Grafted Natural Rubber Research Articles

The Microstructure of GNR and the Mechanical Properties of Biobased PLA/GNR Thermoplastic Vulcanizates with Excellent Toughness

A series of different contents of glycidyl methacrylate (GMA)-grafted natural rubber (GNR) copolymers were fabricated via green bulk melt-grafting reactions, and super-tough bio-based poly (lactic acid) (PLA)/GNR thermoplastic vulcanizates (TPVs) were achieved by in-situ dynamic vulcanization. Increasing the graft yield, gel fraction, and crosslinking density of GNR vulcanizates effectively improved the ductility of the PLA/GNR TPVs, while prolonging the dynamic vulcanization time and increasing the GMA graft yield led to a notable enhancement in the impact toughness of the PLA/GNR TPVs. PLA/30 wt % GNR TPVs exhibited a significantly increased elongation (410%) and notched impact strength (73.2 kJ/m2), which were 40 and 15 times higher than those of the PLA/30 wt % NR TPVs, respectively. The new bio-based PLA/GNR TPVs offer promise as replacements for petroleum-based polymers in the automotive, 3D printing, and packaging fields.

Poly(butyl acrylate-co-fluorinated acrylate)-graft-natural rubber: Synthesis and application as compatibilizer for natural rubber/poly(butyl acrylate-co-fluorinated acrylate) films

Poly(butyl acrylate-co-fluorinated acrylate)-graft-natural rubber was successfully prepared via emulsion graft copolymerization and applied as a compatibilizer for improving phase compatibility and toughness of natural rubber/poly(butyl acrylate-co-fluorinated acrylate) films. From graft copolymerization step, butyl acrylate (BA) acted as a co-monomer to be initially grafted onto the natural rubber (NR) and then copolymerized with 2,2,2–trifluoroethyl methacrylate (3FMA) to form a grafting poly(BA-co-3FMA) chain onto the NR backbone. The appropriated BA/3FMA ratio at 30/70 (w/w) provided the highest graft copolymer fraction of 72.8 wt% with 25.3 mol% grafted 3FMA and 68.5% grafting efficiency under center reaction condition. Transmission electron microscopy analysis indicated that the graft product had core-shell morphology, which NR was a core and covered by poly(BA-co-3FMA) shell. The results from Molau test and atomic force microscopy showed that the addition of 5–10 wt% graft product could enhance the compatibility between NR and poly(BA-co-3FMA) phases in the NR/poly(BA-co-3FMA) films (20/80 (w/w)) and provided the obtained films with a greater elongation at break to 266% than that of poly(BA-co-3FMA) film (27%). The compatibilized films also exhibited a high hydrophobicity (water contact angle = 109°) and oleophobicity (hexadecane contact angle = 54°) with a low surface energy (8.04 mN/m), which can be further applied as self-sealing films for moisture and oil protection.

Conductivity-Temperature Dependent Studies on MG49 Doped Lithium Triflate Salt

This paper reports on the conductivity-temperature studies of gel polymer electrolytes (GPEs) based on 49% poly (methyl methacrylate) grafted-natural rubber (MG49) doped with lithium triflate salt (LiTf) and plasticized with ethylene carbonate (EC). The GPE films are prepared by solution cast technique. The X-ray diffraction (XRD) studies reveal the polymer electrolyte systems are amorphous. AC impedance spectroscopy is carried out in the temperature range between 303 and 373 K. The magnitudes of conductivity observed are strongly dependent on salt concentration and temperature. The high ionic conductivity at elevated temperatures of GPE is attributed to the high ionic mobility of charge carriers. The ionic migration is seen to follow the VTF behavior and approaches to Arrhenius rule at high and low at temperature. Ionic conductivity relaxation appears to be a characteristic of the ionic polarization and the modulus formalism studies confirmed the GPEs in the present investigation are ionic conductors.

Styrene grafted natural rubber reinforced by in situ silica generated via sol–gel technique

Abstract The filling of styrene graft natural rubber (ST-GNR) with in situ formed silica was performed using the sol–gel reaction via the latex solution method. The mechanical properties of ST-GNR/NR vulcanizate were improved when using the in situ formed silica to levels higher than those obtained with the commercial ex situ formed silica filled ST-GNR/NR vulcanizates at a comparable silica content of 12 parts by weight per hundred parts of rubber. Transmission electron microscopy analysis revealed that the in situ silica particles were small (∼40 nm diameter) and well dispersed, while the commercial silica particles were larger (∼60 nm diameter) and markedly agglomerated in the rubbery matrix. The mechanical properties of the composites prepared via both the solid rubber and latex solution methods were comparable.

