Low-density Polyethylene Composites Research Articles

Thermal and optical studies on the compositions of low-density polyethylene with highly refined mineral oil

An original optical method and differential scanning calorimetry were used to construct an experimental phase diagram for the binary composition low-density polyethylene – highly refined mineral oil. This diagram includes the polymer full amorphization curve and the oil solubility curve that describes the osmotic equilibrium between the swollen polymer and pure mineral oil. Within the domain between these curves, the system can be identified with a single-phase microheterogeneous gel with polymer crystallites as physical crosslinks. Two critical compositions containing 17 and 36 wt% of polyethylene were found. The first one corresponds to the least amount of polymer needed to form a capillary-porous body upon cooling down the pre-homogenized mixture. The second composition contains the fraction of oil above which the polymer full amorphization temperature is no longer decreased. Comparing with the optical method, calorimetry is much faster and able to catch weak mineral oil crystallinity, but less accurate and unable to supply any data for the solubility curve. An empirical analysis of the parameters describing the polymer full amorphization curve allowed us to conclude that mineral oil is less miscible with low-density polyethylene than decane and tridecane. The results obtained can be useful for the optimization of the properties of rubber-based vibration-damping compositions filled with polyethylene and mineral oil.

Highly filled biochar/ultra-high molecular weight polyethylene/linear low density polyethylene composites for high-performance electromagnetic interference shielding

Highly filled (up to 80 wt%) biochar/ultra-high molecular weight polyethylene (UHMWPE)/linear low density polyethylene (LLDPE) composites with excellent electromagnetic interference (EMI) shielding performance were successfully prepared using mass-producing extrusion and hot-compression methods. Carbonizing bamboo charcoal (BC1100) at 1100 °C resulted in a graphite-like structure leading to good electrical conductivity and a high specific surface area. The surface morphology and crystalline structure, as well as the thermal, mechanical, electrical, and EMI shielding properties of the composites, were characterized. The addition of BC1100 enhanced the Young's modulus, tensile strength, and hardness of the composites, but reduced the ductility. Most importantly, the BC1100 biochar remarkably improved the electrical conductivity and EMI shielding effectiveness (SE) of the composites. In particular, the composite with 80 wt% BC1100 exhibited a conductivity of 107.6 S/m, one of the highest values among reported conductive polymer composites fabricated by melt processing, and a very high EMI SE of 48.7 dB (99.998% attenuation) at 1500 MHz. The specific EMI SE of the 80 wt% BC1100 composite was 39.0 dB cm3/g, nearly four times higher than that of copper (10 dB cm3/g). These results suggest a new, scalable way of effectively utilizing renewable biochar in conductive polymer composites, especially for EMI shielding applications.

The performance of mengkuang leaf fiber reinforced low density polyethylene composites

The performance of mengkuang leaf fiber (MLF) reinforced low density polyethylene (LDPE) composites with different fiber volume and different mesh sizes were studied. The fibre weight percentage used in the research were 10%, 20%, and 30% and for different fiber size were <0.5 mm, 0.5-1 mm, and 1-2 mm. The extrusion and hot compression molding were used to fabricate the specimen testing. The mechanical testing performed were impact and flexural test which follows the ASTM standards D790-10 and Izod D256. It was observed that by increasing the fiber volume and fiber size, the flexural strength and the flexural modulus were increased. However the impact strength shows different results for fiber length and fibre content where the impact strength increases with fibre length but decreases with the increase of fiber content. It can be concluded that the 30% fibre content is the optimum fibre loading for the MLFLDPE composite with the flexural strength of 12.31 MPa, flexural modulus of 378.88 MPa and impact strength of 589.86 J/m whereby the 1.0-2.0 mm fibre length is the best fibre size for the MLF-LDPE composite with the flexural strength of 12.86 MPa, flexural modulus of 267.76 MPa and impact strength of 1511.57 J/m. In future studies fibres should undergo surface modification to increase the available surface area for reaction to increase the strength of the composite by better mechanical interlocking.

