Linear Low Density Polyethylene Composites Research Articles

Electrical and Electro-Thermal Characteristics of (Carbon Black-Graphite)/LLDPE Composites with PTC Effect.

Electrical properties and electro-thermal behavior were studied in composites with carbon black (CB) or hybrid filler (CB and graphite) and a matrix of linear low-density polyethylene (LLDPE). LLDPE, a (co)polymer with low crystallinity but with high structural regularity, was less studied for Positive Temperature Coefficient (PTC) applications, but it would be of interest due to its higher flexibility as compared to HDPE. Structural characterization by scanning electron microscopy (SEM) confirmed a segregated structure resulted from preparation by solid state powder mixing followed by hot molding. Direct current (DC) conductivity measurements resulted in a percolation threshold of around 8% (w) for CB/LLDPE composites. Increased filler concentrations resulted in increased alternating current (AC) conductivity, electrical permittivity and loss factor. Resistivity-temperature curves indicate the dependence of the temperature at which the maximum of resistivity is reached (Tmax(R)) on the filler concentration, as well as a differentiation in the Tmax(R) from the crystalline transition temperatures determined by DSC. These results suggest that crystallinity is not the only determining factor of the PTC mechanism in this case. This behavior is different from similar high-crystallinity composites, and suggests a specific interaction between the conductive filler and the polymeric matrix. A strong dependence of the PTC effect on filler concentration and an optimal concentration range between 14 and 19% were also found. Graphite has a beneficial effect not only on conductivity, but also on PTC behavior. Temperature vs. time experiments, revealed good temperature self-regulation properties and current and voltage limitation, and irrespective of the applied voltage and composite type, the equilibrium superficial temperature did not exceed 80 °C, while the equilibrium current traversing the sample dropped from 22 mA at 35 V to 5 mA at 150 V, proving the limitation capacities of these materials. The concentration effects revealed in this work could open new perspectives for the compositional control of both the self-limiting and interrupting properties for various low-temperature applications.

Eco-friendly tiles: fabrication and testing of composite tile made from industrial gypsum wastes

Purpose The purpose of this study is to utilize two types of gypsum mold wastes from two different factories as novel and economical reinforcing fillers for composites that may be useful for building materials and floors. Two types of gypsum mold wastes from two different factories as raw materials were incorporated into linear low density polyethylene (LLDPE) aiming to get rid of that waste in one hand and obtaining useful economical composites suitable for building materials and floors. Design/methodology/approach Composites were prepared from two types of gypsum mold wastes substituted with different ratios from raw gypsum and LLDPE throughout the melt blending technique. The physico-mechanical and electrical investigations in addition to the morphology of the composites were included. Findings The mechanical results illustrate that substituting commercial gypsum with gypsum mold waste positively affects tensile strength, flexural strength and hardness shore D for the LLDPE composites. The tensile strength increased from 5 MPa for LLDPE filled with commercial gypsum as blank samples to 11.2 and 13.2 MPa for LLDPE filled with D and S waste. Also, electrical properties which include both permittivity ɛ′ and dielectric loss ɛ″ increased with increasing the waste content in the LLDPE matrix. In addition to the electrical conductivity values, σ lies in the order of insulation materials. Consequently, it is possible to produce materials with a gypsum matrix by adding industrial waste, improving the behavior of the traditional gypsum and enabling those composites to be applied in various construction applications as eco-friendly tiles. Originality/value This study aims to prepare eco-friendly composites based on LLDPE and waste gypsum mold to preserve resources for the coming generations, other than lowering the environmental footprint and saving the costs of getting rid of it.

Thermal and Morphological Analysis of Linear Low-Density Polyethylene Composites Containing d-limonene/β-cyclodextrin for Active Food Packaging.

