Rheological properties of styrene‐co‐2‐furfuryl methacrylate copolymers

The copolymerization of styrene with furfuryl methacrylate (FMA) led to a very significant molecular weight increase and to branching, as measured by standard gel permeation chromatography (GPC) and tri‐angle laser light‐scattering GPC. This increase was also confirmed by dynamic mechanical spectroscopy. Extensional viscosity analysis showed that styrene‐co‐2‐furfuryl methacrylate copolymers exhibited strain hardening at low strain rates. This strain hardening is explained as a result of the copolymers' polydispersity features rather than a result of their topology. The presence of strain hardening in extensional viscosity experiments is believed to be advantageous in the production of foamed materials with lower densities. A reduction in density was corroborated by foaming experiments on a development extrusion line. The mechanism of density lowering was related more to cell growth than to increased nucleation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1062–1071, 2005     

The synthesis and application of Pb‐doped GLYMO/chelated‐zirconium complex coating materials for UV‐light absorption

New glass coating materials containing γ‐glycidoxypropyltrimethoxy‐silane/zirconium(IV)‐n‐propoxide(2‐methoxyethylacetoacetate)/lead(II) nitrate were developed for UV‐light absorption by sol‐gel process. The effect of agitation time, temperature, and Zr complex and Pb²⁺ ion concentrations on UV light absorption were investigated. Zr complex was characterized by using ¹H‐NMR, ¹³C‐NMR, and FTIR spectroscopy. Ultraviolet visible spectroscopy was utilized to determine the optical properties of coating materials. Results showed that coated glass has very low transmission in the UV region (300–400 nm) relative to uncoated glass, especially at 150°C for 15 h agitation. UV light transmission of coated glasses treated at 80, 100, 450, or 500°C was not different from uncoated glass. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1175–1179, 2006     

Synthesis and magnetic properties of novel poly(N‐2‐thiazolyl(meth)acrylamide)‐Fe(II) complexes

N‐2‐thiazolyl(meth)acrylamides were polymerized by a radical route to obtain polymers in good yields. The polymers, with a pendent heterocyclic group, are soluble in common organic solvents, which allow the corresponding metal complexes with higher loads to be prepared easily. FTIR, ¹H NMR, and energy‐dispersive X‐Ray spectroscopy (EDX) were applied to characterize these materials. The magnetic behavior of poly(N‐2‐thiazolyl(meth)acrylamide)‐Fe(II) complexes was examined as a function of applied magnetic field at 4 K and as a function of temperature (4 ～ 300 K) at an applied magnetic field of 1 ～ 3 kOe, exhibiting the characteristics of a ferromagnet. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 83–87, 2005     

Shielding‐effectiveness modeling of carbon‐fiber/nylon‐6,6 composites

We have formulated a linear theory for the shielding effectiveness of composite matrix materials and have tested the theory for various amounts of ThermalGraph DKD X carbon fiber within nylon 6,6. The theory predicts that the most important parameters for the shielding effectiveness of a sample are the carbon‐fiber volume percentage and the frequency of the wave to be shielded. Although we expected the model to be valid at low filler‐loading levels, it actually performs remarkably, covering an electrical‐resistivity range of 10¹⁶ (at low filler‐loading levels) to 10¹ Ω cm (at high filler‐loading levels), well above the percolation threshold of electrical‐resistivity theory. The model performs much better than those reported in the literature and can be used to determine filler loadings needed to provide a certain level of shielding of electromagnetic waves. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 62–69, 2005     

Chain structure and mechanical properties of polyethylene/polypropylene/poly(ethylene‐co‐propylene)in‐reactor alloys synthesized with a spherical Ziegler–Natta catalyst by gas‐phase polymerization

Two polyethylene/polypropylene/poly(ethylene‐co‐propylene) in‐reactor alloy samples with a good polymer particle morphology were synthesized by sequential multistage gas‐phase polymerization with a spherical Ziegler–Natta catalyst. The alloys showed excellent mechanical properties, including both toughness and stiffness. With temperature‐gradient extraction fractionation, both alloys were fractionated into five fractions. The chain structures of the fractions were studied with Fourier transform infrared, ¹³C‐NMR, and thermal analysis. The alloys were mainly composed of polyethylene, polyethylene‐b‐polypropylene block copolymer, and polypropylene. There also were minor amounts of an ethylene–propylene segmented copolymer with very low crystallinity and an ethylene–propylene random copolymer. The block copolymer fraction accounted for more than 44 wt % of the alloys. The coexistence of these components with different structures was apparently the key factor resulting in the excellent toughness–stiffness balance of the materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 640–647, 2005     

