潜伏酸法纳米二氧化硅的制备和表征及对聚乙烯复合物性能的影响

Preparation and Characterization of the Nano-silicas via Adding Latent Acid and Its Effect on Properties of the LDPE Composites

以硅酸钠为原料、己二酸二甲酯为酸潜伏剂,采用溶胶—凝胶法制得纳米二氧化硅(SiO2)粉体,运用红外光谱(FT-IR)、布鲁纳尔—埃梅特—泰勒(BET)比表面积、孔径分布和透射电镜(TEM)等对二氧化硅粉体进行表征。红外光谱表明二氧化硅表面硅羟基与己二酸二甲酯水解产物己二酸的羧基形成氢键。制得的二氧化硅粉体具有较大的比表面积[388～400(m2.g-1)],根据比表面积计算出一次粒径小于10 nm。透射电镜观察到二氧化硅粒子聚集使得二次颗粒尺寸在(80—100)nm之间。采用熔融共混法制备SiO2/低密度聚乙烯(LDPE)复合材料(SiO2/LDPE),研究纳米二氧化硅对LDPE的力学性能和热稳定性的影响。结果表明纳米二氧化硅的加入提高了LDPE的拉伸强度,含3%二氧化硅的复合物的拉伸强度从6.88 MPa提高到8.32 MPa。并且随着纳米粒子含量的增加其断裂伸长率降低,但高温热稳定性增强。

The nano-silica（nano-SiO2） was prepared by reacting sodium silicate with dimethyl adipate as latent acid via the sol-gel process and characterized by Fourier transform infrared spectroscopy（FTIR）,Brunauer-Emmett-Teller（BET） specific surface area,pore size distribution and transmission electron microscope（TEM）.The FTIR result verified that the hydroxyl groups on the surface of the resulting nano-SiO2 form hydrogen bondings with adipic acid generated by hydrolysis of dimethyl adipate during reaction.The nano-SiO2 particles possessed a higher BET specific surface area of about 388—440（m2 ·g-1）depending upon the reaction temperature and their primary particle size calculated was below 10 nm.TEM image showed that the nano-silica particle size was in the range of 80 to 100 nm.In addition,the low density polyethylene（LDPE） composites with different nano-SiO2 content ranging from 1%—6% were prepared by the melt blending.The mechanical properties of the composites were determined.It was found that the tensile properties of all LDPE composites were improved,and the tensile strength of the composite with 3% SiO2 content increased from 6.88 to 8.32 MPa,while their broken elongation decreased gradually with increasing nano-silica loading.The thermal decomposition temperature of the LDPE composites increased slightly with increasing nano-SiO2 content.