Pristine High Density Polyethylene Research Articles

Polyethylene microplastic can adsorb phosphate but is unlikely to limit its availability in soil

In plant growth experiments, the presence of microplastics (MPs) often reduces plant growth. We conducted laboratory experiments to investigate the potential of microplastics to adsorb the major soil nutrient phosphate; adsorption to MPs was then compared to adsorption to soil. Adsorption experiments used two contrasting soils, pristine high density polyethylene and artificially weathered material (the same material but exposed to 185 nm UV light for 420 h over 105 days), phosphate solutions (dissolved KH2PO4) ranging from 0.2 to 200 mg L−1 and a solid (g) to liquid (mL) ratio of 1: 150 at different values of pH (2–12) and different concentrations of background electrolyte (0.00–0.10 M NaNO3). The adsorption data were best fitted to linear and Freundlich isotherms. In initial experiments where pH was not fixed and with a background electrolyte of 0.10 M NaNO3, Kd values ranged from 3.37 to 27.65 L kg−1, log Kf from 1.21 to 1.96 and 1/n from 0.36 to 0.84. Exposure of the MP to 185 nm UV radiation led to the appearance of a C=O functional group in the MP; the partition coefficient Kd, calculated from the linear isotherm did not increase but the logKf value derived from fits to the Freundlich isotherm increased by a factor of 1.5. Kd values for soils were 3–7.5 times greater than those for MPs and log Kf values 1.1–1.7 greater. In the experiments in which initial pH and ionic strength were varied, adsorption was similar across all treatments with adsorption parameters for the higher organic content soil sometimes having the highest values and the pristine microplastic the lowest. In the desorption experiments most of the adsorbed phosphate desorbed. Overall our findings indicate that despite their ability to adsorb phosphate, MPs are unlikely to control the fate and behaviour of phosphate in soil.

A novel approach for preparation of nanocomposites with an excellent rigidity/deformability balance based on reinforced HDPE with halloysite

An innovative approach, designated as supported activator (SA), allows preparation of high density polyethylene (HDPE)-based highly performant hybrid materials. This procedure makes use of a nano-sized supported methylaluminoxane (MAO)-activator, based on halloysite natural nanotubes (HNT), combined with an in situ supporting concept. The new protocol when compared with a more conventional approach gives rise to higher polymerization activities as well as ultimate materials with better morphological features, greater crystallinity, thicker crystals, and highly increased stiffness. Moreover, a remarkable synergy between rigidity and toughness is attained. The Young’s modulus of a film obtained from the nanocomposite with the highest HNT content increases more than 70 % relatively to a pristine HDPE film, while retaining the limit stretching ability of pristine HDPE (more than 800%). A beneficial impact of using a high aspect ratio support such as HNT in the mechanical properties is also observed, when compared to similar HDPE hybrid materials derived from dendrimer-like silica (DS) nanospheres. Interestingly, polymerization activity, polymer features and derived properties found in the ultimate materials are less impacted by support/filler nature than by preparation method. This fact highlights the crucial role of the synthetic methodology used and corroborates the high potential of the SA route for the preparation of high-performance polyethylene-based nanocomposites with an excellent balance between stiffness and deformability.

Investigation of Mechanical Properties of Coffee Husk-HDPE-ABS Polymer Composite Using Injection-Molding Method

Waste biomass-based natural fibers are being extensively researched nowadays as a composite material with various waste-based high-density polyethylene (HDPE) to utilize the waste biomass and recycle the plastic waste in an effective approach. In this study, chemically modified spent coffee husk (CH) has been applied with different ratios of HDPE to produce composite material and characterized comprehensively to determine the mechanical stability of the products. The injection molding method was used for composite development containing HDPE with untreated and 10 wt% NaOH-treated CH weight ratios of 0%, 15%, 20%, and 25% together with 10 wt% coupling agent and filler materials of acrylonitrile butadiene styrene (ABS) and kaolin clay, respectively. Physicochemical characteristics of untreated CH, 10 wt% NaOH treated CH, pristine HDPE and HDPE-CH composites have been analyzed comprehensively in this study. Adding 25 wt% fiber with 65 wt% HDPE and 10 wt% of ABS (7 wt%)-kaolin clay (3 wt%) increased the tensile and bending properties significantly. This composite presented the maximum tensile, flexural, and impact strengths, which were 36 MPa, 7.5 MPa, and 2.8 KJ/m2, respectively. The tensile strength and bending strength of NaOH-treated coffee husk fibers (CHF) were enhanced by 32% and 29%, respectively. The microstructural characteristics of HDPE with treated and untreated CHF composites analyzed by scanning electron microscopy (SEM) demonstrated the fibers’ and matrix’s excellent adhesion and compatibility. Thus, HDPE polymer-treated CH composite presented excellent stability, which can be expected as a new addition for construction, food packaging, and other industrial applications.