N2‐filled hollow glass beads as novel gas carriers for microcellular polyethylene

N₂‐filled hollow glass beads (HGB) were first used as novel gas carriers to prepare microcellular polymers by compression molding. Dicumyl peroxide was acted as crosslink agent to control the produced microcellular structure of low density polyethylene (LDPE)/HGB. The effect of temperature, pressure and the content of gel on the embryo‐foaming, and final‐foaming structure are investigated. Scanning electronic microscopy shows that the average cell size of microcellular LDPE ranges from 0.1 to 10 μm, and the foam density is about 10⁹–10¹¹ cells/cm³. A clear correlation is established between preserving desirable micromorphologies of microcellular LDPE in different processing stage and tuning processing factors. The pertinent foaming mechanism of microcellular materials foamed with HGB is proposed. Because of the good mechanical strength, low density, weak water‐absorption, and excellent heat insulate ability, microcellular LDPE has great potential application in energy building materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Monodisperse‐porous poly(styrene‐co‐divinylbenzene) beads providing high column efficiency in reversed phase HPLC

A multistage polymerization protocol, the so‐called “modified seeded polymerization,” was developed for the production of monodisperse‐porous poly(styrene‐co‐divinylbenzene) providing high column efficiency as a packing material in reversed phase high performance liquid chromatography (RPLC). In the first stage of the multistage production, uniform polystyrene seed particles, produced by dispersion polymerization, were swollen by an organic agent (i.e., the diluent) and then by a monomer mixture containing styrene and divinylbenzene. The final porous particles were obtained in the monodisperse form by the polymerization of monomer mixture in the seed particles. By the use of a small size seed latex with low molecular weight and by the selection of the appropriate diluent, relatively small monodisperse‐porous particles with suitable pore structure could be achieved. In the reversed phase separation of alkylbenzenes, under isocratic conditions, theoretical plate numbers up to 40,000 plates/m were achieved by using 5.2 μm porous particles, obtained by a toluene‐dibutyl phthalate mixture as the diluent. No significant decrease in the resolution power was observed by the fourfold increase in the mobile phase flow rate. The column efficiency and the resolution observed with 5.2 μm monodisperse‐porous particles were significantly higher with respect to the currently available polymer based packing materials used in the reversed phase HPLC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1430–1438, 2005     

Process efficiency and long‐term performance of α‐tocopherol in film‐blown linear low‐density polyethylene

α‐Tocopherol was compared with a commercial phenolic antioxidant (Irganox 1076) as a long‐term and process antioxidant in film‐blown and compression‐molded linear low‐density polyethylene. The antioxidant function of α‐tocopherol was high in the film‐blown material, especially in the processing, according to oxygen induction time measurements with differential scanning calorimetry. The residual content of α‐tocopherol after processing, determined with chromatographic techniques, was less than that of the commercial phenolic antioxidant in both the film‐blown and compression‐molded materials. The process stabilizing efficiency was nevertheless higher for the material containing α‐tocopherol. During the long‐term stabilization, the efficiency of α‐tocopherol was less than that of the commercial phenolic stabilizer Irganox 1076 in the thin films, according to chemiluminescence and infrared measurements. The long‐term efficiency in the compression‐molded samples stabilized with α‐tocopherol or Irganox 1076 was equally good because of the low loss of both α‐tocopherol and Irganox 1076 from the thicker films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2427–2439, 2005     

Influence of radiation structures on positive‐temperature‐coefficient and negative‐temperature‐coefficient effects of irradiated low‐density polyethylene/carbon black composites

The electrical‐resistivity/temperature behaviors of low‐density polyethylene (LDPE)/carbon black (CB) composites irradiated with ⁶⁰Co γ rays were studied. The experimental results showed that the irradiated composites could be separated into insoluble crosslinking networks with CB (gel) and soluble components (sol) by solvent‐extraction techniques. When the sol of an irradiated LDPE/CB composite was extracted, the electrical conductivity of the system increased. The positive‐temperature‐coefficient (PTC) and negative‐temperature‐coefficient (NTC) intensities of the gels of the irradiated composites became extremely small and independent of the radiation dose. The sols and gels of the irradiated LDPE/CB composites, which had different thermal behaviors, played important roles in the appearances of the PTC and NTC effects. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 700–704, 2005     

