Modification Of High-density Polyethylene Research Articles

Modification of High-Density Polyethylene with a Fibrillar-Porous Structure by Biocompatible Polyvinyl Alcohol via Environmental Crazing.

Polymer/polymer nanocomposites based on high-density polyethylene (HDPE) and biocompatible polyvinyl alcohol (PVA) were prepared by tensile drawing of HDPE in the PVA solutions via environmental crazing. The mechanism of this phenomenon was described. The HDPE/PVA nanocomposites were studied by the methods of scanning electron microscopy, atomic force microscopy, gravimetry, tensile tests, and their composition, properties, and performance were characterized. The content of PVA in the HDPE/PVA nanocomposites (up to 22 wt.%) was controlled by the tensile strain of HDPE and concentration of PVA in the solution. Depending on the content of PVA, the wettability of the HDPE/PVA nanocomposite (hydrophilic-lipophilic balance) could be varied in a broad interval from 45 to 98°. The modification of HDPE by the biocompatible PVA offers a beneficial avenue for practical applications of the HDPE/PVA composites as biomedical materials, packaging and protective materials, modern textile articles, breathable materials, membranes and sorbents, etc.

Modification of high-density polyethylene and ethylene-vinyl acetate copolymer by chain-layered silicate «sepiolite»

Composites based on high-pressure polyethylene and ethylene-vinyl acetate copolymer, containing sepiolite clay powder with a chain-layered structure have been investigated, and their physical-mechanical properties have been analyzed. When using sepiolite, the organomodification and compatibilization are not required. It is shown, that composite materials with the addition of sepiolite are superior in a number of characteristics to those containing traditionally applied layered clay powders.

Effect of Temperature Ageing on Injection Molded High-Density Polyethylene Parts Modified by Accelerated Electrons

The temperature ageing of high-density polyethylene (HDPE) modified by accelerated electrons was studied. Commodity plastic HDPE was used as a basic polymer material which was modified by radiation cross-linking. This polymer was used because of its excellent processability and chemical resistance. Plastic injection molding technology was used for the production of test specimens. These specimens were modified with the dose of radiation 33, 66, 99, 132, 165, and 198 kGy. The prepared specimens were tested to determine: gel content, degree of swelling, temperature stability, and changes in mechanical properties after temperature ageing. The results were determined by scanning electron microscopy (SEM) analysis on the fracture surfaces. The results of this study confirm that modification of HDPE by radiation cross-linking has a significant effect on increasing temperature stability. It has been shown that HDPE modified by radiation cross-linking can withstand temperatures exceeding the melting point of the original HDPE for a short-term.

Generation and Characterization of Cold Atmospheric Pressure Plasma Jet for Surface Modification of High-Density Polyethylene

Cold atmospheric pressure plasma technology has a variety of applications in different fields including material science and biomedical science. It has been using for surface modification and material processing in material science and used to improve the wettability, adhesion and biocompability of polymeric surfaces without altering the entire bulk properties. This paper outlines the characterization of cold atmospheric pressure plasma jet, which was generated in a high frequency (20 kHz) and high voltage (3.5 kV) power supply, as well as its application in the surface modification of high density polyethylene. Electrical and optical characteristics are used to estimate the electron density of the plasma. The effect of plasma on the surface properties of the material are analyzed by calculating contact angle, surface energy measurements and analyzing scanning electron microscopy images. Adhesive bonding strength and numerous other attributes have increased, however surface treatment is the process of cleaning, etching, functionalizing, and chemically treating substrates to improve roughness and adhesive properties on the surface. Cold plasma can induce a soft roughening on the surface through ion bombardment with polar functional groups resulting in the decrease in water contact angle.

