Low-density Polyethylene Composites Research Articles

Auto-hybridization of Polyethylene/Maple Composites: The Effect of Fiber Size and Concentration

This work investigated the effect of maple fiber size and content on the auto-hybridization of linear low density polyethylene (LLDPE) composites. The samples were compounded by twin-screw extrusion and molded by compression molding. Different fiber loadings (5 to 20% wt.), fiber sizes (0-425 microns) and size ratios (30/70, 50/50, 70/30 of short, medium, and long fibers) were used to prepare the auto-hybrid composites with 3% of coupling agent (maleated polyethylene). Micrographs and impact strength results showed that the fracture in auto-hybrid composites is mostly dependent on the longer fibers. At 10% wt. the optimum ratio was 30/70 of shorter/longer fibers, which improved tensile strength (20%), tensile modulus (20%), and impact strength (13%) compared with composites with a single fiber size. But at 20% wt., tensile modulus increased by 30% and torsion modulus by 40% above the rule of hybrid mixtures (RoHM) at a 70/30 ratio of shorter/longer fibers.

The effect of environmental factors on biodegradable polylactide-based materials

This study focuses on the effect of environmental factors on composites of polylactide and lowdensity polyethylene with oxidized polyethylene added as an analogue of recyclable materials. Moisture and ultraviolet light were found to significantly affect the polylactide–polyethylene composites at the first stage. The presence of oxidized polyethylene in the composite containing 30 wt % polylactide has a minor effect on water uptake by the composites. The average weight loss in the samples incubated in soil for 360 days is 5–10%.

Development of Novel Biodegradable Polysaccharide-Based Composites and Investigation of Their Structure and Properties

Biodegradable composites of polysaccharides (cellulose, starch, and ethylcellulose) with low-density polyethylene (LDPE) and poly(ethylene oxide) (PEO) as well as composites of two polysaccharides (cellulose–chitin, cellulose–chitosan, starch–chitin, starch–chitosan) with LDPE were produced in a rotor disperser under conditions of shear deformation. Using various physicochemical (mechanical tests, FTIR-spectroscopy) and structural (SEM) methods, the properties and structure of obtained composites were studied. The investigation of the change in the fractional composition depending on the nature of third component has shown that the introduction of PEO leads to appearance of fraction with coarse particles, while the addition of second polysaccharides results in production of finely-dispersed powders. The comparison of the mechanical properties of binary and ternary composites has showed that the presence of third component leads to change in their characteristics. The investigation of sample biodegradability by three independent methods showed that the introduction of third component leads to a significant increase in the biodegradation as compared to the binary polysaccharide–LDPE composites studied earlier.

Antibacterial and Structural Properties and Printability of Starch/Clay/Polyethylene Composite Films

A composite of thermoplastic starch (TPS), low-density polyethylene (LDPE) and citric acid-modified montmorillonite (CMMT) was prepared in a twin screw extruder for packaging film application. Starch was first converted to the thermoplastic state by using sorbitol and water. Composite films were produced on a chill roll system and then were modified for printability by grafting of acrylonitrile onto the starch backbone. Antimicrobial property and printability of the films were studied from which the sample with the highest antimicrobial property and the best printability was selected. This optimal sample was then characterized by Fourier transform infrared, thermal gravimetric analysis, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The composite film showed a matrix/dispersed morphology in which LDPE formed a continuous phase and TPS/CMMT nanocomposite particles appeared as dispersed phase. Biodegradability, water absorption, oxygen permeability, tensile strength and transparency of optimal film were also studied. The results indicated very good properties of the produced composite film for packaging application.

Fabrication and Dielectric, Mechanical, and Thermal Properties of Low-Density Polyethylene (LDPE) Composites Containing Surface-Passivated Silicon (Si/SiO2 Core/Shell Nanoparticles)

ABSTRACTComposites of low-density polyethylene containing between 1 and 5 wt% of Si/SiO2 core/shell nanoparticles were prepared by ball milling method. The thermal, mechanical, and dielectric properties of composites were investigated in terms of composition, frequency, and temperature. The results showed that the dielectric permittivity increased smoothly with a rise of Si/SiO2 particle. The dielectric permittivity and loss decreases and increases with temperature, respectively. The resistance of composites to erosion due to partial discharge was significantly improved by adding nanoparticles. The results have demonstrated that ball milling was an effective method for producing relatively homogeneous nanocomposite up to 4 wt% Si/SiO2.

