Anyaporn Boonmahitthisud

Effects of Silica, Poly(methyl methacrylate) and Poly(methyl methacrylate)-Grafted-Silica Nanoparticles on the Physical Properties of Plasticized-Poly(vinyl chloride)

Nanocomposites of plasticized-poly(vinyl chloride) (PVC) filled with different contents (3-9 parts by weight per hundred of PVC resin) of nanosilica (nSiO2), nanosized poly(methyl methacrylate) (nPMMA) and PMMA-grafted-nanosilica (PMMA-nSiO2) were investigated in this study. nPMMA and PMMA-nSiO2 were synthesized via differential microemulsion polymerization. The addition of either an appropriate type or amount of nanofiller into the plasticized-PVC improved the tensile strength, Youngs modulus, tear strength, and thermal stability of the obtained nanocomposites, whereas the elongation at break decreased with increasing amounts of the nanofillers. Scanning electron micrographs of all the nanocomposites showed typical dimple fracture topologies similar to the neat plasticized-PVC.

Effects of Carbon Black and Carbon Nanotube on Mechanical and Thermal Properties of 80NR/20SBR Composites

This work aims to investigate the effects of carbon black (CB) and carbon nanotube (CNT) on mechanical properties and thermal behaviors of natural rubber (NR)/styrene butadiene rubber (SBR) blend at NR/SBR weight ratio of 80/20. CB loadings from 3-9 phr and CNT with 0.1-0.4 phr loadings were used as fillers in this study. The composites were prepared by latex compounding method. The specimens were examined for their tensile and dynamic mechanical properties and thermal stability using the universal testing machine, dynamic mechanical analyzer and thermal gravimetric analyzer, respectively. The tensile strength and modulus of the composites were improved as a result of the incorporation of CB and CNT. Dynamic mechanical analysis showed that the CB and CNT filled composites possessed high stiffness and low damping characteristics. Thermal stability of the composites was also proved to be better than the unfilled-rubber blend.

Rubber Blend of 80/20 NR/SBR Reinforced with Nanosilica and PS-Encapsulated Nanosilica

In this study, rubber blend of natural rubber (NR) and styrene butadiene rubber (SBR) at 80/20 NR/SBR was reinforced with nanosilica (nSiO2) and polystyrene-encapsulated nanosilica (PS-nSiO2) in the latex state. The latex of PS-nSiO2 was synthesized by in situ differential microemulsion polymerization using sodium dodecyl sulfate and azobisisobutyronitrile as the surfactant and initiator, respectively. The nanoparticles at the amount of 0.1, 0.2, 0.3 and 0.4 parts per hundred of rubber (based on dry weight of nSiO2) were dispersed in the rubber blend compound and subsequently cured at 80°C for 3 h to prepare rubber nanocomposites. Using this technique, nanoparticles could be well dispersed in the rubber matrix. The influences of the nSiO2 and PS-nSiO2 on the mechanical and thermal properties of the resulting nanocomposites were quantified and compared. It is found that the tensile properties and thermal stability of the rubber blends were improved with the appropriate amounts of the nanofillers. However, the PS-nSiO2 exhibited reinforcing efficiency superior to nSiO2 with the same nSiO2 content due to the stronger rubber-filler interfacial adhesion.

Use of Carbon Nanotube and Nanosilica as Reinforcement Nanofillers in NR/SBR Blended Latex

The blended latex of natural rubber (NR) and styrene butadiene rubber (SBR) at dry weight ratio of 80/20 (NR/SBR) was reinforced with a very low loading level of either carbon nanotube (CNT) or nanosilica (nano-SiO2) (0.1-0.4 phr). The CNT and nano-SiO2 were compounded with NR/SBR rubber blend and other chemicals necessary for vulcanization in the latex state. The obtained nanocomposite latex was cast into thin sheet on a glass mold and then cured in an oven at 80°C for 3 h. The cured samples were subjected to the tensile, dynamic mechanical and thermal tests. The results revealed that the nanofillers have improved their tensile strength, modulus at 300% strain, dynamic mechanical properties and thermal stability but reduced the elongation at break. It was also observed that at similar nanofiller loadings the reinforcing effects of CNT are more noticeable than that of nano-SiO2.