Exploration of Mechanical and Thermal Properties of CTAB-Modified MoS2/LLDPE Composites Prepared by Melt Mixing

Molybdenum disulfide (MoS2) was functionalized by cetyltrimethylammonium bromide (CTAB) through a one-pot hydrothermal technique, and subsequently, linear low-density polyethylene (LLDPE) composites were prepared. The attachment of alkyl chains of CTAB onto the MoS2 surface was confirmed by Fourier transform infrared spectroscopy (FTIR). The enhanced mechanical properties of the composites relative to neat LLDPE revealed good compatibility between MoS2 and LLDPE. The improvement in thermomechanical properties further substantiated good interaction between MoS2 and LLDPE. The thermal stability of the prepared composites showed a small decrease in onset degradation temperature. Nevertheless, the char residue formation was found to be promoted in the presence of MoS2.

Comparing the Effect of Fillers on the Mechanical Properties of Recycled Low Density Polyethylene Composites Under Non-Weathered and Weathered Conditions

This work compared the effect of fillers on the mechanical properties of recycled low-density polyethylene composites under non-weathered and weathered conditions. Pure water sachet wastes, glass wastes were sourced from dump-site at Obafemi Awolowo University, Ile-Ife, Nigeria, while the talc was sourced from Lagere, Ile-Ife, Nigeria. Recycling of plastic bags (low-density polyethylene) and the preparation of recycled low-density polyethylene (RLDPE)/glass, RLDPE/ talc and RLDPE/glass/talc composites were carried out using a furnace at compositions of 0 to 40% in steps of 10% by weight. The mixtures were then poured into hand-laid mould for tensile, impact and hardness tests. The samples were divided into two groups; one group was subjected to natural weathering conditions. The results of mechanical tests carried out were subjected to a paired t-test. The study concluded that there was no significant difference between the non-weathered and weathered samples. This implies that both talc and glass were able to reinforce recycled low density polyethylene (RLDPE) under both conditions and can help resist degradation.

Comparing the Effect of Fillers on the Mechanical Properties of Recycled Low Density Polyethylene Composites Under Non-Weathered and Weathered Conditions

This work compared the effect of fillers on the mechanical properties of recycled low-density polyethylene composites under non-weathered and weathered conditions. Pure water sachet wastes, glass wastes were sourced from dump-site at Obafemi Awolowo University, Ile-Ife, Nigeria, while the talc was sourced from Lagere, Ile-Ife, Nigeria. Recycling of plastic bags (low-density polyethylene) and the preparation of recycled low-density polyethylene (RLDPE)/glass, RLDPE/ talc and RLDPE/glass/talc composites were carried out using a furnace at compositions of 0 to 40% in steps of 10% by weight. The mixtures were then poured into hand-laid mould for tensile, impact and hardness tests. The samples were divided into two groups; one group was subjected to natural weathering conditions. The results of mechanical tests carried out were subjected to a paired t-test. The study concluded that there was no significant difference between the non-weathered and weathered samples. This implies that both talc and glass were able to reinforce recycled low density polyethylene (RLDPE) under both conditions and can help resist degradation.

LDPE-나노 ZnO 복합필름의 기능성 및 재질안정성 평가

In this work, nano ZnO was introduced into low density poly ethylene (LDPE) composites films with various contents (0, 0.5, 1.0, 3.0 and 5.0 wt%) by melt-extrusion. Their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. XRD patterns and FTIR peaks intensity were increased in proportion to the ZnO contents. SEM images showed well dispersed nano ZnO in LDPE composite films. Antimicrobial functionality of LDPE-nano ZnO composite films was also studied and the presence of nano ZnO resulted in significant improvement of antimicrobial functionality compared to the pure LDPE film. To evaluate influence of nano ZnO on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano ZnO composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-Vis spectroscopy. As a result, except optical and mechanical properties of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano ZnO and tensile strength was also improved at 0.5wt% ZnO content.