Preparation and characterization of glass fiber–reinforced polyethylene terephthalate/linear low density polyethylene (GF‐PET/LLDPE) composites

Polyethylene terephthalate (PET) was melt blended with linear low density polyethylene (LLDPE) and subsequently compounded with glass fibers (GF) as reinforcements at percentages ranging from 15 to 45 wt% of LLDPE and 5 to 30 wt% of GF. Thermal, morphological, and mechanical properties of the prepared composites were investigated. It was found that compounding PET/LLDPE blends with GF would be beneficial in producing composites that are thermally stable with good mechanical properties. For example, the impact strength of the composites containing 85/15 wt% (PET/LLDPE) at relatively high loading of GF, ie, from 15 to 30 wt%, was higher than that of the GF‐reinforced neat PET. When increasing the percentage of LLDPE in the composites, the impact strength increased with increasing GF content, and this was also better than that of GF‐reinforced PET whose impact strength drastically decreased upon increasing the GF%. The improvement in mechanical properties of the composite, we suggest, should be correlated with the morphologies of the composites where the visualized interface adhesion tended to be better at higher loadings of both LLDPE and GF.

Sandwiched structure effect on space charge characteristics of alumina/polyethylene nanocomposites

In the recent decades, the phenomena of space charge accumulation in the high voltage direct current (HVDC) insulation have been attracted more attention. In this paper, the novel sandwich-structured low-density polyethylene (LDPE) nanocomposites filled with nano-sized Al 2 O 3 particles were prepared by layer-by-layer hot pressing method. For comparison, the homo-dispersed LDPE composites with nano-Al 2 O 3 were also prepared. Morphology, breakdown strength, space charge distribution and electrical conductivity of the specimens were investigated. Morphologies of the composites were characterized by scanning electron microscopy (SEM), and their space charge profiles were measured by pulsed electro-acoustic (PEA) method. SEM images showed that there are no obvious interfaces between the adjacent layers. The breakdown strength of the sandwich-structured LDPE nanocomposites is higher than that of the homo-dispersed ones. Besides, the charge profiles indicated that space charge suppression of the sandwich-structured LDPE composites was better than that of homo-dispersed ones. Under the electrical field of 50 kV/mm at 70 °C, the conductivity of homo-dispersed nanocomposite almost approaches to 1.0 ×10−11 S/m, which is almost four-fold over that of 1%N/LDPE/1%N (i.e, 2.5 ×10−12 S/m). It was concluded that the excellent electrical insulating properties of the sandwich-structured nanocomposites were attributed to the traps existing on the interfaces, which could effectively inhibit the charge injection.

Study of using aluminum hypophosphite as a flame retardant for low‐density polyethylene

AbstractAluminum hypophosphite (AHP) was first used to improve the flame retardance of low‐density polyethylene (LDPE). The flame‐retardant properties of LDPE composites were investigated by the limiting oxygen index, vertical burning test (UL‐94), microscale combustion calorimetry, and cone calorimeter tests. The results showed that the incorporation of AHP could improve the flame retardancy of LDPE dramatically, the limiting oxygen index of LDPE containing 50 phr AHP reached 27.5%, and the UL‐94 could pass V‐0 rating. The cone calorimeter test results indicated that PP/AHP composite exhibited superior performance, and the heat release rate and the total heat release of composites were significantly reduced. In addition, the strength of the char was improved with the load of AHP increased. The structure of the char was researched by Fourier transform infrared spectrometry (FTIR) and scanning electron microscope‐energy dispersive spectrometer, and the results revealed that AHP promoted the formation of compact char layer. The TG‐FTIR analyses proved that AHP could react with LDPE to reduce the production of olefin in gas phase. Moreover, the structure of P–O–C was found, and the effective mechanism of AHP in LDPE composites was also hypothesized in this work.

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

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

Preparation and characterization of some polymer/pharmaceutical-based composites. Part. II ivermectin

Composites of low-density polyethylene, LDPE, poly(ethylene-co-vinyl acetate), EVA, and LDPE/EVA 70/30 and 50/50% (weight) blend plus ivermectin (1 and 3% weight) were prepared through the melt-blending process. Ivermectin resulted homogenously dispersed in polymer matrices. The polymer/ivermectin composites showed thermal behavior similar to those of the original polymer matrices. Ivermectin release from the composites, was examined in vitro for various lengths of time and their release percentages were determined by photometric UV spectroscopy and their release percentages reported. The prolonged release of the drug indicates that ivermectin-loaded film offer potential application to control inflammatory events and also antiparasitic properties.

