Irradiated High-density Polyethylene Research Articles

Correction to: Structural health monitoring of irradiated high-density polyethylene samples with electrical resistance tomography

Correction to: Structural health monitoring of irradiated high-density polyethylene samples with electrical resistance tomography

Structural health monitoring of irradiated high-density polyethylene samples with electrical resistance tomography

Structural health monitoring of irradiated high-density polyethylene samples with electrical resistance tomography

FTIR study of gamma and electron irradiated high-density polyethylene for high dose measurements

A reliable and well-characterized dosimetry system which is traceable to the international measurement system, is the key element to quality assurance in radiation processing with cobalt-60 gamma rays, X-rays, and electron beam. This is specifically the case for health-regulated processes, such as the radiation sterilization of single use medical devices and food irradiation for preservation and disinfestation. Polyethylene is considered to possess a lot of interesting dosimetric characteristics. In this work, a detailed study has been performed to determine the dosimetric characteristics of a commercialized high-density polyethylene (HDPE) film using Fourier transformed infrared spectrometry (FTIR). Correlations have been established between the absorbed dose and radiation induced infrared absorption in polyethylene having a maximum at 965 cm−1 (transvinylene band) and 1716 cm −1 (ketone-carbonyl band). We have found that polyethylene dose-response is linear with dose for both bands up to1000 kGy. For transvinylene band, the dose-response is more sensitive if irradiations are made in helium. While, for ketone-carbonyl band, the dose-response is more sensitive when irradiations are carried out in air. The dose-rate effect has been found to be negligible when polyethylene samples are irradiated with electron beam high dose rates. The irradiated polyethylene is relatively stable for several weeks after irradiation.

Spectroscopic Investigation of Degradation Reaction Mechanism in γ-Rays Irradiation of HDPE

Radiation damage and reaction mechanism of product formation due to γ-irradiation in high-density polyethylene (HDPE) have been studied by Fourier transform infrared (FTIR), UV-vis spectroscopic, and x-ray diffraction (XRD) techniques. A Co60gamma source (with a dose rate of 1.707 kGy/hr) has been used up to the total dose of 570 kGy. There are dose-dependent changes in the polymer. The optical band gap decreases with the increase of the γ-irradiation dose. Formations of unsaturation centers have been observed. FTIR observed that a lower dose of γ-irradiation induces the formation of an unsaturated (-C=C-) group and a ketone carbonyl group. Breaking of the C-H bond is more frequent than the breaking of the C-C bond in irradiated HDPE. Crosslinking dominates over chain scission (breaking of C-C bond of the main chain) at a lower dose (100 kGy). There has been no significant influence of γ-irradiation on the crystalline structure, although crystalline size decreases. Mechanisms of the formation of alkyl, allylic, and polyenyl radicals have been investigated.

Development of marine grade radiation cross-linked high density polyethylene (HDPE) floater pontoon material

Crosslinked High Density Polyethylene (HDPE) was developed using electron beam radiation techniques. The crosslinked HDPE can be used as marine grade cross-linked HDPE floater pontoon material. Thermoplastic resin, HDPE blended with Ethylene Vinyl Acetate (EVA) in various weight percentage compositions before being radiate with electron beams irradiation. These composites showed significant changes in mechanical properties and temperature stability after the irradiations. From this study, the optimum dose for HDPE and HDPE/EVA blends will be obtain. This study also will provide the optimum irradiation dose in order to have a good, high strength and impact for the production of pontoon material. The present of EVA in the blend will act as impact modifier also being investigated in this study. From the study, the result showed some significant changes in thermal and mechanical properties after being irradiated with electron beam. The comparison of the result between these composite composition of irradiated and non-irradiated HDPE composite used for floater pontoon material is presented in this paper

Nano-ZrO2 filled high-density polyethylene composites: Structure, thermal properties, and the influence γ-irradiation

High-density polyethylene (HDPE) composites with different amounts of ZrO2 nanoparticles (1–20 vol%) were prepared by high-pressure thermal pressing. The effect of γ-irradiation on their structural and thermal properties was investigated using small-angle neutron scattering (SANS), X-ray diffraction (XRD), Raman spectroscopy, infrared spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SANS analysis confirmed good dispersion of the nanoparticles in HDPE matrix. Upon exposure to γ-radiation only small changes in the lattice parameters and the crystalinity degree occurred for both HDPE and the nanocomposities. More significant changes for irradiated HDPE were observed in DSC-derived parameters, including the decrease in the melting point, and increase in crystalinity degree. This trend was even more pronounced for the nanocomposities. A possible explanation assuming resonant enchantment of polymer chain scission in the presence of ZrO2 nanoparticles is discussed. The extent of radiation-induced oxidation was essentially the same for pure HDPE and the nanocomposities, suggesting that the process is diffusion controlled. The thermal stability of the irradiated composites was somehow higher than that pure HDPE.

