PVA-7HCPC-DOPO composite film with complementary optical and flame-retardant properties

This study reports the development of multifunctional poly (vinyl alcohol) (PVA) composite films incorporating a phosphorus-based flame retardant such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as a flame-retardant component and a 4-(7-hydroxy-2-oxo-2H-chromen-3-yl)benzoic acid (7HCPC) as a coumarin-derived chromophore, PHDP film prepared through a solution-casting method using water-ethanol as a solvent. The resulting films were characterized by spectroscopic analyses FTIR and NMR that verified the successful incorporation of the functional components and indicated changes in the local chemical environment of the PVA matrix. Optical measurements showed absorption bands at 332 and 422 nm and a fluorescence maximum at approximately 476 nm, confirming retention of the chromophore’s fluorescence after incorporation into the composite. XRD and SEM–EDS analysis indicated partial structural reorganization and a broad distribution of additive-containing domains within the analyzed region. The PHDP film exhibited a tensile strength of approximately 4.75 MPa and a Young’s modulus of 5.94 MPa, together with substantial deformability. Thermal analysis showed multistage degradation and a residual char fraction, while UL-94 and LOI measurements resulted in a V-0 rating and an LOI value of 36%, respectively. The film also exhibited measurable inhibition zones against the tested bacterial and fungal strains. Overall, the results demonstrate that incorporation of DOPO and 7HCPC provides complementary flame-retardant and optical functionalities in a PVA-based composite film, together with measurable thermal, mechanical and antimicrobial characteristics.