Antifertility effectiveness of a novel copper-containing intrauterine device material and its influence on the endometrial environment in rats

This study was designed to investigate the antifertility effectiveness of a novel copper-containing intrauterine device material containing a composite of micro-copper (Cu), low-density polyethylene (LDPE), and methyl vinyl silicone rubber (MVQ) and its effects on the endometrial environment in rats. The contraceptive effectiveness was examined 12 days after pregnancy. The pathological changes; factors associated with bleeding, pain, and inflammation in the endometrium; and the surface condition of the implants were investigated after insertion for 90 days. Furthermore, the release rate of copper ions in simulated uterine solution (SUS) was investigated for 270 days. The contraceptive effectiveness was 100% in both the bulk Cu and micro-Cu/LDPE/MVQ groups, and that in the LDPE/MVQ group was 30%. On day 90 after insertion, histopathological observation and the ultrastructural changes in the endometrium showed that the damage caused by bulk Cu was much more severe than that caused by the Cu/LDPE/MVQ microcomposite and that the surface of the latter was much smoother than that of the former. Furthermore, compared with the sham-operated control group, the concentrations of tissue plasminogen activator and prostaglandin E2 were significantly increased 90 days after insertion in all of the experimental groups except for the LDPE/MVQ group (P < 0.05), and the parameters in the Cu/LDPE/MVQ group were significantly lower than those in the Cu group (P < 0.05). In addition, the expression levels of matrix metalloproteinase 9, metalloproteinase 1 tissue inhibitor, plasminogen inhibitor 1, CD34, vascular endothelial growth factor, substance P, and substance P receptor in the endometrium in all of the experimental groups were significantly lower than those in the Cu group 90 days after insertion (P < 0.05). The results of this study indicate that micro-Cu/LDPE/MVQ exhibits satisfactory contraceptive efficacy and causes fewer side effects than Cu.

Influence of cellulose nanocrystal on strength and properties of low density polyethylene and thermoplastic starch composites

Starch is a renewable and readily available material. Adding starch to low density polyethylene (LDPE) is a sustainable way to reduce the dependency on petroleum based polymers. In this study we investigated the strength and barrier performance of low density polyethylene (LDPE)/thermoplastic starch (TPS) nanocomposites reinforced with cellulose nanocrystals (CNC). In order to assure well dispersion of CNC in nanocomposites, initially CNC was added to TPS and then reinforced TPS were blended in extruder with LDPE at various loading levels. Mechanical properties, glass transition temperature (Tg) and melting point (Tm), moisture absorption and barrier properties of the nanocomposites were studied. All mechanical properties, including tensile strength, modulus of elasticity (MOE) and hardness were considerably improved by CNC. Tg and Tm of the nanocomposites were higher in comparison to CNC free nanocomposites. Water absorption showed a significant decrease as a result of addition of CNC to LDPE/TPS blends. The values of water vapor permeability coefficient (WVP) and water vapor transmission rate (WVTR) were reduced by adding CNC, meaning that CNC considerably improved barrier properties of LDPE/TPS composites. Adding 1% CNC to LDPE/TPS blends was the optimal level of CNC loading leading to the highest improvement in the strength and barrier performance of LDPE/TPS blends and satisfied very well required standard tensile strength for extruded and molded LDPE.

Accelerated aging of pine wood waste/recycled LDPE composite

The production of composites from recycled thermoplastic polymers and natural fibers has been an interesting alternative to generate polymeric materials of low cost, with sufficient properties for application and environmentally adequate. The aim of the present study was to evaluate the effects of the accelerated photochemical aging on properties of a composite produced from recycled low-density polyethylene (LDPE) with pine wood waste (PWW) in the presence of coupling agent. The oxidation, performance of mechanical properties and surface changes of the LDPE and LDPE/PWW composite were monitored at different times of aging. It was observed that LDPE/PWW composite presented a higher resistance to the accelerated photochemical aging than unfilled LDPE, mainly due to the better performance of the mechanical properties of elongation at break and tensile strength, showing that the presence of natural fibers from PWW lead to the stabilization of the polymeric matrix of LDPE.

