Molecular Transportation in Polymer and Composite Materials: Barrier Performance and Mechanical Property Evaluation
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Transport of gasses and liquids through polymers and composites is an important factor to be considered when designing a material for structure and packaging applications. For structural engineering applications, more focus has been given to the transportation of water, vapor and organic liquids rather than gases as diffusion of these liquids into the polymers and polymer-based composites can significantly lower service life. In addition, much attention has been given to the leaching of unreacted reactant molecules, solvents, additives, degradation products from the polymers and composites to the atmosphere (water, soil etc.). We studied the transport of volatile organic compounds and water in cured-in-place-pipe (CIPP) (a representative of FRPC) and gas permeability of highly engineered cellulose nanocrystals (CNC) films.
Cured-in-place-pipe (CIPP) is a popular technology which uses fiber reinforced polymer composite to repair sanitary sewer, stormwater, and drinking water pipe. The liner is installed in the field and exposed to flowing water immediately after installation (curing of the liner) is done. Curing conditions dictate liner properties as undercured liners can contain unreacted styrene monomers, additives, degradation products. These agents can leach out and enter the environment (soil, water, air). The objective of this work was to investigate the curing behavior, volatile content, thermal stability of steam-cured and UV-cured CIPP liners collected from Indiana and New York installation sites. The liner specimens were also exposed to water and other aggressive environmental conditions (saltwater, concrete pore solution at 50 °C) to explore the leaching of unreacted styrene and other organic chemicals from the liners. The influence of transportation of water, salt solution and pore solution through liners on mechanical and thermo-mechanical properties was also examined to study the durability of the liners. Study suggested that the durability of the liners depends on the curing condition and exposed environment conditions.
The function of polymer packaging materials is mainly to inhibit gas and moisture permeation through the films. Cellulose nanocrystals (CNCs) have drawn growing interest for the packaging due to their non-toxicity, abundance in nature, biodegradability and high barrier properties. The objective of this work was to corelate the alignment of CNC with free volume and barrier performance of the film. Furthermore, citric acid (CA) was added to the CNC suspensions with varying quantity to explore the effect of CA on coating quality and barrier performance of CNC coated polypropylene (PP) film. Study revealed that CA addition in CNC suspension can enhance the hydrophobicity and gas barrier performance of coated PP films while retaining the high optical transparency.