Electrical and rheological properties of carbon black and carbon fiber filled low-density polyethylene/ethylene vinyl acetate composites

Abstract In this study conductive composites of low-density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) filled with carbon black (CB) and carbon fiber (CF) were prepared by melt-mixing method. The morphological, rheological, and electrical properties of CB filled composites were compared with CF filled composites by digital multimeter, scanning electron microscope, rotational rheometer, etc. The composites filled with different fillers have same percolation threshold but the EVA concentration has different effect on the two systems. For CB filled composites the increase in EVA concentration decreased resistivity first and reached lowest point when the LDPE:EVA ratio was 70:30; then the resistivity increased, but for CF filled composites the resistivity continued to decrease. The differences were caused by the diverse morphological and filler distribution of two different composite systems. The rheological behaviors of two types of composites also had significant difference; the value of complex viscosity of CB filled composites was about two orders of magnitude more than CF filled composites in low frequency region. It was because CB particles was nano-scale and had large surface area, so it had great influence on the value of complex viscosity of composites.

Surface free energy and mechanical performance of LDPE/CBF composites containing toxic-metal free filler

Heavy-metal contamination in children's toys is a widespread problem, and the international community has issued a series of safety standards to restrict and control the use of toxic metals in toys. In this work, a colored filler (CBF) was prepared using pearl oyster shell (POS) as the green raw material and azo dye as the colorant. Its surface properties were subsequently studied in comparison to those of POS powder using the inverse gas chromatography method. The dispersion surface free energy profiles for both CBF and POS showed that this component contributed the major part (>70%) to the total surface free energy. The CBF possessed lower polar surface free energy and was relatively more hydrophobic. It also showed a lower thermodynamic work of cohesion, allowing its better dispersion in a low density polyethylene (LDPE) matrix. Mechanical performance studies showed that adding CBF could significantly increase the tensile strength, elastic modulus, flexural strength and flexural modulus of LDPE composites. The absence of toxic metals coupled with excellent mechanical performance makes the CBF an ideal candidate as a filler for children's toys fabrication.

Enhanced photocatalytic oxidation and biodegradation of polyethylene films with PMMA grafted TiO2 as pro‐oxidant additives for plastic mulch application

In this work, a series of novel poly (methyl methacrylate) (PMMA) grafted TiO2 (TiO2‐g‐PMMA) nanoparticles were prepared and used as pro‐oxidant additives for production of biodegradable low density polyethylene composites (TiO2‐g‐PMMA/LDPE). The effect of these additives with various grafting percentages of PMMA on the photocatalytic oxidation of TiO2‐g‐PMMA/LDPE under ultraviolet light irradiation and the biodegradation under fungal strains were studied. The changes of weight loss, carbonyl index, molecular weight, mechanical properties of TiO2‐g‐PMMA/LDPE were monitored with time and compared with those of pure polyethylene and polyethylene with as‐received TiO2 as pro‐oxidant additives. It is found the grafting of PMMA on the surface of TiO2 nanoparticle improved the dispersion and compatibility of the additives in the matrix, resulting in enhanced photocatalytic oxidation and biodegradation of polyethylene composites. This study would provide a new perspective and strategy to develop controllable and biodegradable polymeric materials for plastic mulch application. POLYM. COMPOS., 39:3409–3417, 2018. © 2017 Society of Plastics Engineers

Low density polyethylene composites reinforced with Australian King Palm fibers: mechanical and thermal properties

The aim of this work is to obtain and evaluate the mechanical and thermal properties of low Density Polyethylene (LDPE) composites reinforced with fibers from Australian King Palm fibers. Raw fibers were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy. The chemical composition of the fibers was also evaluated. After characterizing the fibers were mixed into the LDPE, in proportions of 5, 10, 15 and 20% (wt/wt) using a thermokinetic mixer model MH-50H. Furthermore tensile, flexural and impact specimens were prepared for evaluation of mechanical properties. The composites were analyzed through SEM micrographs of fractured surfaces and thermal analysis. The results indicate that the reinforcement decreases the thermal stability of the composites, but caused an increase the mechanical properties of the composites. The composites reinforced with of raw fibers 20% (wt/wt) showed significant increase in the tensile strength, flexural and impact.

Polyethylene/polyhedral oligomeric silsesquioxanes composites: Dielectric, thermal and rheological properties

Composites of low-density polyethylene (LDPE) containing 1 wt% and 5 wt% polyhedral oligomeric silsesquioxanes (POSS) of different substituents (methyl, isobutyl, isooctyl) were obtained by extrusion. The composites' potential application in high-voltage (HV) power cable insulation was investigated by broadband dielectric spectroscopy, progressive-stress breakdown tests, and surface partial discharge tests. Thermal conductivity and viscoelastic characteristic were also examined as they play an important role in both material property and manufacture. Additional measurements using scanning electron microscopy and differential scanning calorimetry were carried out to obtain information for possible performance explanations. The results showed that POSS could enhance the erosion resistance and slightly improve the thermal conductivity of LDPE without compromising its dielectric breakdown strength or unfavorably increasing its dielectric permittivity or viscosity.

