Synthesis of Phosphate-Urethane Block Copolymers: Effect of Bound Phosphorus in the Soft Moiety of Block Copolymers on Thermal and Flame Retardant Characteristics of Polyphosphate Polyurethane Block Copolymers

摘要

Oligomers with a phosphorus moiety were prepared. Phosphate urethane block copolymers were made with these phosphorylated oligomers, diisocyanate and a diol as chain extender. Gel permeation chromatography (GPC) was performed on both the oligomeric materials and on block copolymers. Differential scanning calorimetry (DSC) shows a glass transition above room temperature and two melting temperatures for hard and soft blocks of these block copolymers. Thermo-gravimetric analysis results show these phosphorylated block copolymers have a tendency to form char when they were heated in nitrogen and air. Weight residue at 700 ℃ in air was higher for phosphate polyurethanes than ether urethane block copolymers without phosphate. Electron scanning microscopy (ESM) and electron dispersive x-ray spectroscopy (EDX) do not support the segregation of phosphorus onto the surface as is found with silicone block copolymers in polyurethanes. Oxygen indices of these materials were measured. The results show that even with a low level of phosphorus in the building blocks of the copolymers, some of these block copolymers were resistant to ignition and some had higher OI values compared to control and reference materials. Halogen in the building blocks of the copolymer showed "synergistic effects." However, some of these block copolymers containing phosphorus and halogen did not show significant improvement in flame retardancy given the low phosphorus content (under 2%). Based on flammability testing (OI results) these block copolymers were categorized as a) ignition resistant, b)higher Oxygen Index materials, and c) comparable to non-phosphorylated controls. These materials showed less flame retardancy compared to siliconated polyurethane block copolymers previously reported.