Gamma irradiation of polyethylene nanocomposites for food packaging applications against stored‐product insect pests

Films of high‐density polyethylene (HDPE) incorporated with different nanoparticles, ZnO or Ag, were prepared to protect food products from the stored‐product insect pests. The developed composites were irradiated at different radiation doses and the associated properties were investigated in terms of gel content percent, tensile mechanical properties, thermal properties, and morphology. The possible application of the irradiated products in food industry via the insect pest test was investigated. The gel content percentage of the irradiated HDPE films loaded with ZnO and Ag nanoparticles demonstrated higher values than those of unirradiated unloaded films and unirradiated loaded HDPE. The mechanical measurements indicated significant increments by loading with nanoparticles as well as by irradiation. The tensile strength raised up to about 177 and 158% by adding 2% ZnO and Ag, respectively. Conversely, the elongation percentage was decreased by increasing nanoparticle concentration and by radiation dose. Thermogravimetric analysis elaborated that the thermal stability of the nanocomposites was lesser than that of HDPE unloaded films, yet improved by irradiation. The insect pest test revealed that the adults of Sitophilus granarius could not penetrate the loaded and irradiated HDPE film. The most efficient formulation was reported for the HDPE films incorporated with 2% Ag irradiated with a dose of 75 kGy. J. VINYL ADDIT. TECHNOL., 25:E120–E129, 2019. © 2018 Society of Plastics Engineers

The alterations in high density polyethylene properties with gamma irradiation

In the present investigation, high density polyethylene (HDPE) polymer has been used to study the alterations in its properties under gamma-irradiation. Physico-chemical properties have been investigated with different spectroscopy techniques, Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), biocompatibility properties, as well as, mechanical properties change. The FT-IR analysis shows the formation of new band at 1716cm−1 that is attributed to the oxidation of irradiated polymer chains, which is due to the formation of carbonyl groups (C˭O). XRD patterns show that a decrease in the crystallite size and increase in the Full Width at Half Maximum (FWHM). This means that the crystallinity of irradiated samples is decreased with increase in gamma dose. The contact angle measurements show an increase in the surface free energy as the gamma irradiation increases. The measurements of mechanical properties of irradiated HDPE samples were discussed.

Ultra nano-hardness of surface layer of irradiated high–density polyethylene (HDPE)

Using high doses of beta radiation for high-density polyethylene (HDPE) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of high-density polyethylene (HDPE) were made by injection moulding technology and irradiated by high doses of beta radiation (0, 33, 66 and 99 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented ultra nano-hardness test. The results of the measurements showed considerable decrease in micromechanical properties (indentation hardness, indentation elastic modulus) when low doses of beta radiation are used.

Degradation of electron-irradiated polyethylene studied by positron annihilation lifetime spectroscopy

Degradation of electron beam irradiated high-density polyethylene was studied by positron annihilation lifetime spectroscopy (PALS), micro-FT-IR, and gel fraction measurements. The obtained results indicated that ortho-positronium intensity is influenced not only by the irradiation but also the post oxidation, which illustrates that PALS may be a promising tool to monitor/evaluate the degradation of polyethylene induced by irradiation and long-term storage.

Heat shrinkable behavior, physico-mechanical and structure properties of electron beam cross-linked blends of high-density polyethylene with acrylonitrile-butadiene rubber

Abstract In this study, heat-shrinkable composites of electron beam irradiated high-density polyethylene (HDPE) composites with acrylonitrile-butadiene rubber (NBR) were investigated. HDPE/NBR blends at a ratio of components 100/0, 90/10, 80/20, 50/50 and 20/80 wt% were prepared using a two-roll mill. The compression molded films were irradiated high-energy (5 MeV) accelerated electrons up to irradiation absorbed doses of 100–300 kGy. The effect of electron beam induced cross-linking was evaluated by the changes of mechanical properties, gel content and by the differences of thermal properties, detected by differential scanning calorimetry. The thermo-shrinkage forces were determined as the kinetics of thermorelaxation and the residual shrinkage stresses of previously oriented (stretched up to 100% at above melting temperature of HDPE and followed by cooling to room temperature) specimens of irradiated HDPE/NBR blends under isometric heating–cooling mode. The compatibility between the both components was enhanced due to the formation of cross-linked sites at amorphous interphase. The results showed increase of mechanical stiffness of composites with increase of irradiation dose. The values of gel fraction compared to thermorelaxation stresses increased with the growth of irradiation dose level, as a result of formation cross-linked sites in amorphous PP/NBR interphase.