Composites made of linear low-density polyethylene (LLDPE) and β-cyclodextrin/d-limonene inclusion complex (CD-lim) were prepared by melt extrusion to develop a novel food packaging material. Scanning electron microscopy evidenced a fairly good dispersion of the filler within the polymeric matrix. Infrared spectroscopy coupled with thermogravimetric analysis confirmed the presence of CD-lim in the composites, proving that the applied technology of including the essential oil within β-CD cages allows for preventing a sizable loss of d-limonene despite a high temperature and shear applied upon extrusion processing. Moreover, the influence of the filler on the thermal properties of PE was assessed. It was found that the cyclodextrin-based inclusion complex significantly fastens the crystallization path of the polyethylene matrix with an improved crystallization rate of the PE/CD-lim composites compared to the neat polymer.

The Effect of Linear Low-Density Polyethylene and Palm Kernel Shell Ash Mixture on the Physical, Mechanical and Degradation Properties of Paving Blocks

The aim of this research was to evaluate the physical-mechanical parameters of paving stones obtained on the basis of the mixture of linear low-density polyethylene (LLDPE) and palm kernel shell ash (PKSA) waste. The ratio of LLDPE to PKSA waste (% weight) was varied in five treatments: A0 (100:0), A1 (97.5:2.5), A2 (95:5), A3 (92.5:7.5), A4 (90:10) and A5 (87.5:12.5). The physical appearance, thickness, compressive strength, water absorption, and morphological characteristics of the paving blocks were observed. The blocks were observed at ambient temperature, exposed to sunlight, and placed on the ground surface on day 0 and day 365. The results showed that addition of PKSA waste decreased the compressive strength but increased the water absorption capacity without a significant effect on the thickness of the paving blocks. Observation after 365 days showed insignificant decreases of compressive strength and thickness, whereas the water absorption capacity increased slightly. Small cracks and more voids in the surface, and more brittleness were observed. To summarize, composites of LLDPE and PSKA as filler have physical-mechanical properties that can be used for road pavement blocks.

Effect of Fiber Content on Mechanical, Morphological, and Vibration Damping Characteristics of Natural Fiber-reinforced Composite Fuel Tanks

ABSTRACT Rotational molding is a powder processing technology widely used to manufacture hollow plastic products. It is a well-known process used for the manufacturing of large containers, water tanks, fuel tanks, refrigerated containers, etc. This study aimed at the incorporation of Tampico and Palmyra fibers as reinforcement in Linear Low-Density Polyethylene (LLDPE) tanks produced by the rotational molding process. The effect of fiber content on various properties like mechanical, morphological, and vibration damping characteristics of the composites were investigated. The fibers were initially treated with 5% NaOH solution for better reinforcing efficiency and to improve the degradation temperature. Thermo Gravimetry Analysis (TGA) reported that a sufficient increment in degradation temperature is achieved by NaOH treatment on fibers. The short fiber composites considered for the study have obtained better mechanical strength than long fiber reinforced LLDPE composites. The results proved that fiber length has less effect on the vibration damping characteristics of the composites, but the percentage of fiber content is a significant factor for improving the natural frequency of the composites.

Estimation of Mechanical Properties of Copper Powder Filled Linear Low-Density Polyethylene Composites

Estimation of Mechanical Properties of Copper Powder Filled Linear Low-Density Polyethylene Composites

Nonlinear optical properties of LLDPE composites with titanium dioxide anatase phase

In this research work, the linear and nonlinear optical properties of linear low-density polyethylene (LLDPE) composites with anatase phase of titanium dioxide nanoparticles in different weight percentages are investigated. Solvent casting method have been used to synthesize the thin film of LLDPE/anatase nanocomposites. Thin films are characterized via XRD technique and field emission scanning electron microscope (FESEM). Wrinkles formed on the surface of thin films by adding the titanium dioxide. Linear optical and electrical parameters such as linear absorption coefficient, extinction coefficient, refractive indices, optical conductivity, and dielectric constants at various wavelengths from 190 nm to 2700 nm are determined for different weight percentages of nanoparticles in polymer nanocomposites. Z-scan technique has been employed to explore the nonlinear optical properties using CW laser at 532 nm wavelength. The nonlinearity is examined at various irradiance of laser to study the effect of irradiance on nonlinear optical properties. Pure LLDPE has saturable absorption (SA) at low laser irradiance. As the laser irradiance increases, the nonlinearity behavior turns from SA to reverse saturable absorption (RSA). The results show the suitability of the thin films for the applications in optical devices that involve the use of optical limiting properties of materials.

