Preparation And Characterization Of Phenolic Foam Modified With Wood Bio-oil And Nano-montmorillonite

Phenolic foam(PF)has been widely used in many fields thanks to its excellent flame resistance and good thermal insulation,such as construction,transportation,etc.However,traditional PF is easy to crack or even fall off due to its low toughness and high pulverization rate,which limits its application and development.Introducing toughening agents into PF can effectively improve its toughness,but its flame retardant performance will be adversely affected and show a decrease,which will cause hidden safety hazards.Therefore,seeking an eco-friendly PF with good toughness and flame resistance has important practical application value.The aim of this paper is to improve the toughness of PF using wood bio-oil while ensuring its excellent flame resistance with the addition of nano-montmorillonite(MMT).Therefore,the phenolic foam reinforced with bio-oil and MMT(MBPF)was prepared.The effect of the substitution rate of bio-oil to phenol and the addition rate of MMT to phenol on the properties of phenolic resin reinforced with bio-oil and MMT(MBPR)and MBPF was studied,and then the MBPR synthesis process was optimized.Meanwhile,the influence of foaming process on the performance of MBPF was also investigated,and the foaming process of MBPF was optimized.Furthermore,the interaction mechanism of bio-oil and MMT was explored.The main conclusions of this paper are as follows:(1)The optimized performance of MBPR was obtained with the substitution rate of 30 wt % bio-oil to phenol and the addition rate of 4 wt % MMT.MBPR prepared under the optimum condition had a viscosity of 3050±87 m Pa·s,a solid content of 76.3±0.2 % and the curing time of 811±36 s.(2)The optimized performance of MBPF was obtained with the addition rate of 6 wt % blowing agent,the addition rate of 15 wt % composite curing agents,the addition rate of 5 wt % surfactant and the foaming temperature of 75 ?.As a result,the toughness and flame resistance of MBPF were improved and the pulverization rate was reduced under this process compared to PF,exhibiting a compressive strength of 2.50±0.02 MPa,a limited oxygen index of 40.8±0.9 % and a pulverization rate of 5.10±0.34 %.(3)Bio-oil expanded the interlayer spacing of MMT sheets,forming an exfoliating MBPF composite material.The C=O peak appeared in MBPF,and the methylene and ether bond peaks were enhanced compared to PF after adding the bio-oil,indicating the introduction of flexible long chains.After the addition of MMT,the-OH peak in MBPF shifted to a lower frequency,that is,a hydrogen bond was formed between the MMT and molecular chains in PR,thereby improving the compatibility.Both bio-oil and MMT have the effect of reducing the cell size and forming uniform structure,thus the cells within MBPF were uniform and compact.Bio-oil reduced the thermal stability of foam,whereas MMT enhanced the thermal stability of foam.After the co-modification of bio-oil and MMT,the initial decomposition temperature of MBPF was increased,and the maximum weight loss rate temperature was equivalent to PF,indicating that the thermal stability of MBPF was improved compared to PF.