Effect of ethylene ionomers on the properties of crosslinked polyethylene

Most premature failure of underground crosslinked polyethylene (XLPE) cables in service, a matter of great concern, is due to aging induced by water treeing. To improve the water‐tree resistance, sodium‐neutralized poly (ethylene‐co‐acrylic acid) (EAA–Na) ionomers were blended with XLPE; the EAA–Na ionomers were prepared through the neutralization of sodium hydroxide and poly(ethylene‐co‐acrylic acid). A series of XLPE/EAA–Na ionomer blends were investigated through the measurement of the water absorption ratio, water treeing, and mechanical and dielectric testing; the results strongly suggested that EAA–Na ionomers could improve the water‐tree resistance of XLPE, and the XLPE/EAA–Na blends retained excellent mechanical properties and dielectric properties. Moreover, through the characterization of XLPE/EAA–Na blends with Fourier transform infrared spectrometry, dynamic mechanical analysis, and scanning electron microscopy, it was found that the neutralization reaction could be achieved completely; the XLPE and EAA–Na ionomers were partially compatible, so the EAA–Na ionomers could be dispersed well in the matrix with the process examined in this study. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3483–3490, 2007     

Structures and properties of waste silicone cross‐linked polyethylene de‐cross‐linked selectively by solid‐state shear mechanochemical technology

Waste silicone cross‐linked polyethylene (Si‐XLPE) recycling effectively by using solid‐state shear mechanochemical (S³M) technology was investigated to make the better performance thermoplastic polyethylene. To make this thermoplastic material, the cross‐linked structures of waste Si‐XLPE that was consisted of the siloxane bonds must be de‐cross‐linked selectively instead of the destruction of the material main chains. The properties of recycled Si‐XLPE materials were investigated by gel fraction measurements, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter, torque rheological measurements, scanning electron microscope (SEM) and thermogravimetric analyzer (TG). From the results, it could be seen that the cross‐linking bonds of the Si‐XLPE were destroyed selectively by S³M technology and the mechanochemical milling also played a significant role in improving the materials process‐ability and mechanical properties. Gel fraction measurements, GPC and FTIR showed that S³M technology could interrupt the cross‐linked structures of Si‐XLPE rather than the backbone chains by initiating the de‐cross‐linking reaction obviously; Torque rheological results further confirmed that the recycled Si‐XLPE materials gained better plastic characteristics and process‐ability after mechanochemical milling. Compared with the untreated Si‐XLPE, the tensile strength and elongation at break of Si‐XLPE samples after 10 cycles milling increased by 118.4% and 330.4%, respectively. J. VINYL ADDIT. TECHNOL., 25:149–158, 2019. © 2018 Society of Plastics Engineers     

Synthesis and swelling characteristics of poly(4‐vinylpyridine) gels crosslinked by irradiation

The effect of irradiation under vacuum on thermal properties and swelling behavior on poly(4‐vinylpyridine) (P4VP) was investigated. The gel percentage in the irradiated P4VP films was determined by Soxhlet extraction. UV spectroscopy was also used to determine sol percentage, which decreased as the radiation dose increased. The changes in thermal properties, such as glass‐transition temperature (T_g), were followed by differential scanning calorimetry before and after Soxhlet extraction. The gels prepared after irradiation were characterized with respect to their swelling properties and network structures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2609–2614, 2001     

Morphological and structural development of recycled crosslinked polyethylene during solid‐state mechanochemical milling

Waste crosslinked polyethylene (XLPE) was partially decrosslinked to obtain a thermoplastic recycled material through solid‐state mechanochemical milling with pan‐mill equipment at ambient temperature. The gel fraction and size exclusion chromatography measurements showed that the gel content of XLPE decreased remarkably with increasing cycles of mechanochemical milling, whereas the molecular weight of the sol fraction was not significantly reduced; this indicated the realization of partial decrosslinking during mechanochemical milling. Differential scanning calorimetry and X‐ray diffraction analysis showed that the melting temperature of decrosslinked polyethylene increased by 3.5°C because the bigger crystallites size resulting from the higher mobility of the chain segment. The improved thermoplastic characteristic of XLPE after mechanochemical milling were confirmed by scanning electron microscopy and rheological measurement. The mechanical properties of recycled XLPE also achieved significant improvement after mechanochemical milling. Solid‐state mechanochemical milling is a cost‐effective, reliable, and environmentally friendly method for recycling XLPE at ambient temperature without any additional materials or chemicals. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation of the Effects of Microwave Treatment on the Optical Properties of Apple Slices During Drying

