Effects of Foaming Agents and Calcium Carbonate on Thermo-Mechanical Properties of Natural Rubber Foams

Pjene od prirodnog kaučuka pripremljene su umreživanjem prirodnog kaučuka u sustavu sumpornog umreživanja pri 396 K s pomoću dvovaljčanog mlina s pjenilima: natrijev bikarbonatom (NaHCO3) ili N, N´-dinitrosopentametilen tetraminom (DNPT, C5H10N6O2), te s 0, 20, 40 i 60 phr kalcijeva karbonata (CaCO3) kao punilom. Dobivene pjene od prirodnog kaučuka su lagane, dobrih toplinskih i mehaničkih svojstava, prikladne za toplinsku izolaciju, apsorpciju energije i strukturne uporabe. Oba pjenila dodana u smjesu s prirodnim kaučukom, NaHCO3 i DNPT, razgradila su se i oslobodila plinove pri temperaturi umreživanja (umreživalištu) od 396 K, kako bi se stvorile otvorene i zatvorene stanične strukture. Dodavanje 60 phr CaCO3 čestica punila u pjene prirodnog kaučuka poboljšalo je mehanička i toplinska svojstva kako su ionski naboji Ca2+ i CO 3+ 2- proizveli veze među atomima unutar matrice pjene prirodnog kaučuka. Dobivena pjena od prirodnog kaučuka s punilom 60 phr CaCO3 i s NaHCO3 imala je nasipnu gustoću od 240,5 kg/m3, zaostalu pritisnu deformaciju od 32,60 % i toplinsku provodnost od 0,066 W/mK. Dobivena pjena od prirodnog kaučuka s punilom 60 phr CaCO3 i s DNPT imala je nasipnu gustoću od 219,0 kg/m3, zaostalu pritisnu deformaciju od 11,30 % i toplinsku provodnost od 0,070 W/mK, pri temperaturama iznad 800 °C.Natural rubber foams were prepared from the vulcanization of natural rubber in a sulfur curing system at 396 K by a two roll mill with foaming agents; sodium bicarbonate (NaHCO3) or N, N´-dinitrosopentamethylene tetramine (DNPT, C5H10N6O2), and with 0, 20, 40, and 60 phr calcium carbonate (CaCO3) as a fi ller. The obtained natural rubber foams are lightweight, with good thermal and mechanical properties, suitable for thermal insulation, energy absorption, and structural uses. Both foaming agents added in the natural rubber, namely NaHCO3 and DNPT, decomposed and released gases at the vulcanization temperature of 396 K to produce open and closed cell structures. Adding of 60 phr CaCO3 fi ller particles into the natural rubber foams enhanced the mechanical and thermal properties as the ionic charges Ca2+ and CO3+ 2- produced the interatomic bondings within the natural rubber foam matrix. The obtained natural rubber foam with the 60 phr CaCO3 fi ller and with NaHCO3 possessed the bulk density, compression set, and thermal conductivity of 240.5 kg/m3, 32.60%, and 0.066 W/mK, respectively. The obtained natural rubber foam with the 60 phr CaCO3 fi ller and with DNPT possessed the bulk density, compression set, and thermal conductivity of 219.0 kg/m3, 11.30%, and 0.070 W/mK, respectively, temperatures above 800°C

Dynamics of vorticity stretching and breakup of isolated viscoelastic droplets in an immiscible viscoelastic matrix

The effect of droplet elasticity on transient deformation of isolated droplets in immiscible polymer blends of equal viscosity was investigated. In terms of the deformation parameter, Def*= a* − c/a* + c where a * and c are apparent drop principal axes, it undergoes two cycles of positive oscillations before reaching a negative value, followed by one cycle of oscillation before attaining a steady state negative value. This behavior was observed when Capillary number, Ca , was varied between 3 and 9 at a fixed Weissenber number, Wi, of 0.31, and when Ca number was held fixed at 8 and Wi number was varied between 0.21 and 0.40. In another blend of relatively lower Wi number of 0.21, one cycle of oscillation in Def* was observed before reaching steady state negative values when Ca number was varied between 3 and 14. The steady state Def* varies inversely with Ca number, with a stronger dependence for the blend with higher Wi number. The magnitude of oscillation increases with increasing Ca and Wi numbers. The critical Ca was found to be 12 and 14 for the two blends studied; these values are about 30 times greater than that of Newtonian blends.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47214/1/397_2003_Article_340.pd

Lead zirconate (PbZrO3) embedded in natural rubber as electroactive elastomer composites

