Functionalization of HDPE powder by CF4 plasma surface treatment in a fluidized bed reactor

The surface of HDPE polymer powder was fluorinated by CF₄ plasma in a fluidized bed reactor. Plasma is generated by an inductively coupled electrode at 13.56 MHz (rf) frequency, connected to an auto matching network and an rf power generator. In plasma surface fluorination, the CF₄ gas is diluted with He gas. The experimental variables are treatment time and rf power. The chemical property of the modified powder has been determined by using ESCA and FTIR. Plasma surface fluorination with the powder in a fluidized bed reactor results from the formation of CHF-CF₂, CHF-CHF and CF₂ groups. These fluorine functionalities and the fluorine atomic ratio on the surface increase with the treatment time and rf power. It has been found that the composite parameter is a good measure for determining the effect of total energy input on the plasma surface treatment of polymer powder in a fluidized bed reactor.     

Thermal characteristics of surface-crosslinked high density polyethylene beads as a thermal energy storage material

High density polyethylene (HDPE) beads were surface-crosslinked in a modified plasma reactor by using argon plasma. The modified plasma reactor can treat a large amount of beads to be uniformly surface-crosslinked. The objectives of this study were to develop a shape-stabilized functional thermal energy storage material and to find an optimum plasma reaction condition out of various operations. To achieve these objectives, we systematically studied the effects of the gas pressure, the radio frequency (RF) power and the treatment time on the degree of crosslinking. The degree of crosslinking was measured by solvent extraction method (BXM: boiling xylene method). The chemical and physical characterization of the material was performed by using fourier transform infra-red (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Finally, we confirmed the thermal stability of surface-crosslinked HDPE through about 50 thermal cycling tests.     

Surface modification of tetrafluoroethylene–perfluoroalkyl vinylether copolymer (PFA) by plasmas for copper metallization

Tetrafluoroethylene–perfluoroalkyl vinylether copolymer (PFA) sheet surfaces were modified with argon, helium, oxygen, and hydrogen plasmas. How the four plasmas modified the PFA sheet surfaces was investigated. All plasmas modified the PFA surfaces and at the same time initiated degradation of the PFA polymer chains. The balance between modification and degradation was strongly influenced by the magnitude of the discharge current in the plasmas. Efficiency of the plasmas in modification was hydrogen plasma > oxygen plasma > argon plasma > helium plasma. The modification involved defluorination of CF₂ carbons into CHF and CH₂ carbons and oxidation into O? CH₂, O? CHF, and O? CF₂ groups. The surface‐modification technique (a combination of hydrogen plasma treatment and silane coupling treatment) proposed in this study was applied for copper metallization of the PFA surface. The utility of the technique was confirmed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1087–1097, 2002     

Effects of plasma treatment on CO2 plasticization of poly(methyl methacrylate) gas‐separation membranes

To suppress undesirable plasticization effects of condensable gas (CO₂) in high pressure gas‐separation process, a surface‐modified poly(methyl methacrylate) (PMMA) membrane prepared by a plasma treatment was synthesized in this study. The pressure dependencies of permeability were analyzed to characterize the plasticization phenomenon and how it can be controlled by the plasma modification. FTIR‐ATR and TGA results suggest that the plasma treatment leads to surface crosslinking of PMMA membrane. Thus, the plasticization effect resulting from sorbed CO₂ on the Ar‐plasma–treated PMMA membrane was significantly reduced, but the reduction in permeability was lower than that of other crosslinking modification methods. The reduction of the CO₂ permeability contributes to a major part to the selectivity of He/CO₂ for the Ar‐plasma–treated PMMA membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 395–401, 2004     

Mechanical properties and microstructure of HDPE/AL(OH)3/silicone oil composite

The effect of surface modification on the mechanical properties and microstructure of the composites of high‐density polyethylene (HDPE), silicone oil, and aluminum hydroxide [Al(OH)₃] was investigated. The dispersion of silicone oil in the HDPE composites was studied by scanning electric microscope (SEM) and differential scanning calorimetry (DSC). In the HDPE/Al(OH)₃/silicone oil composites, two types of dispersion structure of silicone oil were observed resulting from different surface modifications. In the composites surface modified with titanate NDZ‐130, calcium stearate, or oleic acid, silicone oil encapsulates around Al(OH)₃ particles, and both the notched impact strength and the elongation at break are very high. However, in the composites surface modified with silane KH‐550 or silane‐g‐HDPE, silicone oil and Al(OH)₃ particles separately disperse in HDPE, and both the notched impact strength and the elongation at break are very low. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1896–1903, 2002     