Mechanical properties, thermal behaviors and oil resistance of epoxidized natural rubber/multiwalled carbon nanotube nanocomposites prepared via in situ epoxidation

Epoxidized natural rubber (ENR)/multiwalled carbon nanotube (MWCNT) nanocomposites were prepared via in situ epoxidation of natural rubber (NR) using a molar ratio of formic acid/hydrogen peroxide to isoprene unit at 0.75/0.75 with five loadings of MWCNTs, ranging from 0.5–2.5 parts per hundred parts of rubber (phr), at 50°C for 4 h. Based on Fourier transform infrared spectra, the epoxide content of ENR in the nanocomposites was about 32.5–33.2 mole%. Accordingly, the products were referred to ENR30/MWCNT nanocomposites. The curing characteristics, mechanical properties (tensile properties, tear strength, and hardness), glass transition temperature (T g), thermal stability, and oil resistance of these in situ ENR30/MWCNT nanocomposites were investigated and compared with NR and neat ENR30. The results showed that the scorch and cure times of ENR30/MWCNT nanocomposites were the longest followed by NR and ENR30. The incorporation of an appropriate amount of MWCNTs into the in situ epoxidation apparently improved the properties of NR. Among them, the nanocomposites filled with 2 phr MWCNTs exhibited the highest mechanical properties, T g, thermal stability, and oil resistance. The mechanical properties of the in situ nanocomposites were also compared with those of the control nanocomposites prepared by adding MWCNTs directly in the prepared ENR30 latex. It was found that at similar MWCNT loadings, the in situ nanocomposites exhibited higher mechanical properties than the control nanocomposites.

Use of TBzTD as Noncarcinogenic Accelerator for ENR/SiO2 Nanocomposites: Cured Characteristics, Mechanical Properties, Thermal Behaviors, and Oil Resistance

This study reported the use of tetrabenzylthiuram disulphide (TBzTD) as a noncarcinogenic accelerator in a traditional sulfur curing system of epoxidized natural rubber (ENR)/nanosilica (nSiO2) composites. ENR used in this work was synthesized via in situ epoxidation of natural rubber (NR) in the presence of performic acid generated from the reaction of formic acid and hydrogen peroxide at 50°C for 8 h to acquire the epoxide content of about 40 mol%. Accordingly, the resulting ENR was referred to as ENR 40. The curing characteristics, mechanical properties, thermal behaviors, dynamic mechanical properties, and oil resistance of ENR 40/nSiO2 nanocomposites filled with three loadings of nSiO2 (1, 2, and 3 parts per hundred parts of rubber) were investigated and compared with NR and neat ENR 40. The results revealed that the scorch and cure times of ENR 40/nSiO2 nanocomposites were slightly longer than those of NR but slightly shorter than those of ENR 40. The tensile properties and tear strength for both before and after aging of all ENR 40/nSiO2 nanocomposites were higher than those of ENR 40, while the glass transition temperature, storage modulus at −65°C, thermal stability, and oil resistance of ENR 40/nSiO2 nanocomposites were higher than those of NR and ENR 40.

Mechanical and Electrical Properties of Natural Rubber/Carbon Nanotube Nanocomposites Prepared by Latex Compounding

In this study, natural rubber (NR) nanocomposites containing different loadings of multi- walled carbon nanotubes (CNTs) (0.1-0.4 phr) were prepared by latex compounding. The as-prepared nanolatex composites were cast into 3-mm sheets on a glass mold and then cured at 80°C for 3 h. The obtained vulcanizates were evaluated for their mechanical properties (tensile properties, tear strength and hardness) and surface electrical resistivity. The results showed that the incorporation of CNTs at a very low loading can reinforce NR by enhancing the tensile strength (0.2 phr optimal), modulus at 300% strain (0.2 phr optimal), elongation at break (0.4 phr optimal), tear strength (0.4 phr optimal) and hardness (0.4 phr optimal) and also increase the electrical conductivity (0.2 phr optimal). The reinforcing effect of CNTs is primarily attributed to its very high aspect ratio and great specific surface area, whilst the electrical conductivity of the nanocomposites is due to the formation of a continuous conductive network of CNTs in the NR matrix.

