Rubber, natural

• CAS: 9006-04-6
• Catalog Number: ACM9006046-1
• Category: Other Products
• Molecular Weight: 68.12g/mol
• Molecular Formula: C5H8;CH2=C(CH3)CH=CH2;C5H8
• Description: Isoprene, stabilized appears as a clear colorless liquid with a petroleum-like odor. Density 5.7 lb / gal. Flash point -65°F. Boiling point 93°F. May polymerize exothermically if heated or contaminated. If polymerization takes place inside a closed container, the container may rupture violently. Less dense than water and insoluble in water. Vapors heavier than air.;Liquid; OtherSolid;OtherSolid;VERY VOLATILE COLOURLESS LIQUID WITH CHARACTERISTIC ODOUR.
• Synonyms: RUBBER LATEX;RUBBERFUME
• IUPAC Name: 2-methylbuta-1,3-diene
• Canonical SMILES: CC(=C)C=C
• InChI: InChI=1S/C5H8/c1-4-5(2)3/h4H,1-2H2,3H3
• InChI Key: RRHGJUQNOFWUDK-UHFFFAOYSA-N
• Boiling Point: 93 °F at 760 mm Hg (NTP, 1992);34.0 °C;34.067 °C;34 °C
• Melting Point: -184 °F (NTP, 1992);-145.9 °C;-145.95 °C;The generally accepted crystal melting temperature of natural rubber is 30 °C.;-146 °C
• Flash Point: -65 °F (NTP, 1992);-65 °F (-54 °C) (Closed cup)
• Density: 0.681 at 68 °F (USCG, 1999);0.679 g/cu cm at 20 °C;0.906-0.916 g/cu cm @ 20 °C;Relative density (water = 1): 0.7
• Solubility: less than 1 mg/mL at 70.7° F (NTP, 1992);0.01 M;In water, 642 mg/L at 25 °C;Practically insoluble in water;Miscible with ethanol, ethyl ether, acetone, benzene;Soluble in alcohol, ether, hydrocarbon solvents;Natural rubber is soluble in most aliphatic, aromatic, and chlorinated solvents, but its high molecular weight makes it difficult to dissolve.;Practically insol in water, alcohol, dil acids, or alkali; sol in abs ether, chloroform, most fixed or volatile oils, petroleum ether, carbon disulfide, oil of turpentine.;Raw rubber dissolves (or at least swells very strongly) in many organic liquids such as benzene, petroleum ether, crude petroleum, and carbon tetrachloride. In contrast, vulcanized rubber can only swell because the chemical cross-liking prevents dissolution.;Solubility in water, mg/l at 25 °C: 642 (very poor)
• Autoignition Temperature: 743 °F (USCG, 1999);743 °F (395 °C);220 °C
• Color/Form: Colorless volatile liquid;Colorless, watery liquid;Nearly colorless and transparent in thin layers.;Amorphous when unstretched, but has oriented crystalline structure on stretching /Cured (unvulcanized)/
• Complexity: 51.1
• Covalently-Bonded Unit Count: 1
• Decomposition: When heated to decomposition, it emits acrid smoke and fumes.;Decomposes at 120 °C.;When heated to decomposition it emits toxic fumes of sulfur oxides (SOx).
• EC Number: 201-143-3;232-689-0;614-502-8;618-362-9;618-550-0
• Exact Mass: 68.0626g/mol
• Formal Charge: 0
• H-Bond Acceptor: 0
• H-Bond Donor: 0
• Heat of Vaporization: 26.39 kJ/mol at 25 °C; 25.87 kJ/mol at 34 °C
• Heavy Atom Count: 5
• ICSC Number: 0904
• LogP: 2.42 (LogP);log Kow = 2.42;2.30
• Monoisotopic Mass: 68.0626g/mol
• NSC Number: 9237
• Odor: Petroleum-lke;Odorless
• Other Experimental: 1 mg/L equivalent to 358 ppm and 1 ppm equivalent to 2.79 mg/cu m at 25 °C, 760 mm Hg;Heat of fusion: 4.88 kJ/mol at -145.95 °C;Forms binary azeotropes with methanol, methylamine, acetonitrile, methyl formate, bromoethane, ethyl alcohol, methyl sulfide, acetone, propylene oxide, ethyl formate, isopropyl nitrate, methylal, ethyl ether, and n-pentane.;VP: 400 mm Hg at 15.4 °C;Henry's Law constant = 7.7X10-2 atm-cu m/mol at 25 °C (est);Hydroxyl radical reaction rate constant = 1.01X10-10 cu-cm/molc sec at 25 °C;Ozone reaction rate constant = 1.43X10-17 cu cm/molecule-sec at 25 °C;Thermoplastic until mixed