Phase structure and viscoelastic properties

Abstract

The phase structure and dynamic mechanical properties of three polypropylene/polystyrene (PP/PS) systems of similar composition but various dispersion of the minor PS component have been examined. Two different PP/PS systems were prepared by polymerization of styrene (ST) molecularly dispersed in PP matrices (with the same initial structure) under the conditions leading to a linear or erosslinked PS component. The third PP/PS system has been prepared blending the homopolymers in the molten state. Studies of materials containing in situ polymerized PS revealed nanoscale phase separation of PS (atomic force microscopy) and pointed to the presence of physical entanglements between PS and non-crystalline phase of PP (DSC, dynamic mechanical analysis). The PS component in material prepared by melt mixing appeared to be completely phase-separated into micron-sized domains. Dynamic mechanical analysis revealed also the dependence of viscoelastic behavior of the PP/PS systems on dispersion of the PS inclusions and on the nature of the interface.

Measurement and interpretation of elastic and viscoelastic properties with the atomic force microscope

“…Perhaps the most common type of study is tapping mode imaging, where the phase information is used to deduce local dissipation due to viscoelastic behavior. A number of such studies have been performed, and examples include polymeric surfaces [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], non-Newtonian fluids [16,17], and biological cells and sub-structures [18][19][20][21].…”

“…The extended range of the surface force is graphically illustrated here. The data have been fitted for a force of the form 2 , where h is the surface separation, A is Hamaker constant, R is the radius of curvature of the tip, and d is the total thickness of any water films on the surfaces. The evidence for the water film is the hook at the base of the constant compliance data for silica, which is due to the finite time it takes to drain the water from the contact region.…”

Effect of styrene–isoprene–styrene, styrene–butadiene–styrene, and styrene–butadiene–rubber on the mechanical, thermal, rheological, and morphological properties of polypropylene/polystyrene blends

“…The morphology of the resulting blend was similar to that of an interpenetrating polymer network and showed an improved dispersion of one polymer into the other and improved interfacial adhesion between the two polymers. Pluta et al 17 studied the morphology and dynamic mechanical properties of PP/PS blends of similar compositions but of various degrees of dispersion. The blends containing in situ polymerized PS showed the presence of nanoscale phase separation of PS, whereas the blends prepared by melt mixing showed the physical entanglement of the PS phase and noncrystalline PP phase in the macrosize domain.…”

Crystallization and dynamic mechanical properties of polypropylene/polystyrene blends modified with maleic anhydride and styrene

“…Fortelny et al 2 investigated the effects of the rate and time of mixing on the phase structure of PP/PS blends with various rheological properties of the components. Pluta et al 3 examined the phase structure and dynamic mechanical properties of three PP/PS systems of similar compositions but various dispersions of the minor PS component. Blends containing in situ polymerized PS show nanoscale phase separation of PS and physical entanglements between PS and the noncrystalline phase of PP.…”