Quasi in-situ observation of the elastic properties changes of the graphene–low-density polyethylene composites

In this paper we present the results of electromechanical studies of graphene–low-density polyethylene (LDPE) composites. Two types of graphene were transferred onto LDPE using PMMA support: graphene grown by physical vapor deposition on liquid metallic matrix (so called high strength metallurgical graphene, HSMG) and commercial chemical vapor deposited (CVD) graphene. Raman spectroscopy was used for preliminary characterization of graphene, whereas Kelvin probe force microscopy (KPFM) combined with electrical measurement setup and symmetrical stretching stage was used for observations of the electrical properties changes of elongated graphene. Maximum elongation of graphene–LDPE composites were 10%. Resistance of the HSMG graphene was changing from 130kΩ up to 900kΩ for HSMG graphene and from 100kΩ up to 300kΩ for CVD graphene. Observed resistance changes were compared with contact potential difference recorded by KPFM. KPFM showed that resistance changes can be attributed rather to the structural discontinuities for the CVD graphene sample. In case of the HSMG graphene sample such behavior was not observed.

Effects of microcrystalline cellulose on the mechanical properties of low-density polyethylene composites

This work was intended to provide an understanding of the effect of microcrystalline cellulose (MCC) on the mechanical properties of low-density polyethylene (LDPE). The impact resistance and the tensile properties of low-density LDPE/MCC composites were investigated. The weight fraction of MCC was varied at (0, 0.5, 1, 2.5, 5, 10, 20, and 30 wt%). The obtained blends were then used to prepare the required tensile and impact testing samples by hot compression molding technique. It has been found that MCC has a strong influence on the mechanical properties of LDPE. At a low MCC weight fraction, there was a little improvement in the ultimate strength, fracture stress, and elongation at break, but at a high MCC weight fraction, the tensile properties were deteriorated and reduced significantly. The addition of 1 wt% MCC to LDPE enhanced the mentioned properties by 10, 25, and 6%, respectively. While at 30 wt% MCC, these properties were lowered by 36, 25, and 96%. The elastic modulus of LDPE composites was improved on all MCC weight fractions used in the study, at 20 wt% MCC, an increase in the elastic modulus by 12 folds was achieved. On the other hand and compared with the impact strength of pure LDPE, the addition of MCC particles enhanced the impact strength, the highest value obtained was for LDPE composites filled with 10 wt% MCC where the impact strength enhanced by two folds.

A new strategy to produce low-density polyethylene (LDPE)-based composites simultaneously with high flame retardancy and high mechanical properties

In this study, a new strategy which blends low-density polyethylene (LDPE), magnesium hydroxide (MH) and lauryl acrylate by electron-beam radiation for production of LDPE-based composites with high performance was proposed. It was found that, MH played main roles in flame retardancy but reduced processing flow and mechanical properties of the composites. Meanwhile, melt flow rate (MFR) increased while viscosity of the composites decreased with lauryl acrylate content increased, facilitating LDPE composites processing. Electron beam radiation could prompt crosslinking of lauryl acrylate, which significantly enhanced the mechanical properties of LDPE composites. Meanwhile, lauryl acrylate addition only slightly decreased the flame retardancy, suggesting that LDPE composites could remain high flame retardancy even when lauryl acrylate content was high. The study highly demonstrated the feasibility to produce LDPE-based composites simultaneously with high flame retardancy and high mechanical properties by the blending strategy provided in this study.

