Abstract
Specific physical and reactive compatibilization strategies are applied to enhance the interfacial adhesion and mechanical properties of heterogeneous polymer blends. Another pertinent challenge is the need of energy-intensive blending methods to blend high-tech polymers such as the blending of a pre-made hard polyurethane (-urea) with rubbers. We developed and investigated a reactive blending method to prepare the outstanding blends based on polyurethane-urea and rubbers at a low blending temperature and without any interfacial compatibilizing agent. In this study, the polyurethane-urea (PUU) was synthesized via the methylene diphenyl diisocyanate end-capped prepolymer and m-phenylene diamine based precursor route during blending at 100 °C with polar (carboxylated nitrile rubber (XNBR) and chloroprene rubber (CR)) and non-polar (natural rubber (NR), styrene butadiene rubber (sSBR), and ethylene propylene butadiene rubber (EPDM)) rubbers. We found that the in situ PUU reinforces the tensile response at low strain region and the dynamic-mechanical response up to 150 °C in the case of all used rubbers. Scanning electron microscopy reveals a stronger rubber/PUU interface, which promotes an effective stress transfer between the blend phases. Furthermore, energy filtered transmission electron microscopy (EFTEM) based elemental carbon map identifies an interphase region along the interface between the nitrile rubber and in situ PUU phases of this exemplary blend type.
Highlights
The blending of polymers is a useful route to develop new materials of practical importance.Various blending techniques including solution, melt, fine powder, latex, reactive and interpenetrating polymer network (IPN) processes are opted to produce homogeneous or heterogeneous polymer blends [1,2,3,4,5]
We investigated a reactive blending method wherein the polyurethane-urea was synthesized from its monomeric/pre-polymeric precursors during a simple mechanical mixing with both polar and nonpolar rubbers and attempted to benefit from the fact that the opted blending procedure is intrinsically compatibilizing and a low temperature mixing process [23,24]
The value of ML is quite similar for both Natural rubber (NR) and NR/PUU
Summary
The blending of polymers is a useful route to develop new materials of practical importance.Various blending techniques including solution, melt, fine powder, latex, reactive and interpenetrating polymer network (IPN) processes are opted to produce homogeneous or heterogeneous polymer blends [1,2,3,4,5]. Melt blending procedures predominate due to the straightforward mechanical mixing of two or more polymers; in most cases, this requires a high mixing temperature and produces heterogeneous incompatible blends. Such blends require compatibilizing agents to promote interfacial adhesion, morphological stability and overall performance [6,7]. Materials 2018, 11, 2175 blending procedures to prepare high performance heterogeneous blend systems is costly; a new blending method to mix hard polymers such as polyurethane-urea with soft polymers such as rubber was investigated. Numerous studies have reported blending of various types of polyurethanes with rubbers These blends are prepared by energy-intensive mixing processes and offer a very narrow temperature range of usage. The vulcanization of EPDM rubber and formation of polyurethane polymer of blend is realized during compression molding
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