Preparation of titanium dioxide/poly(methyl methacrylate‐co‐n‐butyl acrylate‐co‐methacrylic acid) hybrid composite particles via emulsion polymerization

Titanium dioxide core and polymer shell composite poly(methyl methacrylate‐co‐n‐butyl acrylate‐co‐methacrylic acid) [P(MMA‐BA‐MAA)] particles were prepared by emulsion copolymerization. The stability of dispersions of TiO₂ particles in aqueous solution was investigated. The addition of an ionic surfactant, sodium lauryl sulfate, which can be absorbed strongly at the TiO₂/aqueous interface, increases the stability of the TiO₂ dispersion effectively by increasing the absolute value of the ζ potential of the TiO₂ particles. The adsorption of the nonionic surfactant, Triton X‐100, on the surface of TiO₂ particles is less than that of the ionic surfactant. Fourier transform IR spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering characterized the composite particle size and size distribution. The field‐emission scanning electron microscopy results for the composite particles showed a regular spherical shape, and no bare TiO₂ was detected on the entire surface of the samples. The composite particles that were produced showed good spectral reflectance compared to bare TiO₂. Thermogravimetric analysis results indicated the encapsulated TiO₂ and estimated density of composite particles. There was up to 78.9% encapsulated TiO₂ and the density ranged from 1.76 to 1.94 g/cm³. The estimated density of the composite particles is suitable at 1.73 g/cm³, which is due to density matching with the suspending fluid. The sedimentation experiment indicates that reducing the density mismatch between the composite particles and suspending fluid may enhance the stability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 72–79, 2005     

Compatibilizer‐tracer: A powerful concept for polymer‐blending processes

Polymer blending is a very important polymer processing operation. It aims at preparing new polymer materials by blending existing polymers without the need of creating new molecules. For immiscible polymer blends, it is always challenging, if not impossible, to choose an appropriate compatibilizer and assess its compatibilizing efficiency under pilot or industrial polymer‐blending conditions. The concept of compatibilizer‐tracer developed in this work is able to take this challenge. This is shown using polystyrene (PS)/polyamide 6 (PA6) blends and fluorescent labeled graft copolymers of PS and PA6 as compatibilizer‐tracer. Transient experiments allow using very small amounts of compatibilizer‐tracer to obtain emulsification curves, namely, the evolution of the dispersed phase domain size as a function of the compatibilizer‐tracer concentration. Other potential applications of this concept are discussed and its limitations are investigated. © 2010 American Institute of Chemical Engineers AIChE J, 58: 1921–1928, 2012     

Nanocomposites based on MWCNT and polystyrene,styrene‐acrylonitrile copolymer,or polymethylmethacrylate,obtained by miniemulsion polymerization

Free radical miniemulsion polymerization of styrene (St), St/acrylonitrile 3 : 1 mixture or methylmethacrylate in the presence of multiwalled carbon nanotubes (MWCNT) was proven as a convenient way to obtain homogenous hybrids with perspectives in associated applications like foams specialties materials. Miniemulsion polymerization was viable up to 2% wt. MWCNT to monomer, without agglomerations. The grafting on MWCNT during the polymerization occurs without the need for supplementary functionalization and the polymer grafted nanotubes showed stable dispersions in the polymer solvent. Monomer polarity affected the grafting ability during the polymerization process. The nanocomposites obtained after purification and drying were used in foaming process. MWCNT presence in the related nanocomposites decreased the pore sizes in foam‐like materials (for all three different matrices). At 1 wt % MWCNT content, low density (< 0.3 g/cm³), low pore size (< 10 μm) and high cell density (>10⁹ cell/cm³) were achieved. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41148.     

