Polypropylene drops of varying viscosity and elasticity were sheared in a polystyrene matrix. Two transparent, counter‐rotating parallel disks provided simple shear flow. By adjusting the speed of one disk the drop center was fixed in the laboratory frame and deformation followed via high magnification video camera. It was found that with high matrix elasticity drops of the minor phase stretched perpendicular (x3) to the flow direction (x1). This is the first report of widening of drops in shear flow. An analytical relation was established between the second normal stress differences of the phases and degree of widening. The formation of sheets and the phenomena of widening results in a larger than affine area generation.

When an alternating stack of molten polymer sheets is pulled in uniaxial tension parallel to the layers, interfacial area per unit volume increases, amplifying interfacial effects. Multilayers of several polymer pairs were prepared by lamination (up to 100 layers). Pairs with low and high interfacial tension, Γ, and pairs with functional groups which could react were selected. These were stretched at 220 °C at various constant extension rates in a rotating clamp extensional rheometer. At low rates the extra measured stress could be related to Γ and the number of interfaces. At higher extension rates extra stress exceeded Γ. This method for measuring interfacial tension can be applied to opaque samples and does not require knowing sample density or viscosity. For the reactive pairs there was pronounced strain hardening caused by coupled and even cross linked chains at each interface. The contribution of the cross linked interface was shown to follow rubber elasticity theory. As a result of the reaction the measured stress was two orders of magnitude higher than for the nonreactive case. Extra stress due to the grafting reaction was also measured. It increased with extension rate, presumably due to entanglements of the grafts across the interface. No evidence of graft reaction reducing Γ was found.

The influence of block copolymers (BCP) and interfacial reaction on the deformation of 30-100 µm polymer drops inside an immiscible polymer matrix was visualized in a parallel plate, counterrotating apparatus. Symmetric diblock copolymers were blended into polypropylene (PP), poly(methyl methacrylate) (PMMA), and polyethylene (PE) homopolymers. These were dispersed as drops in a polystyrene (PS) matrix. Addition of BCP significantly increased the amount of area the deforming drop generates when subjected to simple shear flow. Polymers with terminal amine groups (PMMA and PS) were coupled with maleic anhydride functional PS and PE. This reaction results in the formation of graft copolymer at the interface. These reactive pairs appear to be even more effective than BCP at generating interfacial area. The enhancement in area may be attributed to reduction in interfacial tension or to reduction in slip, but more likely a combination of both and a gradient in interfacial tension.