Investigating the Durability of PHA-Coated Burlap for Coastal Restoration

Many synthetic textiles are used in coastal restoration because natural fiber materials have lower durability and may degrade too quickly; however, these synthetic materials pose environmental risks, such as microplastic pollution. Motivated by the need for materials that balance durability with environmental sustainability, we assessed the feasibility of polyhydroxyalkanoate (PHA) coatings as a strategy to prolong the service life of burlap fabric. Three PHA-based polymers were applied by dip-coating, single-sided melt pressing, and double-sided melt pressing and then immersed in seawater at ∼5 m depth for 288 days. Visual observations, evaluation of the end-point mass loss data, and complementary molecular weight and X-ray scattering analyses show that durability depends on the processing method and polymer crystallinity: double-sided melt-pressed samples retained the most mass (compared to single-sided, dip-coated, and uncoated), and mass loss decreased with increasing initial PHA polymer crystallinity. Additionally, these data support a degradation pathway in which amorphous domains are preferentially eroded and crystalline lamellae thicken due to relaxation of entanglement constraints. These processing-crystallinity-durability relationships suggest that the residence time may be tuned to match restoration schedules, positioning melt-pressed PHA coatings as an ecologically sustainable alternative to persistent plastic materials.