Nano SiO₂ Grafted With Polyether And Its Application In Polyurethane Foam （PUF）

Polyurethane (PU) is a polymer containing chain segment of carbamate and prepared by polyether polyol and isocyanate, which has braod prospect of application. Nano silica (NS) as filler has excellent performance such as light quality, high temperature resistant, good chemical stability and electrical insulation to effectively modify polyurethane foam (PUF). The method of polymer grafting, which is easy to prepare new materials with unique properties and meet special requirements of different fields, is more and more widely applied to the surface modification of nanoparticles due to its controllable molecular weight and ordered molecular structure.In this article, PUF with density of 0.3 g/cm3 was chosen to be the matrix and prepared by reaction molding method using polyether polyol and isocyanate as raw materials. The NS particles were synthesized by the way of "Stober" and treated with grafting on its surface using polyglycidol (PG) and poly(propylene oxide) (PPO) via anionic ring-opening polymerization and ring opening polymerization, respectively. NS/PUF, PG-NS/PUF and PPO-NS/PUF composites with different contents were prepared and the morphologies and properties of those composites were discussed. In order to further explore the effect of polymer grafting nanoparticles on the properties of PUF, PPO grafted multi-walled carbon nanotubes (MWNT) were synthesized by ring opening polymerization (ROP) catalytic process, considering more performance of MWNT. The PPO grafted MWNT (PPO-MWNT) were subsequently used to prepare MWNT/PUF composites by reaction molding method. The effects of pristine MWNT and PPO-MWNT on morphology and properties of MWNT/PUF composites were investigated. The results are showed as followed:1. PG and PPO were grafted on the surface of NS particles successfully and the grafting ratio of PG and PPO was about 6 wt% and 10 wt%, respectively. Moreover, PPO was effectively grafted on the surface of MWNT with grafting ratio of 25 wt%.2. The contents of NS particles had great influence on morphology and properties of NS/PUF composites. With the increase of contents, the average cell size decreased, the density of cells increased and the distribution of cell size became more uniform. Meanwhile, the mechanical properties were enhanced obviously. However, until the content of 1.5 php, the cell size increased and the distribution of cell size became nonuniform along with rupture in cell.3. The addition of PG-NS in PUF composites would result in better cell structure and a reduction in average cell size, also improve the Tg of 10℃ with 2 php, E’ of 12 MPa and E" of 2 MPa with 0.5 php, compared with pristine NS reinforcing PUF composites.4. The low addition of PPO-NS in PUF composites would bring out a reduction of 80μm in average cell size with 1 php, also improve the Tg of 4℃ with 1 php, E’of 25.6 MPa with 0.5 php and E" of 3.5 MPa with 0.5 php. Moreover, the compressive specific strength was improved of 1.89 MPa·cm3·g-1 with 0.5 php, compared with NS reinforcing PUF composites.5. The addition of PPO-MWNT in PUF composites would bring out a reduction of 42.31 nm from 222.11μm to 179.80μm in average cell size, also improve the Tg of 2℃, E’ of 65.2 MPa and E" of 4.1 MPa. Moreover, the compressive specific strength was improved of 2.20 MPacm3·g-1, compared with pristine MWNT reinforcing PUF composites.