Research On The Construction And Application Of Formaldehyde Release Model Of Wood-based Panels

As the main material for interior decoration,wood-based panels have always attracted people’s attention for their safety and environmental performance.Wood-based panels made of aldehyde-containing resin will slowly release formaldehyde to indoor air during using time.Therefore,the amount of formaldehyde released by wood-based panels is one of the key indicators for its quality control,and it is also one of the important factors affecting indoor air quality.At present,the detection methods of formaldehyde content/release in wood-based panels mainly include 1m3 climate chamber method,perforated extraction method and desiccator method.The 1m3 climate chamber method is the only legal ruling method for the amount of formaldehyde released from wood-based panels specified in the mandatory national standard GB18580-2017.However,this method has problems such as long detection cycle and high detection cost,and it is difficult to meet the daily production control in wood-based panel enterprises.Therefore,it is necessary to establish the correlation between the 1m3 climate chamber method and the perforated extraction method/desiccator method.At the same time,the indoor air formaldehyde concentration is also affected by the board loading ratio and indoor environmental factors,such as indoor temperature,relative humidity and air exchange rate.In order to make the indoor air formaldehyde concentration qualified after decoration,it is necessary to study the loading ratio limit of the board in the use area under the extreme temperature and humidity.When determining the concentration of formaldehyde in indoor air,China’s current indoor air quality standards GB 50325-2020 and GB/T 18883-2002 are inconsistent with the time requirements for closing doors and windows:GB 50325-2020 requires to close doors and windows for 1 hour,while GB/T 18883-2002 requires that the indoor air formaldehyde concentration can be measured only after the doors and windows are closed for 12 hours.Closeing time is often the focus of conflict between building providers and residents.In order to solve the above-mentioned problems,this research first deduces the mathematical relationship between the climate chamber method and the perforated extraction method/desiccator method detection results theoretically,and then taked various types of wood-based panels as the research object and adopted the 1m3 climate chamber method to study the formaldehyde release of the board,meanwhile obtained the mass transfer coefficient of the board formaldehyde release process and the correlation equation parameters of the climate chamber method between the perforated extraction method/desiccator method.Based on the study,the formaldehyde limit value of the climate chamber method that corresponds to the perforation method detection value/desiccator method detection value range is obtained.Then,the Berge equation and Merye’s formula were used to investigat the influence of temperature,humidity and air exchange rate on the formaldehyde emission of wood-based panels.According to the data of the highest monthly average temperature,hottest monthly average humidity and air exchange rate in major cities of China,the correction coefficients of formaldehyde emissions from wood-based panels in each city were obtained.According to the single-zone mass balance relationship of indoor decoration formaldehyde pollutants,the calculation formula for the indoor loading ratio limit of wood-based panels based on the limit formaldehyde emission was deduced and verified.Finally,the relationship between the change of the formaldehyde concentration and the sealing time in the climate chamber and the room environment is investigated to determine the appropriate closeing time of the doors and windows.The following conclusions were obtained through the above research:(1)There is a linear calculation equation C∞(t)=A·C0+B between the test result of the climate chamber method and the test result of the perforated extraction method;There is also a linear calculation equation C∞(t)=C·CW+B between the test result of the climate chamber method and the test result of the desiccator method.The formaldehyde emission characteristic parameters of wood-based panels(including convective mass transfer coefficient and distribution coefficient)vary greatly,but the relative deviation of the formaldehyde release characteristic parameters of wood-based panels of the same type and thickness is slightly smaller.(2)To make the formaldehyde detection value of the climate chamber method lower than 0.124mg/m3 for the fiberboard/particle board with a thickness of 7-10mm,the perforated extraction method formaldehyde detection value should be less than 4.1mg/100g;for the fiberboard/particleboard with a thickness of 18mm,the formaldehyde detection value of perforated extraction method should be less than 4.8mg/100g;for the thickness of 9mm plywood,the formaldehyde detection value of the desiccator method should be less than 2.01mg/L;for plywood/blockboard with a thickness of 15-18mm,the formaldehyde detection value of the desiccator method should be less than 2.49mg/L.Whether this result is applicable to all wood-based panels still needs a lot of data to test.(3)High temperature,high humidity and low air exchange rate will increase the measured value of formaldehyde emission from wood-based panels.The formaldehyde emission value of wood-based panels at different temperatures can be corrected by the formula α=e-R(1/(t+273.15)-1/(t0+273.15)).The formaldehyde emission value of wood-based panels at different relative humidity can be corrected by the formula β=1+A(H-H0),and the formaldehyde emission value of the wood-based panel under different air exchange rates can be corrected by the formula 1/C∞=1/keCeq·N+Cq.According to the highest monthly average temperature,hottest monthly average humidity,and temperature and humidity correction equations published by the National Bureau of Statistics,the temperature and humidity correction coefficients for formaldehyde emissions in major cities can be obtained.When the doors and windows are closed the air exchange rate is 0.2 times/h in the heating area,and the air exchange rate is 0.5 times/h in the non-heating area are closed,the correction factor of the formaldehyde emission in major cities can be calculated under extreme temperature,humidity and air exchange rate.The derived calculation formula for the indoor loading ratio of formaldehyde based on extreme conditions was verified in the climate chamber and the actual room,and the accuracy of the calculation formula was proved.(4)The formaldehyde of wood-based panels is released quickly in the closed space at the initial time,and the formaldehyde concentration tends to be stable after 8h-12h.Therefore,it is more reasonable to close 12h before measuring according to GB/T 18883 than for 1h before measuring according to GB 50325.