Polymer-leather composites. IV. Mechanical properties of selected acrylic polymer-leather composites

An extensive study was made of the mechanical properties of the polymer–leather composite materials reported in previous articles. Polymer was deposited into leather by both emulsion and bulk (or solution) polymerization. Either methyl methacrylate, n‐butyl acrylate, or a fixed comonomer mixture of n‐butyl acrylate and methyl methacrylate were used over the widest feasible range of composition. Tensile strengths, in analogy with many polymer‐treated fibers, were generally smaller than untreated controls, but entensions to break remained fairly constant as composition changed. Polymer–leather composites prepared by both methods were rheologically similar when correlated against the volume fraction of the polymer used. Relative tensile and torsional moduli were greater than unity at small volume fractions of polymer, but higher compositions assumed more of the viscoelastic characteristics of the modifying polymer. The constancy of the glass transition temperature of the polymeric component as composition changed indicated poor domain interactions. However, residual porosity reduced low‐temperature moduli anomalously. A modified Halpin–Tsai equation was proposed that qualitatively predicted moduli increase by incremental space filling as either fiber aggregation (from simple air drying of untreated controls) or polymer content increased. The simultaneous rheological dependence of polymer–fiber interactions in composites was also accounted for by the equation.