The objective of this work was to study the changes of optical properties of apple (Golden Delicious) slices during drying. The optical parameters compared on the basis of Hunter values (L, a, b) changes as well as total color difference (Δ E) and browning index (BI). The effect of coating materials including carboxymethylcellulose (CMC), starch, and pectin as well as microwave treatment on optical properties and microstructure of dried samples were investigated. To analyze the effects of these processes on microstructure, scanning electron microscopy (SEM) was employed. Results showed that optical properties as well as microstructure of apple were affected by coating material and drying condition. Coated samples by CMC had a lower L and higher BI, but different results in the presence of starch were obtained. Microwave treatment in the presence of appropriate coating materials could improve the optical properties of dried apple slices.     

The effect of zinc oxide nanoparticles on the weathering performance of wood-plastic composites

In recent years, wood-plastic composites (WPCs) have become among the most popular engineering materials. Most of their usage areas are outdoors, where they encounter various damaging factors. The weathering conditions cause significant deterioration to WPC surfaces, which negatively influences their service life. In this study, zinc oxide nanoparticles at different concentrations (1%, 3%, 5%, 10%) were added to a high-density polyethylene-based WPC matrix. The effect of zinc oxide nanoparticles on the weathering performance of WPC was evaluated after 840 hours of an artificial weathering test. The highest colour changes (∆E*) were monitored with control samples exposed for 840 hours. Adding zinc oxide nanoparticles improved the ultraviolet (UV) resistance and decreased the colour changes. The wood flour content also affected the colour changes on the WPC surface. A combination of 10% zinc oxide nanoparticles and 50% wood flour content provided the lowest colour changes. The barrier effect of nanoparticles protected the WPC surfaces from UV light. Zinc oxide nanoparticles also positively affected the load transfer, which restricted the reduction in mechanical properties after the weathering test. The degradation on the surface of WPCs was also investigated using attenuated total reflectance-Fourier Transform–infrared analysis. The changes in the characteristic bands of polymer and wood indicated that surface degradation was inevitable. Light and scanning electron microscopy images also demonstrated micro-cracks and roughness on the surface of WPCs. It is concluded that UV degradation is unavoidable, but zinc oxide nanoparticles can improve surface resistance against weathering conditions.     

Preparation of granular crosslinkable medium‐density polyethylene

Granular crosslinkable medium‐density polyethylene (XLPE) without scorch inhibitor was prepared adding organic peroxide [2, 5‐dimethyl‐ 2, 5‐ di‐ (t‐butyl‐peroxy) hexyne‐3] through extrution process, in industrial scale. Twin screw extruder was used to mix the polyethylene and the peroxide. The temperature zones of the extruder were controlled very carefully to prevent unwanted crosslinking during extrusion. Compression molding, rotational molding, and injection molding of XLPE at 155°C made no crosslinking in PE, and then they were exposed to higher temperatures at which the organic peroxide decomposed to provide free radicals which led to the crosslinking of the MDPE. The thermal properties (using dynamic mechanical analysis, DMA, differential scanning calorimetric analysis, DSC, and thermogravimetric analysis, TGA, techniques) and mechanical properties (including strain at break and stress at break) of virgin PE, crosslinkable PE, and crosslinked PE have been compared. The crossliked PE and virgin PE were also studied by X‐ray diffraction (XRD) technique. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1873–1879, 2007     

Synthesis and ultraviolet‐curing behaviors of vinyl ether functionalized polyurethane oligomers

