The crystallization behavior of Cis‐polyisoprenes extracted from the guayule plant

Abstract

synopsisThe crystallization kinetics and resultant morphologies of thin films of cis-polyisoprenes from guayule rubber have been studied using osmium tetroxide staining and transmission electron microscopy. Polymers used were extracted from the plant either on a laboratory scale or in a pilot plant operation. The polymers show significantly different behavior with regard to both morphological features and to lamellar growth rates. Freshly extracted cis-polyisoprene as well as freshly prepared specimens of pilot plant rubber show only a growth, as in cispolyisoprene from hevea, but a slightly faster lamellar growth rate. Aged pilot plant rubber shows both a and p growth, both at higher rates than in natsyn, with the rate of a growth being lower than in hevea. Freshly extracted and aged specimens show a maximum lamellar growth rate at -2O"C, whereas the maximum for pilot plant rubber occurs at -24°C. The data are interpreted in terms of oxidation of double bonds during aging to produce pendant ester groups. Lamellar growth rates and infrared analyses are both consistent with 1.2-1.5% of the double bonds being affected. Data from guayule and natayn are now consistent in showing that the effeds of microstructural impurities on the crystallization of cis-polyisoprene are to reduce the rates of a-lamellar growth and to induce the fi growth, which would not otherwise exist. Secondary nucleation analyses show the regime II-In transition, as in hevea; however, the temperature of the transition, as well as the ratio of the slopes, is different for this linear polymer.

Morphology of pyrolyzed polystyrene–isoprene–styrene and polystyrene–butadiene–styrene block copolymers

“…It may be mentioned that the etching of the polymer surface by solvents or acids is widely used technique to observe details of the internal structure, as it removes the amorphous portion from the surface. In the present experiments, the polystyrene does not appear in its typical crystalline form, but is seen as pseudo‐ordered under developed structure 18. The fibers were 20–30 μm in size.…”

Morphology of pyrolysed polystyrene–isoprene–styrene and polystyrene–butadiene–styrene block copolymers

“…In the present experiments, the polystyrene does not appear in its typical crystalline form, but is seen as a pseudo-ordered under-developed structure. 18 The fibers were 20 -30 m in size. At higher magnification, the fibers appear to have wrinkled surface (Fig.…”

High performance waste-derived filler/carbon black reinforced guayule natural rubber composites

“…When filler volume reaches the percolation threshold, this strong fillerfiller interaction promotes the formation of a percolation network that contributes to the overall reinforcement of the material by restricting chain mobility. The linear chain structure of GNR allows it to flow more easily into the filler network than HNR, which has a branched structure (Rensch et al, 1986). Thus, when stress is applied to the materials, entanglement of polymer chains in this filler network allows better load transfer between the filler and the polymer than in HNR (Barrera and Cornish, 2015).…”

“…Differences in macromolecular structure also affect rubber compounding and product performance (Rensch et al, 1986).…”