Mica-Based Multilayer Nanocoating as a Highly Effective Flame Retardant and Smoke Suppressant.

Highly flammable polyurethane foam (PUF) remains a key risk factor associated with bedding and upholstered furniture, contributing to the yearly destruction of property and loss of lives. In an attempt to tackle this issue and develop a more benign flame retardant for PUF, a mica-based nanocomposite was deposited using layer-by-layer assembly. Chitosan (CH) and poly(acrylic acid) (PAA) were used to stabilize high-aspect-ratio mica. Foam treated with eight bilayers of CH- and PAA-stabilized mica preserves the porous foam structure, prevents melt dripping, and self-extinguishes during a 10 s torch test, while uncoated foam is completely consumed. When exposed to 35 kW/m2 heat flux during cone calorimetry, the peak heat release rate is reduced by 54% and less-volatile molecules are released during combustion, resulting in a 76% reduction in the total smoke release. This multilayer coating serves as an environmentally benign template for flame-retarding PUF and various other three-dimensional substrates.

Synthesis, bioactivity and zeta potential investigations of chlorine and fluorine substituted hydroxyapatite.

Chlorine and fluorine substituted hydroxyapatites (HA-Cl-F) with different degrees of ion replacement were successfully prepared by the one step mechanochemical activation method. X-ray diffraction (XRD) and FT-IR spectra indicated that substitution of these anions in milled powders resulted in the formation of pure hydroxyapatite phase except for the small observed change in the lattice parameters and unit cell volumes of the resultant hydroxyapatite. Microscopic observations showed that the milled product had a cluster-like structure made up of polygonal and spherical particles with an average particle size of approximately ranged from 20±5 to 70±5nm. The zeta potential of milled samples was performed at three different pH (5, 7.4, and 9). The obtained zeta potential values were negative for all three pH values. Negative zeta potential was described to favor osseointegration, apatite nucleation, and bone regeneration. The bioactivity of samples was investigated on sintered pellets soaked in simulated body fluid (SBF) solution and apatite crystals formed on the surface of the pellets after being incubated for 14days. Zeta potential analysis and bioactivity experiment suggested that HA-Cl-F will lead to the formation of new apatite particles and therefore be a potential implant material.