• natural rubber;
  • tackifier;
  • miscibility;
  • petroleum resin;
  • phase diagram


Natural rubber (NR) was blended in various ratios with 12 kinds of tackifiers that were prepared from petroleum. The blends were heated to various temperatures (20–120°C) to investigate their miscibility. The blends were visually observed for transparency or opacity at each temperature and further observed under an optical microscope for any existence of phase-separated structure. Miscibility of the blends is illustrated as phase diagrams in this article. NR/aliphatic resin systems and NR/aliphatic-aromatic copolymer systems showed phase diagrams of the lower critical solution temperature type, wherein the blends turned faintly cloudy over the binodal curves. The NR/hydrogenated petroleum resin system also showed a phase diagram of the lower critical solution temperature type. The miscible range of a blend system tends to become smaller as the molecular weight of a tackifier increases. Resins prepared by polymerization of pure aromatic monomers were completely immiscible with NR. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 221–229, 1998