Photo‐induced scission and crosslinking in LDPE,LLDPE, and HDPE

The molecular degradation characteristics of three different polyethylenes were determined by deriving chain scission and crosslinking concentrations from gel permeation chromatography molecular weight distributions obtained after 3 weeks and 6 weeks laboratory ultraviolet exposure. Injection‐molded bars (3 mm thick) made from a low‐density polyethylene (LDPE), a linear low‐density polyethylene (LLDPE), and a high‐density polyethylene (HDPE) were used and all showed strong depth variations in degradation. Degradation was rapid near the exposed surfaces but very little change occurred in the bar centers, due to oxygen starvation. The most rapid rises in scission and crosslink concentrations were observed with LDPE, for which the concentrations after 6 weeks exposure were approximately double those measured after 3 weeks. With LLDPE and HDPE the scission and crosslink concentrations after 6 weeks exposure were very much greater than twice those after 3 weeks. Scission dominated over crosslinking at all depths and for all materials the scission/crosslink ratio was always ≥3, with a value of ～9 recorded for HDPE near the exposed surface after 6 weeks exposure. POLYM. ENG. SCI., 45:579–587, 2005. © 2005 Society of Plastics Engineers     

Analysis of unbound materials in carbon‐black‐filled NR vulcanizates

Extraction of unbound materials from carbon‐black‐filled natural rubber (NR) vulcanizates with different cure systems was studied using various solvents with different dielectric constants of n‐hexane, toluene, THF, acetone, and acetonitrile. The extraction was performed at room temperature and 40°C for 2 days and in the boiling solvent for 8 h. Amounts of extracted materials from the NR vulcanizates increase by increasing the temperature. Amounts of extracted materials from the NR vulcanizates with n‐hexane, toluene, and THF are more than those with acetone and acetonitrile. Amounts of extracted materials from the NR vulcanizate with a high crosslink density are less than those from the NR vulcanizate with a low one. Thermogravimetric analysis of the NR vulcanizates before and after the extraction were carried out to investigate components of the extracted materials. It was found that there were polymer components and metal complexes, as well as organic matters with a low molecular weight in the extracted materials. Abilities of the solvents to extract unbound materials from the NR vulcanizates were discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1995–2005, 1999     

Preparation and cell morphology of ethylene‐vinyl acetate copolymer (EVA)/wood‐flour foams with low density

The main objective of this study is to obtain ethylene‐vinyl acetate copolymer (EVA)/wood‐flour foams with low density (< 0.2 g/cm³) using chemical blowing agent. Stearic acid was used as a compatibilizer to improve not only the compatibility between wood‐flour and EVA but also the compatibility between moisture and EVA in this study. The effects of wood‐flour content on the density and mechanical properties of EVA/wood‐flour foams were studied. Also, the effects of content of stearic acid on the cell morphology of EVA/wood‐flour foams were investigated. The shape of EVA/wood‐flour foams with 20% wood‐flour content becomes more uniform with increasing content of stearic acid. The most stabilized shape of the foams is obtained with 5 wt % stearic acid content. The density of EVA/wood‐flour foams with 20% wood‐flour and 5 wt % stearic acid is 0.11 g/cm³. With increasing content of stearic acid, more gas remains in the EVA matrix and consequently, average cell size and density increase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40894.     

Investigation on the Thermal Expansion and Theoretical Density of 1,3,5‐Trinitro‐1,3,5‐Triazacyclohexane

The CTE and the theoretical density are important properties for energetic materials. To obtain the CTE and the theoretical density of 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), XRD, and Rietveld refinement are employed to estimate the dimensional changes, within the temperature range from 30 to 170 °C. The CTE of a, b, c axis and volume are obtained as 3.07×10⁻⁵ K⁻¹, 8.28×10⁻⁵ K⁻¹, 9.19×10⁻⁵ K⁻¹, and 20.7×10⁻⁵ K⁻¹, respectively. Calculated from the refined cell parameters, the theoretical density at the given temperature can be obtained. The theoretical density at 20 °C (1.7994 g cm⁻³) is in close match with the RDX single‐crystal density (1.7990 g cm⁻³) measured by density gradient method. It is suggested that the CTE measured by XRD could perfectly meet with the thermal expansion of RDX.     