The vinyl ether functionalized oligomer is one of the most basic components of vinyl ether functionalized materials for cationic UV‐curable coatings. In this study, three types of vinyl ether functionalized polyurethane oligomers (i.e., polyether, polyester, and polydimethylsiloxane) were synthesized with diisocyanate, diol, and hydroxyethyl vinyl ether. These oligomers were characterized by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The effect of the raw material ratio on the oligomer, UV‐curing behaviors, and thermal properties of these oligomers were investigated. The UV‐curing behavior was analyzed by real‐time Fourier transform infrared spectroscopy. The vinyl ether terminated polyester urethane oligomer exhibited better UV curing, with a higher final conversion and maximum UV‐curing rates. In addition, the light intensity was enhanced for oligomers with better UV‐curing properties. Research on these vinyl ether functionalized oligomers is essential to the development and applications of cationic vinyl ethers systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40501.     

Analysis of failure of crosslinked polyethylene cables because of electrical treeing: A physicochemical approach

The present work investigated the breakdown characteristics of high‐voltage crosslinked polyethylene (XLPE) cable by electrical trees under ac and composite voltages. The electrical trees resemble either a tree or a bushy structure. The importance of the Weibull parameters for the present study was emphasized. The failure zone of the XLPE cables was characterized by experimental techniques such as wide‐angle X‐ray diffraction, differential scanning calorimetry, and thermogravimetric–differential thermal analysis, to understand the phase constituents affected by electrical trees. The impact test and flexural test results indicate that material with high stiffness/toughness allows tree formation and causes early failure of the material. The characteristic variation of the aged XLPE cables was investigated by a dynamic mechanical analyzer (DMA). The activation energy values were calculated from the DMA data. The rate of tree propagation was found to be less for materials (XLPE) with high activation energy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2169–2178, 2004     

Effects of sulfonation on bis-styrylbiphenyl fluorescent whitening agents for polypropylene

Three derivatives of bis-styrybiphenyl with different degrees of sulfonation to be used as fluorescent whitening agents (FWAs) were synthesized. Studies on their spectroscopic properties were performed using a combination of computational methods. Whitening effects of FWAs and the improved thermal stability of polypropylene (PP) were investigated. The morphology of plastic samples was examined by scanning electronic microscopy (SEM). In order to improve the compatibility between FWA and PP, PP grafted with maleic anhydride (MAH) was applied as compatibilizer. The optical properties were further clarified by the results of frontier molecular orbital modeling, which show that the presence of sulfonic sodium group leads to a red shift of maximum UV absorption wavelength and a low HOMO–LUMO energy band gap. It is observed that the addition of 0.010 wt % of the sulfonated FWA would result in the expected whitening effect as well as improved PP thermal stability, while at or above 0.015 wt %, such effects worsen sharply owing to phase separation. Furthermore, the use of MAH-grafted PP as compatibilizer results in improvement of phase behavior and thermal stability. The study provides new insights into the effect of FWA structure on the properties of PP that are related to the whitening of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47635.     

Antimicrobial activity of organic photosensitizers embedded in electrospun nylon 6 nanofibers

Nylon 6 nanofibers containing organic photosensitizers were investigated to demonstrate the antimicrobial properties in the application of the material to protective clothing and home appliances. Benzophenone (BP), 4, 4′‐bis(dimethylamino)benzophenone (MK) and thioxanthen‐9‐one (TX) were used as photosensitizers and the nylon 6 nanofibers were prepared using electrospinning. Field emission scanning electron microscopy morphology of the nanofibers showed that even and continuous nylon 6 nanofibers were well prepared through electrospinning and that the organic photosensitizers were evenly distributed in the nanofibers. There was no significant reduction of crystallinity in the nylon 6 nanofibers through the insertion of the organic photosensitizers. After UV (365 nm) irradiation of the photosensitizers, the intensity of peak photon excitation in the electron spin resonance spectra was increased. Antimicrobial properties of the prepared nanofibers were tested against Staphylococcus aureus and Escherichia coli according to JIS Z 2801. It was found that antimicrobial properties of nylon 6 nanofibers containing MK and TX were superior to those of nylon 6 nanofibers containing conventionally used BP. The antimicrobial effects of the nanofibers for S. aureus were superior to those for E. coli. The antimicrobial activity gradually increased as the UV irradiation time increased. Copyright © 2012 Society of Chemical Industry     