Use of Magnesium Hydroxide as Flame Retardant in Poly(Lactic Acid)/High Impact Polystyrene/Wood Flour Composites

This work aimed to use magnesium hydroxide (MH) as a flame retardant in poly(lactic acid) (PLA)/high impact polystyrene (HIPS)/wood flour (WF) composite. The 80/20/20 PLA/HIPS/WF composite was melt mixed with three loadings (20, 30 and 40 phr) of MH on a twin screw extruder, followed by an injection molding. The prepared wood-plastic composites (WPCs) were investigated for their impact strength (IS), tensile strength (TS), Young’s modulus (E), elongation at break (EB), flammability and morphology. The results showed that the 80/20/20 PLA/HIPS/WF composite exhibited higher IS, TS and E than the neat PLA, but at the expense of reducing the EB. It was also found that the WPCs filled with MH at all loadings provided much higher flame resistance and E over the neat PLA, HIPS, PLA/HIPS blend and PLA/HIPS/WF composite. Therefore, the MH could play an effective role as flame retardant in the WPCs.

Preparation and Properties of Poly(Lactic Acid)/Epoxidized Natural Rubber/Nano-Silica Composites

This study aimed to improve the toughness property of poly(lactic acid) (PLA) by incorporating epoxidized natural rubber (ENR), an elastomeric material and silica nanoparticle (nSiO2), a spherical inorganic nanofiller. ENR with 30mol% epoxidation (ENR 30) was first prepared via in situ epoxidation of natural rubber by performic acid generated from the reaction between formic acid and hydrogen peroxide in the latex stage. The PLA was melt blended with three weight percentages (10, 20 and 30wt%) of ENR in an internal mixer, followed by a compression molding. The effects of ENR loadings on the mechanical properties and thermal stability of the blends were first investigated. It was found that the addition of ENR 30 increased the toughness property of the blends. The blend at 20wt% ENR 30 exhibited the highest impact strength and elongation at break, and so was selected for preparing nanocomposites with three loadings (1, 2 and 3 parts per hundred of resins) of nano-silica (nSiO2). The results showed that all PLA/ENR 30/nSiO2 nanocomposites exhibited higher impact strength and thermal stability than the neat 80/20 PLA/ENR 30 blend.

Effects of Poly(Methyl Methacrylate)-Encapsulated Nanosilica on Mechanical Properties of Poly(Lactic Acid)/Ethylene Vinyl Acetate Nanocomposites

In this study, poly(lactic acid) (PLA) was melt mixed with three weight percentages (10–30wt%) of ethylene vinyl acetate copolymer (EVA) in an internal mixer, followed by a compression molding. According to a better combination of mechanical properties, the 90/10 (w/w) PLA/EVA was selected for preparing hybrid nanocomposites with three loadings (1, 3 and 5 parts per hundred of resin , phr) of poly(methyl methacrylate)-encapsulated nanosilica (PMMA-nSiO2). The nanolatex of PMMA-nSiO2 was synthesized via in situ differential microemulsion polymerization. The obtained PMMA-nSiO2 showed a core-shell morphology with nSiO2 as a core and PMMA as a shell, having an average diameter of 43.4nm. The influences of the EVA and PMMA-nSiO2 on the impact strength and the tensile properties of the PLA/EVA nanocomposites were studied and compared. It is found that the impact strength and the tensile properties of the 90/10 (w/w) PLA/EVA were improved with the appropriate amounts of the EVA and PMMA-nSiO2.