with sulfur and vulcanized; supports combustion;The chain-like molecules are quite separate and only when they have been cross-linked by the process of vulcanization are the physical properties of rubber fully realized.;The properties of elasticity and resilience which first attracted man stem from the unusual molecular structure of rubber. This comprises a particular type of long chain-like molecule consisting of a large number of small molecular units joined together end to end.;Durometer hardness (or shore)= 20-100; ultimate elongation= 750-850 % at 23 °C /From table/;Natural rubber crystallizes below 20 °C because of its stereoregular molecular structure. The rate of crystallization varies with temperature and the type of rubber.;The best grades of raw rubber (pale crepe or smoked sheet) contain about 95% rubber hydrocarbon. The rest consists of proteins (2-3%), acetone-sol resins and fatty acids (2%), small amounts of sugar and a little mineral matter. Vulcanization, which consists of heating rubber with 1-3% of sulfur, introduces cross links between chains to produce a 3-dimensional lattice of improved elasticity, strength, temp sensitivity. Accelerators such as zinc dimethyldithiocarbamate greatly decrease the time or lower the temp required for vulcanization.;Natural rubber comprises a range of polymers with varying molecular weight estimated as <100,000 to 4 X 10 + 6.;Properties: Chemically unsaturated, not stable to temperature changes (thermoplastic), readily oxidizable by mastication; soluble in acetone, carbon tetrachloride, and most organic solvents; refraction index 1.52; dielectric constant 2.5. Processed by calaendars and extruders; can be injection-molded with low sulfur and high accelerator. Cured by hot-molding or in open steam, at temperatures from 120-150 /degree/ C after addition of 3% sulfur, 1% organic accelerator, 3% zinc oxide, plus fillers or reinforcing agents. The only factors of significance in vulcanization are the time of exposure to heat and the temperature used. /Crude (unvulcanized) natural rubber/;Properties: High tensile strength; relatively low permanent set; insensitive to temperature changes. Attacked by heat, atmospheric oxygen, ozone, hydrocarbons, and unsaturated fats and oils. Insoluble in acetone. Permeable to gases; supports combustion; abrasion resistance poor unless compounded with carbon black; dissipates vibration shock; high electrical resistivity. /Cured (vulcanized, i.e. sulfur cross-linkages)/;Specific heat: 1.905 kJ kg-1 K-1;Viscosity stablizing agent: hydroxylamine-neutral sulfate
• Refractive Index: Index of refraction: 1.42160 at 20 °C/D;Index of refraction: 1.5195 at 20 °C /Ribbed smoked sheets/;Index of refraction: 1.5218 at 20 °C /Pale crepe/;Index of refraction: 1.52 /Cured (unvulcanized)/
• Rotatable Bond Count: 1
• RTECS Number: NT4037000
• Stability: Stable under recommended storage conditions. Contains the following stabilizer(s): 4-tert-Butylpyrocatechol (≥ 100 to ≤ 150 ppm);Latex can be defined as a stable aqueous dispersion containing discrete polymer particles about 0.05 to 5 um in diameter.
• UNII: 0A62964IBU
• UN Number: 1218;1218;1218;1218
• Vapor Density: 2.35 (NTP, 1992) (Relative to Air);2.35 (Air = 1);(Air= 1);Relative vapor density (air = 1): 2.4
• Vapor Pressure: 400 mm Hg at 59.7 °F ; 493 mm Hg at 68° F (NTP, 1992);550.05 mmHg;550 mm Hg at 25 °C;Vapor pressure, kPa at 20 °C: 53.2
• Viscosity: The viscosity of natural rubber can be stabilized with the addition of small amounts of hydroxylamine hydrochloride or semicarbazide hydrochloride.;0.3 mm2/s at 20-25 °C
• XLogP3: 2.5

