Abstract
Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings.
Highlights
Polyurethanes (PUR) are used in a wide range of industries due to their adjustable parameters [1]
It points to the synergy between the applied modifiers and confirms previous works of other research groups, as well as the conclusions based on the limiting oxygen index (LOI) investigation morillonite and aluminum diethyl phosphinate were analyzed
The efficiency of the coating comprised of five bilayers was confirmed by a 22.7% drop of peak value of the heat-release rate (pHRR) and a 52.7% reduction of total heat released (THR) comparing to the uncoated foam
Summary
Polyurethanes (PUR) are used in a wide range of industries due to their adjustable parameters [1]. Flexible polyurethane foams have gained a significant position among foam materials due to their application in the furniture industry, mainly in mattresses production, where their light weight and mechanical performance can be combined. It is associated with the open cell structure leading to increased flexibility, and high water and air permeability [4]. An important feature of these materials is the possibility to apply them on site as sprayed foams, which enables the manufacturing of thermal insulation without joints, which significantly reduces heat loss due to gaps or seams This translates into energy efficiency and reduced costs of heating/air conditioning of buildings. Different state-of-the-art strategies applied in the improvement of flame retardancy of PUR foams using clays are reviewed and discussed
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