Perovskite lead zirconate (PbZrO3) was synthesized in an orthorhombic form at a temperature below the Curie temperature, TC. The orthorhombic form is a noncentrosymmetric structure which is capable of spontaneous polarization. Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns confirm the successful synthesis of the lead zirconate; and scanning electron microscopy (SEM) micrographs indicate that PbZrO3 particles are moderately dispersed in the natural rubber (NR) matrix. Without an electrical field, the particles merely act as a ferroelectric filler, which can absorb and store additional stress. Under an electrical field, particle-induced dipole moments are generated, leading to interparticle interaction and a substantial increase in the storage modulus. At a small amount of lead zirconate particulates present in the natural rubber matrix, at a volume fraction of 0.007306, the electrical conductivity increases dramatically by nearly two orders of magnitude at the electrical frequency of 500 kHz

Electrical Conductivity Response of Poly(Phenylene-vinylene)/Zeolite Composites Exposed to Ammonium Nitrate

Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3. The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy

Fabrication of Poly(p-Phenylene)/Zeolite Composites and Their Responses Towards Ammonia

Poly(p-phenylene) (PPP) was chemically synthesized via oxidative polymerization using benzene and doped with FeCl3. The electrical conductivity response of the doped PPP (dPPP) towards CO, H2 and NH3 is investigated. dPPP shows no electrical conductivity response towards the first two gases (CO and H2), but it shows a definite negative response towards NH3. The electrical conductivity sensitivity of dPPP increases linearly with increasing NH3 concentration. To improve the sensitivity of the sensor towards NH3, ZSM-5 zeolite is added into the conductive polymer matrix. The electrical sensitivity of the sensor increases with increasing zeolite content up to 30%. The effect of the type of cation in the zeolite pores is investigated: namely, Na+, K+, NH4+ and H+. The electrical conductivity sensitivity of the composites with different cations in the zeolite can be arranged in this order: K+ < no zeolite < Na+ < NH4+ < H+. The variation in electrical sensitivity with cation type can be described in terms of the acid-base interaction, the zeolite pore size and surface area. The PPP/Zeolite composite with H+ possesses the highest electrical sensitivity of −0.36 since H+ has the highest acidity, the highest pore volume and surface area, which combine to induce a more favorable NH3 adsorption and interaction with the conductive polymer

Synthesis and Characterization of Hollow-Sphered Poly(N-methyaniline) for Enhanced Electrical Conductivity Based on the Anionic Surfactant Templates and Doping

Poly(N-methylaniline) (PNMA) is a polyaniline derivative with a methyl substituent on the nitrogen atom. PNMA is of interest owing to its higher solubility in organic solvents when compared to the unsubstituted polyaniline. However, the electrical conductivity of polyaniline derivatives suffers from chemical substitution. PNMA was synthesized via emulsion polymerization using three different anionic surfactants, namely sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and dioctyl sodium sulfosuccinate (AOT). The effects of surfactant structures and concentrations on electrical conductivity, doping level, crystallinity, morphology, and thermal stability were investigated. The re-doping step using perchloric acid (HClO4) as a dopant was sequentially proceeded to enhance electrical conductivity. PNMA synthesized in SDBS at five times its critical micelle concentration (CMC) demonstrated the highest electrical conductivity, doping level, and thermal stability among all surfactants at identical concentrations. Scanning electron microscopy (SEM) images revealed that the PNMA particle shapes and sizes critically depended on the surfactant types and concentrations, and the doping mole ratios in the re-doping step. The highest electrical conductivity of 109.84 &plusmn; 20.44 S cm&minus;1 and a doping level of 52.45% were attained at the doping mole ratio of 50:1

Screen-printed electrode designed with MXene/doped-polyindole and MWCNT/doped-polyindole for chronoamperometric enzymatic glucose sensor

The enzymatic glucose sensors as modified by MXene-dPIn and MWCNT-dPIn on a screen-printed carbon electrode (SPCE) were investigated. Herein, MXene was molybdenum carbide (Mo3C2) which has never been utilized and reported for glucose sensors. The biopolymer type to support the enzyme immobilization was examined and compared between chitosan (CHI) and κ-carrageenan (κC). MWCNT-dPIn obviously showed a larger electroactive surface area, lower charge transfer resistance and higher redox current than Mo3C2-dPIn, indicating that MWCNT-dPIn is superior to Mo3C2-dPIn. For the chitosan-based sensors, the sensitivity value of CHI-GOD/Mo3C2-dPIn is 3.53 μA mM−1 cm−2 in the linear range of 2.5–10 mM with the calculated LOD of 1.57 mM. The sensitivity value of CHI-GOD/MWCNT-dPIn is 18.85 μA mM−1 cm−2 in the linear range of 0.5–25 mM with the calculated LOD of 0.115 mM. For the κ-carrageenan based sensors, κC-GOD/MWCNT-dPIn exhibits the sensitivity of 15.80 μA mM−1 cm−2 and the widest linear range from 0.1 to 50 mM with the calculated LOD of 0.03 mM. The presently fabricated sensors exhibit excellent reproducibility, good selectivity, high stability, and disposal use. The fabricated glucose sensors are potential as practical glucose sensors as the detectable glucose ranges well cover the glucose levels found in blood, urine, and sweat for both healthy people and diabetic patients