Preparation Of Natural Rubber Research Articles

Nanomaterials and nanotechnology for composites: synthesis, structure, properties and new application opportunities

Nanomaterials and nanotechnology for composites: synthesis, structure, properties and new application opportunities

Design of Dual Hybrid Network Natural Rubber-SiO2 Elastomers with Tailored Mechanical and Self-Healing Properties.

The preparation of natural rubber (NR)–silica (SiO2) elastomeric composites with excellent mechanical properties along with better self-healing ability remains a key challenge. Inspired by the energy dissipation and repairability of sacrificial bonds in biomaterials, a strategy for combining covalent and noncovalent sacrificial networks is engineered to construct a dual hybrid network. Here, the approach used to fabricate the composites was self-assembly of NR, bearing proteins and phospholipids on its outer bioshell, with SiO2 via metal-ion-mediated heteroaggregation effected by reversible electrostatic and H-bonds. Further, covalent cross-links were incorporated by a silane coupling agent, bis [3-(triethoxysilyl) propyl] tetrasulfide. The intrinsic self-healing ability of the composite at the molecular level was studied by broadband dielectric spectroscopy that unraveled the mechanism of the healing process. The synergistic effect between the molecular interdiffusion of the cross-linked NR chains and the electrostatic and H-bonding interactions imparted an exceptional self-healing characteristic to the liquid–liquid-mixing-prepared NR–SiO2 composites with improved mechanical performance. Specifically, the segmental relaxation dynamics of the healed composite was largely restricted due to increased number of ion–dipole interactions and S–S cross-links at the junction of the cut surface. We envisage that this extraordinary healing property, unreported yet, would be of great importance toward the design of novel NR–SiO2 elastomeric hybrids with superior mechanical properties.

Preparation of novel flame-retardant organoclay and its application to natural rubber composites

In this study, a novel type of flame-retardant montmorillonite (MMT) was prepared using a new approach to obtain highly branched polymer chains. First, MMT was modified using a small liquid crystal molecule comprising N,N,N tris(2-hydroxyethyl)N-dodecylammonium bromide and organic MMT (OMMT) was obtained. Next, three generations of dendrimer-modified organoclay comprising DOMMT-1, DOMMT-2, and DOMMT-3 were successfully prepared using OMMT and branching units of ethylenediamine and methyl acrylate. Their chemical structures were characterized and confirmed by different methods. The DOMMT organoclay was used in the preparation of natural rubber (NR) composites. The tensile strength and elongation at breakage for NR/DOMMT-10 were 17.3 MPa and 697%, respectively, which were about 13.8% and 10.8% higher, respectively, compared with that for the pure NR. After the addition of DOMMT, the horizontal burning time increased by about 69% and the thermal stability was also improved. We also propose a possible flame-retardant and reinforcing mechanism for this novel organoclay in an NR matrix.

Preparation of Natural Rubber‐graft‐Poly(lactic acid) Used as a Compatibilizer for Poly(lactic acid)/NR Blends

SummaryPoly(lactic acid) (PLA) is a biodegradable plastic with good properties in terms of high tensile strength and high tensile modulus, but the brittleness and low impact strength behavior limit its applications. To enhance the impact strength of PLA, natural rubber (NR) with excellent elastic property should be applied to PLA. However, the polarity difference of these constituents leads the incompatibility resulting in poor mechanical properties of PLA/NR blends. Thus, the chemical modification of NR to increase its polarity is required. This research aimed to synthesize NR‐graft‐PLA (NR‐PLA) as a compatibilizer for PLA/NR blends. There were 2 steps to prepare NR‐PLA compatibilizer. Firstly, NR was functionalized by various maleic anhydride (MAH) contents (5‐20 phr) to produce NR‐MAH having higher polarity than NR. Then, NR‐MAH was grafted with PLA via esterification using 4‐dimethyaminopyridine (DMAP) as a catalyst. The structural characterization of the NR‐MAH and NR‐PLA was conducted by FT‐IR and 1H NMR spectrooscopy. This was observed that the increase in the MAH contents increased the amount of grafted MAH in the NR‐MAH structure. The higher grafted MAH content induced the greater efficiency for grafting PLA in preparation of NR‐PLA. The effects of DMAP, NR/PLA wt ratio and temperature in the esterification step on the grafted PLA were investigated.

Preparation and characterization of natural rubber latex/modified montmorillonite clay nano-composite

In this study, new biopolymer nano-composites have been prepared. Fatty amides (FAs) which were synthesized from palm olein, have been used as an organic compound to modify natural clay, sodium montmorillonite. The clay modification was carried out by stirring the clay particles in an aqueous solution of FAs by which the clay layer distance increases from 1.24 to 2.65 nm. The modified clay was then used in the preparation of the natural rubber (NR) nano-composite. The interaction of the modifier in the clay layer was characterized by ray diffraction (XRD), and Fourier transform infrared. The nano-composite was synthesized by melt blending of the modified clay and NR. The nano-composite was then characterized using XRD, transmission electron microscopy, thermogravimetric analysis (TGA), and tensile properties measurements. The XRD and transmission electron microscopy results confirmed the production of nano-composites. NR-modified clay nano-composites show higher thermal stability and significant improvement of mechanical properties in comparison with those of the pure NR.