Preparation of interpenetrating polymer network gel beads for dye absorption

Preparation of interpenetrating polymer network (IPN) gel beads for dye absorption was carried out by using simultaneous crosslinking method. First, sodium alginate (SA), 3‐(methacrylamido) propyl trimethyl ammonium chloride (MAPTAC), and/or acrylamide (AM), K₂S₂O₈, and N,N′‐methylenebisacrylamide (MBAM) were mixed in aqueous solution. The beads were prepared using K₂S₂O₈ and MBAM as the initiator and crosslinking agent, respectively. Then, the solution was dropped into CaCl₂ solution mixed with N,N,N′,N′‐tetramethylethylenediamine (TMEDA). The former was used as the crosslinking agent of alginate and the latter was used as the accelerator for the polymerization of monomer in the alginate solution. The gel bead composed of only alginate was also prepared to compare the properties with IPN gel bead. The components in IPN gel bead were examined by FTIR analysis. The factors effecting the particle size of alginate and IPN gel beads were investigated. In alginate gel bead, the concentration of solution affected the particle size, whereas type of monomer affected the particle size of IPN gel bead. The IPN gel bead had smooth surface (from SEM results), different from the alginate bead. Alginate content caused the swelling behavior of dried IPN beads. Cationic dye was absorbed by crosslinked alginate gel bead. The absorption of reactive dye by IPN gel bead was a result of its cationic charge. The absorption density of IPN gel beads was the reciprocal of the absorbent dosage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1585–1591, 2006     

Surface and bulk properties improvement of HDPE by a batch plasma treatment

High‐density polyethylene (HDPE) pellets were modified via atmospheric plasma treatment using nitrogen flushing. The new application of plasma treatment was introduced in this work, namely a batch treatment on plastic pellets just prior to its feeding to the extrusion process in comparison with the conventional surface treatment of the plastic sheet. The effect of treatment time (15–120 s) on wettability, chemical, thermal, and mechanical properties of the modified HDPE were investigated and compared with the typical surface‐treated HDPE and untreated HDPE. The pellet treatment distributed well the hydrophilicity groups so that both surface and bulk properties were improved. It showed an enhancement of wettability similar to surface treatment at short treatment time (15 s). Attenuated total reflection‐Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy revealed the presence of new chemical groups (nitrogen and oxygen up to 5 and 42 at %, respectively). In addition, crosslinked structure was also disclosed by solvent extraction (gel content of 3.5–5.5 wt % increased with treatment time) and significantly affected to decrease the crystallinity from 76% in the untreated sample to 63%. The decomposition process of the pellet treatment samples was delayed. Lastly, pellet treatment yielded advantages in remaining hydrophilicity during aging and improving mechanical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43011.     

Influence of crosslinking on crystallization,rheological, and mechanical behaviors of high density polyethylene/ethylene‐vinyl acetate copolymer blends

High density polyethylene (HDPE)/ethylene‐vinyl acetate copolymer (EVA) blends with selective crosslinking the EVA phase were prepared and the crystallization, rheological, and mechanical behaviors were studied. Selective crosslinking of EVA component could greatly improve both tensile and impact strengths of the HDPE‐rich blends and influence melting enthalpy at different annealing temperature in successive self‐nucleation and annealing procedure. Dynamic mechanical analysis reveals that glass transition temperatures of both the HDPE and EVA components are lowered upon blending and are raised upon crosslinking. The uncrosslinked HDPE/EVA blends are unstable in the melt and show increment in storage modulus (G′) and decay in loss tangent (tanδ) with annealing time associated with phase coarsening. However, morphology of selectively crosslinked blends in the melt state is highly unstable, characterized by a fast migration of uncrosslinked HDPE component out of the crosslinked EVA phase to the surface resulting in a rapid decay in G′ and an increment in tanδ at the early stage of annealing. POLYM. ENG. SCI., 54:2848–2858, 2014. © 2014 Society of Plastics Engineers     

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007     

Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

Asymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (T_g) and crosslinking densities. The difference in T_g of these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polymeric sodium alginate interpenetrating network beads for the controlled release of chlorpyrifos

Novel polymeric sodium alginate (Na‐Alg) interpenetrating network (IPN) beads have been prepared by crosslinking Na‐Alg blend with gelatin (GE) or egg albumin (EA) using glutaraldehyde (GA) as the crosslinking agent. These beads were used for the controlled release of chlorpyrifos. The swelling experiments were performed in water at different temperatures, and these data were used to calculate the molecular mass (M_C) between crosslinks as well as diffusion coefficients. Diffusion coefficients calculated from desorption data were lower by about two orders of magnitude than those calculated from sorption results. Higher values of M_C were obtained for the gelatin‐based IPNs than the neat Na‐Alg and egg albumin‐based matrices. Size of the beads did not vary significantly either by the network or by increasing the exposure time to the crosslinking agent. The scanning electron microscopy (SEM) was used to understand the surface characteristics of the beads. Differential scanning calorimetry (DSC) indicated a molecular level dispersion of chlorpyrifos in the polymer matrix. The percentage entrapment efficiency showed a dependence on the type of network polymer as well as time of exposure to the crosslinking agent. The encapsulation efficiency decreased with an increase in time of exposure to the crosslinking agent. In vitro release experiments have been performed to follow the release kinetics of chlorpyrifos from the matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 911–918, 2002     