Case Study

Preparation of Natural Rubber and Nanocellulose Nanocomposites

Thomas, Martin George, et al. International journal of biological macromolecules, 2015, 81, 768-777.

Nanocomposite films can be prepared by introducing nanocellulose and cross-linking agents into natural rubber (NR). In the NR matrix, cellulose nanofibers can form three-dimensional networks (cellulose/cellulose network and Zn/cellulose network), thereby improving the properties of cross-linked nanocomposites. The Young's modulus and tensile strength of material increased, but elongation at break decreased.
Preparation of NR-based nanocomposites
· Nanocomposite materials were obtained by casting and evaporating a mixture of NR latex and aqueous suspension of cellulose nanofibrils as follows:
· The extracted nanocellulose was mixed with the NR latex along with other cross linking components according to the formulation.
· The composite films were prepared from prevulcanised latex by casting on a glass plate followed by drying at ambient temperature.
· The prevulcanization of the compounded latex was conducted at 70 °C for 2 h using water bath with constant gentle stirring.
· The sample numbers 0, 1, 2 and 3 indicate the weight percentage of nanocellulose used.

Characterization of Natural Rubber

Tanaka, Yasuyuki. Rubber chemistry and technology 74.3 (2001): 355-375.

Structural characterization of naturally occurring polyisoprenes was performed to unravel the mysteries of natural rubber (NR), such as the biosynthetic mechanism of rubber formation, the origin of NR's excellent properties, and the role of rubber in the rubber tree. NMR analysis using terpenes and polyprenols as models revealed the structures of the end groups of the rubber chain. Structural evidence suggests that rubber biosynthesis in Lactarius and leaves of higher plants starts with trans, trans-geranylgeranyl diphosphate and terminates by dephosphorylation to form hydroxyl end groups. It is hypothesized that the biosynthesis of NR starts from an unidentified starting material containing two trans-isoprene units and a peptide group and terminates with the formation of a phospholipid end group. The protein-bound NR starter group forms a branch point that can be degraded by enzymatic deproteinization. The branch point formed by the phospholipid group is degraded by transesterification with sodium methoxide.
Structure of Natural Rubber Model Compounds Naturally occurring linear isoprenoid compounds are composed of cis- or trans-isoprene units. Terpenes consisting of two to four isoprene units are in trans configuration except nerol (cis-C). Farnesol (trans-C) and geranylgeraniol (trans-C) can be isomerized and separated into four and eight geometric isomers, respectively, by high performance liquid chromatography (HPLC). Polyisoprenols are a general term for oligoisoprenols consisting of 9 to 23 isoprene units, which are isolated from plants, animals, and microorganisms. Polyisoprenols are divided into three categories, namely di-trans polyisoprenols, tri-trans polyisoprenols, and all-trans. Isomers of terpenes and polyisoprenols include Considering the assumed biosynthetic steps of rubber formation, the general structure H-(C H)-OH will be a good model for the structural characterization of NR.

Study on Properties of Composites Made of Natural Rubber

Salaeh, Subhan, and Charoen Nakason. Polymer composites 33.4 (2012): 489-500.

Carbon black-filled natural rubber composites were prepared with various types of natural rubber: unmodified natural rubber, epoxidized natural rubber with two epoxy groups (25 and 50 mol %, respectively) [epoxidized natural rubber (ENR)-25 and ENR-50], and maleated natural rubber. Two types of carbon black (HAF and ECF) with different structures and surface areas were used. The functional groups present in natural rubber and carbon black were characterized by FTIR and H-NMR. In addition, the curing characteristics, mechanical, morphological, and electrical properties of the composites and rubber compounds were studied. It was found that the presence of polar functional groups in the rubber molecules and the different structures of carbon black significantly affect the vulcanization characteristics and mechanical properties. This is attributed to the physical and chemical interactions between the carbon black surface and the rubber molecules. It was also found that natural rubber filled with ECF exhibited the highest Young's modulus and hardness, which is due to the increased degree of entanglement between the rubber chains and carbon black particles due to the high surface area and structure of ECF. The frequency dependence of the dielectric constant, loss tangent, and AC conductivity were also studied. An increase in dielectric constant, loss tangent and AC conductivity was observed in ENR/ECF composites. High carbon black loading resulted in network formation of these conductive particles, thereby increasing the AC conductivity of the composites.
Carbon black filled natural rubber composites were prepared using the formulation and mixing scheme. The mixing was carried out in two stages where rubber, ZnO, stearic acid and carbon black were first mixed in an internal mixer of 80 capacity. The mixture was run at 608°C with a rotor speed of 60 rpm for 13 min. The second mixing stage was the addition of curing agent to the premixed compound at 508°C in a lab scale two roll mill. The curing characteristics of the carbon black filled NR compounds were determined using a rotorless rheometer under oscillation. The vulcanized rubber composite sheets of 150×3×160×3×1 mm were then obtained using compression molding technique at 1608°C for respective cure times (t). The surface morphological properties of the carbon black filled rubber composites were characterized using scanning electron microscopy. Composite samples were cryogenically fractured to form new cross sections and sputter-coated with a thin layer of gold under vacuum conditions in preparation for SEM examination.

Custom Reviews

July 19, 2024

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Impressive performance on reducing microbial burden
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