Thin,highly crosslinked polymer layer synthesized via photoinitiated graft copolymerization on a self‐assembled‐monolayer‐coated gold surface

A thin, highly crosslinked layer was grafted onto an alkyl thiol self‐assembled‐monolayer (SAM)‐coated gold surface with N,N′‐methylene bisacrylamide (MBAA), a widely used crosslinker with two polymerizable groups, as the monomer. Surface‐initiated photografting copolymerization was achieved through the immobilization of the hydrogen‐abstraction photoinitiator benzophenone on the hydrophobic alkyl surface via physical adsorption and subsequent UV irradiation in the presence of an MBAA solution. The growth of the grafted poly‐MBAA layers seemed to produce dendritic structures with low surface coverage. At a higher monomer concentration (15 g/L of water), full coverage of the gold surface with a thin layer was obtained and proved by scanning force microscopy and contact‐angle measurements. The evaluation of the gold, gold–SAM, and gold–SAM/grafted poly‐MBAA layers with a surface plasmon resonance sensor system revealed that the photografted, thin, highly crosslinked polyacrylamide layers had a very low affinity toward the adsorption of protein. Therefore, this provides a very promising approach to tailoring materials for sensors and other applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 158–164, 2005     

Nonlinear electrical conductivity of tin‐filled urea‐formaldehyde‐cellulose composites

This work reports on the elaboration and characterization of composite materials prepared by compression molding of mixtures of tin powder and a commercial grade thermosetting resin of urea‐formaldehyde filled with alpha‐cellulose in powder form. The morphology of constituents and composites has been characterized by optical microscopy. The porosity rate of the composites has been determined from density measurements. These results show that the composites are homogeneous. Furthermore, it has been shown that the hardness of samples remains almost constant with the increase of metal concentration. The electrical conductivity of the composites is <10⁻¹¹ S/cm unless the metal content reaches the percolation threshold at a volume fraction of 18.6%, beyond which the conductivity increases markedly by as much as 11 orders of magnitude. The results have been well interpreted in the statistical percolation theory frame. POLYM. COMPOS., 26:401–406, 2005. © 2005 Society of Plastics Engineers     

Preparation of polyethylene‐octene elastomer/clay nanocomposite and microcellular foam processed in supercritical carbon dioxide

Polyethylene‐octene elastomer (POE)/organoclay nanocomposite was prepared by melt mixing of the POE with an organoclay (Cloisite 20A) in an internal mixer, using poly[ethylene‐co‐(methyl acrylate)‐co‐(glycidyl methacrylate)] copolymer (E‐MG‐GMA) as a compatibilizer. X‐ray diffraction and transmission electron microscopy analysis revealed that an intercalated nanocomposite was formed and the silicate layers of the clay were uniformly dispersed at a nanometre scale in the POE matrix. The nanocomposite exhibited greatly enhanced tensile and dynamic mechanical properties compared with the POE/clay composite without the compatibilizer. The POE/E‐MA‐GMA/clay nanocomposite was used to produce foams by a batch process in an autoclave, with supercritical carbon dioxide as a foaming agent. The nanocomposite produced a microcellular foam with average cell size as small as 3.4 µm and cell density as high as 2 × 10¹¹ cells cm^?3. Copyright © 2005 Society of Chemical Industry     

Crystallization and chemi‐crystallization of recycled photodegraded polyethylenes

Test bars (3 mm thick) made from a high‐density polyethylene (HDPE), a low‐density polyethylene (LDPE), and a linear low‐density polyethylene (LLDPE) were injection‐molded from virgin polymer and from blends containing recycled photodegraded polymer of the same kind. The molded bars were then subjected to ultraviolet (UV) exposure. Crystallinity measurements were made at different depths from the exposed surface using differential scanning calorimetry. The effects caused by processing and photodegradation were separated by comparing thermograms obtained in the initial DSC run and in a reheating run, respectively. Chemi‐crystallization was produced by UV exposure. The results are interpreted in terms of molecular scission and photo‐initiated molecular defects. Scission accounts for the observed chemi‐crystallization, whereas the molecular defects inhibit crystallization and eventually limit chemi‐crystallization. After remelting, crystallization of the photodegraded materials is influenced both by the molecular mass distribution and by the defect content of the material. The changes in crystallization behavior caused by photodegradation are different for the three polyethylenes. The results obtained using blends that included photodegraded recyclate were consistent with this material acting as a pro‐degradent. The recyclability of the materials is discussed. POLYM. ENG. SCI., 45:588–595, 2005. © 2005 Society of Plastics Engineers