Natural rubber-styrene butadiene rubber latex blends: Time-dependent rheological behavior and film formation

Abstract

This article focuses mainly on the effect of maturation time on the rheological behavior of unvulcanized natural rubber (NR) -styrene butadiene rubber (SBR) latex blends. Viscosity shows a composition-dependent behavior with maturation time. It was found that there is a marginal decrease in viscosity for all the systems with maturation time except for the 70/30 NR-SBR blend. In this blend, there is a sharp decrease in viscosity with maturation time. This is associated with the exchange of stabilizers with one another until an equilibrium is reached; that is, all the particles of the blend are stabilized with random mixture of stabilizers. The structural build up observed in 70/30 NR-SBR blend was found to be diminished as the maturation time increases. At equilibrium, there is no further exchange of stabilizers. The behavior of this blend has been explained with the help of a schematic model. The effects of blend ratio and surface active agents on the viscosity were also studied. In addition, the time-dependent flow behavior of prevulcanized latex blends was evaluated as a function of vulcanizing systems and prevulcanization time. There is a regular increase in viscosity with prevulcanization time. However, after 3 h, the viscosity of almost all blends levels off, indicating that the curing reaction is complete within this time. Finally, the morphological changes occurred during film formation of the blends were studied using scanning electron microscopy.

Flow properties of unvulcanised natural rubber/carboxylated styrene butadiene rubber latices and their blends

“…Power law is widely used as a model for non‐Newtonian fluids 14, 15, 24. It holds for many polymer solutions and can be described by Newtonian, shear‐thinning, and shear‐thickening behavior in terms of the power factor n .…”

“…The viscosity of the system on the other hand, depends on factors like hydrodynamic interaction between the particles or droplets and the liquid, particle–particle interactions, and interparticle attractions that promote the formation of aggregates, flocs, and networks. Recently, Thomas and coworkers14, 15 investigated the influence of surface‐active agents, shear rates, temperature, blend composition, prevulcanisation, and maturation time on the rheological behavior of natural rubber (NR) and styrene butadiene rubber latices and their blends.…”

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

“…Two master curves were plotted using this shift factor (Figs. 23,24). It is important to mention that using the timetemperature superposition principle makes it possible to predict the viscoelastic behavior of a material well above the frequency or time range of the mechanical instrument.…”

Surface morphology of asymmetric latex film prepared from blends of natural rubber and poly(methyl methacrylate) latexes

“…More recent work by Varkey et al 22,23 was on the rheological behaviour of NR/SBR and NR/epoxidized NR latex blends, including a time-dependent effect. 24 There seems to be a complete lack of information on film formation and film morphology of NR/synthetic latex blends. In addition, mixed latex blends of different polymer types and particle sizes can cause incipient destabilization, leading to hetero-coagulation and aggregation of the particles.…”