Optimized titanium dioxide loading for properties of natural rubber latex and acrylic emulsion blends

Blends of prevulcanized natural rubber (PVNR) and acrylic emulsion (AC) were prepared at the fixed PVNR/AC ratio of 30/70. Effects of titanium dioxide (TiO₂) addition were optimized across the contents 0, 10, 20 and 30 parts per hundred parts of polymer (php) with respect to various properties. Morphological analysis revealed a two-phase system in which the PVNR particles were dispersed in the AC matrix. Incorporation of TiO₂ induced a finer blend morphology in which a part of the TiO₂ was located at the interfaces of blend components. The tensile strength increased with initial TiO₂ loading and reached its maximum at 10 php loading, with an improvement by about 127% over the blend without filler. However, further increase in filler loading reduced the tensile strength, and the filler tended to agglomerate at those higher loadings. Thermal stability and storage modulus in rubbery region of the blends containing TiO₂ were also improved over the unfilled blend, due to the improved morphology and the hydrogen bonds between TiO₂ filler and polymer matrix. TiO₂ improved water wettability and adhesion of the blend. The maximum peel strengths on wood and metal substrates were about 120% and 26% larger than for the reference unfilled blend. Such drastic improvements suggest that the filled blends may find applications as coating materials.