Modification Of Low Density Polyethylene Research Articles

Influence of ethanol vapor addition on the surface modification of polyethylene in a dielectric barrier discharge

In this paper, ethanol vapor up to 50% is added to an argon, air or nitrogen dielectric barrier discharge at medium pressure to profoundly investigate the effect of ethanol addition on the surface modification of low density polyethylene (LDPE). Water contact angle (WCA) and X-ray photoelectron spectroscopy (XPS) measurements show that the ethanol vapor addition effect on the LDPE surface depends on the used carrier gas. Adding ethanol to an argon plasma has no significant effect on the wettability nor on the chemical composition of LDPE compared to a pure argon plasma treatment. Ethanol addition does however slightly increase the LDPE surface roughness. Addition of small amounts of ethanol vapor to an air plasma makes it possible to incorporate additional nitrogen and oxygen groups on the LDPE surface, resulting in an extra decrease of 11% in WCA value. Moreover, the LDPE surface roughness is slightly increased due to the ethanol vapor addition. The most significant effect of ethanol addition is however observed when nitrogen is used as carrier gas. After an N2/2% ethanol plasma treatment, an 85% reduction in WCA value to 8.5° is found compared to a pure N2 plasma treatment. This very hydrophilic LDPE surface is obtained due to a significantly high incorporation of oxygen and nitrogen groups on the surface with an O/C and N/C ratio reaching 32% and 53% respectively. FTIR measurements also reveal that the observed extremely high wettability of LDPE is not the result of plasma activation but is due to plasma polymerization effects occurring on the surface resulting into the deposition of a plasma polymer containing ketones, amides as well as CN groups. In addition, ageing studies have also been conducted and these studies reveal that for all carrier gases, ethanol addition to the discharge gas significantly suppresses the ageing effect. All the above mentioned conclusions therefore indicate that ethanol vapor based plasmas can be an excellent tool to increase the surface energy of polymers.

Modification of Low Density Polyethylene with 2-Hydroxyethyl Acrylate by a Swollen-Phase Grafting Method

ABSTRACTLow-density polyethylene (LDPE) was modified with 2-hydroxyethyl acrylate (HEA) by a swollen phase grafting method with azobisiso-butyronitrile (AIBN) as initiator and xylene as a swelling agent. Fourier transform infrared spectroscopy (FTIR) and 1H-nuclear magnetic resonance (1H-NMR) showed that the HEA was grafted onto the PE molecular chains and the copolymer (LDPE-g-PHEA) was formed. The rheological data illustrated that the content of long chain branches (LCB) in LDPE-g-PHEA was higher than in LDPE. Melt flow index (MFI) measurements indicated that the LDPE backbone was degraded slightly when the HEA content was small in the process of grafting. X-ray diffraction (XRD) and water contact angle measurements demo-nstrated that the grafting degree had an influence on the crystallinity and polarity of the graft polymer. A staining analysis indicated that the dyeing of the product was improved continuously with increasing of the grafting degree. Polyvinylpyrrolidone (PVP), NaCl, and ultrasound were shown to contribute to the staining, with ultrasound being the most productive. The probable grafting reaction mechanism is pro-posed. The results of the influence of monomer concentration on the grafting reaction revealed that the grafting ratio and gel content of the product increased with increasing of HEA amount.

Surface modification of polyethylene in an argon atmospheric pressure plasma jet

The surface properties of polyethylene can successfully be altered using argon plasmas. In this work, the surface modification of low density polyethylene (LDPE) using an argon atmospheric pressure plasma jet (APPJ) is profoundly investigated. The surface modification is examined using different analysing techniques namely, water contact angle (WCA) measurements for the wettability and X-ray photoelectron spectroscopy (XPS) for the chemical composition. Particular attention is paid to the treatment distance between the plasma jet capillary and the LDPE foil and the applied treatment time. At treatment distances between 5 and 15mm, the WCA can be reduced with more than 70% within a treatment time of a few ms. XPS measurements reveal that this is due to the incorporation of oxygen containing groups and especially the increased implementation of the O–CO group has a big influence. At treatment distances above 15mm, the wettability decreases with increasing treatment distance. The wettability can however be enhanced by increasing the treatment time. Ageing considerations show that the loss in treatment efficiency is restricted to only 25%, meaning that even after 14days of ageing the WCA reduction upon plasma treatment is still more than 40%. Based on the above mentioned results, the most appropriate parameters can thus be selected to provide an efficient plasma treatment of LDPE using the argon APPJ.