Preparation of novel hyperbranched flame‐retardant polymer and its application into natural rubber systems

AbstractFlame‐retardant hyperbranched pentaerythritol (FR‐HPER) was prepared by condensation polymerization between pentaerythritol (PER), the monomer, and phosphate acid we prepared. It was then characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and matrix‐assisted laser desorption ionization time of flight mass spectrometer (MALDI‐TOF‐MS). This FR‐HPER was used in the preparation of natural rubber (NR)/FR‐HPER composites. Different types of NR/FR‐HPER composites were prepared with different amounts of FR‐HPER, and compared with the composites directly incorporated with PER. Then, the tensile, wear resistant, thermal, and FR properties were researched and compared. Results showed that some mechanical and FR properties of NR/FR‐HPER composites showed obvious improvements compared with that of NR and NR/PER systems. Schemes of toughening, wear resistant, and FR mechanism were proposed. The hyperbranched polymer may reduce the amount and size of voids in NR matrix, and thus increase the tensile properties. Meanwhile, the synergistic effect between nitrogen in PER and phosphorus in phosphate acid can increase the amount of carbonaceous layers, and thus may inhibit the pyrolysis degree of NR matrix during burning. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and characterization of natural rubber with soft nanomatrix structure

Preparation of natural rubber (NR) with a soft nanomatrix structure was made by graft-copolymerization of butyl acrylate (BA) onto deproteinized natural rubber with tert-butyl hydroperoxide/tetraetylenepentamine in latex stage. The resulting graft-copolymer of deproteinized natural rubber and poly (butyl acrylate) (DPNR-graft-PBA) was characterized by Fourier-transform infrared spectroscopy. Conversion and grafting efficiency of BA were dependent upon BA concentration, which were more than 90 mol% under a suitable condition of the graft-copolymerization. Morphology of DPNR-graft-PBA was observed by transmission electron microscopy after staining film specimens with I2 vapor for 5 min. The NR particles of about 0.5 μm in diameter were dispersed in PBA matrix of about 15 nm in thickness. Storage modulus and loss tangent of DPNR-graft-PBA were measured, and they were related with the soft nanomatrix structure. The tensile strength and elongation at break decreased as monomer concentration increased.

Preparation of natural rubber (NR) latex/low density polyethylene (LDPE) blown film and its properties

Heat-shrink composite films based on LDPE and NR latex blends were prepared. The effect of varying the NR latex content on the physical, mechanical and dynamic properties and the heat-shrinkability of the composite films were investigated. The addition of NR latex into the LDPE films at up to 7.5 phr did not affect the clarity of the film but affected the color due to the β-carotene content of the NR latex. The degree of crystallinity of the LDPE/NR composite films increased with increasing NR latex content up to 7.5 phr, as did the tear strength and impact resistance up to a NR latex content of 5 phr. However, the tensile strength and hardness of the LDPE/NR composite films decreased with increasing NR latex content. The heat-shrinkability of LDPE films was improved by adding NR latex. A mechanism for the strain-induced crystallization of the LDPE/NR composite films during the blown film process is proposed.

Synthesis of Hyper-branched 4A Zeolite and its Application in Natural Rubber Systems

Hyper-branched 4A zeolite (HB-4A zeolite) was prepared by condensation reaction between 4A zeolite and the monomer we prepared. It was then characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). This HB-4A zeolite was then used in the preparation of natural rubber (NR)/HB-4A zeolite composite. Different types of NR/HB-4A zeolite composites were prepared with different amounts of HB-4A zeolite and compared with the composites directly incorporated with 4A zeolite. The cure characteristics of different 4A zeolite filled NR composites were studied. Then, the tensile and thermal properties were compared. Results revealed that the mechanical properties of NR/HB-4A zeolite, especially elongation at break, showed a remarkable enhancement compared with that of NR/4A zeolite and NR systems. SEM studies showed that hyper-branching modification might increase the compatibility between 4A zeolite and NR matrix. A reinforcing mechanism was proposed, assuming that the ‘anchor’ effect caused by the hyper-branched polymer may reduce the amount and size of voids and increase the length of the crack spread path during tensile drawing.

Natural rubber/clay nanocomposites: Influence of poly(ethylene glycol) on the silicate dispersion and local chain order of rubber network

A novel preparation of natural rubber (NR)/Na +–montmorillonite (MMT) nanocomposites in only one step by using poly(ethylene glycol) (PEG) has been investigated. PEG behaves as dispersing agent favouring the intercalation of rubber chains into the silicate galleries and providing substantially improved clay dispersion. Intercalated/exfoliated miscible hybrids were observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The influence of PEG on the network structure has also been evaluated by static proton double-quantum nuclear magnetic resonance spectroscopy ( 1H DQ NMR) at low-field. Silicate nanoparticles with a high aspect ratio (clay tactoids) and a more crosslinked rubber network have been obtained for an optimum PEG/MMT ratio. Both effects were responsible of the enhancement on mechanical properties.