Tribological modification of high-density polyethylene by using carbon soot from diesel combustion

Purpose The purpose of this paper is to explore the tribological properties of high-density polyethylene (HDPE) modified by carbon soot from the combustion of No. 0 diesel. Design/methodology/approach Carbon soot is characterized using X-ray diffraction, transmission electron microscopy and scanning electronic microscopy. The tribological properties of HDPE samples with carbon soot are investigated on a materials surface tester with a ball-on-disk friction pair. Findings The collected carbon soot mainly comprises amorphous carbon nanoparticles of 50-100 nm in diameter. The main wear behaviours of pure HDPE include abrasive wear and plastic deformation. After adding carbon soot nanoparticles to HDPE, HDPE wear decreases. The appropriate carbon soot content is 8 per cent in HDPE under the selected testing conditions. Compared with other HDPE samples, HDPE with 8 per cent carbon soot has higher melting temperature, lower abrasive wear and better wear resistance. The lubrication of HDPE with carbon soot is due to the formation of a transferring film composed of HDPE, amorphous carbon and graphite carbon. Originality/value The paper reveals the HDPE modification and lubrication mechanisms by using carbon soot from the combustion of diesel. Related research can perhaps provide a potential approach for the treatment of carbon soot exhaust emission.

Modification of high density polyethylene by gold implantation using different ion energies

High density polyethylene (HDPE) samples were modified by Au+ ion implantation at a dose of 5 × 1015 ions cm−2, using energies of 50, 100, 150 and 200 keV. The existence of implanted gold in the near-surface region of HDPE samples was confirmed by X-ray diffraction analysis. Surface roughness and Power Spectral Density analyses based on Atomic Force Microscopy (AFM) images of the surface topography revealed that the mechanism of HDPE modification during gold ion implantation depended on the energy of gold ions. Histograms obtained from phase AFM images indicated a qualitative change in the chemical composition of the surface during implantation with gold ions with different energies. Depth profiles obtained experimentally from cross-sectional Force Modulation Microscopy images and ones obtained from a theoretical simulation are in agreement for gold ions energies lower than 100 keV. The deviation that was observed for higher energies of the gold ions is explained by carbon precipitation in the near surface region of the HDPE, which prevented the penetration of gold ions further into the depth of the sample.

Rice husk ash – A valuable reinforcement for high density polyethylene

This paper presents the results of a study on the use of rice husk ash (RHA) for property modification of high density polyethylene (HDPE). Rice husk is a waste product of the rice processing industry. It is used widely as a fuel which results in large quantities of RHA. Here, the characterization of RHA has been done with the help of X-ray diffraction (XRD), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICPAES), light scattering based particle size analysis, Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Most reports suggest that RHA when blended directly with polymers without polar groups does not improve the properties of the polymer substantially. In this study RHA is blended with HDPE in the presence of a compatibilizer. The compatibilized HDPE-RHA blend has a tensile strength about 18% higher than that of virgin HDPE. The elongation-at-break is also higher for the compatibilized blend. TGA studies reveal that uncompatibilized as well as compatibilized HDPE-RHA composites have excellent thermal stability. The results prove that RHA is a valuable reinforcing material for HDPE and the environmental pollution arising from RHA can be eliminated in a profitable way by this technique.

Comparison of glow argon plasma-induced surface changes of thermoplastic polymers

Modification of high-density polyethylene (PE), polytetrafluoroethylene (PTFE), polystyrene (PS), polyethyleneterephthalate (PET) and polypropylene (PP) by Ar plasma was studied. The amount of the ablated material was determined by gravimetry. Wettability of polymers after the plasma treatment was determined from the contact angle measurement. The changes in the surface morphology of polymers were observed using atomic force microscopy (AFM). Chemical structure of modified polymers was characterized by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). Surface changes were also studied by the determination of electrokinetic potential ( ζ-potential). It was found that under the plasma treatment the polymers are ablated and their surface morphology and roughness are changed dramatically. XPS measurements indicate an oxidation of the polymer surface. The plasma treatment results in a dramatic increase of the ζ-potential. EPR data show different radical amount present on the treated surface of all polymers. Most significant changes due to the degradation of polymer chains are observed on PTFE.