Hydrophilization of Hydrophobic Mesoporous High-Density Polyethylene Membranes via Ozonation.

This work addresses hydrophilization of hydrophobic mesoporous membranes based on high-density polyethylene (HDPE) via ozonation. Mesoporous HDPE membranes were prepared by intercrystallite environmental crazing. Porosity was 50%, and pore dimensions were below 10 nm. Contact angle of mesoporous membranes increases from 96° (pristine HDPE) to 120° due to the formation of nano/microscale surface relief and enhanced surface roughness. The membranes are impermeable to water (water entry threshold is 250 bar). The prepared membranes were exposed to ozonation and showed a high ozone uptake. After ozonation, the membranes were studied by different physicochemical methods, including DSC, AFM, FTIR spectroscopy, etc. Due to ozonation, wettability of the membranes was improved: their contact angle decreased from 120° down to 60°, and they became permeable to water. AFM micrographs revealed a marked smoothening of the surface relief, and the FTIR spectra indicated the development of new functionalities due to ozonolysis. Both factors contribute to hydrophilization and water permeability of the ozonated HDPE membranes. Hence, ozonation was proved to be a facile and efficient instrument for surface modification of hydrophobic mesoporous HDPE membranes and can also provide their efficient sterilization for biomedical purposes and water treatment.

Advanced epithelial lung and gut barrier models demonstrate passage of microplastic particles

Micro- and nanoplastics (MNP) can be found virtually everywhere around us in the biosphere and food chain, therefore humans are continuously exposed to MNP, mainly via inhalation and ingestion. Here, we have applied physiologically relevant human-based advanced in vitro models representing the lung (MucilAir™) and gut (InTESTine™ and Intestinal Explant Barrier Chip (IEBC)) to study membrane passage of various MNP and their potency to induce cytotoxic effects, barrier disturbances or pro-inflammatory cell activation. Selected MNP of various materials (polystyrene, polyethylene, nylon, car tire, and marine MNP collected from the ocean), shapes (spheres, fragments and fibers), sizes (0.05–100 μm), some of which were fluorescently labelled for tracking, were included. Without affecting cell viability, nylon fibers and (cleaned) HDPE (high density polyethylene) disrupted the MucilAir™ epithelial barrier. Luminal exposure to polystyrene particles (1 and 10 μm) and pristine HDPE fragments significantly decreased human colon tissue functionality. Furthermore, all polystyrene particles (0.05, 1 and 10 μm) affected tissue viability in porcine jejunum, ileum and colon tissue after 5 h exposure, and this was further confirmed in the IEBC after 24 h of exposure to 10 μm polystyrene particles and nylon fibers. Exposure to nylon fibers and its supernatant led to pro-inflammatory cell activation, as shown by increased IL-6 release in MucilAir™ and in human colon tissue after 96 or 24 h, respectively. Regarding transepithelial penetration of the MNP, permeability of 0.05 μm polystyrene spheres in the MucilAir™ lung cell model reached 3.6 ± 1.2% after 24 h. With 3.37 ± 0.46% after 5 h under static conditions and 5.5 ± 1.3% after 24 h under microfluidic conditions MNP permeability across intestinal tissue was highest for the largest (10 μm) polystyrene spheres. Confocal microscopy confirmed the translocation of MNP across the lung and intestinal epithelial barrier. In conclusion, we present a study revealing the passage of MNP over the epithelium of advanced in vitro models for the lung and intestine barrier. Furthermore, pro-inflammatory cell activation and disrupted barrier integrity were observed after exposure to several of the tested MNP. Future research is needed to further identify the effects of shape, size and material on these processes and subsequently the health effects of humans.