Surface Modification of Low Density Polyethylene by Corona and Atmospheric Pressure Discharge

Surface Modification of Low Density Polyethylene by Corona and Atmospheric Pressure Discharge

Modification of low density polyethylene for manufacturing of oxo-biodegradable films

Modification of low density polyethylene for manufacturing of oxo-biodegradable films

Investigating the thermal properties of polyethylene plasma modified by using unconventional chemical vapors

In this work, we presented plasma modification of low-density polyethylene (PE) powder using unconventional chemicals. This work focused on the thermal behavior of modified PE. Plasma modification of PE was carried out using unconventional chemical vapor i.e., acetone, toluene, ethanol, methanol, isopropanol, and chloroform, respectively. For all the process, the modification time was kept constant for 2 min. Chamber pressure of 100 Pa was used for the study. The thermal behavior of the plasma-modified and unmodified PE was carried out by differential scanning calorimetry and thermogravimetric analysis. We have found that there is a maximum improvement of crystallinity and thermal stability of PE when ethanol is used for plasma modification. Results obtained from DSC showed that plasma modification of PE in ethanol vapors increases the crystallinity of the PE without damaging the surface properties. Thermal stability of PE plasma modified in ethanol gives maximum thermal improvement to almost 25 °C at 5 mass% mass loss compared to unmodified PE.

Rheological behaviors of randomly crosslinked low density polyethylene and its gel network

Dicumy peroxide (DCP) modification of low density polyethylene (LDPE) below gel point (GP) produces modified LDPE (mLDPE) with wide molecular weight distributions while the random crosslinking beyond GP yields crosslinked LDPE (XLPE). Molecular weight distributions of mLDPE below GP and the sol-fractions of XLPE above GP were investigated. The sol-fractions in XLPE were extracted to prepare XLPE gels of different crosslinking densities. Both XLPE and the gels were subjected to shear action for studying dynamic rheology and relaxation modulus in the linearity region for revealing the role of entanglements and dangling chains to viscoelasticity of the randomly crosslinked network. The results revealed that the sol-fractions with molecular weight much higher than entanglement molecular weight contributed to equilibrium modulus in addition to the gel network, which lowered the DCP dosage for appearance of critical gel behavior of XLPE in comparison with the XLPE gel. However, rheological method yielded critical DCP dosages for appearance of apparent gel behaviors far beyond the chemical GP from the extraction experiment. The sol-fraction residing in the network gave rise to additional contribution to relaxation modulus of XLPE, shortening network relaxation time and improving equilibrium modulus.

Determination of electron density and energy influx in a hollow cathode glow discharge used for powder modification

The electron density and energy influx in an argon hollow cathode glow discharge were determined to obtain adequate parameters for subsequent surface modification of low density polyethylene (LDPE) powder to change the wettability. The electron density was studied by Langmuir probe measurement in dependence on process gas pressure and hollow cathode material. Besides the determination of the rate of increasing electron density with input power an optimal experimental pressure was determined. The energy influx was studied by thermal probe measurements in dependence on process gas pressure, bias voltage, axial position and hollow cathode material. Inside the hollow cathode the energy influx is nearly constant along the whole cathode length. With increasing pressure the energy influx decreased. At biased thermal probe the energy influx was observed to decrease up to the floating potential and beyond it increases with increasing voltage. Using different hollow cathode materials the electron density as well as the energy influx reach higher values for aluminum than for copper and stainless steel.