Correlation between mechanical properties and degradation processes of poly(methyl methacrylate-co-butyl acrylate) films

Copolymer systems based on various molar ratios of methyl methacrylate (MMA)/butyl acrylate (BA) and different mass content of N-methylolacrylamide (NMA), as a crosslinking agent, were investigated. The influence of temperature, 150°C, under conditions similar to those used in the textile industry, and effect of ultraviolet (UV) irradiation were examined. The changes of mechanical properties were found to be connected with the cross-linking and/or degradation mechanisms. The effect of copolymer composition on the mechanical properties was established, especially during UV degradation. © 1994 John Wiley & Sons, Inc.     

Preparation,characterization, electrical and antibacterial properties of sericin/poly(vinyl alcohol)/poly(vinyl pyrrolidone) composites

In this study, we focused on the fabrication of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/sericin composites via a simple solution‐blending method. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, UV spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and measurements of the conductivity, tensile strength, and antibacterial activity against Staphylococcus aureus. The results of FTIR and UV spectroscopy implied the occurrence of hydrogen bonding between sericin and the PVA/PVP blend. The structure and morphology, studied by XRD and SEM, revealed that the sericin particles were well dispersed and arranged in an orderly fashion in the blend. The glass‐transition temperature (T_g) of the composite was higher than that of the pure blend, and the T_g value shifted toward higher temperatures when the volume fraction of sericin increased. TGA indicated that sericin retarded the thermal degradation; this depended on the filler concentration. The mechanical and electrical properties, such as the tensile strength, alternating‐current electrical conductivity, dielectric constant, and dielectric loss of the composites, were higher than those of the pure blend, and these properties were enhanced when the concentration of sericin was increased up to 10 wt % filler content, whereas the elongation at break of the composite decreased with the addition of sericin particles. The antibacterial properties of the composite showed that sericin had a significant inhibitory effect against S. aureus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43535.     

Extrusion processing of green biocomposites: Compounding,fibrillation efficiency,and fiber dispersion

The efficiency of twin‐screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch (TPS) with 10 wt % fibers was examined. The effect of the processing setup on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO‐oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy, and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the TPS. Moisture uptake study revealed that the material containing TEMPO‐oxidized fibers had higher moisture absorption than the other composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39981.     

Weathering of High-Density Polyethylene-Wood Plastic Composites

Due to the widespread use of wood-plastic composites (WPCs), high-density polyethylene-wood flour composites (HDPE/WF) were studied in order to determine their stability in different application conditions. UV degradation and periodic absorption/desorption of moisture cause damaging changes to material during WPCs’ exterior application, so it is necessary to ensure WPCs’ durability against atmospheric influences. Samples were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) in order to study the degradation after simulated weathering. The degree of water absorption was also determined. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used for the determination of composites’ thermal properties. Results show that the stability of the HDPE/WF composites to UV treatment highly depends on stabilizer content and its dispersion in the polymer matrix. Incompatibility of HDPE and wood particles is a major problem that should be solved to achieve good durability and satisfying properties in use.     

Influence of the environment during a photodegradation of multilayer films

The influence of different stratosphere parameters on the degradation of a multilayer film was investigated. The selected multilayer was a three polymeric layers film, a polyamide 6 film inserted between two poly(ethylene terephthalate) (PET) films. Samples were exposed for several ageing under ultraviolet radiations (filtered at 270 nm), varying the atmosphere at 55 mbar pressure (atm, atm + ozone, N₂, and T = ?55 °C or +23 °C). Evolution of it mechanical properties defined by uniaxial tractions, thermo‐optical properties defined by spectrophotometry UV–vis‐NIR, chemical properties defined by FTIR‐ATR, and thermal and dielectric properties defined, respectively, by differential scanning calorimetry (DSC) and dynamical dielectric spectroscopy (DDS), were investigated. Our results showed that UV irradiation causes multilayer films degradations, that is, principally decrease of UV transmittance and stress and strain at break (?50%). An increase of the ageing temperature causes an acceleration of these degradations. Degradations principally occur on the PET side of the multilayer exposed to UV radiation. Moreover, the DDS analysis shows a plasticization effect of the primary mode in the polyamide 6 due to photo‐oxidation. Oxygen diffusion is the principal element for this plasticization, indeed it not occurs in a nonoxidative environment (nitrogen), or at low ageing temperature (?55 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44075.     