Impact of Cotton Stalk Biomass Weathering on the Mechanical and Thermal Properties of Cotton Stalk Flour/Linear Low Density Polyethylene (LLDPE) Composites

Impact of Cotton Stalk Biomass Weathering on the Mechanical and Thermal Properties of Cotton Stalk Flour/Linear Low Density Polyethylene (LLDPE) Composites

Organic Solvents Transport Through Alkali-Treated Agro-waste Microfibre Incorporated with Low Density Polyethylene Composites

We report the transport behaviour of low density polyethylene composites containing both untreated and alkali-treated agro-waste microfibre in three aromatic organic solvents (benzene, toluene, and xylene) at 40, 60 and 80°C by the conventional weight-gain method. The effects of fibre content, alkali treatment, and filler particle size on solvent sorption were analysed. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated in terms of microfibre content, particle size, nature of the solvent, and temperature. It was observed that all the systems follow the Fickian mode of transport on increasing temperature. The van’t Hoff’s relationship was used to determine the thermodynamic parameters and was found that the estimated free energies of sorption were all positive, indicating non-spontaneity of the solubility of micro fibre/LDPE composites. The first order kinetic rate constant and swelling parameters were also evaluated.

Effects of Coir Fiber Loading on the Physio-mechanical and Morphological Properties of Coconut Shell Powder Filled Low Density Polyethylene Composites

Coconut shell filled composites were prepared from recycled low density polyethylene polymer matrix containing up to 15% weight of coconut shell powder as filler. The effect of coir fiber loading on the properties of the composites was then investigated. It was shown that the values of tensile strength, flexural strength and hardness increased up to 7.1MN/m2,18.0GPa and 92.7 respectively. Impact energy decreased with increase in fiber length. With the introduction of fiber length from zero to 10mm, a decrease in density and increase in water absorption was observed.

Study of the effect of the incorporation of TiO2 nanotubes on the mechanical and photodegradation properties of polyethylenes

TiO2 nanotubes (TiO2-Ntbs) synthesized by a hydrothermal method with a diameter of ca. 5 nm were used as filler to prepare polyethylene (PE) and linear low density polyethylene (LLDPE) composites by melt blending. Nanotubes were used either as synthesized or organically modified with hexadecyltrimethoxysilane (Mod-TiO2-Ntbs). In some cases nanoparticles form secondary structures with sizes around 100 nm and agglomerates larger than 2 μm are also seen by transmission electron microscopy (TEM). In terms of mechanical properties, the addition of TiO2-Ntbs resulted in a composite, LLDPE/TiO2-Ntbs, with improved properties. Compared with the pure polymer, Young's modulus increased by ca. 50%, while yield stress increased by ca. 35%. On the other hand, PE/Mod-TiO2-Ntbs and LLDPE/Mod-TiO2-Ntbs with 5 wt% filler loading showed higher E′ values in the storage modulus at low temperatures than either neat PE and LLDPE. The photodegradation properties of the PE/Mod-TiO2-Ntbs and LLDPE/Mod-TiO2-Ntbs composites were studied. The largest increase of chemiluminescence emission (CL) and carbonyl index (CI) was found for LLDPE/Mod-TiO2-Ntbs during photoaging. That behavior may be due to large branching of the polymer, and to the presence of the nanotubes incorporated into the LLDPE, which promoted and accelerated its photodegradation due to reactive species generated during irradiation.

Utilization of banana stalk fiber as reinforcement in low density polyethylene composite

Natural fibers could serve as viable and abundant alternatives to the expensive and non - renewable synthetic fibers as reinforcement in thermoplastic composites. The potentiality of banana stalk fiber at reinforcing a low density polyethylene matrix was examined in this study. Fibers were extracted from the stalk of banana plant and characterized for its chemical composition and fiber contents. The fibers were modified by pulping with caustic soda to increase it wettability. The fiber dimension was measured using a binocular light microscope. FTIR spectra was used to identify the functional groups of modified and unmodified fibers. The composites were produced using a single -- screw extruder, pelletized and then processed into test specimen samples by injection molding. The fiber volume in the polymer matrix was varied from 5.4 to 20 %. The effects of chemical treatment and increasing fiber content on the moisture absorption and mechanical properties of the composites were examined. The results showed that fiber of banana plant were characterized by medium to long fiber length (2.84 mm). The lignin content (7.99 %) was relatively low indicating a lower value of chemical consumption in the modification step. The SEM micrograph of the composite cross section showed good fiber/matrix interfacial bonding. The water absorption capacity of the composites increased with increase in fiber loading while the treated fibers showed a reduction in hydrophylicity of the composites. The treated fibers showed improved tensile strength and can thus be utilized in the production of composites with better properties Keywords: Banana fiber, composites, reinforcement, polyethylene, mechanical properties