Rubber research and technology at the National Bureau of Standards/

Wood, Lawrence A.

doi:10.6028/nbs.mp.185

Cited by 2 publications

(3 citation statements)

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“…Crystallization studies of cis-polyisoprenes have been carried out for many years, the earliest being the now-classic investigation of Wood et a1. 6 Detailed investigations of morphology and lamellar growth became possible with the introduction of osmium tetroxide staining by Andrews.' Essentially, spherulites grow in unstrained films as a crystals (a -crystallographic axis along the lamellar length) in the temperature range -40°C to +lO"C. Osmium tetroxide staining permitted both lamellar growth rates and lamellar thicknesses to be obtained concurrently, resulting in tests of 'secondary nucleation theory.…”

Section: Introductionmentioning

confidence: 99%

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

Rensch

Phillips

Vatansever

et al. 1986

J Polym Sci B Polym Phys

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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.

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Section: Introductionmentioning

confidence: 99%

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

Rensch

Phillips

Vatansever

et al. 1986

J Polym Sci B Polym Phys

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show abstract

“…Standard deviation corresponding to intrinsic variability. It has been found that residual impurities amounting to 0.14% sodium stearate, 0.14% stearic acid, or 0.07% ethyl alcoholtoluene azeotrope will decrease, or 0.07% phenyl-2-naphthylamine will increase the index by 0.0001 (11). It is therefore necessary to extract completely all extraneous material.…”

Section: Sources Of Errormentioning

confidence: 99%

“…Although the method, as given in this paper, has been described only in report form (2, 7, 8), it has been used for several years as a basis for the determination of bound styrene in copolymers of butadiene and styrene (7,11), and is currently employed for control purposes in the government-owned synthetic rubber plants. It has also been used by other investigators in deter-1 Present address, Johns Hopkins Applied Physics Laboratory, Silver Spring, Md. mining the per cent of rubber hydrocarbon in natural rubber (5), and for locating the second-order transition temperatures of natural and various synthetic rubbers (10).…”

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confidence: 99%