Effects of Polarity on the Filler-Rubber Interaction and Properties of Silica Filled Grafted Natural Rubber Composites

The grafting of an olefinic monomer like acrylonitrile (AN), methyl methacrylate (MMA), and styrene (ST) onto natural rubber (NR) was carried out to enhance the polarity of the new chemical groups on the NR backbone and, in turn, to improve the filler-rubber interaction. The grafted natural rubber (GNR) produced was compounded and then vulcanization was carried out in the presence of silica as a reinforcing filler. The physical properties and aging resistance provided by the presence of the polar functional groups of the GNR composites were investigated and compared with other rubbers such as SBR, NBR, and NR. The GNRs provided significant improvements in resistance of the composites to thermal, oil, and ozone while maintaining the mechanical properties of the rubber. Therefore, these properties can be controlled as a function of the polarity of functional groups on the NR backbone. Morphological studies confirmed a shift from ductility failure to brittle with the presence of the polar group on the rubber chains.

2,2,2-Trifluoroethyl methacrylate-graft-natural rubber: Synthesis and application as compatibilizer in natural rubber/fluoroelastomer blends

The incompatibility and immiscibility of natural rubber (NR)/fluoroelastomers (FKM) blends were improved by incorporation of a graft copolymer synthesized from the free radical graft copolymerization of 2,2,2-trifluoroethyl methacrylate (TFEM) onto NR initiated by benzoyl peroxide via a melt-mixing process. The grafting properties were investigated as functions of the initiator and monomer concentrations, reaction temperature and time. At the optimal conditions, the obtained graft NR (GNR) purified by Soxhlet extraction contained a maximum grafting efficiency of 1.34% with 49.1% monomer conversion. The structure of the purified GNR was analyzed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy (1H NMR and 19F NMR). The gross GNR was then applied as the compatibilizer for NR/FKM vulcanizates (20/80 (w/w)) cured by peroxide vulcanization. The addition of GNR at 15 parts per hundred of rubber (phr) gave a vulcanizate with the highest tensile strength (9.93 MPa), some 5.31-fold higher than that of the incompatibilized one (1.87 MPa). This is likely to be due to the higher degree of homogeneity of the constituent phases in the GNR-compatibilized blends, as observed by scanning electron microscopy (SEM). The GNR-compatibilized NR/FKM vulcanizates were also resistant to gasohol E85 (85% (w/w) of ethanol).

Styrene/Acrylonitrile Graft Natural Rubber as Compatibilizer in Rubber Blends

A graft copolymer of acrylonitrile (ACN) and styrene (ST) on natural rubber (NR) was prepared by solution polymerization initiated by benzoyl peroxide. The effect of graft NR (GNR) applied as a compatibilizer for NR/nitrile rubber (NBR) blends on their mechanical and physical properties was investigated. The results revealed that the tensile properties and oil-swelling resistance of the blends increased with increasing %graft copolymer of GNR. The tensile fracture surfaces of the compatibilized NR/NBR vulcanizates attested by scanning electron microscopy indicated the improvement of interfacial adhesion between two rubber phases. Moreover, the dynamic mechanical properties of compatibilized vulcanizates were also reported.

Catalytic hydrogenation of methyl methacrylate-g-natural rubber (MMA-g-NR) in the presence of OsHCl(CO)(O2)(PCy3)2

Abstract The graft copolymerization of methyl methacrylate onto natural rubber (NR) was carried out by using cumene hydroperoxide as redox initiator. The monomer conversion, grafting efficiency, and graft copolymer composition were examined. The purified graft copolymer was then hydrogenated by using a homogeneous osmium catalyst, OsHCl(CO)(O2)(PCy3)2. The purified graft copolymer and hydrogenated graft copolymer samples were characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. A detailed kinetic investigation of the hydrogenation was carried out by monitoring the amount of hydrogen consumption using a gas-uptake apparatus. The kinetic results for the hydrogenation of graft natural rubber indicated that the rate of hydrogenation exhibited a first-order dependence on the catalyst concentration. The hydrogenation exhibited a first-order dependence on hydrogen pressure which then decreased toward a zero-order dependence at higher hydrogen pressure. The addition of a small amount of acid provided a beneficial effect on the hydrogenation of grafted natural rubber. The hydrogenation rate was dependent on the reaction temperature and the apparent activation energy over the range of 120–160 °C was found to be 70.3 kJ/mol. The mechanistic aspects of these catalytic processes are discussed based on the observed kinetic results. Thermal properties of the grafted copolymer and hydrogenated grafted copolymer were also determined.

