Society Of Plastics Engineers Research Articles

Preparation of AgNPs/PS composite via reverse microemulsion polymerization

Silver nanoparticles (AgNPs) were synthesized in reverse microemulsions using silver nitrate as silver source, hydrazine hydrate as reducing agent, n-heptane as oil phase, cetyl trimethyl ammonium bromide (CTAB) as surfactant, and isoamyl alcohol as cosurfactant. A uniform silver nanoparticles/polystyrene (AgNPs/PS) composite was further prepared by a reverse microemulsion polymerization method. The morphologies and structures of the AgNPs and the AgNPs/PS composite were characterized by UV-visible spectroscopy (UV–vis), X-ray diffraction (XRD), fourier transform infrared spectra (FTIR), and transmission electron microscopy (TEM). Furthermore, the molecular weight of the AgNPs/PS composite was measured by gel permeation chromatography (GPC), and the thermal stability of the AgNPs/PS composite was determined by thermal gravimetric (TG) analysis. Results show that the AgNPs have a particle size of 3–10 nm, and are almost spherical, uniform, and monodisperse both in a AgNPs colloid and in the AgNPs/PS composite. There are no characteristic peaks of silver oxide in the synthetic AgNPs and AgNPs/PS composite. The AgNPs/PS composite has a better thermal stability and a higher molecular weight than virgin PS. POLYM. COMPOS., 35:1325–1329, 2014. © 2013 Society of Plastics Engineers

Synthesis and thermal properties of poly(ethylene 2,6-naphthalate) copolyesters containing modified diacid monomer

A series of poly(ethylene 2,6-naphthalate) (PEN) copolyesters was synthesized using three monomers (newly prepared 1,4-bis[(methoxycarbonylethoxy)methyl]benzene, dimethyl 2,6-naphthalenedicarboxylate, and ethylene glycol) with various molar ratios to investigate the effects of these compositions on thermal properties of the copolyesters. Copolyesters having weight average molecular weights of 11,000–22,000 were obtained by melt polycondensation in the presence of metallic catalysts. The structures and thermal properties of the resulting random PEN copolyesters were characterized by nuclear magnetic resonance, differential scanning calorimetry, thermal-mechanical analyzer, and X-ray diffraction analysis. The results of thermal measurements revealed that thermal properties depended on the corresponding new diacid comonomer content of the PEN copolyesters. Nonetheless, the crystal structures of PEN copolyesters and PEN homopolymer are identical. POLYM. ENG. SCI., 54:2641–2644, 2014. © 2013 Society of Plastics Engineers

Polyacrylonitrile reinforced PVA based-polymeric networks: Structural, morphological, and mechanical aspects

Various bioengineering and industrial applications demand hard, tough, and mechanically strong polymeric blends. A novel combination of polyvinyl alcohol (PVA) and polyacrylonitrile was used to synthesize semi-IPNs using redox polymerization method in order to achieve desired property combinations in terms of toughness, generally not found in a single polymeric material. The synthesized end products in the form of polymer matrix were characterized by FTIR spectral analysis in order to confirm the incorporation of PAN into PVA, while the morphological aspects studied by AFM analysis showed fair compatibility between the component polymers exhibiting quite smooth surface and nanosize domains. Microhardness investigations were undertaken using the Vicker's indentation technique and the results were analyzed in terms of strain hardening phenomenon. Increase in surface hardness was observed as a result of variation of PVA content within the gel matrix whereas the presence of acrylonitrile as the second network was found to impart toughness as observed by the tensile strength measurements. POLYM. ENG. SCI., 54:2579–2586, 2014. © 2013 Society of Plastics Engineers

Functionalized multiwalled carbon nanotubes in mild polyphosphoric acid/phosphorous pentoxide/phosphoric acid and their composites with epoxy resin

Multiwalled carbon nanotubes (MWCNTs) were functionalized through “Friedel-Craft” acylation with 1,3,5-Benzenetricarboxylic acid (BTC) in mild polyphosphoric acid (PPA)/ phosphorus pentoxide (P2O5)/phosphoric acid (PA) medium at 130°C. The high-resolution transmission electron microscopy, Raman spectra, and X-ray photoelectron spectra (XPS) were used to characterize the surface microstructure nature of functionalized MWCNTs in optimum PPA/P2O5/PA medium. The thermostability of functionalized MWCNTs was characterized by thermogravimetric analysis. The maximum rate of weight loss temperature increased as compared with pristine MWCNTs. The dispersion properties of MWCNTs and the flexural properties of the MWCNTs/epoxy composites affected by MWCNTs functionalization are investigated. It is demonstrated that the functionalized MWCNTs exhibit much better dispersability than pristine MWCNTs. The attached BTC molecules arising from the functionalization effectively improved interfacial adhesion between the epoxy resin and functionalized MWCNTs through covalent bonds, resulting in improved flexural properties compared with those without functionalization. POLYM. COMPOS., 35:1275–1284, 2014. © 2013 Society of Plastics Engineers

