Nonionic surfactants as zero-shear compatibilizing agents for polyethylene/polyamide blends

This work explores the utility of low molecular weight, nonionic surfactants as compatibilizing agents to improve the physical properties of rotationally moulded parts formed using a physical mixture of immiscible polymers, high-density polyethylene (HDPE) and polyamide 11 (PA11). Selective control of melt-phase morphology during rotomoulding motivated the selection of functionally dissimilar emulsifiers, Tween 20 (polyoxyethylene sorbitan monolaurate; HLB 16.7) and Span 85 (sorbitan trioleate; HLB 1.8) at concentrations of 0.1–1.0 wt% to investigate a viable single-step alternative to the comparatively complex industry standard for manufacturing plastic fuel tanks (PFTs). Dry blends of HDPE and PA11 coated with Tween 20 showed the PA11 phase preferentially migrating bidirectionally towards the outer surfaces of the mould walls while also yielding an improvement in impact strength compared to a mixture of uncoated particles. Conversely, moulded parts prepared with ground particles of extrusion-compounded Tween 20-coated HDPE/PA11 blends adversely affected impact properties while having a negligible difference on morphology. Span 85, albeit negatively affecting porosity, showed improved impact properties while having no characteristic influence on morphology. In all scenarios, compared to the 50/50 mixtures, the 75/25 HDPE/PA11 dry blends showed either inconsequential or poorer gains at similar concentrations for both surfactant species.