Characterization of fatty acids linked to natural rubber—role of linked fatty acids on crystallization of the rubber

Abstract Structural characterization of naturally occurring polyisoprenes was carried out to solve the mystery of natural rubber (NR), such as the biosynthesis mechanism of rubber formation, the origin of outstanding properties of NR and the role of rubber in rubber trees. The NMR analysis, based on terpenes and polyprenols as models, disclosed the structure of both terminal groups of rubber chain. Structural evidence indicated that the biosynthesis of rubbers from Lactarius mushroom and leaves of high plants starts from trans, trans-farnesyl diphosphate or trans, trans, trans-geranylgeranyl diphosphate and terminates by dephosphorylation to form a hydroxyl terminal group. The biosynthesis of NR was presumed to start from unidentified initiating species containing two trans-isoprene units and peptide group and to terminate forming a phospholipid terminal group. The initiating group of NR associated with proteins formed branch points, which can be decomposed by enzymatic deproteinization. The branch points formed by phospholipid group were decomposed by transesterification with sodium methoxide. Rapid crystallization of NR was explained by the presence of mixed fatty acids synergistically with linked fatty acids, which were included in phospholipid. Saturated fatty acids linked to rubber chain induced crystallization, while mixed unsaturated fatty acids acted as plasticizer and accelerated the crystallization rate. This was confirmed by the preparation of model cis-polyisoprene grafted with stearic acid. The green strength of NR decreased to the same level as synthetic cis-polyisoprene after transesterification, indicating the effect of branching formed by the phospholipid terminal group and fatty acids in NR. The role of NR in Hevea trees was analyzed using NR from Hevea trees never tapped before. The formation of hard gel and oxidative degradation during the storage of NR in Hevea trees suggested that NR acted as a radical scavenger to remove hydroperoxide.

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Crystallization Behavior and Strength of Natural Rubber. Role of Fatty Acids.

NIPPON GOMU KYOKAISHI ◽

10.2324/gomu.72.683 ◽

1999 ◽

Vol 72 (12) ◽

pp. 683-689

Author(s):

SEIICHI KAWAHARA

Keyword(s):

Fatty Acids ◽

Natural Rubber ◽

Crystallization Behavior

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Factors influencing green strength of commercial natural rubber

Green Processing and Synthesis ◽

10.1515/gps-2018-0019 ◽

2018 ◽

Vol 7 (5) ◽

pp. 399-403 ◽

Cited By ~ 2

Author(s):

Nghiem Thi Thuong ◽

Phan Trung Nghia ◽

Seiichi Kawahara

Keyword(s):

Fatty Acids ◽

Natural Rubber ◽

Small Strain ◽

Green Strength ◽

Acetone Extraction ◽

Factors Influencing ◽

Removal Of Impurities ◽

Nmr Signals ◽

C Nmr

Abstract The factors influencing the green strength of commercial solid rubbers were investigated in the present study through characterization of commercial natural rubber (NR). Various solid commercial rubbers such as standard Vietnam rubber (SVR10), standard Indonesia rubber (SIR10), India standard natural rubber (ISNR10), ribbed smoked sheets (RSS3), and FNR (commercial Sumitomo Rubber) were used as a source. Purification of the samples was carried out through acetone extraction and purified samples were characterized by nuclear magnetic resonance (NMR) and Fourier-Transform infrared spectroscopy. Degradation was found for SVR10, ISNR10, and SIR10 but not for RSS3 and FNR through the assignment of 13C-NMR signals. Acetone extraction was found to improve the green strength of commercial NR due to the removal of impurities. Linked fatty acids and proteins contributed to the upturn of stress at small strain. However, the network structure of degraded rubbers had an insignificant role in enhancing the green strength of commercial NR.

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Composition of Color Substances of Hevea Brasiliensis Natural Rubber

Rubber Chemistry and Technology ◽

10.5254/1.3539403 ◽

2007 ◽

Vol 80 (2) ◽

pp. 212-230 ◽

Cited By ~ 4

Author(s):

Jitladda Sakdapipanich ◽

Kittipong Insom ◽

Nataphon Phupewkeaw

Keyword(s):

Fatty Acids ◽

High Resolution ◽

Natural Rubber ◽

Structural Characterization ◽

Unsaturated Fatty Acids ◽

Rubber Latex ◽

Naturally Occurring ◽

Bottom Fraction ◽

Light Color

Abstract It is accepted that NR gives naturally occurring color, which restrict many applications such as light-color products. Therefore, characterization of color substances presenting in NR is very useful to develop the certain methodology to eliminate them completely or partly from NR in the future. In this work, an attempt was made to purify and characterize the color substances extracted from various fractions of Hevea rubber latex by certain methods, using high-resolution structural characterization techniques. It was found that the content of color substances extracted from fresh latex (FL), rubber cream, bottom fraction (BF), Frey Wyssling (FW) particles and STR 20 were different. Based on the high-resolution spectroscopic analyzes, it was found that the color substances extracted from NR were composed of carotenoids, tocotrienol esters, fatty alcohol esters, tocotrienols, unsaturated fatty acids, fatty alcohols, diglyceride and monoglyceride. The results will be useful for rubber-technologist to identify the origin to make obnoxious color in natural rubber, especially in some applications which are restricted by such the color.

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Better characterization of raw natural rubber by decreasing the rotor speed of Mooney viscometer: Role of macromolecular structure

Polymer Engineering & Science ◽

10.1002/pen.21525 ◽

2009 ◽

Vol 50 (2) ◽

pp. 240-248 ◽

Cited By ~ 7

Author(s):

Chandy Kim ◽

Marie-Hélène Morel ◽

Jérôme Sainte Beuve ◽

Stéphane Guilbert ◽

Frédéric Bonfils

Keyword(s):

Natural Rubber ◽

Macromolecular Structure ◽

Rotor Speed

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Digital x-ray mapping of nanometer-size supported bimetallic catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104716 ◽

1988 ◽

Vol 46 ◽

pp. 530-531

Author(s):

L. T. Germinario

Keyword(s):

Background Radiation ◽

Metal Cluster ◽

Single Element ◽

Beam Diameter ◽

X Rays ◽

X Ray ◽

Major Interest ◽

Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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