Study On Environmental Safety Performance Of Bio-oil Phenol Formaldehyde Plywood

Pyrolysis bio-oil was used to partially substitute for phenol in reacting with formaldehyde for the production of bio-oil phenol formaldehyde plywood（BPFP）panels was considered one of the most promising ways to modify phenol formaldehyde resins.However,in previous studies about BPFP,few researchers paid attention to its environmental and safety performance.Then,in this study,the free formaldehyde and total volatile organic compound（TVOC）emission from the BPFP was detected by the headspace gas chromatography-mass spectrometry（HS-GC/MS）,and analysis of safety performance by comparison with Phenol Formaldehyde Plywood（PFP）.According the results,the effect of pyrolysis bio-oil on the safety performance of BPFP was analysis.In the second study,in order to reduce the negative impact and expand the positive impact of pyrolysis bio-oil on the safety performance of BPFP,six factors including the substitution rate of bio-oil to phenol,the molar ratio of formaldehyde and phenol(n_（F/P）),the amount of glue applied and three factors in the hot pressing stage:time,temperature and pressure were selected and an L₂₅（6⁵）orthogonal experiment design was executed.Main conclusions of this study as follows:（1）When the preparation process of PF and PF are exactly the same,the free formaldehyde content in BPFP is about 4 times that in PFP.There are four main reasons:first,there are also non-phenols in the pyrolysis bio-oil,except the phenols;second,the active sites of some phenolic compound in the pyrolysis bio-oil are partially or completely replaced by other functional groups;third,the phenolic compound with active site are all macromolecular,and their relative molecular mass is greater than PF;fourth,pyrolysis bio oil has many acidic substances which will affect the effect of catalyst.The above four reasons lead to the relatively excessive formaldehyde content in the synthesis of BPF,or produce more unstable compounds,which leads to the increase of free formaldehyde content in BPFP.However,according to the analysis of the influence of the process parameters on the content of free formaldehyde in BPFP,it can be seen that the content of free formaldehyde in BPFP can be reduced by properly reducing the molar ratio of formaldehyde and phenol,increasing the amount of catalyst,increasing the temperature and time of hot pressing.（2）When the preparation process of PF and PF are exactly the same,In terms of VOC quantity,there are 35 VOCs in BPFP,about 1.75 times of PFP,of the 35 VOCs,24 were affected by the fast pyrolysis bio oil,accounting for 68.6%.In terms of TVOC content,the TVOC content in BPFP is much lower than that in PFP,and the TVOC content in 40%BPFP is the lowest,about 15.1%of that in PFP.In carcinogenicity analysis,there are 5（possible）carcinogenic substances in BPFP and 3 in PFP,and the results of non-carcinogenicity analysis showed that bio oil had little effect on the safety of BPFP.（3）The influence of 6 factors on the free formaldehyde content in BPFP is as follows:Amount of glue<Bio-oil replacement rate<Hot pressing time<n_（F/P）<Hot pressing pressure<Hot pressing temperature,and the effect on TVOC content is as follows:Hot pressing pressure<Amount of glue<Hot pressing time<Hot pressing temperature<Bio-oil replacement rate<n_（F/P）.It can be seen from the ranking that these six factors have differences in the influence of free formaldehyde and TVOC content in BPFP.The difference mainly caused from two aspects:The first is that formaldehyde is easier to dissolve in water than other VOCs,during the hot-pressing phase,when the water vapor inside the plywood is discharged outside the plywood,it is discharged more quickly out of the plywood because the formaldehyde dissolves in water vapor.On the other hand,the volatility of formaldehyde is better than other VOCs,so formaldehyde is more volatile when it’s affected by temperature.