Cellulose nanowhisker (CNW) prepared by acid hydrolysis of softwood Kraft pulp was incorporated as nanofiller in rigid polyurethane (PU) foam synthesis. The density, morphology, chemical structure, mechanical properties and thermal behavior of the products were characterized. The nanocomposites exhibited better performance especially at high CNW¡¯s content which was probably due to the high specific strength and aspect ratio of CNW, the hydrogen bonding and crosslinking between CNW and polymer matrix, a higher crosslinking density compared to the control, and the function of CNW as an insulator and mass transfer insulator. Lignin polyol was synthesized through oxypropylation and used for rigid PU foam preparation. The density, morphology, chemical structure, compressive property and thermal behavior of the product were characterized. Lingin-based rigid PU foam showed improved compressive property compared to its commercial counterpart. Ethanol organosolv lignin-based PU showed a slightly stronger compressive property than Kraft lignin-based PU. The enhancement was primarily attributed to the rigid phenolic structure and the high hydroxyl functionality of lignin. Lignin-based PU generated more char than common PUs which was possibly related to the better flame retardant property. This study provided an alternative way to valorize the two most abundant biopolymers and resulted in relatively environmentally benign rigid PU nanocomposite foam.

The thesis deals with the processes that occur in the course of the manufacturing of rigid polyurethane-polyisocyanurate (PU-PIR) foams, their properties and technology. It deals above all with principles of foam nucleation and stability. The purpose of understanding these principles is their possible use for improving thermo-insulating properties of the material. The experimental part of the thesis studies the influence of additives and ultrasound on the PU-PIR foam properties. It has been found that low molecular weight compounds with perfluorinated chain leads to decreasing foam cell size and its lower thermal conductivity. The additives mentioned act probably on the surfactants principle by facilitating nucleation and stabilizing growing centres of bubbles. They probably form also part of blowing agents mixture inside the foam cells which cause lowering of thermal conductivity as well. Compounds with similar chemical structure have unique influence on the properties of rigid PU-PIR foams. Further research ought to be focused on cheaper modes of producing perfluorinated compounds.