Enhancing the performance of HTPB‐IPDI‐based polyurethane composite liner through effective carbon black dispersion**

Abstract This study aims to improve the dispersion of Carbon Black (CB) filled Hydroxyl‐Terminated Polybutadiene (HTPB)‐Isophorone Diisocyanate (IPDI) based polyurethane liner by both adding a dispersant and developing a production process to obtain improved mechanical, rheological, thermal, and adhesion properties. Printex‐U (CB1) and Thermax N‐991 (CB2) carbon blacks were used as fillers. Three different dispersants, which are BYK 9076 (D1), BYK 9077 (D2), and BYK Silclean 3700 (D3) were added to the liner formulation at various amounts. BYK 9076 (D1) was found as the most effective dispersant due to its bifunctional chemical structure. By adding 2 wt.% of BYK 9076 (D1) dispersant to the polyurethane liner comprising 10 wt.% CB1, viscosity was reduced by 45 %, and tensile strength and elongation at break were improved from 1.77 MPa to 1.88 MPa and from 375 % to 385 % respectively. The dispersion of the CB in the polyurethane liner was further improved by the ultrasonication process and tensile strength and elongation at break were increased to 2.03 MPa and 425 %, respectively. This process also contributed to an improved Limiting oxygen index (LOI), elevating it from 20 % to 22 % initially and further by 25 % through ultrasonication. Scanning Electron Microscopy (SEM) verified that the addition of D1 dispersant and ultrasonication effectively reduced CB particle agglomeration. The migration of plasticizer was also assessed over 12 months through bonding testing, TGA, and FTIR analysis. It was noticed that the effective dispersion of CB particles made the liner more resistant to the plasticizer migration.