Fiber Reinforced Multiphase Polymer Composites by In situ Fiber Alignment
- PDF / 980,456 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 77 Downloads / 277 Views
1054-FF05-09
Fiber Reinforced Multiphase Polymer Composites by In situ Fiber Alignment Wantinee Viratyaporn, Nancy Twu, and Richard Lehman Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, NJ, 08854-8065 ABSTRACT A novel approach has been explored for the efficient dispersion and uniaxial alignment of fibers in dual phase polymer matrices based on the streaming flow that occurs when two immiscible polymer blends are melt processed under high shear conditions. Such conditions improve the alignment and distribution of fibers in the matrix, a feature of particular importance when fine nanofibers are used. This self-alignment mechanism seeks to produce optimum properties from relatively small volume fractions of fiber. Recent efforts have focused on a model system containing micron-size glass fibers in immiscible polymer blends. This paper presents selected mechanical properties measured for the model system and the flow/orientation paradigm that produces the observed morphologies.
INTRODUCTION The high modulus and high strength of glass fibers are attractive attributes that are often utilized in polymer composites to produce a wide range of useful engineering materials that exhibit not only the good strength and stiffness of the fibers but also the toughness and ductility of the polymer matrix. These glass fiber polymer composites are fabricated by a range of methods and in the whole they are highly cost effective for many mid-value applications in transportation and general commerce. Many approaches, such as glass mat infiltration, molding and hand layup of long strands, lamination, and other methods have been used for decades to fabricate glass fiber-reinforced thermoplastics1-3. Even though these approaches provide excellent mechanical properties, many are relatively expensive and time consuming -- not suitable characteristics for mass production. A more desirable approach, sought by many, is the melt-dispersion of glass fibers by extrusion followed by injection molding4, 5. The injection molding of short and long fibers in a polypropylene matrix has shown promising results,5 and properties if this system were observed to increase with increasing fiber lengths. This observation is consistent with the concept of critical fiber length, in which the length of fiber required to achieve load transfer to the maximum extent supported by the fiber is dependent upon the interfacial shear strength of the fiber matrix bond. Given the nearly 100:1 ratio between Young’s modulus of glass fibers and typical polymer matrices, critical fiber lengths are typically quite long. Furthermore, the successful dispersion and melt processing of these long fibers is quite difficult and expensive. In general chemical incompatibility of polar, oxide glass fiber surfaces with the non-polar hydrocarbon character of polymer matrices is well-known. Also well-know are the many coupling agents, often silane based, that are used to compatibilize the polymer-glass interface6, 7. Fiber orientation in the matrix is ano
Data Loading...