Thermal and dielectric properties of two‐dimensional layered MXene (Ti3C2Tx) filled linear low‐density polyethylene composites

AbstractExploring a new material MXene‐based polymer composite with high‐dielectric constant and low‐dielectric loss is important because of their potential applications in modern electronics and power systems. The two‐dimensional layered Ti3C2Tx(MXene)/linear low‐density polyethylene (LLDPE) composite have been fabricated via the solution casting method in the weight ratio of 1 to 10 of Ti3C2Txto the total weight of the polymer matrix. The formation of Ti3C2Tx filled LLDPE composite is revealed by the X‐ray diffraction, Field Emission Scanning Electron Microscope (FESEM), Fourier‐transform infrared, differential scanning calorimetry, and thermogravimetric analysis investigations. The room temperature transport behavior of the composites was studied by impedance spectroscopy technique within the frequency range of 5 Hz–5 MHz. The composites show significantly improved real dielectric permittivity of and low‐dielectric dissipation loss of the composite (maximum ε' = 9.35 × 103 with tan δ = 0.48 at 5 Hz at 25°C) at 5 phr of Ti3C2Tx loading. This work gives an auspicious idea to build polymer films with improved dielectric permittivity and low‐loss tangent for potential application in flexible electronic materials.

Tailoring flexible interphases in bamboo fiber-reinforced linear low-density polyethylene composites

Traditional modifiers with low-molecular-weight often result in a rigid interface between reinforcing fibers and matrix. This study built a flexible interphase for a linear low-density polyethylene and bamboo fiber (LLDPE/BF) composite by synthesizing a silane-based flexible macromolecular modifier (γ-APS-PAEE). FTIR analysis indicated that γ-APS-PAEE bridged BF and LLDPE by chemical bonding and good inter-molecular compatibility. Scanning electron microscope (SEM) showed the shear fracture behavior of BF pulled from the LLDPE matrix. The flexible interface was detailly analyzed. Compared with the traditional vinyltriethoxysilane and γ-aminopropyltriethoxysilane modifications, the new flexible interphase contributed simultaneous strengthening and toughening to the LLDPE/BF composite (70:30 mass fraction), resulting in increases of 20.63%-36.12% in tensile strength, 46.33%-78.97% in impact toughness, 24.59%-72.52% in fracture elongation, and 104.62% in fracture work. By introducing γ-APS-PAEE, a strong and tough LLDPE/BF composite was developed, which was comparable to high-density polyethylene based wood-plastic composite. This would benefit to reuse the recycled LLDPE.

Influence of Filler Surface Modification on Static and Dynamic Mechanical Responses of Rice Husk Reinforced Linear Low-Density Polyethylene Composites

Influence of Filler Surface Modification on Static and Dynamic Mechanical Responses of Rice Husk Reinforced Linear Low-Density Polyethylene Composites

Optimal Use of Industrial Hemp for PLA Biocomposite and LLDPE Composite Reinforcement

This study investigated the optimal use of industrial hemp fibers for polylactide (PLA) biocomposite and linear low density polyethylene (LLDPE) composite reinforcement. In these samples both low-grade fiber, waste and high-quality hemp fiber are used. To optimize the use of hemp fiber in both the biocomposite and the fossil-based polymer matrix composite, the first phase of the technology envisages the use of high-quality hemp fibers in the production of the PLA biocomposite. This process also produces a by-product (hemp waste). Further, in the second stage, the technology envisages the use of hemp waste in the production of LLDPE (semi-fossil) composite. PLA and hemp fiber biocomposites have high mechanical properties, which allow reducing the amount of materials in the product. Also, low-grade fiber composites show remarkable mechanical properties. The advantage of extracting hemp fibers is that it is possible to use all parts of the plant at the same time for the production of different products – hemp seeds, their shells, hemp shives, thus maximizing the value added of this resource, that conforms to the concept of sustainable development and circular economy principles. Also, it improves the ecological assessment (Life Cycle Assessment) of the product and reduces the environmental impact. Annually renewable hemp fiber resource has the potential to create new products and develop the renewable material industry in EU. Considering the Europe Green Deal guidelines [1], it is important for the manufacturer to provide a sustainable, economically justified and environmentally friendly material (switch to recyclable materials till 2021, switch to recycled, reusable or alternative materials till 2025).