Mesomorphic properties of cholesteric side‐chain liquid crystalline polysiloxanes and elastomers

A series of crosslinked liquid crystalline polymers and corresponding uncrosslinked liquid crystalline polymers were prepared by graft copolymerization. Their liquid crystalline properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The results showed that the crosslinking obtained in the isotropic state and the introduction of nonmesogenic crosslinking units into a polymeric structure could cause additional reduction of the clearing point (T_i) of the crosslinked polymers, compared with the corresponding uncrosslinked polymers. The crosslinked polymers (P‐2–P‐4) with a low crosslinking density exhibited cholesteric phases as did the uncrosslinked polymers. In contrast, a high crosslinking density made the crosslinked polymer P‐5 lose its thermotropic liquid crystalline property. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 773–778, 2004     

Facile fabrication of pH-responsive and swellable slow release microparticles of chlorpheniramine maleate with chitosan-starch matrices and their crosslinks

Abstract

We synthesized chitosan and modified same by blending with starch, crosslinking the matrices with sodium tripolyphosphate (TPP) and encapsulation with the drug chlorpheniramine maleate (CPM). These microparticles were characterized by FTIR, TGA, and SEM techniques. The amounts of CPM released from the microparticles generally decreased for the TPP-crosslinked beads but increased as the starch composition increased. Their release rates were best described by zero-order kinetics while their release mechanisms followed less-Fickian diffusional release. Our findings show that both the uncrosslinked and crosslinked chitosan-starch beads are promising carriers for the slow release of CPM.     

Hydrophobic properties of ethylene–vinyl alcohol copolymer treated with plasma source ion implantation

The industrial use of ethylene–vinyl alcohol copolymer (EVOH) film is limited because it is easily degraded by moisture. The plasma source ion implantation (PSII) technique with CF₄ or CH₄ gas was used for the EVOH film to improve the surface hydrophobic properties. Variables examined in implantation were ion energy (0–10 keV), treatment time (5 s–5 min), and ion species. The hydrophobic properties of EVOH films were greatly enhanced after a CF₄ PSII treatment, as evidenced by an increased contact angle from 66° to above 100° at ‐5 keV, and remained relatively unchanged during the period of 28 days. X‐ray photoelectron spectroscopy, atomic force microscopy, and O₂ permeability were used to characterize the surface properties of EVOH films treated with PSII. The improved hydrophobic properties were closely related to the formation of fluorine‐containing functional groups such as CF, CF_2, and CF₃ on the modified surface. The percentage distribution of carbon functional groups supports the role of CF₂ and CF₃ groups in surface modification. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2069–2075, 2004     

Hg(II) removal with polyacrylamide grafted crosslinked poly(vinyl chloride) beads via surface‐initiated controlled/“living” radical polymerization

Polyacrylamide grafted crosslinked poly (vinyl chloride) beads (PAM‐PVC) were prepared by the surface‐initiated controlled/“living” radical polymerization (SI‐CLRP) methodology from the crosslinked poly(vinyl chloride) beads with surface modification with diethyldithiocarbamyl groups under UV irradiation. The macroiniferter, diethyldithiocarbamyl crosslinked poly(vinyl chloride) beads (DEDTC‐PVC) were prepared by the reaction of the surface C? Cl groups with sodium N,N‐diethyl dithiocarbamate. The “grafting from” polymerization exhibited some “living” polymerization characteristics and the percentage of grafting (PG%) increased linearly with polymerizing time and achieved 47.6% after 6 h UV irradiation. The beaded polymer with polyacrylamide surface was also characterized with Fourier transform infrared (FTIR) and scanning electron microscope (SEM). Its adsorption property for Hg(II) ion was also investigated preliminarily. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3385–3390, 2006     

Multifunctional formaldehyde resins as curing agent for epoxy resins

Formaldehyde resins (FR) at 1/1/2 molar ratios of monomers (Cl‐phenol/amino monomers/p‐formaldehyde) were synthesized under acid catalysis. The obtained resins were characterized using elemental analysis, FTIR and RMN spectroscopic methods, being used as crosslinking agents for epoxy resin formulations. The curing of epoxy resins with FR were investigated. The glass transition temperature (T_g) and decomposition behavior of crosslinked resins were studied by differential scanning calorimetry (DSC) and thermogravimetric (TGA) techniques. All DSC scans show two exothermic peaks, which implied the occurrence of cure reactions between epoxy ring and amine or carboxylic protons, in function of chemical structures of FR. The crosslinked products showed good thermal properties, high glass transitions, and low water absorption. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adhesion of copper to poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) surfaces modified by vacuum UV photo-oxidation downstream from Ar microwave plasma

