Rubber Solutions

Abstract

In my earlier publications the hypothesis was suggested that rubber is a homogeneous substance and not a mixture of homologous polymers. This hypothesis has been criticized from many sides. My conclusions were based on the fact that the diminution of the vapor pressure and of the osmotic pressure of rubber solutions is independent of the origin of the rubber and of the treatment it receives. With regard to the discussion of the objections which have been made, I have obtained evidence that this hypothesis is also supported by other quantitative measurements of the state of equilibrium, e. g., the specific heat. In the course of this discussion, Bary questioned the basic theory by which I arrived at this conclusion when the incompatibility of the Raoult law has been established. Kroepelin calls attention to the fact that, in concentrated swollen substances, molecular groups and not molecules are united with the solvent. In the case of rubber these have double bonds. I do not know any reason that can justify this conclusion of Kroepelin. The investigations which I have undertaken on more dilute solutions do not support such a theory. A little later I shall go into more detail about Bary's comment.

Development of novel processes for the aqueous extraction of natural rubber from Taraxacum kok‐saghyz (TK)

“…Moreover, pebble milling could have entrapped residual root tissue in the rubber (Fig. ), as previously reported . The higher rubber yield in treatments subjected to alkaline pretreatment (A) followed by pebble milling (M) as compared to those that were just pebble milled (M) was likely due to the degradation of lignin, cellulose and hemicellulose by the alkaline pretreatment.…”

“…). The methods to quantify rubber in TK roots and rubber yield were not reported in previous literature . Rubber content in TK roots in these studies was likely determined by rubber extraction with organic solvents (e.g.…”

“…The lower yield in treatments including only E compared to those including A followed by E could be partially due to a portion of the rubber being attached to un‐hydrolyzed root debris which hindered separation by centrifugation. While centrifugation can improve rubber purity as compared to simple flotation, rubber attached to bigger pieces of root tissue still do not easily separate using centrifugation.…”

“…TK rubber recovery and purification research dates back to the 1940s when the allies tried to establish TK as a source of NR to replace supplies cut off during World War II (WWII) . In the United States, the Eskew process was developed in which dried, chopped roots were treated with hot water to extract inulin and other water soluble components, then pebble milled to separate root material from the rubber, which was then recovered by flotation . Approximately 75% of the rubber in TK roots can be recovered by this method, but root material was entrained in the rubber at concentrations as high as 12–15% w / w dry NR, adversely impacting its mechanical properties, preventing it from meeting the ASTM purity standard (ASTM D2227‐96 standard), and limiting its commercial utilization.…”

“…To address this, two methods were patented (now expired) that claimed to improve TK rubber yield and purity . The first claimed that milling whole roots rather than chopped roots improved yield to 90%, but purity was not reported.…”