Experimental investigation of linear low density polyethylene composites based on coir for rotational molding process

Rotational Molding is a plastic manufacturing process mainly implemented to produce stress free hollow products. Linear Low Density Polyethylene (LLDPE) is widely preferred as base resin for molding roto molded product, but it displays moderate value in some critical applications where strength is the major criteria. Additives can fill the gap in sustaining the necessary strength needed. In the present work, an attempt has been made to analyze the optimum percentage of coir reinforced with LLDPE for rotational molding technique to provide requisite processability for rotational molding process. Coir in its powder form is mixed at concentrations varying in the range of 3% to 20% with respect to LLDPE. In order to justify the prerequisite of processability for rotational molding, various experiments namely FTIR, MFI, rheology and thermal analysis were conducted. FTIR suggested the range of 5% to 15% wherein the significance of LLDPE and coir peaks can be observed. MFI test supported FTIR result which ended in considering 3% to 12% by weight ratio suitable in terms of flow ability. Rheological and thermal analysis subjecting to shear and heat parameter respectively, confirmed the range of 10 weight percentage of coir or below is suitable in terms of material processability. From the experimental results, it is concluded that 10% or less concentration of coir fiber in LLDPE as an optimum range of blend yielding better processability for rotational molding process.

Impact of hybrid nanosilica and nanoclay on the properties of palm rachis-reinforced recycled linear low-density polyethylene composites

The main goal of this work was to assess the technical feasibility of palm rachis (PR) as a reinforcing agent in the production of wood–plastic composites. Recycled linear low-density polyethylene/PR fiber composites were prepared at constant content (3 phc (per hundred compounds)) of maleic anhydride-grafted polyethylene as compatibilizer by melt blending method utilizing a two-roll mill and compression molding. The effect of nanosilica (NS), nanoclay (NC), and hybrid nanoparticles (NSNC) at different concentrations (2, 4, and 6 phc) on mechanical, physical, thermal, and morphological properties was investigated. The results of mechanical properties measurements demonstrated that when 6 phc NS, 4 phc NC, and 4 phc NSNC were added, tensile, modulus strength, and hardness reached their optimum values. At a high level of NC loading (6 phc), the increased populace of NC layers led to agglomeration and stress transfer gets restricted. Elongation at break and Izod impact strength were decreased by the incorporation of different nanoparticles. Water absorption and thickness swelling of prepared composites were found to decrease on the incorporation of NS and NC. In addition, the thermal stability showed slightly improved by the addition of nanoparticles, but there are no perceptible changes in the values of melting temperature by increasing the content of NS and NC or NSNC. Scanning electron microscopy study approved the good interaction of the PR fibers with the polymer matrix as well as the effectiveness of NS and NC in the improvement of the interaction. The finding indicated that wood–plastic composite treated by NS had the highest properties than other composites.

Heptene-functionalized graphitic nanoplatelets for high-performance composites of linear low-density polyethylene

Heptene-functionalized graphitic nanoplatelets (HGNs) were prepared as a new reinforcing additive for linear low-density polyethylene (LLDPE). HGNs were synthesized using a mechanochemical reaction between graphite and 1-heptene. The formation of HGNs is confirmed using a variety of analytic techniques. Because HGNs were well dispersible in organic solvents, HGN/LLDPE composites were easily prepared using a solution process. Compared to neat LLDPE, the HGN/LLDPE composites showed significantly enhanced mechanical properties (i.e., tensile strength, yield strength, Young's modulus, and tensile toughness) and thermal stability. Considering cost, efficiency, and practicality, HGNs could become promising candidates for reinforcing additives for LLDPE.

