Coated biodegradable building article
View Patent ↗A composite material includes a matrix composed of a polyhydroxyalkanoate (PHA) polymer and a filler composed of particles dispersed in the matrix. The particles are composed of naturally-derived materials (e.g., ground bone meal or pumice powder), have a microporous microstructure, have a low hygroscopic expansion, and are less than 1.0 mm in size. Preferably, the matrix and the filler together constitute 100% by weight of the composite material, and at most 30% by volume of the composite material is consumed by the filler. The composite material may take the form of an anaerobically biodegradable article of manufacture such as a building material a coating of a building material or other article.
1. A building article composed of a biodegradable composite structural building material coated with a layer of anaerobically biodegradable composite material;
wherein the layer of anaerobically biodegradable composite coating material is composed of
a polyhydroxyalkanoate (PHA) polymer matrix, and
a filler composed of particles dispersed in the PHA polymer matrix;
wherein the particles have pores with diameters less than 2 nm, wherein the particles have diameters within the range 0.1 mm to 1.0 mm, and wherein the particles have a hygroscopic expansion of at most 2%;
wherein the hygroscopic expansion of at most 2% is defined to mean that a fractional amount of linear expansion the particles experience as a result of being saturated by moisture is at most 2%;
wherein the particles dispersed in the PHA polymer matrix are composed of ground bone meal.
2. The building article of claim 1 wherein the layer of biodegradable composite coating material has a thickness of at most 5 mm.
3. The building article of claim 1 wherein the filler consumes between 15% and 25% by volume of the biodegradable composite coating material.
4. The building article of claim 1 wherein the particles dispersed in the PHA polymer matrix are composed of pumice.
5. The building article of claim 1 wherein the PHA is poly(B-hydroxybutyrate)-co-poly(B-hydroxyvalerate).