Electrophoretic deposition of different carbon nanoscale reinforcements on carbon fiber fabrics and mechanical properties of the resulting hybrid multi-scale epoxy composites

Three types of carbon nanoscale reinforcements (CNRs) including the shortened electrospun carbon nanofibers (ECNFs, with diameters and lengths of ∼200 nm and ∼15 µm, respectively), carbon nanofibers (CNFs), and graphite nanofibers (GNFs) were electrophoretically deposited on carbon fiber (CF) fabrics for the fabrication of hybrid multi-scale epoxy composites. The results indicated that the electrophoretic deposition (EPD) of CNRs onto CF fabrics led to substantial improvements on mechanical properties of hybrid multi-scale epoxy composites; in particular, the hybrid multi-scale epoxy composite containing surface-functionalized ECNFs (with amino groups) exhibited the highest mechanical properties. The study also indicated that some agglomerates of CNRs (particularly GNFs) could form during the EPD process, which would decrease mechanical properties of the resulting composites. Additionally, the reinforcement mechanisms were investigated, and the results suggested that continuous (or long) ECNFs would outperform short ECNFs on the reinforcement of resin-rich interlaminar regions in the composites. POLYM. COMPOS., 35:1229–1237, 2014. © 2013 Society of Plastics Engineers

Sustained delivery of hydrocortisone acetate by CS/N-vinyl-2-pyrrolidone/CaCO3 microparticle hybrid hydrogels

The goal of this research is to develop a composite hydrogel system for sustained release of therapeutic agents. The hybrid hydrogels were prepared by radiation crosslinking on aqueous solution of Chitosan (CS)/N-vinyl-2-pyrrolidone (NVP) with different loads of CaCO3 in the presence of hydrocortisone acetate (HCA), an anti-inflammatory drugs. Physical characteristics of CS/NVP/CaCO3 were studied using X-ray diffraction (XRD) and infrared spectrophotometery (IR). The porous structure of resulted hydrogel was confirmed by SEM micrographs. The effect of doses and calcium carbonate amount on the swelling of the hydrogels was investigated. The ability of the prepared CS/NVP/CaCO3-based hybrid hydrogels to be used as drug carriers for anti-inflammatory-specific drug delivery system was estimated using HCA as a model drug. POLYM. COMPOS., 35:1176–1183, 2014. © 2013 Society of Plastics Engineers

Polymerization properties of polyamide in bottom-up prepared polyamide-calcium carbonate composites

Polyamide/calcium carbonate composites (CaCO3) were prepared by bottom-up process, using a precipitated CaCO3 with polyamide monomers followed by the polymerization of the polyamide. The composites before and after the polymerization treatment were studied by gel permeation chromatography, differential scanning calorimetry, X-ray powder diffraction, and attenuated total reflectance—Fourier transform infrared spectroscopy. A van der Waals interaction between monomer molecules and CaCO3 surface, which was suggested by the blue shift in IR absorption band of NH2 and CH2, restricted the molecular motions of monomers on the CaCO3 surfaces to inhibit the proceeding of polymerization reactions. A resembled blue shift was also observed in the polyamide/CaCO3 composites. Besides the hydrophilic; hydrogen bonding and ionic, interactions, the van der Waals interaction should not be ignored and had a significant effect on the polymerization reactions. POLYM. COMPOS., 35:1132–1139, 2014. © 2013 Society of Plastics Engineers

Preparation and properties of waterborne polyurethane/antimony doped tin oxide nanocomposite coatings via sol-gel reactions

Various amounts of antimony doped tin oxide (ATO) nanoparticles were incorporated into waterborne polyurethane (WPU) dispersions by sol–gel reactions. The dispersion state and morphology investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that the nanoparticles can disperse in the matrix uniformly. The analysis of visible–near infrared spectra (VIS–NIR) suggested that the WPU/ATO coatings show both low near infrared transmittance (35%) and high visible light transmittance (76%). The heat-insulation effect measurement demonstrated that the WPU/ATO coatings could prevent heat transmission effectively. It was also found that the introduction of ATO nanoparticles can improve the mechanical properties significantly. POLYM. COMPOS., 35:1169–1175, 2014. © 2013 Society of Plastics Engineers

