Continuously decreasing availability and increasing costs create incentives to identify suitable
alternatives to natural rubber. Adhesive formulators have blended natural rubber latex with small
amounts of styrene-butadiene latex, albeit with a negative impact on adhesive performance. For some
pressure sensitive adhesive applications natural rubber has been hard to replace due to its superior autoadhesion
characteristics, low tack and good compatibility with tackifiers. Newly engineered SBR latexes
might enable adhesive formulators to substantially substitute SBR for NR. Such latexes offer improved
auto-adhesion through molecular architecture and polymer characteristics. These new SBRs are fully
miscible up to 20% with NR, and the homogeneous blends show the same or better autohesion
properties as natural rubber in a certain ratio. The autohesion characteristics are gradually changing with
increasing SBR concentration higher than 20%.
In this paper we discuss the design of new synthetic SBR which can be blended in with NR at high
concentrations without sacrificing adhesive performance for cold seal, tamper evidence, and similar
applications. The SBR latexes are fully miscible up to 20% with NR and the homogeneous blends show
the same or better (90/10 NR/SBR) autohesion properties as natural rubber. Autohesion gradually
deteriorates with an increasing SBR concentration over 20%. However, natural rubber’s low tack is
preserved over a wide range of SBR.