MISCIBILITY BETWEEN NATURAL-RUBBER AND TACKIFIERS .1. PHASE-DIAGRAMS OF THE BLENDS OF NATURAL-RUBBER WITH ROSIN AND TERPENE RESINS

Natural rubber (NR) was blended in various ratios with 17 kinds of tac kifiers, which were prepared from rosin and terpenes. The blends were heated to various temperatures (20-120 degrees C) in order to investig ate their miscibility. The blends were visually observed for transpare ncy or opacity at each temperature and further observed under an optic al microscope for any existence of phase-separated structure. Miscibil ity of the blends is illustrated as phase diagrams in this article. Ph ase diagrams of all blends investigated in this study were classified into four types: completely miscible, lower critical solution temperat ure, upper critical solution temperature, and completely immiscible. T he miscible range of a. blend system tends to become smaller as the mo lecular weight of a tackifier increases. The data also indicate that t he esters of hydrogenated rosin and of disproportionated rosin show co mparatively good miscibility with NR whereas polymerized rosin and its esters have poor compatibility with NR in most cases. (C) 1997 John W iley & Sons, Inc.