In situ intercalation green polymerization, characterization, and kinetics of poly(lactic acid)/zinc oxide pillared saponite nanocomposites

Poly(lactic acid) (PLA)/Zinc oxide (ZnO) pillared saponite nanocomposites were prepared with ZnO pillared saponite as the green catalyst and lactic acid as monomer through in situ intercalation polymerization method. The optimum polymerization parameters were as follows the addition content of ZnO pillared saponite was 1% (wt) and the reaction was running at 180°C for 7 h. The Fourier transform infrared and 1H NMR results showed that the polymerization sample was PLA; Gel permeation chromatography result showed the PLA had a narrow molecular weight distribution, which arranged from 3,000 to 5,000 and the polydispersity index of PLA was 1.2. Differential scanning calorimetry showed ZnO pillared saponite improved the crystallinity of PLA. Thermogravimetric analysis showed the thermal stability of PLA-based nanocomposites were improved by ZnO pillared saponite. It was shown that in situ intercalative polymerization kinetics model of PLA/ZnO pillared saponite nanocomposites accorded with third order, and the activation energy of polymerization reaction was 49.3 kJ/mol under the polymerization reaction conditions as follows: the vacuum degree was 0.085 MPa, the temperature was 130°C, and the reaction extent was 2.35∼47.69%, the content of ZnO pillared saponite catalyst was 1 wt%. POLYM. COMPOS., 35:1023–1030, 2014. © 2013 Society of Plastics Engineers

Modification of sisal fiber by in situ coating steam explosion and electromagnetic interference shielding effectiveness of sisal fiber/PP composites

The technology of steam explosion was adopted to modify sisal fiber (SF) material and two different carbon particles, expanded graphite and conductive carbon black (CCB), were in situ coated on the surface of SF during steam explosion process. The DC conductivity and electromagnetic interference shielding effectiveness (SE) of the modified SF/polypropylene (PP) composites were studied and the measurement of electromagnetic interference (EMI) SE was conducted in two frequency ranges of 400–1,000 MHz and 1–18 GHz. The experimental results showed that this novel coating technology could improve the SE of the modified SF/PP composites significantly, which has a strong dependence on the loadings of the expanded graphite modified sisal fiber (SF-EG) and conductive carbon black modified sisal fiber (SF-CCB). When the loadings of SF-EG and SF-CCB reached 50 wt%, the maximum values of the SE were 33 dB and 51 dB, respectively. For the modified SF/PP composites, the experimental EMI SE values are in good correlation with the theoretical calculation values in far field of electromagnetic radiation. POLYM. COMPOS., 35:1038–1043, 2014. © 2013 Society of Plastics Engineers

Well dispersion of rGOs in PLLA matrix mediated by incorporation of EVA and its resultant electrical property

In this work, a new method was introduced to improve the dispersion of the reduced graphene oxides (rGOs) in polymer host, and the corresponding electrical properties of the composites were discussed. The method was related to incorporation of the third component ethylene-co-vinyl acetate (EVA) into the poly(l-lactide) (PLLA)/rGOs composites. Because of a better affinity of the rGOs to the EVA than the PLLA, rGOs were attracted to adsorb on the EVA particles. Consequently, homogeneous dispersion of the EVA particles directed a better dispersion of the rGOs in polymer host. In this case, compared with the PLLA/rGOs binary composite, the ternary composite showed a 10 orders decrease of electrical resistance with a lower electrical percolation threshold than that of the binary composite. This work opens up a viable strategy to the melt blending of polymer/graphene composites with good dispersion and markedly improved properties. POLYM. COMPOS., 35:1051–1059, 2014. © 2013 Society of Plastics Engineers

