Moisture-mechanical performance improvement of thermal insulating polyurethane using paper production waste particles grafted with different coupling agents.

• Titanate coupling agents reduce particle-polyol mixture viscosity more than 2 times. • Titanate coupling agents form hydrophobic monomolecular layer on the particle surface. • Coupled paper waste particles increase compressive and tensile strengths. • Coupled paper waste particles initiate nucleation process in particle-polyol mixture. Current efforts are focused on transforming renewable resources into advantageous polymers and the utilisation of waste for the same application and others. However, the utilisation of waste into polymer systems causes forming mixtures with high viscosities; therefore, this study analyses different types of titanate coupling agents (TCAs), TCA-L44, TCA-L38 and TCA-K44, and their effects on the rheology of bio-based polyol premixes filled with paper waste particles and the physical-mechanical properties and microstructures of polyurethane foams (RPUFs). It is found that TCAs improve the dynamic viscosity of polyol premixes by a factor of two. Based on the scattering of the apparent density results, TCA-L44 and TCA-K44, at amounts of 1–3 wt%, ensure an even distribution of waste particles, while TCA-L38 does not show evidence of coupling. Compared to RPUF without TCAs, the apparent density increased on average from ∼65 to ∼69 kg/m3 for TCA-L44, to ∼71 kg/m3 for TCA-L38 and to 69 kg/m3, indicating a weak cross-link effect. The compressive strength increases by an average of 6.5–9.1% and the tensile strength increases by 26.0–42.2% when TCA-K44 is used, while the water absorption decreases by up to ∼62% and the water vapour diffusion resistance factor decreases by ∼39% when TCA-L44 is used. [ABSTRACT FROM AUTHOR]