A Novel Two-Step Procedure for Plasma Surface Modification of Low-Density Polyethylene for Improved Drug Adhesion in Intra Uterine Devices (IUDs)

The Intrauterine Devices (IUDs) are unable to prevent STDs (Sexually Transmitted Diseases) and PIDs (Pelvic Inflammatory Diseases) which seriously restricts their usage. RISUG® (Reversible Inhibition of Sperm under Guidance), a potent spermicidal and antimicrobial drug is being coated over copper-T frame (made of polyethylene) by exposing it to vacuum plasma treatment twice to increase the adhesion property of polyethylene. First, the polyethylene alone is exposed to certain process conditions of RF (radiofrequency) plasma which increases the surface roughness by creating micro-and nano-pores (as indicated by scanning electron microscopy and atomic force microscopy). Thereafter RISUG® is smeared over the polyethylene of copper-T frame and subjected to the same plasma treatment again. The second plasma treatment causes a "micro-hammering" effect, pushing the drug in the pores and pits formed by the first plasma treatment, resulting in improved bonding. The present study shows that RF plasma treatment alters the surface properties of the copper-T frame without affecting its mechanical properties or primary fabrication.

The mesh disturbance effects in a low‐temperature cascade arc torch for surface modification of low density polyethylene

AbstractA stainless steel mesh was placed in a low‐temperature cascade arc torch (LTCAT) to study its disturbance effects on the plasmas and on the surface modification of low density polyethylene (LDPE). It was found that the photoemitting species were deflected by the screen and only faint glow was observed after the mesh. Optical emission spectroscopy examination indicated that the amount of electronically excited species in the plasma was greatly reduced after passing through the mesh. Grounding the mesh altered the nature of the discharge and a greater intensity of O emission was observed in Ar LTCAT + O2 discharge, which indicated greater energy transfer to the oxygen. Although a decrease in surface damage was observed on the treated LDPE samples by placement of the mesh in the Ar LTCAT discharges, the wettability achieved was also greatly reduced. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Optimization of adhesive joints of low density polyethylene (LDPE) composite laminates with polyolefin foam using corona discharge plasma

AbstractIn this work, surface modification of low density polyethylene (LDPE) film has been carried out to optimize adhesive joints with polyolefin foam for uses in technological applications. LDPE films were modified in a continuous way using corona discharge plasma with different powers, ranging from 200 to 600 W and several film advance rates in the 5–20 m min−1 range. Changes in surface wettability have been studied with contact angle measurements and subsequent solid surface energy calculation. A polyurethane adhesive was used to join the LDPE film to a polyethylene foam. Mechanical performance of the adhesive joints has been determined by T‐peel tests and also the aging effects of several hydrothermal conditions have been studied to evaluate the usefulness of these laminate composites in technological applications. Results show that corona discharge powers between 400 and 600 W are suitable in terms of wettability improvement; on other hand, a slight decrease in surface wettability as the film advance rate increases is detected but the overall changes as a consequence of the film advance rate in the 5–20 m min−1 range are small if compared to changes derived from working powers in the 200–600 W range. Adhesive joints offer excellent mechanical performance and good durability in hydrothermal conditions thus being appropriate for technical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Blending of low‐density polyethylene with vanillin for improved barrier and aroma‐releasing properties in food packaging

AbstractModification of low‐density polyethylene (LDPE) with vanillin to obtain flavored packaging film with improved gas barrier and flavor‐releasing properties has been studied. The modification of LDPE with vanillin was monitored by Fourier transform infrared spectroscopy, wherein the appearance of new peaks at 1704.7, 1673.6, and 1597.2 cm−1 indicates the incorporation of vanillin into LDPE matrix. Films of uniform thickness were obtained by the extrusion of modified LDPE. Modified LDPE was found to have significantly higher gas barrier properties and grease resistance. Sensory quality of food products viz, doodhpeda (milk‐based solid soft sweet), biscuit, and skimmed milk powder packed in LDPE‐vanillin film showed that the doodhpeda sample had clearly perceptible vanilla aroma, whereas biscuit had marginal aroma and skimmed milk powder did not have noticeable aroma. When viewed in the light of imparting desirable vanilla aroma, results of the study indicated that LDPE‐vanillin film has better prospects as a packaging material for solid sweets with considerable fat content when stored under ambient conditions. The release of vanilla aroma was further confirmed by gas chromatography–mass spectrometery analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Plasma-Treated Superhydrophobic Polyethylene Surfaces: Fabrication, Wetting and Dewetting Properties

