镁铝尖晶石对磷酸二氢铝固化作用研究

Curing effect of MgAl_2O_4 spinel to aluminum dihydrogen phosphate

首次采用镁铝尖晶石粉体为反应助剂开展了水溶性磷酸二氢铝溶胶的低温固化作用研究,并制备了石英织物增强磷酸铝基复合材料。通过XRD、TGA-DSC、SEM等分析测试手段,研究了尖晶石粉体对磷酸二氢铝树脂的固化温度、固化产物及最佳计量比,探讨了尖晶石固化磷酸铝复合材料的内部结构、力学强度及抗吸湿性能。结果表明,采用镁铝尖晶石为磷酸铝树脂固化助剂,可以实现酸式磷酸二氢铝树脂在170℃附近中低温脱水交联固化,并有利于减少基体内生孔洞缺陷;尖晶石参与反应时固化产物为低温石英型磷酸铝(B-AlPO_4)和单斜磷酸镁(Mg_3(PO_4)_2),阻止了低温下Al(H_2PO_4)_3向亲水型多聚磷酸盐的转变,改善了复合材料抗吸湿性能;当尖晶石添加量达到18%时,复合材料力学性能最佳,室温弯曲强度达到165 MPa、800℃弯曲强度达到75 MPa,且材料介电性能保持稳定(介电常数3.5～3.6、损耗角正切值<0.01)。

MgAl 2O 4 spinel powders were first applied for aluminum dihydrogen phosphate hydrosol curing reaction. The solidification of spinel powders to phosphate hydrosol was studied in middle and low temperature condition. Besides,composites were prepared with quartz textile as reinforcing part,aluminum hydrogen phosphate hydrosol as matrix and spinel MgAl 2O 4 as firming agent. Curing temperature of phosphate hydrosol and the additive content of spinel MgAl 2O 4 powders were measured by thermogravimetric analysis and differential scanning calorimeter. At the same time,the crystalline phase of curing products was identified by X-ray powders diffraction. Microstructures of the composites were observed by scanning electron microscope. Moreover,the mechanical and resistant moisture absorption properties of phosphate composites were investigated. The results showed that aluminum dihydrogen phosphate resin had occurred dehydration reaction and formed into cross-linkage net in the temperature near to 170 ℃,while the resin was added spinel MgAl 2O 4 powders. And it was contributed to reduce original pores and flaws in the matrix with mild reaction process. Owing to the promoting effect of spinel,the mainly reaction products were aluminum phosphate with the style of quartz and magnesium phosphate with monoclinic structure. Meanwhile,the reaction that aluminum dihydrogen phosphate changed into aluminum polyphosphate was prevented,which was benefit to enhance the resistant moisture absorption property of the composite. When the content of spinel MgAl 2O 4 powders arrived at 18wt%,the composite obtained the highest properties,which the flexual strength at room temperature and at 800 ℃ were about 165 MPa and 75 MPa. And dielectric properties of the composite were remained stably during long time storage,which dielectric constant was about 3.5 to 3.6 and loss tangent was less than 0.01 at room temperature respectively.