Factors influencing green strength of commercial natural rubber

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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Preparation and Characterization of Dimer Fatty Acids-Based Vinyl Ester Resin Monomer

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.721.86 ◽

2013 ◽

Vol 721 ◽

pp. 86-89 ◽

Cited By ~ 2

Author(s):

Shou Hai Li ◽

Xue Juan Yang ◽

Kun Huang ◽

Mei Li ◽

Jian Ling Xia

Keyword(s):

Fatty Acids ◽

Vinyl Ester ◽

Catalyst System ◽

Raw Material ◽

Esterification Reaction ◽

Vinyl Ester Resin ◽

Dimer Fatty Acids ◽

Addition Amount ◽

C Nmr

Novel dimer fatty acids-based vinyl ester resin monomer was prepared via simple ring-opening and esterification reaction with the aid of dimer fatty acids (DA) and glycidyl methacrylate (GMA) as raw material. The effects of different catalyst system, reacting time and reacting temperature on the yield, color, and viscosity of the final product were analyzed. The results of optimal experiments showed that BTEAC catalyst could make the final product with moderate viscosity and lighter color, the optimal BTEAC catalyst addition amount was 0.5wt.%, the optimal reacting temperature and reacting time was 115 °C and 2h, respectively. FTIR and 13C-NMR demonstrated that the target product had been successfully synthesized.

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Structure and Biosynthesis Mechanism of Rubber from Fungi

Rubber Chemistry and Technology ◽

10.5254/1.3538238 ◽

1990 ◽

Vol 63 (1) ◽

pp. 1-7 ◽

Cited By ~ 30

Author(s):

Yasuyuki Tanaka ◽

Makio Mori ◽

Koichi Ute ◽

Koichi Hatada

Keyword(s):

Fatty Acids ◽

Molecular Weight ◽

Natural Rubber ◽

Main Chain ◽

Terminal Group ◽

Conclusive Evidence ◽

Farnesyl Pyrophosphate ◽

Direct Esterification ◽

Biochemical Modification ◽

Nmr Signals

Abstract The structure of both terminal units and alignment of the isoprene units give conclusive evidence for the initiation and termination mechanisms of rubber formation in fungi. As shown in Figure 4, the polymerization is estimated to start from trans, trans-farnesyl pyrophosphate and proceeds by successive condensation of IPP to form isoprene units in the cis configuration. The termination is presumed to occur by direct esterification of polyisoprenyl pyrophosphate (PIP-PP) or dephosphorylation of PIP-PP followed by esterification with fatty acids. It is remarkable that the hydroxyl terminal group corresponding to the saponification product from the esterified terminal group was observed in the rubber samples by extraction from sporophores of L. volemus after storage for 2–3 days in a refrigerator without the addition of salt. In these samples, unidentified 13C-NMR signals were also detected. These findings suggest that the direct esterification of PIP-PP is more likely as a termination reaction. It also suggests the occurrence of a chemical or biochemical modification of both terminal groups and the main chain during storage. This is the first information on the termination mechanism of controlling the molecular weight of natural rubber.

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Structural Characterization of Natural Polyisoprenes: Solve the Mystery of Natural Rubber Based on Structural Study

Rubber Chemistry and Technology ◽

10.5254/1.3547643 ◽

2001 ◽

Vol 74 (3) ◽

pp. 355-375 ◽

Cited By ~ 138

Author(s):

Yasuyuki Tanaka

Keyword(s):

Fatty Acids ◽

Natural Rubber ◽

Structural Characterization ◽

Unsaturated Fatty Acids ◽

Saturated Fatty Acids ◽

Terminal Group ◽

Radical Scavenger ◽

Branch Points

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

Polymer ◽

10.1016/s0032-3861(00)00098-7 ◽

2000 ◽

Vol 41 (20) ◽

pp. 7483-7488 ◽

Cited By ~ 40

Author(s):

S Kawahara ◽

T Kakubo ◽

J.T Sakdapipanich ◽

Y Isono ◽

Y Tanaka

Keyword(s):

Fatty Acids ◽

Natural Rubber

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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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Preparation and characterization of natural rubber compounds with filler of oil palm empty bunches powder and carbon black

Functional materials ◽

10.15407/fm27.01.140 ◽

2020 ◽

Vol 27 (1) ◽

Keyword(s):

Carbon Black ◽

Natural Rubber ◽

Oil Palm ◽

Rubber Compounds

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Carbon-13 and nitrogen-14 NMR spectra of 1-(substituted phenyl)pyridinium salts

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19802766 ◽

1980 ◽

Vol 45 (10) ◽

pp. 2766-2771 ◽

Cited By ~ 8

Author(s):

Antonín Lyčka

Keyword(s):

Heavy Water ◽

Nmr Spectra ◽

Chemical Shifts ◽

Coupling Constants ◽

Pyridinium Salts ◽

Nmr Signals ◽

C Nmr

The 13C and 14N NMR spectra of 1M solutions of 1-(substituted phenyl)pyridinium salts (4-CH3, 4-OCH3, H, 4-Cl, 4-Br, 4-I, 3-NO2, 4-NO2, 2,4-(NO2)2 (the 13C NMR only)) have been measured in heavy water at 30 °C. The 13C and 14N chemical shifts, the 1J(CH) coupling constants, some 3J(CH) coupling constants, and values of half-widths Δ 1/2 of the 14N NMR signals are given. The 13C chemical shifts of C(4) correlate with the σ0 constants (δC(4) = (1.79 ± 0.097) σ0 + (147.67 ± 0.041)), whereas no correlation of the nitrogen chemical shifts with the σ constants has been found. The half-widths Δ 1/2 correlate with the σ0 constants (Δ 1/2 = (76.2 ± 4.9) σ0 + (106.4 ± 2.2)) except for 1-phenylpyridinium chloride.

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Material parametrization of natural rubber based compound and characterization of crack propagation under consideration of dissipative effects

Journal of Rubber Research ◽

10.1007/s42464-021-00094-8 ◽

2021 ◽

Author(s):

Dan Pornhagen ◽

Konrad Schneider ◽

Markus Stommel

Keyword(s):

Energy Dissipation ◽

Crack Propagation ◽

Natural Rubber ◽

Experimental Tests ◽

Material Behavior ◽

Prony Series ◽

Material Forces ◽

Cracking Behavior ◽

Dissipative Effects

AbstractMost concepts to characterize crack propagation were developed for elastic materials. When applying these methods to elastomers, the question is how the inherent energy dissipation of the material affects the cracking behavior. This contribution presents a numerical analysis of crack growth in natural rubber taking energy dissipation due to the visco-elastic material behavior into account. For this purpose, experimental tests were first carried out under different load conditions to parameterize a Prony series as well as a Bergström–Boyce model with the results. The parameterized Prony series was then used to perform numerical investigations with respect to the cracking behavior. Using the FE-software system ANSYS and the concept of material forces, the influence and proportion of the dissipative components were discussed.

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