Extensional mixing elements (EMEs) were developed for twin-screw extruders (TSEs) to incorporate extension-dominated flows through stationary hyperbolic convergence-divergence channels. These were made aggressive by incorporating double hyperbolic contraction meaning extensional stresses are imparted on the melt in both horizontal and vertical direction. This EME concept was extended to single-screw extruders (SSEs), which are known for their high pumping characteristics but have limited dispersive mixing capability, to enhance the latter through modular metering section having EMEs and pin section to provide dispersive and distributive mixing respectively. The modular metering zone is also validated computationally using mesh superposition technique to calculate torques and specific mechanical energy. Mixing simulations were performed to have distributive mixing analysis and also residence time distribution. Experiments were also performed on immiscible polymer blends (low-viscosity ratio and high-viscosity ratio) and nanocomposites on both SSE and TSE with same rotation speed and throughput. Morphological, rheological and mechanical results show tremendous improvement in mixing capability of SSE when equipped with EME and mainly comparable to conventional TSE, i.e., with kneading blocks as mixing sections, if not as good as TSEs equipped with EMEs. Differential scanning calorimetry (DSC) experiments were conducted on blends to assess the effect of smaller droplets of minor phase on crystallinity of major phase.