Rapid Rubber Extraction and NMR Spectroscopy of Rubber, Extracted from the Endemic Species Scorzonera Tau-Saghyz

Scorzonera tau-saghyz Lipsch. et G.G. Bosse is an endemic rubber producing plant, growing in mountain regions in South Kazakhstan. The rubber content in plants and the quality of biopolymer has an important impact on industrial rubber production. The results of this study showed that the amount of rubber in S. tau-saghyz roots fluctuates between 7.74% and 38.75%. The amount of synthesized and deposited rubber biopolymer particles depends on various factors such as physiological age of plant, origin, temperature, moisture and environmental conditions. We optimized the extraction method of natural rubber by using n-hexane as a solvent for direct extraction. This method allows extracting the maximum amount of rubber from 3‒4-year-old plants. NMR results show structural links of natural isoprene rubber in the root extract sample. There is a clear relationship between methyl, methine and methylene protons which corresponds to isoprene rubber structure. The samples having strongly marked singlets that are inherent for rubber functional groups confirms the stereospecific structure of rubber. Good solubility of the root extract in deuterated chloroform can characterize the low molecular weight of the polymer. NMR characterization of rubber, extracted from S. tau-saghyz roots, is reported for the first time. Regeneration in vitro provides an important opportunity for endemic preservation by rapidly increasing the number of plants. The best regeneration of adventitious shoots was obtained on MS medium containing 5.5 μM kinetin and 0.5 μM NAA. The plants were successfully acclimatized in a glasshouse with 75% of S. tau-saghyz plantlets, respectively surviving after transfer to ex vitro conditions.

Earthquake modeling in a homogeneous half-space

Ground motion produced by finite, kinematic fault surface is modeled at the surface of a homogeneous half-space. The Green's functions for point dislocations are summed to investigate the effects of different rupture velocities and source rise times. Displacements and velocities are compared for a bilateral and unilateral rupture. The method is used to model the displacements for a laboratory experiment involving a dynamic rupture in a homogeneous block of foam rubber. Good agreement between synthetic and model displacements is obtained at distances ranging from zero to somewhat greater than one fault length. The half-space Green's function summation method is then used to model the N65°E (transverse) component of displacement for the 1966 Parkfield earthquake. The 26-cm displacement pulse on this record is fit with a buried dislocation of 100 cm over a rectangular fault 30 km long and 6 km wide, with a depth of 3 km.

Stress Relaxation in Rubber I. Evaluation of Antioxidants

Conventional evaluation techniques for rubber antioxidants are very time consuming. A method of evaluation based on stress relaxation due to oxidation at elevated temperatures, and an apparatus developed for the study of this phenomenon in a large number of natural rubber stocks, are described in this article. Results are compared with those obtained using conventional air- oven and oxygen bomb aging tests. The apparatus is suitable for testing six rubber samples simultaneously, and uses unbonded resistance wire strain gauges for the measurement of stresses in the samples. The stress vs. time curves are recorded automatically on a roll chart recording potentiometer. It has been found that the curves approximate to exponential decay curves, and, as such, can be characterized by a single parameter—the half life. This parameter, used as a measure of antioxidant efficiency, can be correlated with the loss of tensile strength for samples aged in a conventional air oven. The use of the half-life period as a measure of antioxidant efficiency leads to a rapid and easily interpreted method of evaluation for antioxidants in natural rubber. Good reproducibility and discrimination are features of the method.