Superhydrophobic surfaces correspond to hydrophobic surfaces whose water contact angle is higher than 150°. Two new routes involving plasma technique are proposed to prepare such surfaces: the first one is a one-step process (CF4 plasma modification of low density polyethylene), and the second involves two steps (O2 plasma treatment followed by CF4 plasma treatment). The plasma parameters are defined to optimize the degradation and/or the functionalization. The O2 plasma allows to create a variable roughness while CF4 plasma accentuates this roughness and creates a non-polar layer. With the two-step treatment, plasma parameters were found which produced superhydrophobic surfaces with a controlled roughness and whose chemical structure was close to a Teflon-like structure. The wetting and dewetting of these superhydrophobic surfaces are compared to those of only hydrophobic polyethylene. The behavior of surfaces, whether dry or prewetted with water vapor, is found to be different. The dewetting of the dried surface previously prewetted is found to be discontinuous, and slower than that of the dry one. This specific behavior is interpreted as a roughness effect on trapped water. However, its dewetting is still faster than that of the corresponding hydrophobic surface such as PTFE.

Study of polymer composites by methods of thermoactivated spectroscopy

Variations in the temperatures of structural transitions and stabilization of charges depending on the degree of filling of low density polyethylene (LDPE) are studied by the methods of radiothermoluminescense (RTL) and thermally stimulated current (TSC). The RTL spectrum of the initial LDPE exhibits three maxima at temperatures of 130, 173, and 227 K (γ-, α-, and β-relaxation). The low-temperature maxima are assumed to be related to recombination of trapped electrons with products of radiolysis (radicals) and the relatively high-temperature peak at 228, to recombination of trapped electrons with luminescence centers after tunneling through a potential barrier. Modification of LDPE by introduction of a special additive (SA) in an amount up to 2 wt % shifts the γ- and α-peaks on the RTL curve to lower temperatures and the β-peak, to higher temperatures. The TSC spectrum exhibits two maxima at temperatures of 303 and 418 K, respectively. Modification of LDPE leads to a sharp decrease in the amplitude of both peaks and shifts the maxima to higher temperatures. The peak at 418 K is due to the release of trapped charges from traps in the crystalline phase of LDPE at melting.

Influence of chemical modification of the surface of polyethylene with phosphorus, boron, titanium, vanadium, and silicon halides on its vapor permeability

The influence of a gas-phase chemical modification of low-density polyethylene with volatile halides of various elements [PCl3, TiCl4, VOCl3, BBr3, and Si(CH3)2Cl2] on the surface layer morphology and vapor permeability of polymeric formulations was examined by atomic-force microscopy, chemical analysis, and adsorption method.

Surface modification of low density polyethylene (LDPE) film by low pressure O 2 plasma treatment

In this work, low pressure glow discharge O 2 plasma has been used to increase wettability in a LDPE film in order to improve adhesion properties and make it useful for technical applications. Surface energy values have been estimated using contact angle measurements for different exposure times and different test liquids. In addition, plasma-treated samples have been subjected to an aging process to determine the durability of the plasma treatment. Characterization of the surface changes due to the plasma treatment has been carried out by means of Fourier transformed infrared spectroscopy (FTIR) to determine the presence of polar species such as carbonyl, carboxyl and hydroxyl groups. In addition to this, atomic force microscopy (AFM) analysis has been used to evaluate changes in surface morphology and roughness. Furthermore, and considering the semicrystalline nature of the LDPE film, a calorimetric study using differential scanning calorimetry (DSC) has been carried out to determine changes in crystallinity and degradation temperatures induced by the plasma treatment. The results show that low pressure O 2 plasma improves wettability in LDPE films and no significant changes can be observed at longer exposure times. Nevertheless, we can observe that short exposure times to low pressure O 2 plasma promote the formation of some polar species on the exposed surface and longer exposure times cause slight abrasion on LDPE films as observed by the little increase in surface roughness.

