Jennifer Lynch

The Utilization of Recycled Thermoplastic Composites for Civil and Military Load Bearing Applications

Long-term performance and extended service life are issues of vital importance to the Department of Defense (DoD). The DoD seeks alternative construction materials to replace more traditional materials, such as wood and steel, for heavily loaded infrastructure to combat this expensive corrosion and bio-degradation problem. Recently, two military bridge installations were completed, composed entirely of a reinforced thermoplastic composite lumber (RTCL) material that is capable of supporting the load of an M1 Abrams tank at approximately 64,410 kg (71 tons). The RTCL material selected for these applications is polypropylene (PP) coated fiberglass blended with high-density polyethylene (HDPE). Advantages of using RTCL include the following qualities: corrosion, insect, and rot resistance; no toxic chemical treatments required to increase service life; environmentally friendly; diversion of waste plastics from landfills; reduction of deforestation, green house gases, and global warming. RTCL has many advantages but does behave differently than traditional materials and certain properties must be addressed during the design stage. Both bridges are continually monitored, have performed well over the first year and a half, and are more cost-effective than any other construction material. Details of the material, design considerations, and construction are reviewed.

Applications of Functional Nanocomposites

The length scales defining structure and organization determine the fundamental characteristics of a material. Traditional polymeric materials exhibit organization on two length scales: the molecular scale, e.g., the unit cell of the crystal through folding chain or the local arrangement of amorphous polymer phase, and the scale particles/phases within the composite typically much longer length and on the order of micrometers or greater. In immiscible polymer blend, materials (IMPB), however, that melt domains in the nanoscale range, have been observed with ratios that are capable of being generated by manipulating shear rate, temperature, and viscosity during melt processing and by selecting the polymer pair to conform to the requisite viscosity/volume fraction relationship. Properties of IMPB’s have recently shown remarkable enhancements. Nanotechnology of dispersion of nanoparticles in IMPB’s has also been found to be critical component in fabricating nanocomposites of extraordinary structural and functional performance. Among the various methods that are currently used, are functionalization techniques such as coating of nanoparticles with proper material in order to maximize homogeneity of dispersed nanoparticles in the polymer matrix. This approach provides an opportunity for the processing of polymer/ceramic composites at the nanoscale level. Specific examples of ceramic nanoparticle nanocomposite will be discussed with emphasis on mechanical and magnetic properties.