Effects of B2 O3 addition on structural and dielectric properties of PVDF

α-Crystalline form of PVDF doped with Boron oxide (B2O3) composite films were produced between 0.2 and 1% weight ratio via the casting procedure. This low-level doping rate did not change the crystalline structure of PVDF; however, they increased the lower and upper glass transition temperatures, which are associated with the amorphous ratio of polymer. This increment was found to be the highest for the sample 0.8% B2O3-doped PVDF as 25 and 9.7%, respectively. Because of the low specific volume occurred in the 0.8% doped sample, B2O3 molecules are closer to the side groups of PVDF and, therefore, the coordination bonds also occurred according to the interaction between them and as a result of this interaction a geometric deformation occurred on the morphology of B2O3. In consequence of this deformation, morphology of B2O3 gained net dipole moment and provided a contribution to the dipole moment density of the structure. Hence, higher dielectric constant values obtained than that of pure PVDF. At 1 kHz and 300 K, the real dielectric constant increased by 236% compared to that of pure PVDF. It was shown experimentally by the 0.8% doping level of B2O3 that decreasing porous and gap structure resulted a high dielectric constant. POLYM. ENG. SCI., 54:2536–2543, 2014. © 2013 Society of Plastics Engineers

Microporous gel electrolyte for quasi-solid-state dye-sensitized solar cell

The extension of electrocatalytic reaction of I−/I3− from counter electrode/gel electrolyte interface to gel electrolyte can significantly enhance the redox kinetics and therefore conversion efficiency of dye-sensitized solar cells. Microporous gel electrolyte from polypyrrole integrated poly(hydroxyethyl methacrylate/cetytrimethylammonium bromide) [PPy-integrated poly (HEMA/CTAB)] is successfully synthesized by in-situ polymerization of pyrrole monomers in three-dimensional framework of porous poly(HEMA/CTAB) matrix. An ionic conductivity of 12.72 mS cm−1 and activation energy of 8.65 kJ mol−1 are obtained from PPy-integrated poly(HEMA/CTAB) gel electrolyte. Tafel polarization and electrochemical impedance spectroscopy are employed to characterize the electrocatalytic behaviors of the gel electrolytes. The resultant quasi-solid-state dye-sensitized solar cell shows a light-to-electrical conversion efficiency of 6.68%. POLYM. ENG. SCI., 54:2531–2535, 2014. © 2013 Society of Plastics Engineers

Evaluate the nonlinear viscoelasticity of polyolefin melts using the Larson model

Nonlinear rheological properties of polyolefins have long been studied and predicted by using the Larson model with the damping function generally obtained from the stress relaxation measurements. In this study, we investigate the nonlinear rheological properties of high density polyethylene (HDPE) and polypropylene (PP) using the Larson model with damping functions obtained from either the dynamic frequency sweep or the stress relaxation test. Experimental measurements and their corresponding model predictions for the rheological parameters were then compared to evaluate the applicability of the Larson model to the nonlinear rheology, and the following conclusions could be achieved. The steady shear viscosity could be satisfactorily described by the Larson model with the damping functions obtained from the two different methods, except at shear rates higher than 103 s−1. The predicted first normal stresses also account for the measured data, except for those using the stress relaxation data showing a little deviation for the PP sample. In addition, the predictions for elongation viscosity are also in good agreement with the experimental results within the short range of elongation rate achieved in this work. POLYM. ENG. SCI., 54:2354–2361, 2014. © 2013 Society of Plastics Engineers

Synthesis of organic montmorillonite contained polyhedral oligomeric silsesquioxane and its nanocomposites with poly(l -lactide)

Three kinds of novel organic montmorillonites (OMMTs) were prepared by reacting the amino polyhedral oligomeric silsesquioxanes (POSSs) with the OMMTs that had already been modified by cationic surfactants. The layer spacing of OMMT increased from 1.68 to 3.81 nm after being intercalated by POSS. Poly(l-lactide) (PLLA) based nanocomposites with montmorillonites were produced by melt compounding. The PLLA nanocomposites with POSS modified OMMT were comprised of a random dispersion of intercalated/exfoliated aggregates of layered silicates throughout the PLLA matrix. The incorporation of POSS modified OMMT resulted in a significant increase in both crystallization temperature and decomposition temperature for 5% weight loss in comparison with the virgin PLLA. Gas Permeation Analysis showed that the increase of the montmorillonite concentration in the polymer matrix led to an expected decrease in permeation values. Gas barrier properties of the nanocomposites were compared with those predicted by phenomenological models such as the Nielsen model and Cussler model. POLYM. ENG. SCI., 54:2489–2496, 2014. © 2013 Society of Plastics Engineers

Computer-aided mathematical modeling and numerical simulation and theoretical analysis of the polypropylene polymer air drawing in spunbonding nonwoven process

