Study On Reducing Noxious Aldehyde Emission From Scots Pine MDF

Indoor air environmental pollution has attracted more and more attention.Wood-based panel as indoor decorate materials are major sources for elevated volatile organic compounds(VOC)concentrations in door air.However,source of various groups of VOC emission from wood panels are not very clear as yet.It is very important measure for elevated and improved indoor air quality by understanding VOC emission principle and control mechanism to control the release of VOC from fountainhead of Wood-based panels.Based on analysis the release principle of VOC,the method of reduce hazardous aldehyde emission from Scots pine MDF was proposed.Firstly,the appropriate parameters of rapid test method for testing aldehyde emission from Scots pine MDF are determined by studying the effect of several major factors,micro-chamber temperature,chamber gas flow and sampling start time and analyzing the relationship of between two different volumes environmental chamber test.Hereafter,the physical adsorptive method and mechanical method for avoiding aldehyde release were screened and their effects were verified.Then the impact factors which affected aldehyde release of MDF as resin consumption,moisture content of mat,dosage of antioxidants and the synergistic reaction among them were also studied.At last,optimized hot-pressing parameters and the addition of antioxidants which could reduce aldehyde release based on response surface methodology were confirmed.The effects of these parameters on aldehyde,non-aldehyde VOC,formaldehyde and mechanical properties of MDF were studied and the optimized processing for controlling aldehyde release was obtained.The main results in this paper were shown as follows:(1)Basing on analyzing the releasing source of formaldehyde of Scots pine MDF,two methods which were porous materials absorptive method(physical method)and antioxidant method for reducing formaldehyde release were proposed.The source of formaldehyde of MDF was unsaturated fatty acid which was from its auto-oxidation process.Combination reaction,reaction temperature and metal ion were the main factors of auto-oxidation.These results were the basis for controlling formaldehyde release of MDF.(2)The aldehydes release gradually increased with the exposed time going on,but the VOC release descended with the testing time.The main components of panel's VOC were aldehydes,acids,terrenes and other chemical compound.The release rates of 15L and 23L environment chamber tests were almost same when the temperature,relative humidity,ventilation rate and unit area ventilation were same,above all,the relevance between two testing results was good.The starting time,temperature of chamber and air flow velocity could significantly affect release amount of aldehydes and VOC.Release of aldehydes and VOC of MDF increased as the temperature raised,but descended as the air flow velocity and sampling time raised.(3)The molecular sieve modified by coupler had the best effect among physical absorptive methods,the second one was alumina and the last was zeolite molecular sieve.As the effect for restraining aldehydes and VOC of MDF,the alumina was the best while the silane coupling agent has an adverse effect on VOC's release.(4)The control effect of mixing of potassium permanganate and alumina on VOC is better than potassium permanganate alone,but both of them have non effect on reducing aldehyde emission.The control effect of three kinds of radicals on aldehydes in Europe red pine MDF is related to activation energy of initiator.The results show that only the 2,5-dimethyl-2,5-di(t-butylperoxy)hexane(DHBP)has the best control effect on the aldehydes emission Europe red pine MDF,and the influence of antioxidants(TBHQ?DLTP?BHT?BHA?CA?EDTA)on the aldehydes emission of Europe red pine and other VOC emission is good in the experiment added with different antioxidants.(5)It was verified that antioxidants(TBHQ?DLTP?BHT?BHA?CA?EDTA)had beneficial control effect on release of aldehydes and VOC of Europe red pine through the environmental release cabin method.The control effect of TBHQ and DLTP is significant.The effect of EDTA is not good than the other antioxidants because the action principle is different.It shows that the antioxidants used in food and animal feed can be used as additive for the control of aldehydes release of Europe red pine MDF.(6)The release of the Scots pine MDF aldehydes reduces with the resin consumption increasing.However,the impact of the latter on the former has a range.that's to say,the release of 4%resin content of aldehydes is close to that of 6%resin content of aldehydes,and the concentration of releasing aldehydes is near between 10%resin content and that of 12%MDF.It can be conferred that the scope is approximately 6-10%of the obvious impact that the resin content of the Scots pine MDF has on the release of aldehydes.(7)The increase of release of aldehydes and acids emitted from Scots pine MDF with the inscreases of moisture content.And the release of aldehydes accounts for a large proportion of the VOC emissions,whereas the moisture content has no clear effect on the other VOC components.After the inscreased amount is compared with the amount of the release of terpene,VOC still affects the general trend of aldehydes,showing a similar law that aldehydes are affected by the moisture content of mat.(8)The release of aldehydes in Scots pine MDF increases with the added DLTP increasing.But DLTP has an adverse effect on the release of other non-aldehydes,of which dodecanol contributes a lot.Considering the impact that DLTP has on the release of aldehydes and non-aldehydes,5%of the added amount is recognized as the most suitable for controlling the release of aldehydes in MDF.(9)The release of aldehyde from Scots pine MDF was no increase or decrease with the increase of TBHQ content.Besides,the effects of TNHQ on the release of non-aldehyde VOC were investigated and the adverse effects were not found.The same amount was released from TBHQ aldehyde at the end of tests when adding 0.3%and adding 1.5%,showing that the amount of 0.3%was more suitable for the release control of MDF aldehyde.(10)Synergic effects between DLTP and EDTA were superior to their single operation of DLTP or EDTA,presenting DLTP and EDTA had synergic effects to the aldehyde control for Scots pine MDF.Synergic effects on the adverse influence for non-aldehyde panel were not obvious based on the results of tests and the synergic effects between TBHQ and EDTA were less apparent in this experiment.TBHQ content of 0.5%in the control of the oxidation reaction of panel aldehyde release have excess and the effects of EDTA on the control of aldehydes release were just not shown.Therefor,synergic effects between TBHQ and EDTA were inferior to effects between DLTP and EDTA.(11)The optimized process conditions for DLTP and EDTA were the followings:hot-pressing temperature was 183?,hot pressing time was 10.21 s/mm,antioxidant content was 0.3%(accounting for the weight of dry cellulose),the ratio between DLTP and EDTA was 0.2.