Preparation And Performance Of Phenolic Foam With Low Formaldehyde Release Based On Biomass Tannin

In recent years,with the vigorous development of China's construction industry,the demand for new fire protection and thermal insulation materials is increasing.Phenolic foam has received more and more attention and favor from the government and researchers in recent years due to its good flame retardant effect.At present,the flammability level of phenolic foam is V0 grade,which is a flame retardant level.Therefore,phenolic foam materials can be promoted in places and fields such as aircraft,ships,stations,hospitals,sports facilities,household doors and windows for thermal insulation and flame retardancy,which can effectively reduce fire occurrence and fire loss.However,due to the presence of free aldehyde,the phenolic foam produced will slowly release formaldehyde over time,which will cause great damage to the human body in the long run.Moreover,phenolic foam uses acid as a curing agent.The foam shows acidity,which can cause corrosion to metals and reduce the service life of ships,home doors and windows.Therefore,it is necessary to modify the phenolic foam to produce a foam with low acidity and low formaldehyde emission to meet the requirements of these fields and places.In recent years,the use of biomass materials to modify phenolic foam has attracted more and more attention,because biomass raw materials not only have cheap and low cost,but also can replace phenol,reduce people's dependence on petroleum products,ease the energy crisis,and protect surroundings.In the past,the use of tannin modified phenolic resin was mainly used to improve the mechanical properties of phenolic foam.This study mainly used the high activity of tannin to reduce the formaldehyde content.This is because the presence of the trihydric phenol structure in the tannin molecule allows it to undergo a phenol-like reaction.Each trihydric phenol has two reactive sites and has a very high reactivity with formaldehyde,so it can improve formaldehyde utilization,reduce the residual formaldehyde in the resin,which in turn reduces the amount of formaldehyde released from the phenolic foam.Therefore,based on the original literature,the author optimized the synthetic route of the resin and added quantitative urea to the phenolic resin in two batches to react with the residual formaldehyde to further reduce the free aldehyde content in the resin.Compared with previous studies,in addition to reducing formaldehyde emission,the phenolic foams prepared also improved thermal stability and flame retardancy without losing their mechanical properties.Biomass tannin was used to replace part of phenol,urea was used as formaldehyde trapping agent,and the mixed acid of sulfuric acid and p-toluenesulfonic acid was used as curing agent.The structure of the product was characterized by a Fourier transform infrared spectrometer,the effects of different tannin additions on the mechanical properties and flame retardancy of phenolic foam were tested using an electronic universal testing machine and a limiting oxygen index meter,and the effect of different amounts of tannin on the release of formaldehyde from phenolic foam was detected by GB/T 30694-2014.The results show that the pH of the modified phenolic foam is about 6,when the amount of tannin added is 3%of the mass of phenol,the minimum formaldehyde emission of phenolic foam is1.1875mg/L,which meets the E1 standard of wood-based panels,and the compression strength is 0.2166MPa.,the strength is 2.81kJ/m~2,the pulverization rate is as low as2.01%,and the limiting oxygen index is 37.0%,its comprehensive performance is the best.Compared with pure phenolic foam,the mechanical properties of tannin-modified phenolic foam have been improved,and the brittleness is significantly improved.In terms of flame retardancy,the limiting oxygen index of the modified phenolic foam is increased,and the flame retardancy is improved.