Investigation on the thermal-flammability and mechanical performance of coir fiber reinforced biocomposites

In this study coir fiber reinforced high density polyethylene (HDPE) composites containing varying amount of raw and alkali treated coir fiber were investigated. The thermal stability of the raw and treated fiber and its corresponding composites were evaluated by Thermo gravimetric analysis (TGA). Alkali treated fiber exhibited single-step degradation due to removal of lignin with remarkable amount of residual char. Incorporation of both raw and alkali treated fiber in composites resulted in early-stage decomposition process. The treated fiber composites (HDPE-ACF) showed improved thermal stability with considerable amount of residual char which can be correlated to the limiting oxygen index (LOI) studied. The 30% fiber loaded composites recorded 14%, 12% and 10% increase in LOI value compared to pristine HDPE, 10% and 20% fiber loaded composites respectively. A comparative analysis of experimental and theoretical LOI value were done and correlated to the TGA results. Composites of treated fibers exhibited better impact strength compared to its corresponding untreated ones. The hardness of the composites increased with increase in fiber dosage for both type of composites.

Enhancing mechanical properties of high‐density polyethylene/polydopamine‐modified basalt fiber composites via synergistic compatibilizers

AbstractThe mechanical properties of polymer‐based composites are generally determined by the interfacial adhesion between the inorganic component and the polymer itself. In this work, high‐density polyethylene (HDPE) composites were prepared with polydopamine(PDA)‐modified short basalt fibers (D‐BF) as an inorganic filler, in which the interface between HDPE and D‐BF was mediated by maleic anhydride‐grafted polyethylene (PE‐g‐MAH) and maleic anhydride‐grafted poly(ethylene‐co‐octene) elastomer (POE‐g‐MAH). The adding mass ratio of both the compatibilizers had a significant effect on the mechanical properties of the prepared HDPE/D‐BF composites. When total 5 wt% of both PE‐g‐MAH and POE‐g‐MAH with a mass ratio of 1/3 was introduced, the tensile strength and elongation at break of the composite containing 2.5 wt% D‐BF reached 53.7 ± 0.8 MPa and 1174 ± 17%, respectively, about 73% and 157% higher than those of the pristine HDPE. Therefore, this work demonstrated a feasible way to prepare polymeric composites with high strength and high toughness via the dual‐compatibilizer and PDA modification of the fillers.

Thermally conductive microcapsule/high-density polyethylene composite for energy saving and storage

Phase change material (PCM) is useful for the storage and release of latent heat. However, its ability to conduct has hindered its engineering application. This study prepares a novel microencapsulated phase change material (MEPCM) by suspension polymerization. To improve the adhesion between the shell and the inorganic additive, triethoxyvinylsilane was incorporated copolymerizing with methyl methacrylate. Thermally conductive nanographite particle was added. This MEPCM was then incorporated into high-density polyethylene (HDPE) to form a series of thermally conductive PCM microcapsules that approached sphere shapes with diameters less than 2 [Formula: see text]m. Thermal analysis showed that the thermal stability and heat resistance of the microcapsule were improved. The thermal conductivity of HDPE was increased by 39% to 0.6358 W/m[Formula: see text]K, and the surface resistivity was lowered to [Formula: see text]/sq after the addition of MEPCM. The temperature on the top of the composite tested was lower than pristine HDPE. This was close to the onset melting temperature of the MEPCM (38.5[Formula: see text]C), [Formula: see text] lower than pure HDPE. The reduction is a significant improvement in temperature regulation. This enables MEPCMs to store and release heat much more effectively, and can thus be applied to medical construction materials to meet the temperature requirements of COVID-19 patients.

High-density polyethylene/asphaltene composites: Thermal, mechanical and morphological properties

In this work, a series of high-density polyethylene (HDPE)/asphaltene composites were fabricated via the melt blending method. The composites were characterized, and the degradability, thermal, and mechanical stabilities of the products were analyzed. TGA results showed that HDPE/asphaltene composites had better thermal properties, e.g. higher degradation temperatures than asphaltene-free pristine HDPE. The high intermolecular interactions between the asphaltene and HDPE resulted in the degradation mechanism break, delaying the decomposition of composites and increasing their thermal stabilities. The results of DSC analysis indicated that the presence of asphaltene induces higher crystallinity and melting temperature in the composite matrix. According to the XRD results, the crystalline size was increased by increasing the asphaltene loading level due to the nucleating effect of asphaltene and the proper interactions developed between the asphaltene particles and HDPE chains. The proper dispersion of asphaltene in the composite matrix was confirmed by SEM images. The obtained results from the hardness analysis indicated higher mechanical stability for the composites, proportional to the content of the incorporated asphaltene to the composite. The results showed that asphaltene can be considered as an appropriate choice to improve the HDPE properties.