In this article, as a nonlinear mathematical problem, the air-drawing model and the air jet flow field model of the polymer during spunbonding process are also presented, because the continuous filament fiber not always occurs in the spunbonding process, therefore, there exists the filament fiber breakage, the broken fibers occur in the flow field of spunbonding process is a two-phase flow problem, we suggested a new model called the sphere–spring model that can best described the broken fibers movement features. At the same time, the air-drawing model of the polypropylene polymer in a spunbonding process is presented and solved by introducing the numerical computation results of the air jet flow field of aerodynamic device. The model's predictions of the filament fiber diameters, crystallinities, and birefringences are coincided well with the experimental data. The effects of the processing parameters on the filament fiber diameter are discussed. A lower polymer throughput rate, lower quench air temperature, higher polymer melt initial temperature, higher air initial temperature, higher air initial speed, medium smaller venturi gap, higher air suction speed, higher quench air pressure, higher air suction speed, higher extrusion temperature, higher quench air pressure, higher cooling air temperature, and so on can all produce finer filament fiber. The results show great prospects for this research in the field of computer-assisted design of spunbonding technology. POLYM. ENG. SCI., 54:481–492, 2014. © 2013 Society of Plastics Engineers

Manufacturing and impact characterization of soy-based polyurethane pultruded composites

Composites have several advantages such as high corrosion resistance, high strength to weight ratio, and lower maintenance costs over conventional materials. The major cost drivers for composites are raw materials and manufacturing process. Automated manufacturing processes like pultrusion and low cost raw materials can significantly lower the cost of composites. Polyurethane (PU) resin systems are commonly used in the pultrusion industry as they have higher performance characteristics and manufacturing feasibility when compared to conventional resin systems such as polyester and vinyl ester. Manufacturing cost can be further decreased by the use of bio-based materials such as soy-based resin systems. In the present work, solid pultruded panels have been manufactured using the base PU and two soy-based PU resin systems. Pultruded panels were subjected to low velocity impact testing. Soy-based PU resin systems showed comparable properties to that of the base PU resin system and is a viable alternative to the conventional petroleum-based PU. POLYM. COMPOS., 35:1070–1077, 2014. © 2013 Society of Plastics Engineers

Mechanical properties and nonisothermal crystallization kinetics of polyamide 6/functionalized TiO2nanocomposites

Titanium dioxide (TiO2) nanoparticles were pretreated with excessive toluene-2,4-diisocyanate (TDI) to synthesize TDI-functionalized TiO2 (TiO2-NCO), and then polymeric nanocomposites consisting of polyamide 6 (PA6) and functionalized-TiO2 nanoparticles were prepared via a melt compounding method. The interfacial interaction between TiO2 nanoparticles and polymeric matrix has been greatly improved due to the isocyanate (NCO) groups at the surface of the functionalized-TiO2 nanoparticles reacted with amino groups (NH2) or carboxyl (COOH) groups of PA6 during the melt compounding and resulted in higher tensile and impact strength than that of pure PA6. The nonisothermal crystallization kinetics of PA6/functionalized TiO2 nanocomposites was investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization DSC data were analyzed by the modified-Avrami (Jeziorny) methods. The results showed that the functionalized-TiO2 nanoparticles in the PA6 matrix acted as effective nucleation agents. The crystallization rate of the nanocomposites obtained was faster than that of the pure PA6. Thus, the presence of functionalized-TiO2 nanoparticles influenced the mechanism of nucleation and accelerated the growth of PA6 crystallites. POLYM. COMPOS., 35:294–300, 2014. © 2013 Society of Plastics Engineers

Magnetic and electrical properties of polypyrrole nanocomposites with iron nanoparticles attached to 2-acrylamido-2-methyl-1-propanesulfonic acid

Polypyrrole (PPy) nanocomposites with iron nanoparticles attached to 2-acrylamido-2-methyl-1-propanesulfonic acid (AMP) were chemically prepared by varying the concentration of AMP using ammonium persulfate as an oxidant. The synthesized composites were characterized by using Fourier transform infrared (FTIR) spectroscopy, and their surface morphology and amended crystallinity were determined by using the transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The electrical and magnetic properties of PPy–Fe–AMP composites were investigated at room temperature. The increase of AMP has brought out a significant increase of DC conductivity and magnetic saturation moment of the composites, which might have been caused by the increased mobility of charge carriers due to the hydrophilic AMP components. POLYM. COMPOS., 35:364–371, 2014. © 2013 Society of Plastics Engineers

Properties of polyethersulfone ultrafiltration membranes modified with polyethylene glycols

Fil: Mendez, Mercedes Liliana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Salta. Instituto de Investigacion Para la Industria Quimica (i); Argentina