| Phenolic foams(PF)has excellent flame resistance performance.Since PF keeps many other advantages such as low thermal conductivity,low density and low cost,it can be widely used in building exterior wall as thermal material.But,some other characteristics of PF,like easy powder dregs and weak mechanical strength,limit its popularization and application with a large scale.Cardanol can replace a part of phenol to prepare phenolic resol resin that modified by cardanol.So as to achieve the purpose of improve the mechanical performance of PF.The reaction system of foaming resol resin keeps highly polar,while its oligomer is solubility in water.But one hurdle that prevents cardanol large usage in foaming resol resin is its low polar which decide by its structure.Because its reaction active point can not contact formaldehyde effectively.So,in this work,C=C in the unsaturated side chain of cardanol was oxidized to hydroxyl to improve its compatible,because hydroxyl keeps highly polar.The synthesis of polyhydroxylated cardanol(PHC)PHC helps it integrated the reaction system of foaming resol resin more easily than cardanol did.It made substitution phenol with PHC possible in the process of foaming resol resin preparation,and such foaming resol resin was successfully applied to fabricate PF by combining proper curing agent,surfactant,and foaming agent.In the first step,C=C in the unsaturated side chain of cardanol was oxidized by H2O2 and HCOOH as catalyst and turned into epoxied cardanol(EC).Then some sodium hydroxide aqueous solution was added in the flask after it cooled to room temperature,p H of the system was adjusted to 10-12.And the resultant was PHC.Phenolic resol resin was synthesized by phenol and paraformaldehyde instead liquid formaldehyde,and zero discharge of wastewater in the production process.Phenolic resol resin modified by cardanol and PHC are synthesized successfully.And the condition were shown as: mole ratio of total phenols with formaldehyde was 1:1.7,temperature of condensation polymerization was 95 oC and Na OH as catalyst.Viscosity of phenolic resol resin was between 6000 – 10000 m Pa·s.By analyzed every performance of modified phenolic resol resin,it was found that with the increase of cardanol or PHC,the influence of phenolic resol resin are as follows:(1)The solid content of phenolic resol resin were about 80% and got little change with the condition that resin keeps similar viscosity that between 6000 – 10000 m Pa·s;(2)As the result of TG analyzed,the mass residue ratio of phenolic resol resin were decreased gradually under the condition at 900 oC.The mass residue of phenolic resol resin was 54.81%.41.75% and 39.21% while the replacement percentage of phenol by cardanol or PHC were up to 20%;(3)As the result of gel temperature analyzed,the introduction of cardanol and PHC has little effect on the activity of resin.The gel temperature of phenolic resol resin was 138.5 oC.145.6 oC and 147 oC while the replacement percentage of phenol by cardanol or PHC were up to 20%,increased by 5.1% and 6.1%,respectively.By analyzed every performance of PF,it was found that PF modified by PHC is better than PF modified by cardanol and pure PF overall.The density of foams were between 45 – 50 kg/m3:(1)While the replacement percentage of phenol by PHC or cardanol was 10%,PF modified by PHC keeps the highest limit oxygen index(LOI),39.2%,the highest LOI of PF modified by cardanol was 37.7% and PF was 33.1%;(2)The flexural strength and compressive strength of PF were 0.18 MPa and 0.14 MPa.While the replacement percentage of phenol by PHC was 10%,the flexural strength and compressive strength of PF modified by PHC was 0.34 MPa and 0.22 MPa,increased 57% and 61%,respectively.At the same time,the highest flexural strength and compressive strength of PF modified by cardanol were 0.24 MPa and 0.17 MPa,while the replacement percentage of phenol by cardanol was 5%,increased by 33% and 21%,respectively.(3)The introduction of cardanol and PHC has little effect on the thermal conducitivity of PF that modified by cardanol and PHC.Thermal conducitivity of PF and PF that modified by cardanol or PHC were between 0.040 ± 0.003 W/(m·K).(4)While the replacement percentage of phenol by PHC was 5%,PF modified by PHC keeps the lowest sleg rate with 19.8%.And while the replacement percentage of phenol by PHC was 10%,PF modified by cardanol keeps the lowest sleg rate with 24.4%,as the same as pure PF.(5)While the replacement percentage of phenol by PHC was 10%,PF modified by PHC got the best bubbles,because the bubbles are small and uniform distribution.At the same time,PF modified by PHC keeps the lowest total smoke release,based on the result of cone calorimeter. |
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