ANALYSIS OF THE ELECTROPHYSICAL AND PHOTOELECTRIC PROPERTIES OF NANOCOMPOSITE POLYMERS BY THE MODIFIED KELVIN PROBE

At present for analysis of the homogeneity of materials properties are becoming widely used various modifications of a scanning Kelvin probe. These methods allow mapping the spatial distribution of the electrostatic potential. Analysis of the electropotential profile is not sufficient to describe any specific physical parameters of the polymer nanocomposites. Therefore, we use an external energy impact, such as light. Purpose of paper is the modification of the Kelvin scanning probe and the conduct of experimental studies of the spatial distribution and response of the electrostatic potential of the actual polymer nanocomposites to the optical probing.Carried out the investigations on experimental Low density polyethylene composites. Carbon nanomaterials and nanoparticles of silicon dioxide or aluminum as fillers are used. As a result, maps of the spatial distribution of the electrostatic potential relative values and the surface photovoltage. Statistical analysis of the electrophysical and photoelectric properties homogeneity, depending on the component composition of the composites carried out. In addition, with reference to matrix polymers, the Kelvin scanning probe, in combination with the optical probing, made it possible to detect a piezoelectric effect. The latter, can used as a basis for the development of new methods for studying the mechanical properties of matrix polymers.

Effect of Aluminum Oxide Nanoparticles on Nanomechanical and Viscoelastic Properties of Low Density Polyethylene Composites

Polymer nanocomposites based on low-density polyethylene (LDPE), containing 1.5, 3, and 6 wt.% of aluminum oxide (Al2O3), are fabricated by melt-mixing and injection-molding. The effective ratio of nanoparticles that maximize the mechanical behavior of LDPE composites was estimated using different techniques. The nanomechanical (nanohardness, nanomodulus) properties were studied using the nanoindentation technique. An Instron testing machine and a dynamic mechanical analyzer were utilized to study the flexural and viscoelastic behaviour (storage, Loss modulus, creep-relaxation rate and creep compliance) of the nanocomposites. Generally, the nanoindentation results indicated that the hardness and modulus of LDPE composite improved due to the addition of nanoparticles. In addition, the viscoelastic results indicated that the addition of nanoparticles improves the shear modulus, creep resistance and relaxation behaviour of the tested composite. On the other hand, the creep compliance decreased due to addition of nanoparticles. The results of tests that performed in this study indicated that the maximum improvements in the LDPE matrix mechanical behaviour were observed when composited with nanoparticle of 1.5 wt.%. A slight reduction in these properties was observed when the loading of nanoparticles increased more than that ratio but still superior to those of the pure LDPE matrix.

Polyethylene green composites modified with post agricultural waste filler: thermo-mechanical and damping properties

The aim of the study was to determine thermo-mechanical properties and applicability of sunflower husk waste as a filler for ultra low density polyethylene composites. The post agricultural waste filler was milled and chemically treated with (3-aminopropyl)triethoxysilane (3-APS). The amount of filler used was 5, 10 and 20 wt%. The mechanical and thermal properties of the composites containing unmodified and modified natural fillers were determined in the course of static tensile test, rebound resilience by Schob method, and dynamic mechanic thermal analysis. The influence of filler loading and chemical modification of the filler on the morphology of natural composites was evaluated by SEM analysis.

Evaluating weathering of food packaging polyethylene-nano-clay composites: Release of nanoparticles and their impacts