Hardness/Microhardness Properties of HDPE Blends

This paper deals with utilization of recycled irradiated high-density polyethylene (rHDPEx) as a filler which was blended with non-modified high-density polyethylene (HDPE). Two blends were tested regarding the original state of the mixing components – HDPE granules/rHDPExgrit and HDPE granules/rHDPExpowder. Results show that the increasing amount of the rHDPEx, regardless its form, results in worsening both observed parameters – hardness and micro-indentation hardness.

Influence of Recycled Irradiated HDPE on Mechanical Behavior of LDPE/Hdpex Blends

This research paper deals with utilization of recycled irradiated high-density polyethylene (HDPEx). Grit prepared of irradiated HDPEx was used as a filler into virgin low-density polyethylene (LDPE). Concentrations from 10 to 60 % were made and their influence on mechanical properties was investigated. Tensile test at ambient and elevated temperature was used to describe mechanical properties of resulting blends. Results show that there is an upward trend of elastic modulus and ultimate tensile strength and downward trend of nominal strain at ambient temperature. Similar findings were observed at elevated temperature, which might suggest possible utilization of such modified thermoplastic materials. However other material properties have to be tested to make final conclusion.

Utilization of Terahertz Spectroscopy for Optical Behavior Determination of Recycled Modified HDPE

Little research was done to investigate possible utilization of irradiated materials after the end of their lifetime. This research paper deals with the possible utilization of irradiated high-density polyethylene (HDPEx) after its service life. Irradiated HDPE was used as filler into the virgin low-density polyethylene (LDPE). Three material combinations were investigated (powder/powder, granules/powder and granules/grit) and influence of the filler on optical behavior was measured. Terahertz spectroscopy at wide range of frequencies was used for refractive index determination. According to measured data there is significant influence by the amount of the filler. Moreover influence of particle size was also observed. All three combinations have similar curve courses; however the most consistent results were achieved at the powder/powder combination. Behavior of virgin LDPE and virgin HDPE is in correlation with previous findings.

Compatibilization of irradiated HDPE

The C–O, C=O, and C(=O)O groups were introduced onto high-density polyethylene (HDPE) chains by ultraviolet irradiation in air and the groups’ content increased with increase in the irradiation time. When they irradiated for 16 h, gels were formed in the irradiated HDPE, and the content of the gels increased with increase in the irradiation time. Compared with HDPE, the crystal form of the irradiated HDPE did not change and still retained the orthorhombic structure, and its melting temperature decreased, while its crystallinity increased. The irradiated HDPE was added in HDPE/CaCO3 composites as a compatibilizer, and HDPE/irradiated HDPE/CaCO3 composites were obtained. Compared with those in HDPE/CaCO3 composites, the dispersion of the CaCO3 and interfacial interaction between CaCO3 and HDPE matrix in HDPE/irradiated HDPE/CaCO3 composites improved due to compatibilization of the irradiated HDPE, and its mechanical properties (especially impact strength), thus, showed remarkable enhancement. With increase in irradiation time, the tensile strength of HDPE/irradiated HDPE/CaCO3 composites enhanced and its impact strength increased during irradiation time of 16 h and then decreased slightly. In the same irradiation time, the tensile strength and impact strength of HDPE/irradiated HDPE/CaCO3 composites increased with increase in the content of the irradiated HDPE.

Structure and properties of irradiated HDPE high-density polyethylene/calcium carbonate composites

First, some groups of C=O and C–O were introduced onto high-density polyethylene (HDPE) chains by ultraviolet irradiation for short time in ozone atmosphere. The content of the groups was increased with increasing the irradiation time. The irradiated HDPE was blended with calcium carbonate (CaCO3) to prepare the composites. The melting temperature and crystallinity of HDPE in irradiated HDPE/CaCO3 composites were lower than the HDPE in HDPE/CaCO3 composites. Compared with the HDPE/CaCO3 composites, the dispersion of CaCO3 and the interfacial interaction between CaCO3 and HDPE in the irradiated HDPE/CaCO3 composites increased respectively. With increasing the irradiation time, the mechanical properties (especially impact strength) of the irradiated HDPE/CaCO3 composites were markedly enhanced, while their thermal stability decreased slightly. For example, the tensile strength and impact strength of the irradiated (20 min) HDPE/CaCO3 composites increased from 25.7 MPa and 72 J m−1 to 30.3 MPa and 416 J m−1, respectively, compared with those of the HDPE/CaCO3 composites, and stiffened and toughened HDPE composites were obtained.

