Gel Formation in Natural Rubber Latex: 1. Effect of (NH4)2HPO4 and TMTD/ZnO Additives

2003 ◽  
Vol 76 (5) ◽  
pp. 1177-1184 ◽  
Author(s):  
L. Tarachiwin ◽  
J. T. Sakdapipanich ◽  
Y. Tanaka
Keyword(s):  
Natural Rubber Latex ◽  
Gel Formation ◽  
Rubber Latex ◽  
Tetramethylthiuram Disulfide ◽  
Gel Content ◽  
Gel Fraction ◽  
Initial Stage ◽  
High Ammonia ◽  
Long Time ◽  
Long Storage

Abstract The rubber from commercially obtained high-ammonia latex (commercial HA-latex) increased in gel content significantly after long preservation of the latex with 1.0% w/v tetramethylthiuram disulfide (TMTD) and zinc oxide (ZnO). Deproteinization of the HA-latex did not decrease the gel content. The gel fraction of deproteinized commercial HA-latex (DPHA-latex) was not solubilized by toluene containing 1.0% ethanol, showing that the gel fraction is composed of chemically crosslinked rubber. The addition of (NH4)2HPO4, which is usually added to fresh latex (FL-latex) to remove excess amounts of Mg2+ ions by centrifugation, decreased the gel formation in FL-latex preserved with 0.6 % v/v NH4OH due to the removal of Mg2+ ions. The excess amounts of (NH4)2HPO4 accelerated the gel formation in preserved FL-latex and commercial HA-latex. The addition of 0.1% w/v TMTD/ZnO to preserved FL-latex treated with 5% w/v (NH4)2HPO4 caused an increase of gel content during storage. The gel formation in the commercial HA-latex during long time storage was presumed to be caused by excess amounts of Mg2+ ions, TMTD/ZnO and (NH4)2HPO4. Here, TMTD/ZnO accelerated the gel formation at the initial stage of storage, while (NH4)2HPO4 affected in long storage.

Gel Formation in Natural Rubber Latex: 2. Effect of Magnesium Ion

2003 ◽  
Vol 76 (5) ◽  
pp. 1185-1193 ◽  
Author(s):  
L. Tarachiwin ◽  
J. T. Sakdapipanich ◽  
Y. Tanaka
Keyword(s):  
Natural Rubber ◽  
Natural Rubber Latex ◽  
Storage Period ◽  
Gel Formation ◽  
Gel Content ◽  
Gel Fraction ◽  
Rate Of Increase ◽  
2So4 Concentration ◽  
Gel Phase ◽  
Long Storage

Abstract The effect of Mg2+ ions on the gel formation in fresh and commercial high ammonia natural rubber latices (FL-latex and commercial HA-latex) was analyzed from the gel content and 2+ content after treatment with (NH4)2SO4. The gel content of rubber from commercial HA-latex decreased significantly after (NH4)2SO4 treatment comparable to that of FL-latex. Long-storage commercial HA-latex containing 50% gel fraction showed no decrease in 2+ content after (NH4)2SO4 treatment. This gel fraction was not solubilized in toluene by the treatment of a proteolytic enzyme in latex or ethanol/toluene mixed solvent extraction of rubber. The 2+ content of rubber in long-storage commercial HA-latex, 0.005% (w/w rubber), decreased after treatment with (NH4)2SO4, while the same treatment showed little change on FL-latex, 0.035%. The toluene soluble fraction of these latices showed a decrease in the Mn value with an increase in the (NH4)2SO4 concentration. The gel content of FL- and HA-lattices increased with an increasing storage period in the presence and absence of (NH4)2SO4. The initial rate of increase in the gel content was slow in the case of FL-latex. These findings indicate that the gel fraction in HA-latex is partly formed by ionic crosslinks caused by 2+ ions. Whereas, the gel phase in long-storage commercial HA-latex is presumed to be a hard gel predominantly formed by covalent bonding.

EFFECT OF DECELERATED FERMENTATION ON MORPHOLOGY AND MECHANICAL PROPERTIES OF NATURAL RUBBER LATEX

2013 ◽  
Vol 86 (4) ◽  
pp. 615-625 ◽  
Author(s):  
Oraphin Chaikumpollert ◽  
Osamu Wakisaka ◽  
Akio Mase ◽  
Yoshimasa Yamamoto ◽  
Krisda Suchiva ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Scanning Probe Microscopy ◽  
Natural Rubber Latex ◽  
Rubber Latex ◽  
Gel Content ◽  
High Ammonia ◽  
The Relationship ◽  
Nanomatrix Structure ◽  
Morphology And Mechanical Properties

ABSTRACT Decelerated fermentation of natural rubber latex was performed to investigate the relationship between the morphology and mechanical properties of natural rubber. Natural rubber latex was preserved with sodium hydroxymethylglycinate, as a bactericide, to decelerate the fermentation of nonrubber components such as proteins, phospholipids, carbohydrate, and so forth. Gradual increases in the viscosity of the latex and gel content of the resulting rubber took place as the preservation period was prolonged, which were distinguished from less change in the viscosity of high-ammonia natural rubber (HANR) and high gel content of its rubber. The particle size distribution was dramatically changed during decelerated fermentation, although that of the HANR latex did not change. The pH and nitrogen content of the rubbers were independent of the preservation time. Morphology of the fermented natural rubber and the HANR was observed with scanning probe microscopy. Fewer mechanical properties of the fermented natural rubber were related to the destruction of the nanomatrix structure of the nonrubber components, which resulted from the decrease in the fatty acid ester groups with bacteria as compared with the good mechanical properties of the HANR.

