Abstract
Three novel nanocomposites including Polysilicic acid nanoparticle (PN)、PTMS-PN 、TMPE-PN / Waterborne Polyurethane (WPU) have been prepared. Two methods were used to well disperse inorganic nanoparticles in the polymer matrix：the sol-gel process and blending process. The OH functional groups attatched on surface of PN nanoparticles would react with end-capped silane on WPU via sol-gel process. These PN nanoparticles were modified by Phenyltrimethoxysilane (PTMS) and 3-(trimethoxysilyl) propyl ester (TMPE). The nanostructure, thermal, mechanical, gas permeation properties of the three nanocomposites were investigated. Size distribution of PN nanoparticles was measured by dynamic light scattering method ranging from 3 to 25 nm. The average size of PN nanoparticles was 9 nm. From GPC result, it was found that the number molecular weight of WPU was 10,000~15,000 and Polydispersity was 1.6~2.0. The morphology study results showed that PN nanoparticles were well dispersed in waterborne polyurethane within a nano-scale (50 nm). When PN content was over 20 wt%, phase separation may occur. Si-mapping technique was used to observe the dispersion of PN in the polymer matrix. When PTMS-PN and TMPE-PN contents went up to 30 wt.%, phase separation may take place. FT-IR results showed that the fraction of hydrogen bonded carbonyl group reached the maximum when PN content was 10 wt.%. The PTMS-PN and TMPE-PN nanocomposites showed more transparency which was further proved by UV-visible measurement. The crystalline structure of hard segment of waterborne polyurethane was greatly influenced by nanoparticles from DSC spectrum. The XRD results revealed that α-form, γ-form, or triclinic crystallization could be found in waterborne polyurethane matrix at different inorganic contents. TGA results showed that introducing inorganic fillers could increase the thermal stability of WPU. For example, the 10% weight loss of nanocomposite increased from 269.2℃ to 318.5℃ (increased by 50℃) when the PN content was 20 wt%; in the PTMS-PN system, the degradation temperatures were increased from 269.2℃ to 324.2℃ (increased by 55℃); in TMPE-PN system, the degradation temperatures were enhanced from 269.2℃ to 332.4℃ (increased by 63℃). The TMPE-PN system exhibited the best thermal stability. The tensile stress and Young’s modulus of nanocomposite increased with the increasing of PN content. Results showed that maximum tensile stress of nanocomposite increased from 0.09 MPa to 3.40 MPa (increased by 37 times)，and Young’s modulus raised 27.01 MPa (increased by 11 times). In the PTMS-PN system, the maximum tensile stress of nanocomposite increased from 0.09 MPa to 3.65 MPa (increased by 40 times)，and Young’s modulus raised 37.82 MPa (increased by 15 times). In the TMPE-PN system, the maximum tensile stress of nanocomposite raised 1.25 MPa (increased by 15 times), and Young’s modulus raised 15.17 MPa (increased by 7 times). PTMS-PN nanocomposites displayed the best tensile properties. Oxygen permeability of PN nanocomposites increased from 4.56 X 10-11 to 9.24 X 10-11 ( cc •(STP) •cm) / (cm2•sec•cmHg) (increased 103%). In the PTMS-PN system, the oxygen permeability of nanocomposite increased from 4.56 X 10-11 to 10.4 X 10-11 ( cc •(STP) •cm) / (cm2•sec•cmHg) (increased 128%) when the PTMS-PN content was 10wt%. In the TMPE-PN system, the oxygen permeability of nanocomposite increased from 4.56 X 10-11 to 8.84 X 10-11( cc •(STP) •cm) / (cm2•sec•cmHg) (increased 94 %). The dynamic mechanical properties of nanocomposite were measured by a Dynamic Mechanical Analysers (DMA). Results revealed that the storage modulus of PN nanocomposite was 9.83 X 108 Pa (increased 12 times) when the PN content was 10wt% at -25℃. In PTMS-PN system, the storage modulus of nanocomposite was increased from 0.76 X 108 Pa to 13.3 X 108 Pa (increased 17 times) when the PTMS-PN content was 5wt%. In TMPE-PNsystem, the storage modulus of nanocomposite was from 0.76 X 108 Pa to 8.97 X 108 Pa (increased 12 times). From the results it could be found that PTMS-PN nanocomposite possessed better dynamic mechanical properties than others.