Rigid PU foam panels are essential for building insulation but are notoriously difficult to recycle. Mechanical recycling offers low recovery, incineration is polluting, and chemical recycling requires stringent control. Now, researchers at Guilin University of Aerospace Technology have devised a novel method that employs whisker-toughened aerogels to recycle and reuse these panels.
SiO2 aerogels, known for their excellent thermal insulation properties, suffer from mechanical limitations due to high porosity, restricting their use in construction. The research team had previously improved the thermal and chemical stability of these aerogels with mullite whiskers. They explored incorporating these whiskers into recycled rigid PU through chemical recycling.
Their process involved cleaning, drying, and crushing waste PU sheets, followed by an alcoholysis reaction with diethylene glycol and sodium hydroxide as catalysts. The whisker aerogel was added, and the mixture heated for hours. The regenerated polyols were then combined with commercial polyether polyol in a 1:2 ratio to produce new foam.
The team believed the aerogel would enhance the recycled PU's thermal insulation and heat preservation properties, which their results confirmed. Optimal performance was observed at 0.9% whisker content by weight, beyond which thermal conductivity increased
and strength decreased due to aerogel agglomeration.
The researchers attributed the enhanced properties to the whiskers' role in bridging and transferring stress, improving the toughness of the recycled PU composite. They concluded that these recycled PU foam composites have significant potential for building insulation and provide an efficient recycling method for waste rigid PU panels.
Source :Utech
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