Study On Preparation And Properties Of Polyacrylic Acid Dispersant For Nano-SiO₂aqueous System

Polyacrylic acid dispersant can improve the dispersion stability of nano-SiO₂aqueous system by electrostatic repulsion and steric hindrance.However,it still needs to be studied how to obtain a high solid content nano-SiO₂ aqueous system with good dispersion stability through simple process conditions.In order to obtain a high solid content nano-SiO₂ aqueous system with good dispersity and stability,a series of polyacrylic acid dispersant with methoxysilicon end groups?KH590-PAA?was synthesized by photopolymerization of acrylic acid?AA?initiated with?3-mercaptopropyl?trimethoxysilane?KH-590?.The structure of the obtained products was characterized by Fourier transform infrared?FT-IR?spectroscopy,nuclear magnetic resonance?NMR?spectroscopy and gel permeation chromatography?GPC?.Using a polyacrylic acid dispersant?PM-PAA?with a propyl end as a control,the properties of the dispersion system were tested after the obtained KH590-PAA was added to the nano-SiO₂ aqueous system.The tested results showed that the introduction of methoxysilicon end group was beneficial to enhancing the adsorption capacity of polymer dispersant on the nano-SiO₂ surface,thereby improving its dispersion effect.Besides,the dispersity and stability of SiO₂ nanoparticles in water was closely related to the addition amount and the molecular weight of KH590-PAA.When the KH590-PAA content was 1.0 wt%and the molecular weight was 16 000 g/mol,nano-SiO₂ aqueous system with 20 wt%solid content had good dispersity and stability.In order to better exert the steric hindrance effect of the polyacrylic acid dispersant,a series of polymer dispersants?KH590-AA_x-APEG_y?with different compositions and molecular weights was synthesized by photopolymerization of acrylic acid?AA?and allyl polyoxyethylene ether?APEG?with different feed ratios.And the structure of the obtained products was characterized by the same methods described above.The test results showed that the dispersity and stability of SiO₂ nanoparticles in water was closely related the composition,the molecular weight and the addition amount of KH590-AA_x-APEG_yandthesystem'ssolidcontent.When0.1wt%of KH590-AA_x-APEG_y-2 was added,the nano-SiO₂ aqueous system with 20 wt%solid content had the best dispersity and stability.The dispersion stability of the nano-SiO₂aqueous system significantly decreased with increasing the solid content.It could be seen that the introduction of APEG into the dispersant can better exert its steric hindrance in the dispersion system,so that it can exhibit excellent dispersion effect on the nano-SiO₂ aqueous system with a low addition amount.