Measurement of high disorder state of high-density polyethylene (HDPE) on irradiation by gamma rays

High-density polyethylene (HDPE) is irradiated to moderate gamma doses 10, 20, 30, 40 and 50 kGy to carry out the study of change in its states. It is conducted by measuring resistivity and capacitance due to scissoring of chains; hence, immergence of various functional groups in the bulk of samples is irradiated to three doses 10, 30 and 40 kGy. Enhanced resistivity is found to follow sequential change as ρ10kGy > ρ30kGy > ρ40kGy > ρpris. Fractional change of resistivity, (ρ − ρ0)/ρ0, at small frequencies is correlated with fractional change of volume which is measured using the positron annihilation lifetime spectroscopy to estimate index of disorder, X. Disorder index, X, is the highest in the case of sample irradiated to 10 kGy gamma dose. Electrical capacitance, C, measured across the bulk of HDPE is found maximum in the case of 10 kGy dose, while samples irradiated to 30 and 40 kGy show capacitance smaller than the pristine HDPE indicating different dielectric behavior. Similarly, dissipation factor is found to be the smallest in the case of 10 kGy than 30 and 40 kGy doses up to several thousands of frequency in Hz. In all cases, electrical capacitance is found to be sustainable at high frequencies in the pristine as well as samples irradiated to the 10, 30 and 40 kGy doses.

Uncertainty in the life cycle greenhouse gas emissions and costs of HDPE pipe alternatives

High density polyethylene (HDPE) is a thermoplastic used in many engineering applications but one that imposes environmental burdens when produced and environmental costs at end-of-life (EOL). Replacing pristine HDPE with post-consumer recycled (PCR) HDPE or bio-based polymer (bio-HDPE) in long-lived goods could mitigate those impacts. We investigate cradle-to-gate and cradle-to-grave greenhouse gas (GHG) emissions and costs of four alternative resins, pristine HDPE, pristine/PCR HDPE, bio-HDPE and nanoclay-pristine/PCR HDPE composite, and their use in 100-year drainage pipe, respectively. We construct stochastic LCA models that combine service life prediction from experiments with parametric and scenario uncertainty modeling using Monte Carlo simulation and non-parametric bootstrapping. Results differ significantly on a resin versus pipe product basis owing to the functional unit requirement for meeting pipe service life, if governed by crystallinity and fracture energy, properties that call for greater quantities of material in recycled and nanoclay composite HDPE compared to pristine HDPE. The nanocomposite pipe has varying GHG emissions compared to all alternatives due to high mass requirement if assuming crystallinity and fracture energy govern failure, but this predicted mass may be reduced given that the nanoclay can prolong fracture time, which would reduce GHG emissions and pipe production cost. Despite a large GHG reduction relative to pristine HDPE, the bio-HDPE resin has the highest material production cost; however, considering life cycle costs, the incremental difference among all alternatives is small over a range of discount rates, rendering the bio-HDPE pipe a promising solution for addressing climate change in long-lived thermoplastic assets.

Effect of Natural Macromolecule Filler on the Properties of High‐Density Polyethylene (HDPE)

This study investigates the thermal and viscoelastic properties of High‐Density Polyethylene (HDPE) filled with the natural macromolecule, asphaltene, with different loading ratios. The thermal and viscoelastic properties of the composites are studied using DSC, WAXD and other mechanical techniques. The addition of 2.5 wt% asphaltenes presents a slightly higher degree of crystallinity compared to pristine HDPE. The addition of asphaltenes does not seem to alter significantly the mechanical tensile properties of the material, while only the composite with 2.5 wt% found to have improved tensile and yield strength. Specifically, the initial thermal degradation temperature increases by almost 40 °C as it came from TGA measurements where degradation of the composites shifted to higher values. In addition, the thermal degradation activation energy of HDPE and the composites is estimated assuming a first order kinetic model. The activation energy of neat HDPE is estimated to be 287 kJ mol−1, whereas that of the above‐mentioned composites significantly increases. This is another indication that the addition of asphaltenes into HDPE serve as a thermal barrier delaying the kinetics of the thermal degradation of the material. Inclusion of large amount of asphaltenes (i.e., 15%) results in a material presenting thermal degradation similar to pristine HDPE, with lower activation energy. Overall, from this study it comes that the optimum amount of asphaltenes that could be added to HDPE is around 2.5 wt% resulting in the best dispersion in the polymeric matrix, larger crystallite size, higher relative degree of crystallinity, somehow improves mechanical tensile properties and significantly enhances thermal stability.

