Flame-Retardant Coatings via Polyelectrolyte Complexes

The patent applies preliminary action by pre-forming polyelectrolyte complexes (PECs) in solution before deposition. The PECs are prepared in advance with controlled stoichiometry and character, then applied to wood substrates in a single step rather than building layer-by-layer. This preliminary preparation of the coating material resolves the contradiction by enabling effective flame-retardant coating in one deposition step instead of requiring multiple time-consuming bilayer assemblies.

The patent merges multiple functions into a single coating layer. Instead of depositing separate polyelectrolyte layers sequentially (LbL assembly), the invention combines cationic and anionic polyelectrolytes into a pre-formed complex that deposits simultaneously. This merging of the coating process into a single step dramatically reduces processing time while maintaining flame-retardant effectiveness.

The patent applies segmentation by separating the complex formation step from the deposition step. The polyelectrolyte complexes are formed separately in solution with controlled composition and properties, then applied as a unified coating material. This segmentation allows the complex to be optimized for flame-retardant performance independently from the deposition process, simplifying the overall coating application to a single step while maintaining effective multi-layer equivalent protection.

The patent changes key parameters of the coating approach by using pre-formed PECs with controlled charge ratios, molecular weights, and stoichiometry. Instead of varying the number of bilayers (a parameter in LbL assembly), the invention controls coating performance by adjusting PEC formation parameters such as mixing ratios and solution conditions. This parameter transformation simplifies the process from multiple deposition cycles to a single optimized deposition step.

The patent changes the fundamental parameter of flame-retardant mechanism from inorganic filler loading to polyelectrolyte complex composition. Instead of adding high amounts of inorganic fillers that compromise mechanical properties, the invention uses organic polyelectrolyte complexes with tunable chemical structures, charges, and molecular weights. This parameter change enables achieving effective flame-retardant properties at lower loadings that preserve the mechanical integrity of the wood substrate.

The patent employs composite materials by creating polyelectrolyte complexes through electrostatic interactions between cationic and anionic polyelectrolytes. These composite structures combine the benefits of both polyelectrolyte components, forming a coordinated complex that provides flame-retardant properties without the high loading requirements and mechanical property deterioration associated with inorganic filler systems.

The patent changes the chemical composition parameters of the flame-retardant system from conventional toxic chemicals to biocompatible polyelectrolytes. The cationic and anionic polyelectrolytes can be selected from natural or biodegradable sources, fundamentally altering the chemical nature of the flame-retardant coating to eliminate toxicity and bioaccumulation concerns while maintaining effective flame-protection properties.

The patent applies this principle by using biodegradable and environmentally benign polyelectrolyte materials that can safely decompose after serving their flame-protection function. Unlike persistent conventional flame retardants that accumulate in the environment, these polyelectrolyte complexes are designed to be environmentally safe and non-toxic, aligning with the principle of using materials that do not create long-term environmental harm.