Effects of Cationic Polyacrylamide on Hydrothermal Formation of Ultralong α‐CaSO 4 ·0.5H 2 O Whiskers

Herein, ultralong α‐CaSO 4 ·0.5H 2 O whiskers with an average length above 500 µm and aspect ratios of 200–500 are hydrothermally produced employing trace amount (0.06 mg L −1 ) of cationic polyacrylamide (CPAM) as the morphology modifier. The hydrothermal formation mechanisms of α‐CaSO 4 ·0.5H 2 O involving the initial nucleation of bassanite nanocrystals/nanorods and their subsequent self‐assembly into long whiskers through oriented attachment are revealed for the first time. Experimental results indicate that CPAM is electrostatically adsorbed onto the initial bassanite nanorods and results in their near‐neutral surfaces, favoring the assembly of the initial nanorods into larger aggregates, thus finally leading to the formation of ultralong α‐CaSO 4 ·0.5H 2 O whiskers with high aspect ratios. Moreover, α‐CaSO 4 ·0.5H 2 O whiskers are calcined to CaSO 4 whiskers for the fabrication of polyvinyl chloride (PVC)/CaSO 4 composites with a high impact strength and flexural strength of 42.0 KJ m −2 and 53.6 MPa, respectively, indicating that the mechanical properties of the PVC/CaSO 4 composites could be significantly improved by these ultralong CaSO 4 whiskers.