Polyethylene Reinforced with Keratin Fibers Obtained from Chicken Feathers

Topics: Composite material, Tensile strength, Elasticity Pages: 16 (5520 words) Published: August 22, 2013
Composites Science and Technology 65 (2005) 173–181 www.elsevier.com/locate/compscitech

Polyethylene reinforced with keratin fibers obtained from chicken feathersq Justin R. Barone *, Walter F. Schmidt
USDA/ARS/ANRI/EQL, Bldg. 012, Rm. 1-3, BARC-West, 10300 Baltimore Ave. Beltsville, MD 20705, USA Received 15 January 2004; received in revised form 22 June 2004; accepted 22 June 2004 Available online 24 August 2004

Abstract Polyethylene-based composites were prepared using keratin fibers obtained from chicken feathers. Fibers of similar diameter but varying aspect ratio were mixed into low-density polyethylene (LDPE) using a Brabender mixing head. From uniaxial tensile testing, an elastic modulus and yield stress increase of the composite over the virgin polymer was observed over a wide range of fiber loading. Scanning electron microscopy revealed some interaction between the polymer and keratin feather fiber. In addition, the keratin fiber had a density lower than the LDPE used in this study resulting in composite materials of reduced density. The results obtained from mechanical testing are compared to theoretical predictions based on a simple composite material micromechanical model. Published by Elsevier Ltd. Keywords: A. Fibers; A. Polymer-matrix composites; A. Short-fiber composites; B. Mechanical properties; B. Microstructure

1. Introduction There has been recent interest in developing composites based on short-fibers obtained from agricultural resources. These fibers are usually of lower density than inorganic fibers, environmentally-friendly, and relatively easy to obtain. It is anticipated that the fibers would not contribute to the wear of polymer processing equipment and may not suffer from size reduction during processing, both of which occur when inorganic fibers or fillers are used. Although the absolute property increase when using organic fibers is not anticipated to be nearly as high as when using inorganic fibers, the specific proper-

q Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. * Corresponding author. Fax: +1 301 504 5992. E-mail address: baronej@ba.ars.usda.gov (J.R. Barone).

ties are anticipated to be high owing to the much lower density of the organic fibers. In short-fiber reinforced polymer composites, the integrity of the fiber/matrix interface needs to be high for efficient load transfer. Ideally, the molten polymer would spread over and adhere to the fiber, thus creating a strong adhesive bond. Inorganic fibers like glass and cellulosic fibers have hydrophilic surfaces that make them incompatible with hydrophobic polymers. Therefore, inorganic and cellulosic fibers usually require chemical modification to increase fiber/polymer interactions [1]. The chemical modification, known as a coupling agent, acts as a ‘‘bridge’’ between the inorganic fiber and the organic polymer matrix. The ‘‘bridge’’ must adhere or bond to the fiber and, in turn, strongly interact with the polymer. When using glass fibers, the coupling agent has a hydrophilic side that is compatible with the fiber and a hydrophobic side that is compatible with the polymer. In glass fibers, the coupling agent reacts with the surface of the glass forming covalent bonds. Without the coupling agent, there is simply adhesion of the polymer to the glass through weak bonding,

0266-3538/$ - see front matter. Published by Elsevier Ltd. doi:10.1016/j.compscitech.2004.06.011


J.R. Barone, W.F. Schmidt / Composites Science and Technology 65 (2005) 173–181

i.e., van der Waals or induction interactions. Organic fibers may offer the possibility of covalently bonding the matrix polymer to the fiber either directly or through a similar type of chemical ‘‘bridge’’ and the chemistry may be easier. Covalent bonds are much stronger than induction or van der Waals...
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