Surface Modification of Low-Density Polyethylene Films via Photografting Polymerization Technique

Surface modification of low-density polyethylene (LDPE) films was carried out via a novel photografting polymerization technique with acrylamide (AAm) as the monomer. The photografting polymerization can be achieved via one-step method and two-step method. The photografting polymerization reactivity of AAm was examined with benzophenone (BP) as the photoinitiator and low-density polyethylene (LDPE) film as the substrate with “sandwich” assembly. Moreover, the occurrence and evolution of grafting polymerization of AAm on the substrate was demonstrated XPS analysis and SEM pictures.

Synthesis of transparent superhydrophobic polyethylene surfaces

Superhydrophobic surfaces, already present in the nature as observed with leaves of plants (lotus) or feathers of some birds, correspond to hydrophobic surface whose water contact angle is higher than 150°. Before running the synthesis of such surface, one must understand the corresponding phenomenon and define the pertinent characteristics. Most of the techniques already developed lead to surfaces with weak physical properties such as optical and mechanical ones. Here, the synthesis in dry medium (plasma) is proposed leading to stable and transparent polymeric superhydrophobic surfaces. Two routes are possible; the first one corresponds to the one-step synthesis (CF 4 plasma modification of low density polyethylene (LDPE)), the second one to the two steps (O 2 plasma treatment followed by CF 4 plasma onto LDPE). The plasma parameters are defined to optimize the degradation and/or the functionalization and the obtained surface structures are characterized. The O 2 plasma allows to create a variable roughness while CF 4 plasma emphasizes this roughness and creates the apolar layer. By the two-step treatments, several plasma parameters were found to elaborate stable transparent superhydrophobic surfaces with a controlled roughness and whose chemical structure is close to a Teflon-like structure. It has been shown that superhydrophobic surface can be obtained even with a low roughness, around 20 nm.

Functionalization of LDPE and PP to Produce Grafted Membranes Used in Dialysis Processes. Part II

Gamma radiation-induced grafting of N-vinyl pyrrolidone (NVP) monomers onto low-density polyethylene (LDPE) and polypropylene (PP) films was studied. The effect of monomer concentration, irradiation dose, and inhibitor concentration on the grafting percent was determined. The swelling behavior of the grafted membranes has been investigated, and it was shown that the modification of LDPE and PP films with hydrophilic monomers results in the growth of the water uptake percent. The permeability of high molecular weight materials such as creatinine and urea, through NVP-grafted membranes increased with increase in grafting percent. Thermal properties of the grafted membranes were studied by using thermo gravimetric analysis (TGA). The morphology of grafted membranes was investigated by using X-ray diffraction (XRD) and the scanning electron microscope (SEM). Structures of the grafted membranes were elucidated by spectroscopic analysis as FTIR, and their mechanical properties were also investigated.

Functionalization of LDPE and PP to Produce Grafted Membranes Used in Dialysis Processes. Part I

: Gamma radiation-induced grafting of acrylamide (AAm) monomer onto low-density polyethylene (LDPE) and polypropylene (PP) films was studied. The effect of monomer concentration, irradiation dose, and inhibitor concentration on the grafting percent was determined. The swelling behavior of the grafted membranes has been investigated, and it was shown that the modification of LDPE and PP films with hydrophilic monomers results in the growth of the water uptake percent. The permeability of high molecular weight materials, such as creatinine and urea, through AAm grafted membranes increased with increase in grafting percent. Thermal properties of the grafted membranes using thermo gravimetric analysis (TGA) were studied. The morphology of grafted membranes was investigated by using X-ray diffraction (XRD) and the scanning electron microscope (SEM). The mechanical properties of the grafted membranes have been studied, and their structures were elucidated by spectroscopic analysis as (FTIR).