MECHANICAL PROPERTIES OF SMC WHISKER REINFORCED HIGH DENSITY POLYETHYLENE COMPOSITES

A new type of SiO2-MgO-CaO (SMC) whisker was used to modify high density polyethylene (HDPE). The melting behavior and crystallinity were investigated by differential scanning calorimetry (DSC). The dispersion of whiskers and interfacial adhesion in the prepared HDPE/SMC whisker composites were investigated by scanning electron microscopy (SEM). The mechanical properties were evaluated by mechanical tests and dynamic mechanical analysis (DMA). DSC data indicated that the melting temperature and the crystallinity of HDPE/SMC whisker composites kept almost constant with the addition of SMC whisker. SEM results revealed that SMC whisker could be well-dispersed in HDPE matrix and had a good interfacial interaction with HDPE, even up to a high content of 30 wt%. Mechanical tests showed that the tensile strength, tensile modulus and flexural strength of HDPE were significantly improved by the addition of SMC whisker. DMA results indicated a much enhanced storage modulus, loss modulus and loss factor. By comparing the literature data from other filler-reinforced HDPE, our work suggested that SMC whisker could be one of the best reinforcing agents for the modification of HDPE.

Modification of high-density polyethylene with binary mixtures of ɛ-caprolactone and ɛ-caprolactam

Modification of high-density polyethylene with binary mixtures of ɛ-caprolactone and ɛ-caprolactam was performed. The composition-property diagrams reflecting the dependences of the physicomechanical, rheological, and optical properties of the resulting polymeric compounds on the content of modifying mixture components were constructed, and the thermal oxidative degradation of the blend samples was studied. Based on the results obtained, the optimal modifier concentrations were suggested.

On the use of micro thermal analysis to characterize compatibility of nitrile rubber blends

The paper describes the use of micro thermal analyzer (μTA) for assessment of compatibilization in blends of nitrile rubber (NBR) with neat high-density polyethylene (HDPE), phenolic resin modified together with dynamically vulcanized HDPE and polyvinyl chloride (PVC). Micro thermal analyzer (μTA) was employed to identify different locations by the study of thermal conductivity of the surface and topographic features. Local thermal analysis (LTA), e.g., micro thermomechanical analysis (μTMA) and micro differential thermal analysis (μDTA), were conducted at these locations. Blending of NBR with unmodified HDPE shows incompatibility. Modification of HDPE by phenolic resin and dynamic cross-linking by peroxide resulted in technological compatibilization of the blend, while NBR and PVC generated characteristics of a miscible blend.

Effect of surface modification of high-density polyethylene by direct current and radio frequency glow discharge on wetting and adhesion characteristics

The present investigation aims to optimize the process parameters of Direct Current (DC) and Radio Frequency (RF) glow discharge treatment through air in terms of discharge power and time of exposure for the surface modification of high-density polyethylene (HDPE) sheet, for attaining best adhesive joint of the polymer to mild steel. In order to estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to glow discharge have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that at a given power level of DC glow discharge, surface energy and its polar component increase with increasing exposure time, attaining a maximum and then decreasing. In the case of RF glow discharge, surface energy and its polar component increase with increasing exposure time and then saturate. Surface modification by DC glow discharge increases the surface energy of HDPE relatively more at a lower power compared to that observed for RF glow discharge. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by electron spectroscopy for chemical analysis (ESCA) and energy-dispersive spectra (EDS). A significant oxygen peak is observed for surface-modified polymer as detected by ESCA and EDS. Lap shear tensile test of an adhesive (Araldite AY 105) joint of HDPE with mild steel has been carried out in optimizing the parameters of DC and RF glow discharge for maximum joint strength. When HDPE is exposed to DC glow discharge, improvement of adhesive joint strength of HDPE to mild steel is found to be by a factor more than 7. On the other hand, when HDPE is exposed to RF glow discharge, results in improvement of adhesive joint strength of HDPE to mild steel by a factor nearer to 7 are found. Thus, DC glow discharge is more capable for increasing wetting and adhesion characteristics of the polymer.

2,3-Dimethyl-2,3-diphenylbutane mediated grafting of vinyltriethoxysilane to polyethylene: a novel radical initiation system

The melt grafting of vinyltriethoxysilane (VTEOS) to polyethylene using 2,3-dimethyl-2,3-diphenylbutane (bicumene) as a radical initiator is demonstrated and compared to conventional peroxide-initiated processes. A bicumene-initiated modification of high density polyethylene at 290 °C provided no benefits in terms of selectivity when compared to a standard peroxide-based process operating at 180 °C. However, the selectivity of linear low-density polyethylene modification was influenced by chain scission, which counteracted the molecular weight effects of macroradical combination. Reactive extrusion data as well as studies of bicumene decomposition kinetics suggest that initiation occurs through an auto-oxidation mechanism that is facilitated by the interaction of cumyl radicals with oxygen.