Femtosecond laser-induced porosity on poly(ethylene) surfaces—A crystallographic and rheological study

In recent years, femtosecond (fs) laser irradiation of polymer surfaces has been shown to produce novel porous topologies that present a multi-scale roughness. In our study, grazing incidence x-ray diffractometry results showed the appearance of a monoclinic crystalline phase on fs laser machined high density polyethylene (HDPE) which is a deformation of the orthorhombic phase typically observed in pristine HDPE. This was accompanied by a local decrease in crystallinity. These findings confirmed that the induced porosity was a consequence of the rapid quenching of a superheated melt layer undergoing phase explosion. In addition, several poly(ethylene) samples with different average molecular weights were machined under the same conditions. Scanning electron micrography, along with small angle oscillatory shear tests, indicated that the final pore size decreases with increasing average molecular weight or increasing melt viscosity since these parameters act against bubble growth during phase explosion. In addition, through computed tomography, the internal structure of the porous layer was investigated. Through this technique, the average pore size and pore size distribution can be computed by chord length analysis. In conclusion, in this study, the mechanisms behind the formation of femtosecond laser-induced porous structures and the parameters that control their dimensions have been established.

Studies on preparation, Characterization and Biodegradation Behavior of HDPE Natural polymers Blends

Polyethylene (HDPE) is widely used in various applications due to its chemical, physical. and biological inertness but its durability presents a great challenge when it is released in the environment. To reduce its adverse effect on environment, currently various efforts are being made to modify its properties using naturally occurring biodegradable polymers but still these modifications found to be costly and required biodegradability in polyethylene is not yet achieved. Therefore, an attempt has been made to deveop biodegradable polyethylene blends using naturally occurring polymers. In this connection biodegradable high density polyethylene (HDPE) blends were prepared by thermally blending 2.0, 5.0 and 10.0 wt % amount of naturally occurring polymers such as; chitosan (CH), cellulose(CE), starch (ST), alginate (AL), pectin (PE), shellac (SH) and xanthan (XA). The observed biodegradabilility in HDPE blends might be due to the presence of hydrolysable linkages and stereo-favourable orientations of blended natural polymers. The added polymers have played a significant role in increasing the hydrophilicity in blended HDPE and acted as a bioassimilative nutrients for seeded microorganisms. The biodegradability of HDPE-polymer blends was evaluated in presence of various fungi such as; aspergillus niger, aspergillus terreus, fusarium solani, tricoderma hariziauum and tricoderrma viride. The disinfected films of pristine HDPE and polymer blened HDPE were inoculated with these fungi and the extend of biodegrdation was evaluated after a incubation period of three months at 28 ± 1˚C. The biodegradability of HDPE-polymer blends was compared with pristine HDPE by evaluating their molecular weights, and weight percent loss in samples incubated for three months along with selected fungus. The biodegrdation in pristine HDPE and its polymer blends was confirmed by comparing their FT-IR spectra and also by evaluating the variations in their mechanical and thermal properties. A significant variation in their morphologies in prsence of fungi has confirmed biodegradation in HDPE-polymer blends in comparison to pristine HDPE films. These studies have provided sufficient evidnces to confirm the role of added natural polymers in developing a biodegradable HDPE by blending various polymers such as chitosan (CH), cellulose(CE), starch (ST), alginate (AL), pectin (PE), shellac (SH) and xanthan (XA). Out of these polymers, the chitosan is found to be quite effective as it is acted better bioassimilative nutrient for microorganisms to cause biodegrdation of HPEF in comparison to other polymers.

