dispersants for nRHP. The curing, mechanical and thermal properties of the resulting nanocomposites in each used chemical modification method were studied by using a Monsanto rheometer, a Zwick tensile testing machine and thermal gravimetric analyses (TGA), respectively. Swelling resistance property was evaluated for 24 hours immersion in toluene. Scanning electron microscopic (SEM) images were analyzed to observe the dispersion of nRHP into EPDM matrix in the chemically modified and unmodified nRHP-EPDM nanocomposites. Fourier transform infrared ray (FTIR) analyses were carried out to confirm the formation of maleated EPDM (M-EP) coupling agent and also to confirm the formation of grafted nRHP with the maleated EPDM. Finally, some of the prepared nanocomposites were selected to examine their dielectric properties for dielectric applications and other were selected to examine their cytotoxicity for biomedical applications
2018
Ph.d
Ain Shams
Science