A comparative study of mechanical, dynamic mechanical and morphological characterization of tampico and coir fibre-reinforced LLDPE processed by rotational moulding

Natural fibres find their application as a reinforcing agent for polymer composites to obtain parts with improved mechanical properties. Manufacturing of non-metallic products is incorporated with natural fibres for better strength and to reduce cost. Rotational moulding is a process used for the manufacturing of hollow plastic products, especially water tanks, plastic fuel tanks, barrels, kayaks, refrigerated panels, etc. Incorporation of natural fibres to reinforce polymers in rotational moulding process is a tedious task; since there is no control over fibre and polymer powder mixture, which is rotating bi-axially, it may lead to fibre agglomeration. The present work investigates the mouldability of linear low density polyethylene composites with tampico and coir fibre as the reinforcement agents using a bi-axial rotomoulding machine. NaOH-treated fibres with 5, 10 and 15% by weight have been added to the linear low density polyethylene matrix, and the composites were prepared by rotational moulding process. Mechanical properties such as tensile strength, flexural strength, impact strength and hardness have been investigated. Dynamic mechanical behaviour such as storage modulus, loss modulus and tan  δ of the different composites has been investigated with dynamic mechanical analyser. Fractured surfaces were examined qualitatively with the help of a scanning electron microscope for determining the interfacial properties and fibre adhesion between the fibres and the linear low density polyethylene matrix.

Investigating the mechanical, thermal and melt flow index properties of HNTs – LLDPE nano composites for the applications of rotational moulding

Linear low density polyethylene (LLDPE) is the one of the most popular polymer used for rotational moulding applications such as storage tanks. But, its inferior mechanical properties and thermal stability restrict the longer service. Hence, this study experimentally demonstrates the effect of Halloysite Nanotube (HNTs) concentration on LLDPE composites for enhancing the mechanical and thermal stability. HNTs were uniformly dispersed with LLDPE matrix through ultra-sonication, followed by compression moulding used to prepare the nano composites plates. The prepared composites are shown 19.2% improved tensile strength for 2 wt% HNTs, whereas 28.9% hike in flexural strength observed for 4 wt% HNTs composite, compare to neat LLDPE. Which shows that higher concentrations of HNTs is favourable in improving the flexural strength rather than tensile properties. In addition to that, higher concentrations of HNTs are also helping in improving the storage modulus of the LLDPE composites. The increase in mechanical properties mainly attributed due to effective load carriers (HNTs) in the composite. Besides, HNTs were also contributing for improving the melting point and residual char of the composites, which is indeed for storage tanks durability. The prepared composite was thermally stable at higher temperature up to 230 °C, because of HNTs chemical structure, the inner layer of HNTs constitute with Al2O3 and outermost layer constitute with SiO2, both are thermally stable. Stated enhancement proves the potential effect of HNTs reinforcement in the LLDPE composite for rotational moulding applications.

Rotational Molding of Linear Low-Density Polyethylene Composites Filled with Wheat Bran.

Application of lignocellulosic fillers in the manufacturing of wood polymer composites (WPCs) is a very popular trend of research, however it is still rarely observed in the case of rotational molding. The present study aimed to analyze the impact of wheat bran content (from 2.5 wt.% to 20 wt.%) on the performance of rotationally-molded composites based on a linear low-density polyethylene (LLDPE) matrix. Microscopic structure (scanning electron microscopy), as well as physico-mechanical (density, porosity, tensile performance, hardness, rebound resilience, dynamic mechanical analysis), rheological (oscillatory rheometry) and thermo-mechanical (Vicat softening temperature) properties of composites were investigated. Incorporation of 2.5 wt.% and 5 wt.% of wheat bran did not cause significant deterioration of the mechanical performance of the material, despite the presence of ‘pin-holes’ at the surface. Values of tensile strength and rebound resilience were maintained at a very similar level, while hardness was slightly decreased, which was associated with the porosity of the structure. Higher loadings resulted in the deterioration of mechanical performance, which was also expressed by the noticeable rise of the adhesion factor. For lower loadings of filler did not affect the rheological properties. However, composites with 10wt.% and 20 wt.% also showed behavior suitable for rotational molding. The presented results indicate that the manufacturing of thin-walled products based on wood polymer composites via rotational molding should be considered a very interesting direction of research.