Depth‐sensing indentation and nano‐dynamic mechanical properties of aluminum nitride nanoparticles reinforced high density poly‐ethylene nanocomposites

Inorganic aluminum nitride (AlN) nanoparticles offer numerous innovative applications in the field of electronic packaging due to its outstanding features; viz., high mechanical strength, stable crystal structure, excellent thermal conductivity, low coefficient of thermal expansion, low‐cost, and non‐toxicity. In this research, attempts have been made to investigate the effect of reinforcement of nano‐AlN particles in high density poly‐ethylene (HDPE) thermoplastic polymer on their nano‐mechanical properties using depth‐sensing indentation (DSI) technique. Polymer‐matrix nanocomposites composed of pure HDPE and 1–20 vol% nano‐AlN/HDPE composites are prepared via melt mixing followed by compression molding. Surface‐morphology and crystallinity of HDPE/nano‐AlN composites are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Nano‐scale hardness, modulus of elasticity, storage modulus, and loss tangent (tanδ) of HDPE/nano‐AlN composites have been evaluated using static and dynamic‐DSI. Both static and dynamic‐DSI results indicate that with increasing concentration of AlN nanoparticles in pristine HDPE, the nano‐mechanical properties display significant improvement. Results are discussed in relation to the surface‐morphology, crystallinity and interfacial adhesion between pure HDPE and nano‐AlN particles. A comparison between nano‐mechanical data extracted from static‐DSI and dynamic‐DSI techniques analysis is also attempted. POLYM. COMPOS., 40:240–254, 2019. © 2017 Society of Plastics Engineers

Effects of recycled HDPE and nanoclay on stress cracking of HDPE by correlatingJcwith slow crack growth

The effects of recycled high density polyethylene (HDPE) and nanoclay on the stress crack resistance (SCR) of pristine HDPE were evaluated using the Notched Constant Ligament Stress (NCLS) test. The test data were analyzed by both linear elastic fracture mechanics (LEFM) and elastic plastic fracture mechanics (EPFM). The LEFM approach uses the stress intensity factorKto define the two failure mechanisms: creep and slow crack growth (SCG). In contrast, using theJ‐integral in EPFM, which emphasizes the nonlinear elastic‐plastic strain field at the crack‐tip, revealed a short‐term failure stage prior to the creep failure. In this article, a power law correlation between the fracture toughnessJcand SCG was found under a plane‐strain condition. Increasing recycled HDPE content lowered the SCG resistance of pristine HDPE by decreasingJc. Adding nanoclay up to 6 wt% also decreasedJcwhile simultaneously, lowering the stress relaxation of nanocomposites, leading to longer SCG failure times at lowJvalues. POLYM. ENG. SCI., 58:1471–1478, 2018. © Published [2017]. This article is a U.S. Government work and is in the public domain in the USA.

Life Cycle Economic and Environmental Implications of Pristine High Density Polyethylene and Alternative Materials in Drainage Pipe Applications

A life cycle assessment (LCA) and cost analysis were conducted to compare the environmental and economic performance of nanocomposite polymers that use pristine and recycled high density polyethylene (HDPE) polymer with pristine, and pristine/recycled HDPE polymeric materials in drainage pipe. We evaluate three performance metrics; (a) non-renewable energy consumption (NRE); (b) greenhouse gas (GHG) emissions; and (c) production costs of the three pipe material alternatives. Original life cycle inventory data for the production of nanoclay from the mineral Montmorillonite were collected for this case study in the United States. Life cycle inventory models were developed for the cradle-to-gate production of drainage pipe used in highway construction that consider the sensitivity of model parameter inputs on the life cycle impact and cost results for the three material options. The GHG emissions for the nanoclay composite pipe are 54 % lower than those for pristine HDPE pipe, and 16 % lower than those for pristine/recycle HDPE pipe. With a slight difference in GHG emissions between the pristine/recycled and nanoclay composite, the production of nanoclay does not introduce a significant environmental burden to the pipe material. On average, the pristine HDPE pipe is 13 and 17 % higher in cost than the pristine/recycled HDPE and nanoclay composite pipes, respectively. Results of the LCA and cost analysis support using recycled HDPE as a substitute for pristine HDPE due to its low energy requirements and production costs. The uncertainty in GHG emissions of manufacturing pristine HDPE causes the largest variation of GHG emissions in nanoclay composite pipe (+3/−2 %). The production cost of the nanocomposite pipe is most influenced by the energy cost of PCR-HDPE (+25/−11 %). Our study suggests that a nanocomposite design that replaces part of the pristine HDPE with recycled HDPE and nanoclay reduces certain environmental risks and material cost of corrugated pipe.