Radiation induced emulsion grafting of glycidyl methacrylate onto high density polyethylene: A kinetic study

Emulsion graft polymerisation of glycidyl methacrylate monomer onto high density polyethylene (HDPE) resin was studied. The radicals required to initiate the reaction were produced in HDPE resin by irradiation with the electron beam accelerator at ambient and vacuum conditions. The grafting reaction of GMA with irradiated HDPE was initiated by emulsion method using Tween 20 as a surfactant and water as a solvent under controlled conditions. The kinetic behavior of grafting reaction was investigated with respect to the degree of grafting under various parameters i.e. monomer concentration, radiation dose, grafting temperature and surfactant concentration. The degree of grafting was found to be a function of the investigated parameters. Particularly, surfactant concentration in the emulsion was found to be crucial for determining the micelle size and eventually the degree of grafting. The order of dependence of the initial rate of grafting on the monomer concentration and the irradiation dose was found to be 0.94 and 0.60, respectively. The initial rate of grafting was also found to increase with the increase in the grafting temperature varied in the range of 308-333 K. The optimum reaction parameters required to obtain desired and reproducible degrees of grafting in the resin could be identified. Moreover, the emulsion radiation grafting method was found to offer essential advantages over the conventional grafting with solvents including low radiation dose, less monomer concentration and cost effectiveness.

Recycling of irradiated high-density polyethylene

Radiation crosslinking of high-density polyethylene (HDPE) is a well-recognized modification of improving basic material characteristics. This research paper deals with the utilization of electron beam irradiated HDPE (HDPEx) after the end of its lifetime. Powder of recycled HDPEx (irradiation dose 165kGy) was used as a filler into powder of virgin low-density polyethylene (LDPE) in concentrations ranging from 10% to 60%. The effect of the filler on processability and mechanical behavior of the resulting mixtures was investigated. The results indicate that the processability, as well as mechanical behavior, highly depends on the amount of the filler. Melt flow index dropped from 13.7 to 0.8g/10min comparing the lowest and the highest concentration; however, the higher shear rate the lower difference between each concentration. Toughness and hardness, on the other hand, grew with increasing addition of the recycled HDPEx. Elastic modulus increased from 254 to 450MPa and material hardness increased from 53 to 59 ShD. These results indicate resolving the problem of further recycling of irradiated polymer materials while taking advantage of the improved mechanical properties.

The effect of gamma radiation on hardness evolution in high density polyethylene at elevated temperatures

This research focuses on characterizing hardness evolution in irradiated high density polyethylene (HDPE) at elevated temperatures. Hardness increases with increasing gamma ray dose, annealing temperature and annealing time. The hardness change is attributed to the variation of defects in microstructure and molecular structure. The kinetics of defects that control the hardness are assumed to follow the first order structure relaxation. The experimental data are in good agreement with the predicted model. The rate constant follows the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The defects that control hardness in post-annealed HDPE increase with increasing dose and annealing temperature. The structure relaxation of HDPE has a lower energy of mixing in crystalline regions than in amorphous regions. Further, the energy of mixing for defects that influence hardness in HDPE is lower than those observed in polycarbonate (PC), poly(methyl methacrylate) (PMMA) and poly (hydroxyethyl methacrylate) (HEMA). This is due to the fact that polyethylene is a semi-crystalline material, while PC, PMMA and PHEMA are amorphous.

Hardness and Micro-Indentation Hardness Comparison of Recycled Modified HDPE

This research paper deals with the possible utilization of irradiated high-density polyethylene (HDPE) after its service life. Powder of recycled irradiated HDPE is used as filler into virgin low-density polyethylene (LDPE) in concentrations from 10 to 60 %. Two combinations of materials were tested granules LDPE/powder HDPE and powder LDPE/powder HDPE. Influence of the filler of the resulting blends on hardness and micro-indentation hardness was investigated. Shore D hardness test and instrumented micro-indentation hardness test were performed and results compared. According to the measured data both tested material characteristics are significantly influenced by the amount of the filler. Hardness increased with increasing amount of the filler at both material combinations; however results of micro-indentation test shows little inconsistency in hardness of surface layer.