Self-Stratification of Ternary Systems Including a Flame Retardant Liquid Additive

Abstract

Particular coating compositions based on incompatible polymer blends can produce coatings having complex layered structures after film formation. The most traditional approaches to their structural modification are the introduction of additives (extenders, inorganic pigments, surface active agents, etc.). As minor additives, some are capable of substantially accelerating the phase separation process with a moderate or negligible influence on the composition equilibrium of solutions. In contrast, in order to be effective, some have to be introduced in significant amounts, thereby substantially changing the resulting distribution of components through the film. Up to now, most of the liquid additives that have been tested destabilized the solutions while impacting the layering process. In this work, two phosphorus based liquid fillers have been introduced (at 2.5 and 5 wt.%) in a partially incompatible polymer blend based on a silicone resin and a curable epoxy resin to fire retard a polycarbonate matrix. Self-stratification was evidenced by microscopic and chemical analyses, flammability by Limiting Oxygen Index (LOI) and UL-94 tests, fire performances by Mass Loss Calorimetry and thermal stability by using a tubular furnace and ThermoGravimetric Analysis. The ternary compositions including 5 wt.% of additives exhibit the best stratification and excellent adhesion onto polycarbonate. Improvements of the fire resistant properties were observed (+7% for the LOI compared to the virgin matrix) when a 200 µm wet thick coating was applied, due to reduced flame propagation and dripping.

Suppression of self-stratification in colloidal mixtures with high Péclet numbers

“…4 Stratified microstructures with designed surfaces 5 are known to tailor coating properties, including the abrasion resistance, 6,7 wetting, 8,9 antifouling, 10 corrosion resistance, 11 and even flame retardancy. 12 Self-stratifying coatings 13 offer greater sustainability through efficient use of resources: materials, time and energy. 14 In certain circumstances, binary mixtures of large and small colloids, [15][16][17] or colloids with soluble polymers in a common solvent, [18][19][20] stratify during drying such that a layer of the smaller species spontaneously assembles at the top of a film, called the ''small-on-top'' structure.…”

Mechanically Enhanced Self-Stratified Acrylic/Silicone Antifouling Coatings

“…Currently, the addition of a bonding layer has been reported to achieve good adhesion ability without reducing the antifouling property [11]. However, this approach is timeconsuming and requires complex procedures and environmental waste generation, which is not always adapted to industrial requirements [27]. As a solution to these short-comings, a new economical and effective self-stratifying system has been developed, allowing a one-step formation of thermodynamically stable multi-layer coating structures after the mixture of two incompatible polymers is applied to a substrate.…”

Self-stratification studies in waterborne epoxy-silicone systems

“…Many attempts for formulating a self-stratified coating system have been reported in the literature [1][2][3][4][5][6]. The most common formulation methods to achieve a spontaneous separation into layers are driven by either the 'evaporation of the solvent or aqueous medium' or the 'selective crosslinking reaction of the polymers with the hardener' or both in systems comprising of immiscible polymers [7,8].…”