Advanced isoconversional and master plot analyses on non-isothermal degradation kinetics of AlN (nano)-reinforced HDPE composites

The non-isothermal degradation kinetics of polymer nanocomposites composed of high-density polyethylene (HDPE) as polymer matrix and aluminum nitride (AlN) as nanofiller has been studied at variable concentration of (nano) AlN. Field emission scanning electron microscopy was used to examine the microstructure of the HDPE polymer and the dispersion of AlN (nano) particles in it. The non-isothermal degradation kinetics of AlN (nano)/HDPE composites has been investigated by thermogravimetric analysis (TG) at multiple heating rates between 5 and 20 °C min−1. This study confirmed that the thermal stability of the filled nanocomposites is improved as compared to pristine HDPE. Thermal transport barrier effect is also enhanced with the increase in concentration of AlN (nano) loading. Dependence of activation energy \( (E_{\text{a}} ) \) on reaction extent (α) of the degradation process is estimated in light of ‘model-free’ methods (viz. Flynn–Wall–Ozawa and Starink) and advanced isoconversional approach. Ozawa’s generalized time ‘θ’ combination of the differential master plots ‘\( f(\alpha ) = ({\text{d}}\alpha /{\text{d}}\theta ) \)’ and combined [integral (θ) and differential \( ({\text{d}}\alpha /{\text{d}}\theta ) \)] master plots ‘\( Z(\alpha ) = ({\text{d}}\alpha /{\text{d}}\theta )\theta \)’ have been employed to investigate the appropriate thermal degradation mechanism(s) for AlN (nano)/HDPE composites. The results on ‘FZmaster plots’ show that thermal decomposition of pristine HDPE follows two-dimensional diffusion mechanism, while AlN (nano)/HDPE composites undergo more complex degradation schematics, being dependent on the applied heating rates.

Fracture characterization of recycled high density polyethylene/nanoclay composites using the essential work of fracture concept

The effect of nanoclay on the plane-strain fracture behavior of pristine High density polyethylene (HDPE) and recycled HDPE blends was studied using the essential work of fracture (EWF) concept. The failure mode of EWF tested specimens was found to be associated with the specific non-EWF (βBwp,B). Adding 6-wt% of nanoclay to pristine HDPE and 2-wt% to recycle-blends greatly decreased the βBwp,B values and led to a transition from ductile to brittle failure mode. A fractographic study revealed that the difference in failure modes was caused by the changes in micro and macro morphologies, which could be related with the specific EWF (we,B). In the ductile failure, we,B is governed by the fibril size; adding nanoclay and recycled HDPE to pristine HDPE decreased the fibril size and subsequently lowered the we,B value. In the brittle failure, the we,B value was enhanced by creating a rough fracture surface. Adding nanoclay to pristine HDPE, a steadily decrease in we,B was measured until 4-wt% after which the change was insignificant. Conversely, nanoclay content more than 2-wt% in recycle-blends greatly decreased the we,B value. A transition map was constructed to illustrate the potential failure mode and the associated fracture morphology based on the tested material compositions. POLYM. ENG. SCI., 56:222–232, 2016. © 2015 Society of Plastics Engineers

Oxygen Permeability Coefficient of High Density Polyethylene/Cu Nanofibers Nanocomposites below Percolation

The main objective of this study was to relate the elastic modulus of a polymer nanocomposite to its permeability coefficient. The materials studied included high density polyethylene (HDPE) filled with copper nanofibers (Cu-nanofibers). Both of the experimental values of the elastic modulus and the gas permeability coefficient of the HDPE/Cu-nanofibers films were obtained from Grigoriadou et al. and Bikiaris & Triantafyllidis studies. In this study, the Halpin-Tsai model was modified and then used to fit the elastic modulus experimental data. It was found that the modified shape factor (ω′) of the Cu fibers as a function of the composite volume fraction is125exp(−41∅). Then, the model was used to predict the oxygen permeability coefficient of the HDPE/Cu-nanofibers films below the percolation point. It was found that the tensile modulus of the nanocomposites increased by 24% whereas the permeability to oxygen coefficients decreased by 65% compared to pristine HDPE. Also, the results from the models match the experimental data.