Polyethylene/graphene oxide composites toward multifunctional active packaging films

The addition of nanoparticles into a polymer can produce multifunctional films having not only gas barrier and antimicrobial characteristics for active packaging, but also improved mechanical and thermal behaviours. Among the different nanoparticles, graphene oxide (GO) has the potential to develope active polymers due to its layer structure and biocide property. In this study, linear low density polyethylene (LLDPE) was melt mixed with GO nanoparticles having different oxidation and exfoliation degrees. Our results shown that the elastic modulus of LLDPE composites increased with the amount of GO, and by using highly oxidated GO this reinforcement effect was observed without reducing the elongation at break. The thermal stability of the composites under either inert and oxygen atmosphere also increased as compared with the pure matrix. Regarding the barrier properties, the oxygen permeability of the composites depended on the amount and kind of filler, and while GO with low oxidation increased dramatically the permeability of the polymer, highly oxidated GO decreased this value. These results were explained through the Felske model. Water vapor permeation otherwise was not affected by the presence of the nanofillers. The LLDPE/GO nanocomposites further presented antimicrobial behaviour against Salmonella Typhi and Listeria monocytogenes strains. These results confirmed that GO can be designed as an active filler in polymer nanocomposites for packaging applications.

Optimization and characterization of the properties of treated avocado wood flour-linear low density polyethylene composites

The research was carried out to investigate the optimization of surface modification for avocado wood flour (ACWF) and the characterization of the treated and untreated of avocado wood flour–linear low density polyethylene composite (ACWF-LLDPE). The variation of treated filler on the mechanical and water sorption properties was investigated. The untreated and treated ACWF-LLDPE composite was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Central Composite design of response surface model (RSM) was used to forecast the mechanical and water sorption properties of ACWF-LLDPE composite. The properties of ACWF-LLDPE composite was statistically analysed and found to be significant. The optimal treatment was particle size of 100 mesh and filler content of 22.97%. At optimum particle size and filler content, the mechanical properties were 24.972 MPa tensile strength (TS), 6.195% elongation (E), 0.863 GPa tensile modulus (TM), 62.664 MPa flexural strength (FS), 0.809 GPa flexural modulus (FM), 699.918 Pa Brinell hardness (BH), and 91.619 kJ/m2 impact strength (IM). The corresponding water sorption (WS) at this condition was 3.338%.

Effect of iron poly(acrylic acid-co-acrylamide) and melamine polyphosphate on the flammability properties of linear low-density polyethylene

Iron poly(acrylic acid-co-acrylamide) (FeAA) and melamine polyphosphate (MPP) were synthesized, characterized by FTIR and blended with linear low-density polyethylene (LLDPE). The thermogravimetric analysis results exhibited that MPP, FeAA and MPP/FeAA increased the char residue of LLDPE at 750 °C. Cone calorimeter data demonstrated that MPP, FeAA and MPP/FeAA decreased the peak of heat release rate (pHRR) and total heat release of LLDPE. Digital photographs, SEM images, EDXS and FTIR analyses of char formed after cone test indicated that the presence of FeAA did not support formation of coherent char during combustion process of LLDPE. In contrast, LLDPE/MPP composite formed high-quality char layer on polymer surface. Moreover, addition of MPP to LLDPE/FeAA composites assisted in formation of char containing iron polyphosphate and polyaromatic structure. The mechanical properties, namely tensile strength, Young’s modulus, elongation at break and hardness of LLDPE composites, were measured.