The electropolymerization of several poly(3‐methylthiophene) films in the same used solution and its consequence in their properties

The effect of the electropolymerization of seven poly(3‐methylthiophene) (P3MT) films in the same used monomer solution have been investigated. Cyclic voltammetry, UV‐visible, scanning electron microscopy, and electrochemical impedance measurements were carried out to understand the effect of the solution reusing on the polymer electrochemical properties. The obtained results show that, as the solution is reused, the polymerization rate increase and the charge in of the cyclic voltammetry decrease. Besides, there are important changes in the sample's morphologies, with the increase of the synthesis number, the amount of fibers increase and this leads to lower the conductivity of the polymer film. In agreement to this, the impedance data analysis shown important changes in the interfacial electronic parameters, i.e., changer transfer resistance and double‐layer capacitance, used to describe the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44368.     

The effect of gamma and electron beam irradiation on the thermal and mechanical properties of injection‐moulded high crystallinity poly(propylene)

In the present study, the effect of gamma and electron beam (EB) irradiation on the thermal and mechanical properties of high crystalline polypropylene (HPP) was studied. To study the structural modifications of HPP polymer which could occur following these treatments at different doses (20, 40, 60, 80, 100, and 120 kGy) were applied to all samples. Nonirradiated HPP were used as control samples, differential scanning calorimetry analysis, thermogravimetric analysis, and Mechanical tests were carried out to evaluate the effect of both irradiation treatments (EB and gamma irradiation) on HPP samples. Irradiated samples of HPP decreases melting temperature (T_m) of matrix in EB more than in gamma rays up to 5°C. The changes of mechanical properties exhibit different radiation stability towards ⁶⁰Co‐gamma radiation and EB radiation. This difference reflects much higher penetration of the gamma radiation through the polymeric material as a function of sample thickness. The degradation on polymer properties caused by gamma irradiation was more than that caused by EB irradiation. Next, we compared the effects of gamma and EB irradiation to determine which of these two processes better maintained the integrity of the irradiated product. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.     

Effect of styrene–ethylene–butadiene–styrene and its synergetic effect with ethylene vinyl acetate on the mechanical,thermal, dielectric,and water‐treeing behaviors of crosslinked polyethylene

In this study, we investigated the effect of an aromatic polymer, styrene–ethylene–butadiene–styrene (SEBS), on the water‐tree resistance of crosslinked polyethylene (XLPE), and the synergetic effect of SEBS and ethylene vinyl acetate (EVA) was also investigated. The XLPE/SEBS and XLPE/SEBS/EVA samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, mechanical measurements, and an accelerated water‐treeing experiment, and the obtained results clearly show the relevant influence of SEBS and EVA, and as expected, the addition of SEBS and EVA was found to synergistically influence the water‐tree resistance of XLPE more positively in comparison with that without the addition of EVA. In addition, it also indicated that the blends possessed excellent dielectric behaviors, such as the dielectric constant and dissipation factor. The crystallization of the blends decreased with increasing SEBS content and addition of EVA. However, the melting temperature of the blends increased with the addition of SEBS and EVA, but the melting temperature of the blends decreased with increasing SEBS content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Photocross-linking of low-density polyethylene. II. Structure and morphology

Morphological structure and other properties of polyethylene photocross-linked in the melt (XLPE) have been studied by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), density, and swelling measurements. The WAXD measurements show that the crystallinity of polyethylene decreases with increasing gel content in the XLPE samples and that the regularity and the size of crystals are affected by photocross-linking. DSC data confirm that photocross-linking occurs preferentially in the amorphous and interfacial regions and causes depression of the melting point and decreases the heat of fusion. The density of XLPE apparently decreases with increasing gel content, which is due to decreased crystallinity and lattice expansion. The cross-link density determined by the swelling measurements and evaluated using the Flory–Rehner equation correlates well with the changes in crystallinity and melting point. © 1993 John Wiley & Sons, Inc.