Nano-fillers are increasingly incorporated into polymeric materials to improve the mechanical, barrier or other matrix properties of nanocomposites used for consumer and industrial applications. However, over the life cycle, these nanocomposites could degrade due to exposure to environmental conditions, resulting in the release of embedded nanomaterials from the polymer matrix into the environment. This paper presents a rigorous study on the degradation and the release of nanomaterials from food packaging composites. Films of nano-clay-loaded low-density polyethylene (LDPE) composite for food packaging applications were prepared with the spherilene technology and exposed to accelerated weathering of ultraviolet (UV) irradiation or low concentration of ozone at 40°C. The changes in the structural, surface morphology, chemical and physical properties of the films during accelerated weathering were investigated. Qualitative and quantitative changes in properties of pristine and aged materials and the release of nano-clay proceeded slowly until 130h irradiation and then accelerated afterward resulting complete degradation. Although nano-clay increased the stability of LDPE and improved thermal and barrier properties, they accelerated the UV oxidation of LDPE. With increasing exposure to UV, the surface roughness, chemiluminescence index, and carbonyl index of the samples increased while decreasing the intensity of the wide-angle X-ray diffraction pattern. Nano-clay particles with sizes ranging from 2 to 8nm were released from UV and ozone weathered composite. The concentrations of released nanoparticles increased with an increase in aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability were also performed on the released nano-clay and clay polymer. The released nano-clays basically did not show toxicity. Our combined results demonstrated the degradation properties of nano-clay particle-embedded LDPE composites toxicity of released nano-clay particles to A594 adenocarcinomic human alveolar basal epithelial cells was observed, which will help with future risk based-formulations of exposure.

LLDPE and Natural Fiber Composites Characterization using AFM

The research is focused on the characterization of matrix and filler adhesion, interfacial modifier effects on matrix crystalline formation with filler, depending on the filler modification strategies. Natural fiber filled linear low density polyethylene (LLDPE) composites made from surface modified hemp fiber and waste, zinc oxide, using matrix modifier were prepared by two rolls mill and characterize by Atomic Force Microscope (AFM).

Improved ampacity of buried HVDC cable with high thermal conductivity LDPE/BN insulation

Polyethylene is widely used as insulation in power cables with its excellent electrical properties except its low thermal conductivity. However, insulation-related thermal problems pose a limitation on the ampacity of HVDC cables. Improving the thermal conductivity of insulation may contribute to heat dissipation of cable system and enhance its ampacity. In this work, in order to investigate the effects of improved thermal conductivity of insulation on temperature field and ampacity in a single buried HVDC cable, a numerical simulation model is established by finite element method (FEM) and the cable ampacity is calculated by a modified iteration method. Meanwhile, a range of low-density polyethylene (LDPE) based composites filled with hybrid boron nitride (BN) particles at different loadings are prepared to get reasonable model parameters. Thermal conductivity of various samples is measured and the obtained result shows that the thermal conductivity of BN filled LDPE composite is improved greatly. The simulation results show that the cable core temperature is reduced obviously and the temperature field distribution in insulation becomes more uniform with increasing the thermal conductivity. Besides, the temperature difference between inside and outside of insulation layer shows a decreasing trend at a given load current. Namely, the cable can transmit higher current under the maximum operating temperature due to the improvement of thermal conductivity. All the conclusions imply that the improved thermal conductivity of insulation is of great benefit to the improvement of HVDC cable ampacity.

Practical Aspects of Sustainability: A Discussion of product design with recyclable materials

Sustainable development is one that can meet the needs of the present generation without compromising the resources needed by future generations (1). The industry represents a great agent in the pursuit of sustainable development, yet only 30% of these companies seek opportunities to invest in sustainability (2). The search for sustainable development associated to the increase in technological power has stimulated the use of raw materials that add greater value to products and that meet environmental, social and economic specificities. In Brazil 352 thousand tons of flexible packaging were consumed in 2014, including long-life packaging (3), which can be used as technological alternatives, mainly for the use of paper, polyethylene and aluminum compounds. The objective of this work is to evaluate a sustainable product design from the discussion of the design of a stool produced with low density polyethylene and aluminum composite, resulting from the recycling process of the long life packaging (Tetra Pak). The project adopts two methodological approaches: the first theoretical, through an exploratory bibliographical research, that works the fundamentals and applications of sustainability, product design planning and production processes, with a sustainable material resources and recycling. The second path works the practice, through a study of the modeling in SolidWorks model of a stool for future prototyping.