Improving properties of modified acrylic sheet via addition of graft natural rubber

The mechanical properties of a modified acrylic sheet prepared by bulk copolymerization of methyl methacrylate (MMA) and styrene (ST) were improved by the addition of a small amount of graft natural rubber (GNR). The graft copolymerization of MMA and ST onto natural rubber latex was carried out by emulsion polymerization using potassium persulfate as an initiator. The properties of the modified acrylic sheet containing GNR with 22.5 wt.% graft copolymer were investigated as a function of GNR content. The results indicated that the impact resistance, tensile strength and elongation at break of the modified acrylic sheet increased with the increase in the amount of GNR in the range of 0.5–4 parts. From the stress–strain behavior, the characteristic of the modified acrylic sheet shifted from brittle to ductile when the amount of GNR was increased. The scanning electron micrographs of the modified acrylic sheets show the relatively smooth fracture surface with relatively few small cracks. This implies that the GNR can be used as an impact modifier for acrylic plastics.

Study on the Properties of Blend Rubber Between Grafted Rubber Latex and Natural Rubber Latex by Gamma Radiation

Blend rubber films were prepared by mixing styrene grafted rubber latex and natural rubber latex (NRL) with varying proportions by gamma radiation from Co-60 source at room temperature. Tensile strength, modulus at 500% elongation, elongation at break, permanent set, and swelling ratio were measured. Tensile strength and modulus at 500% elongation attain maximum at 8 kGy radiation dose for blend rubber films. The increase in tensile strength is insignificant, but modulus increases from 5.61 to 7.46 MPa with increased proportion of grafted rubber latex from 40 to 70% in the blend at this radiation dose. Elongation at break, permanent set, and swelling ratio of blend rubber decreases with increase in radiation dose as well as proportion of grafted rubber.

Modification of Epoxy Resin Using Liquid Natural Rubber

The cure process and the mechanical properties of liquid polymethylmethacrylate grafted natural rubber (LMG30) modified epoxy have been studied. Addition of LMG30 significantly increased the fracture toughness and the impact strength of the epoxy resin. The fracture toughness increased up to 22 fold (17.3 MNm-3/2) when modified with 5 phr LMG30. The glass transition temperature however, decreases as the rubber content increases. The SEM analysis shows uniform dispersion of rubber particles within the epoxy matrix with average particle size between 0.4 to 0.8 0m in diameter.

Synthesis and Characterization of Novel Melt-Processable Ionomers based on Radiation Induced Styrene Grafted Natural Rubber

Graft ionomers based on natural rubber were prepared by sulfonating radiation induced styrene grafted natural rubber (SGNR) with acetyl sulfate reagent, followed by the neutralization of the precursor acid using methanolic zinc acetate. The modified natural rubber was characterized using spectroscopic techniques such as X-ray fluorescence (XRFS), Fourier transform infrared (FTIR), Fourier transform NMR (FTNMR), thermo-gravimetric analysis (TGA) and also by the evaluation of mechanical properties. The IR studies of the ionomers reveal that the sulfonate groups are attached to the para-position of the benzene rings of the polystyrene blocks. NMR studies give credence to this observation. Thermal analyses show that incorporation of ionic groups makes profound improvement in the thermal stability of SGNR. The presence of ionic groups results in enhancement of mechanical properties as well as retention of properties even after three cycles of processing at 150°C.

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

AbstractThe grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001

Toughening epoxy resins with poly (methyl methacrylate)- grafter-natural rubber, and its use in adhesive formulations

Poly(methyl methacrylate)-grafted-natural rubber (Heveaplus MG) has been studied as a novel toughening agent for epoxy resin systems based on diglycidyl ether of bisphenol A (Shell Epikote 828), both in bulk and as an adhesive. Secondary and tertiary phase distributions were shown to be a function of the solubility parameter of the epoxy, and optimum bulk fracture toughness and adhesive joint failure strengths were thus achieved by controlling the resin solubility parameter. Adhesive joint strenghts were measured at −35, 20 and 50°C for formulations containing up to 7 parts per hundred of resin (pph) of MG rubber and 15 pph of carboxyl-terminated butadiene-acrylonitrile rubber, and were compared with that of a proprietary epoxy-based structural adhesive film under the same conditions.

Radiation induced graft copolymerization of acrylonitrile on natural rubber

Acrylonitrile graft natural rubber was prepared by initiating the polymerization of acrylonitrile in natural rubber field latex using γ-rays. The reaction was carried out at different rubber-monomer concentrations and the properties of the modified rubbers were compared with those of natural rubber and nitrile rubber.

Studies on graft copolymerization of methyl methacrylate in natural rubber latex induced by gamma radiation

Methyl methacrylate graft natural rubber was prepared by initiating the polymerization of methyl metacrylate in natural rubber field latex using γ rays. The combined effect of radiation and chemical initiation was also studied. Properties of these graft rubbers were compared with those prepared using only redox catalysts.