Characterization of CO 2 plasma-treated polyethylene surface bearing carboxylic groups

The surface modification of high density polyethylene by a CO 2 microwave plasma is described with the aim of fixing carboxylic groups. The characterization is discussed in terms of functionalization, degradation, crystallization and cross-linking. The formation of carboxylic acids seems mainly favored by the presence of the CO 2 active species. The degradation leading via chain scissions to the formation of volatile byproducts is shown to be heterogeneous by mainly affecting amorphous zones. The structural modification is associated with a twisting motion of macromolecular chains having defects to more organized conformations. Finally, cross-linking appears weak due to the absence of chromophoric sites and of VUV radiations in the plasma.

Modification of Polyethylene with Activated Natural Zeolite

In an attempt to improve its main physical and mechanical characteristics, the modification of high density polyethylene (HDPE) with activated (dehydrated) natural zeolite clinoptilolite, in an attempt to improve its main physical and mechanical characteristics is investigated. After dehydration at 350°C and cooling in an atmosphere of dry air, about 30% of the entire volume of the zeolite particle is freed. This free volume and the ensuing from the specific structure sorption processes-the possibility for sorption of the polymer chain on the surface channel of the zeolite particle-determine the active modification function of dehydrated clinoptilolite.

Surface modification of high density polyethylene and polypropylene by DC glow discharge and adhesive bonding to steel

Abstraet-The surface modification of high density polyethylene (HDPE) and polypropylene (PP) has been carried out by exposure to a DC glow discharge in air at different power levels of 5.28, 11, and 13 W. The surface energies of polymers exposed to glow discharge were estimated by measuring the contact angles of two test liquids: de-ionized water and formamide, whose surface energy components are known. Both the polar and the dispersion components of the surface energy increased rapidly at short exposure times but the increase of the polar component was relatively more than that of the dispersion component. At low power levels of 5.28 and 11 W, the polar component of the surface energy reached a maximum plateau depending on the exposure time, but at a 13 W power level the polar component of the surface energy decreased from a maximum value to a saturation level. For PP, this saturation level could not be attained in this study. The maximum total surface energy measured in this study corresponds to the maximum polar component at 13 W for an exposure time of 120 s. The contact angle of the adhesive, Araldite AY 105 mixed with hardener HY 840 in a weight ratio of 2 : 1, was minimum at this maximum surface energy attained with HDPE and PP by exposure to a glow discharge in air. The measured lap shear strengths of HDPE or PP-Araldite-mild steel joints show a maximum corresponding to the maximum surface energy measured on the above-mentioned polymers.

Modeling the reactive modification of HDPE in a nonintermeshing twin screw extruder

AbstractThe chemical modification of high density polyethylene (HDPE) in a counter‐rotating nonintermeshing twin screw extruder is modeled using a simultaneous random scission and cross‐linking integro‐differential equation. The roles of mixing and kinetics in the free‐radical reaction are investigated. The modification experiments use a masterbatch feed of HDPE with various concentrations of 2,5‐dimethyl‐2,5‐(t‐butylperoxy)‐3‐hexyne. The extruder operating parameters studied were barrel temperature, screw speed, and the degree of screw flight stagger. The reaction model is fit using the molecular weight averages and the gel content measured experimentally. The reaction time for HDPE is determined by use of the residence time distribution of the extruder with a segregation (macromixing) assumption. The segregation model is compared against the plug flow assumption, where the mean residence time of the measured distribution is used for the length of reaction of all polymer species within the extruder. The calculated molecular weight distributions are insensitive to the mixing model used. © 1995 John Wiley & Sons, Inc.

Modification of high-density polyethylene during synthesis

High-density polyethylene (HDPE) was modified by adding small amounts of siloxane compounds during synthesis. The effects of the admixture concentration and the mode of its addition on the properties of HDPE over a broad molecular mass range were established. The investigated admixture does not affect the activity of the catalytic system employed, but influences markedly the structure and deformation behaviour of PE, enhances the ultimate strength and the impact strength. Modification during synthesis facilitates processing of ultra-high molar mass polyethylene below the melting temperature.