Novel Method for Preparation of Low Molecular Weight Natural Rubber Latex

1998 ◽  
Vol 71 (4) ◽  
pp. 795-802 ◽  
Author(s):  
Jitladda Tangpakdee ◽  
Megumi Mizokoshi ◽  
Akiko Endo ◽  
Yasuyuki Tanaka
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Natural Rubber Latex ◽  
Oxidative Degradation ◽  
Low Molecular Weight ◽  
Rubber Latex ◽  
High Ammonia ◽  
Novel Method ◽  
Η Value ◽  
Telechelic Polymer

Abstract Low molecular-weight natural rubber (LNR) and LNR latex was prepared by oxidative degradation of de-proteinized natural rubber (DPNR) latex in the presence of 1 phr of K2S2O8 and 15 phr of propanal, by shaking at 60 °C. The intrinsic viscosity [η] of DPNR with only K2S2O8 decreased from 7.2 to 5.5 after 2 h and then increased to 6.5 after 3 h. By the addition of propanal, DPNR showed a significant decrease in the [η] value of LNR with [η] of about 0.5 after 5 h of the reaction, while rubber from high-ammonia natural rubber (HANR) latex showed a slight decrease in [η]. The concentration of latex and the kind of surfactant used for stabilizing the latex had little effect on the degradation rate of DPNR latex. The LNR latex is stable as the latex form and the dried rubber coagulated from latex is transparent and colorless. The LNR was a telechelic polymer containing aldehyde and ketone groups at both terminals as determined by NMR and molecular weight analyses.

ADSORPTION OF WATER-EXTRACTABLE PROTEINS IN NATURAL RUBBER LATEX SERUMS BY POLY(METHYL METHACRYLATE)/POLYETHYLENEIMINE CORE-SHELL NANOPARTICLES

2016 ◽  
Vol 89 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Aditjaya Jivapongvitoon ◽  
Panya Sunintaboon ◽  
Surapich Loykulnant ◽  
Krisda Suchiva
Keyword(s):  
Electron Microscope ◽  
Natural Rubber ◽  
Methyl Methacrylate ◽  
Natural Rubber Latex ◽  
Core Shell ◽  
Rubber Latex ◽  
Shell Nanoparticles ◽  
High Ammonia ◽  
Core Shell Nanoparticles ◽  
Pei Nanoparticles

ABSTRACT Poly(methyl methacrylate)/polyethyleneimine (PMMA/PEI) core-shell nanoparticles were prepared by emulsifier-free emulsion polymerization. Micrographs from a scanning electron microscope and transmission electron microscope displayed their spherical shape with core-shell morphology in which PMMA was a core and PEI was a shell. The PMMA/PEI nanoparticles' ability to adsorb proteins from the serum of commercial low-ammonia preserved fresh field natural rubber latex was illustrated. The driving force for adsorption was proposed to be mainly via electrostatic interaction between the protonated amino groups of PEI chains on the nanoparticles' surface and phospholipids or protein molecules on NR particles. The reduction percentage was about 50%, depending on the content of PMMA/PEI nanoparticles and mixing time. For comparison, the protein reduction performance by the nanoparticles with two additional extracted serums, high-ammonia preserved concentrated NRL and Thai advanced preservative system NRL, which have different initial protein contents and pH values, was also investigated. The preliminary evaluation of PMMA/PEI nanoparticles' performance in sulfur-prevulcanized high-ammonia preserved concentrated NRL was also studied. Its corresponding sheet had lower extractable proteins by 50% and had tensile strength and elongation at break of 25.5 MPa and 715%, respectively.

A Comparative Study of Styrene Polymerization in Deproteinized and Undeproteinized Natural Rubber Latex

2002 ◽  
Vol 75 (1) ◽  
pp. 111-118 ◽  
Author(s):  
Nguyen V. Tho ◽  
Mohd Omar Abd Kadir ◽  
Azanam S. Hashim
Keyword(s):  
Reaction Time ◽  
Natural Rubber ◽  
In Situ Polymerization ◽  
Natural Rubber Latex ◽  
Lipid Layer ◽  
Rubber Latex ◽  
Styrene Polymerization ◽  
High Ammonia ◽  
Deproteinized Natural Rubber

Abstract An investigation on in situ polymerization of styrene in deproteinized natural rubber (DPNR) latex and high ammonia natural rubber (HANR) latex was carried out. The ratio of styrene to dry rubber was fixed at 25 : 75 by weight. It was observed that, at reaction temperature of 60 °C and reaction time of 10 hours, the styrene-DPNR system could attain a high conversion of 97% without adding surfactant. The degree of chemical bonding estimated for the resultant polystyrene-DPNR dried material was about 80%. The styrene-HANR system, however, required the addition of surfactant to complete the reaction time; but the conversion was found to be relatively low, in the region of 66%. This low conversion could be attributed to the role played by the protein/lipid layer, which is virtually absent in the styrene-DPNR system.

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