Research On Ultrasonic Characterization Of Polymer Blends Compatibility

The new materials with superior performance can be produced by polymer blending.Whether or not the expected performance can be get is influenced by the compatibility ofmixed composition.So it is very necessary to detect the compatibility of polymer blending.Asa mechanical wave, ultrasound is very sensitive to the structure and properties of the polymerstested.And it can provide abundant information of polymers.Sound velocity and attenuationare the two important parameters in ultrasonic testing.Velocity has relationship to do with theelastic modulus and density of the blends, and the attenuation relates to viscoelasticity andstructure of blends closely.So the technology of ultrasound testing provides a quick, economic,convenient and comprehensive method to characterize the compatibility of polymer blends.Ultrasonic immersion method with the tested samples rotated is applied in thisarticle.And compatible system PS/PPO, incompatible system PS/PP and PS/PMMA andpartly compatible system PS/SBS and PS/SEBS are tested by longitudinal wave andtransverse wave. And combined with DSC determinating the glass transition temperature andSEM analysising the structure and morphology, the compatibility of polymer blends can becharacterized,as well as adhesion strength of the two phases and the relative size of the phasesare compared. The proportion of total attenuation caused respectively by the viscous loss inthe process of shear and volume deformation is estimated during the ultrasonic longitudinalwave is spreading in polymers and polymer blends.The study show that ultrasonic velocity and attenuation can be used to characterizedcompatibility of polymer blends. For compatibility system,the ultrasonic velocity andattenuation vary linearly wity composition.But the ultrasonic velocity and attenuation deviatefrom linearity for incompatible and partly compatibility blends. And ultrasonic attenuation ismore sensitive than velocity to the compatibility and morphology structure of polymer blends.Adhesion strength between two phases of polymer blends directly influence ultrasonicvelocity and can be characterized by ultrasonic velocity. With the same component, the soundvelocity of imcompatible or partly compatible system was less than the homogeneous system.Then the relative magnitude of the adhesion strength between two phases can be characterizedby the degree of the deviation of the relation of ultrasonic velocity and compostion fromlinear relation in the homogeneous system. The ultrasonic attenuation can characterize thestructure and morphology of polymer blends.According to the relation of the ultrasonicscattering attenuation and the relative size of acoustic wavelength and phase boundary,relative phase size of incompatible and partly compatible systems can be characterized by the degree of the deviation of the relation of ultrasonic attenuation and compostion from linearrelation in the homogeneous system. When longitudinal wave is spreading in polymers andpolymer blends, most attenuation is caused by the viscous loss along with volumedeformation, and only a small fraction of the longitudinal wave attenuation is related toviscous loss in the process of shear deformation.