| One main reason for fire accidents of high-rise buildings is the poor fireresistance of thermal insulation materials, such as polystyrene foams andpolyurethane foams, which are still widely used in the buildings. However,phenolic foam plastics have gradually received more and more attentionsbecause they possess both exceptional fire proof property and thermalinsulating property. But the application of phenolic foam plastics has beentremendously restricted due to their relatively low mechanical performance,extreme brittleness and friability. Therefore, how to enhance mechanicalproperty has been a hot issue in the heat preservation field. In this study, theinfluence of additives on the mechanical property of phenolic foam plasticswas investigated, and the formula of preparation was optimized throughorthogonal test. In order to further improve mechanical property and obtain thehigh-performance phenolic foam plastics, functional jute fibers prepared byour research group were blended with phenolic resin.In the preparation of phenolic foam plastics, it has a great influence of thetype and content of blowing agent, curing agent and other additives on the properties. In this experiment, n-Pentane, sulfuric acid and P-TSA, Tween-80was employed as blowing agent, curing agent, surfactant, respectively.Phenolic foam plastics were prepared through low-temperature foamingmethod and the influence of additives on the apparent density and compressivestrength was investigated. In addition, the optimum formula was obtainedthrough orthogonal experiment.Many methods have been used to make phenolic foam plastics tougherand the fiber-reinforcement is considered to be an effective approach. Naturalfibers such as jutes have attracted a great deal of interests because of theirexcellent performances: acceptable specific strength properties,biodegradability and low cost. Therefore, jute fibers were used as reinforcedmaterial of phenolic foam plastics. Toughening effect was greatly reducedbecause of the poor compatibility between the hydrophilic raw jute fibers witha lot of hydroxyl groups on the surfaces and hydrophobic phenolic foam. So,in this study, jute fibers had been treated with NaOH solution and oleic acidbefore blended with phenolic resin, and then phenolic foam composites wereprepared by the optimum technological conditions.Universal testing machine was used to analyse the mechanical property;scanning electron microscopy (SEM) and inverted biologic microscope wereemployed to observe the morphology; the valence-bond structures of the fiberswere characterized by fourier transform infrared spectroscopy (FTIR); contactangle was tested by contact angle apparatus; TG curves were used to analyze the thermal properties. The results show that:(1) The optimum formula of curing agent: mass ratio of sulfuricacid/p-TSA was1:2-2:1, mass concentrations were40%-60%; the best formulaobtained by orthogonal test: the content of blowing agent, curing agent,surfactant was7wt.%,18wt.%,4wt.%, respectively, and the temperature was70℃; phenolic foam prepared by the best formula had uniformly distributedand small-sized voids, excellent mechanical and thermal performance.(2) Jute fibers were treated by NaOH and oleic acid. The hemicelluloseand lignin in the oleic acid-treated fibers were drastically reduced and thesurface was successfully modified by non-polar group-CH2-, thus thehydrophilia of fibers reduced.(3) The voids of the phenolic foam with treated fibers were moreuniformly distributed and had smaller sizes than the untreated ones. Also, thetreated fibers could greatly boost mechanical properties. When the content oftreated fibers was1.5wt.%, the compressive strength was281.60kPa whichwas higher than the standard100kPa and the bending strength was453.46kPawhich was far higher than the standard434.03kPa. Phenolic foam plastics with1.5wt.%treated fibers had a lower pulverulent ratio and maintained excellentthermal property. |
PDF Full Text Request