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) surfaces were exposed to vacuum UV (VUV) photo-oxidation downstream from Ar microwave plasma. The modified surfaces showed the following: (1) an improvement in wettability as observed by water contact angle measurements; (2) surface roughening; (3) defluorination of the surface; and (4) incorporation of oxygen as CF—O—CF₂, CF₂—O—CF₂ and CF—O—CF₃ moieties. With long treatment times, a cohesive failure of copper sputter-coated onto the modified surface occurred within the modified FEP and not at the Cu–FEP interface.     

Preparation and rheology of titanium dioxide nanoparticles loaded κ-carrageenan hydrogel beads strengthened by mixed salts for multipollutant water remediation

Hydrogel beads are emerging as alternate adsorbent material for the batch or continuous column treatment of dye wastewater. Polysaccharide-based gel beads are preferred for their uniform shape and size, large specific surface area, and easy separation by filtration and subsequent reuse. In this work, we prepare and rheologically characterize UV-active κ-carrageenan/TiO₂ beads for the adsorption and degradation of dyes. The 3–4 mm sized nanocomposite beads are formed by the extrusion of κ-carrageenan/TiO₂ gel solution in salt solutions. The maximum increase in modulus was observed with the addition of 1% w/v TiO₂ to κ-carrageenan and subsequent crosslinking with mixed salt of KCl and CaCl₂. κ-carrageenan/TiO₂ beads crosslinked by mixed salt of KCl and CaCl₂ have higher adsorption capacity, as compared to beads crosslinked with single salt of KCl. The kinetic study indicated the chemisorption of Methylene Blue on the bead surface. κ-carrageenan/TiO₂ beads showed higher degradation for Methylene Blue and Nile Blue A than Rhodamine B in 5 and 50 ppm each multicomponent dye systems under UV irradiation. The κ-carrageenan/TiO₂ beads could form a porous column for the selective adsorption of positively charged dyes from a multicomponent dye system.     

Synthesis,characterization and crosslinking of functional star‐shaped poly(ε‐caprolactone)

Star‐shaped low molecular weight poly(ε‐caprolactone)s (PCLs) were synthesized and functionalized with crosslinkable terminal groups for subsequent crosslinking. The ε‐caprolactone (CL) prepolymers were polymerized by ring‐opening in the presence of polyglycerine (PGL) as an initiator (1, 3 and 5 mol%) and Sn(II)2‐ethylhexanoate as a catalyst. Characterization of the prepolymer by ¹³C/¹H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a six‐armed star‐shaped structure for the prepolymer with the molecular weight controlled by the ratio of PGL and CL. Functionalization of the hydroxyl‐terminated prepolymer was carried out with maleic or itaconic anhydride. In both cases, the characterization of the functionalized prepolymer showed that the hydroxyl groups were completely substituted. The functionalized PCLs were successfully crosslinked through the reaction of double bonds. The crosslinking was induced either thermally with organic peroxide or photochemically with a photosensitive initiator. Characterization of the crosslinked PCLs by Soxhlet extraction, DSC and FTIR showed that the itaconic double bond was much more reactive in thermal crosslinking than the maleic double bond. Thus, the crosslinked prepolymers that were functionalized with itaconic double bonds achieved a gel content of about 90%. A gel content of 100% was achieved with several compositions where crosslinking agents were employed. © 2002 Society of Chemical Industry     

Generation of antifouling layers on stainless steel surfaces by plasma‐enhanced crosslinking of polyethylene glycol

Polyethylene glycol (PEG) structures were deposited onto stainless steel (SS) surfaces by spin coating and argon radio frequency (RF)‐plasma mediated crosslinking. Electron spectroscopy for chemical analysis (ESCA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) indicated the presence of  CH₂ CH₂ O structure and C C C linkage, as a result of the plasma crosslinking, on PEG‐modified SS surfaces. Scanning electron microscopy (SEM) indicated complete deposition, and water contact angle analysis revealed higher hydrophilicity on PEG‐modified surfaces compared to unmodified SS surfaces. Surface morphology and roughness analysis by atomic force microscopy (AFM) revealed smoother SS surfaces after PEG modification. The evaluation of antifouling ability of the PEG‐modified SS surfaces was carried out. Compared to the unmodified SS, PEG‐modified surfaces showed about 81–96% decrease in Listeria monocytogenes attachment and biofilm formation (p < 0.05). This cold plasma mediated PEG crosslinking provided a promising technique to reduce bacterial contamination on surfaces encountered in food‐processing environments. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 485–497, 2005