The Deforming Evolution Of Rubbery Phase And Its Toughening Mechanism For Amorphous Polymer Via Pressure-induced Flow Processing

In this thesis, the deforming evolution of rubbery phase and its toughening mechanism for amorphous polymer via pressure-induced flow processing are studied deeply and systematically at multip cales (micrometer, nanometer, micro and nanometer), including:mechanical properties, thermodynamic properties and novel energy dissipation initiated by the formed microstructure. So the relationship between mechanical performance and microstructure is set up quantificationally. Finally, we propose toughening model for ordered layered structure in bulk materials and the mechanism on the confinement of craze. The following results are obtained;1. The deformation and toughening mechanism for High Impact Polystyrene (HIPS) via PIF processing are studied systematically. Compared with original samples, the impact and tensile strength increase by100%and30%respectively. The results of Transimission Electron Microscope (TEM), Atomatic Force Microscope (AFM) and Small Angle X-ray Scattering (SAXS) show that isotropic sphere-like salami rubber particles translate into parallel and ordered disk-like salami rubber particles. As the SEM indicated, the scale-like fracture surface become deeper and longer after PIF processing. The roughness enhances dramatically. As TEM showed, parallel and oriented rubber disk can be more effective to initiate craze, meanwhile it also can be more effective to inhibit the craze growing to a crack.2. The deformation and toughening mechanism for StyreneAcrylonitrile Butadiene Styrene (ABS) via PIF processing are studied systematically. As the rubber content is10wt.%, the impact and tensile strength increase by120%and40%respectively. And the fracture elongation for tensile increases greatly, the tensile toughness increases up to600%. Indicated by TEM and SAXS, as compression ratio (CR) increasing, the aspect ratio increase from1to7, and orientation parameter rise up to94%, FWHM decrease14to8. Isotropic sphere-like rubber particles translate into parallel and ordered disk-like rubber particles. The results of Dynamic Mechanical Analysis (DMA) and Fourier Transform Infrared Spectroscopy (FTIR) show that orientation occurs at the inter-phase and increases as CR increasing. As the SEM indicated, compared with original ABS sample’s fracture surface, the fracture surface for the sample after PIF processing is more roughness. As TEM showed, craze can be more effective to be inhibited by parallel and oriented rubber disk, comparing with isotropic sphere-like rubber particles. So the defect can be avoided. And as the rubber content increasing, the inter-particle distance will decrease, which will further confine the craze, so the craze will be more and shorter. According to the analysis of ARAMIS, parallel and oriented rubber disk do not only initiate more craze, but also more effective to avoid the crack in bulk.3. Here we demonstrate how a hierarchical layered microstructure can be generated in commodity bulk polymer blends (PS/SBS and HIPS/SBS) via a pressure-induced flow field. Hereby, minority spherical rubbery SBS in PS/SBS blend turns into lamellar shape of micrometer size within rigid glassy PS phase. Furthermore, within each SBS domain, nano-size layer structure is produced simultaneously, as indicated by TEM and SAXS. Benefit from such hierarchical lamella structure, the resulting strength, stiffness and toughness were simultaneously enhanced, modulus remain constant.(In general, toughness is improved always together with the loss of material strength and modulus for most of rubber-toughened polymer). Enhanced strength of polymer is arising from oriented molecules at the boundary of nano-size lamella domain, as indicated by FTIR, while the toughness is remarkably enhanced due to generated craze during impacting are efficiently terminated by micro-meter size SBS lamella domain. Cooperation of hierarchical lamella structure finally contributes to material together with high strength and toughness. Such idea of design of rubber-toughened glassy materials, and the efficient PIF technique could be easily to transplant into fabrication large amount of new materials consisting of biomimetical hierarchical structures.