High Density Polyethylene Composites Reinforced with Hybrid Inorganic Fillers: Morphology, Mechanical and Thermal Expansion Performance

Impact of Hybrid Fillers on the Properties of High Density Polyethylene Based Composites

The main objective of this work is to develop a variety of hybrid high-density polyethylene (HDPE) micro- and nanocomposites and to investigate their thermal, mechanical, and morphological characteristics as a function of number of fillers and their contents percentage. In this study, 21 formulations of the composites were prepared using fillers with different sizes including micro fillers such as talc, calcium carbonate (CaCO₃), as well as nano-filler (fumed silica (FS)) though the melt blending technique. The morphological, mechanical, and thermal properties of the composite samples were evaluated. The morphological study revealed negligible filler agglomerates, good matrix–filler interfacial bonding in case of combined both CaCO₃ and FS into the composites. Sequentially, improvements in tensile, flexural and Izod impact strengths as a function of fillers loading in the HDPE matrix have been reported. The maximum enhancement (%) of tensile, flexural and impact strengths were 127%, 86% and 16.6%, respectively, for composites containing 25% CaCO₃ and 1% FS without any inclusion of talc filler; this indicates that the types/nature, size, quantity and dispersion status of fillers are playing a major role in the mechanical properties of the prepared composites more than the number of the used fillers.

High-Temperature Tribological Behavior of HDPE Composites Reinforced by Short Carbon Fiber under Water-Lubricated Conditions

The polymer water-lubricated bearing is widely used in marine transmission systems, and the tribological properties can be improved by addition of inorganic nano-fillers. The aim of this study is to investigate the effect of SCFs and temperature on the water-lubricating properties of high-density polyethylene (HDPE) composites. HDPE composites reinforced by varying content of short carbon fibers (SCFs) were fabricated via twin-screw extrusion and injection molding techniques to study the hardness and surface wettability of those composites. The tribological properties under water-lubricated conditions were investigated through a pin-on-disk reciprocating tribometer under different temperatures. The results showed that the increase in hardness of HDPE composites reached maximum to 42.9% after adding 25 wt % SCFs. The contact angle also increased with the increase in SCFs content and reached a maximum of 95.2° as the amount of SCFs increased to 20 wt %. The incorporation of SCFs increased the wear resistance and lubricating property of HDPE composites at different temperatures. The HDPE composite containing 20 wt % SCFs showed the lowest friction coefficient of 0.076 at 40 °C, and the wear track depth reached a maximum of 36.3 mm at 60 °C. Based on the surface wetting property and wear analysis, potential effect mechanisms of fillers and temperature were discussed. The knowledge from this study is useful for designing the anti-wear water-lubricated polymer bearing.

Incorporation of Biochar to Improve Mechanical, Thermal and Electrical Properties of Polymer Composites

The strive for utilization of green fillers in polymer composite has increased focus on application of natural biomass-based fillers. Biochar has garnered a lot of attention as a filler material and has the potential to replace conventionally used inorganic mineral fillers. Biochar is a carbon rich product obtained from thermochemical conversion of biomass in nitrogen environment. In this review, current studies dealing with incorporation of biochar in polymer matrices as a reinforcement and conductive filler were addressed. Each study mentioned here is nuanced, while addressing the same goal of utilization of biochar as a filler. In this review paper, an in-depth analysis of biochar and its structure is presented. The paper explored the various methods employed in fabrication of the biocomposites. A thorough review on the effect of addition of biochar on the overall composite properties showed immense promise in improving the overall composite properties. An analysis of the possible knowledge gaps was also done, and improvements were suggested. Through this study we tried to present the status of application of biochar as a filler material and its potential future applications.

Use of iron mine tailing as fillers to polyethylene

The iron mine tailings accumulation in dams is an environmental and economic problem. The composite based on high-density polyethylene/iron mine tailing production for the application of wood plastic and some items of domestic plastic industry can be a good alternative to reduce the rejects in the environment. This work presents the influence of the processing methodology in the mechanical, thermal and morphological properties of composites based on the high-density polyethylene/iron mine tailing. Four methodology processing by continuous and/or batch mixing were available. The iron mine tailing particles in the polymer matrix promoted an increase in mechanical strength and thermal stability. Besides, the particles acted as flame retardant. The iron mine tailing materials produced using batch mixing showed more significant modifications in the properties due to the better dispersion of the filler as shown by scanning electron microscopy.

UHMWPE/CaSiO3 Nanocomposite: Mechanical and Tribological Properties

This paper studied the effect of additives of 0.5-20 wt.% synthetic CaSiO3 wollastonite on the thermodynamic, mechanical, and tribological characteristics and structure of polymer composite materials (PCM) based on ultra-high-molecular weight polyethylene (UHMWPE). Using thermogravimetric analysis, X-ray fluorescence, scanning electron microscope, and laser light diffraction methods, it was shown that autoclave synthesis in the multicomponent system CaSO4·2H2O-SiO2·nH2O-KOH-H2O allows one to obtain neeindle-shaped nanosized CaSiO3 particles. It was shown that synthetic wollastonite is an effective filler of UHMWPE, which can significantly increase the deformation-strength and tribological characteristics of PCM. The active participation of wollastonite in tribochemical reactions occurring during friction of PCM by infrared spectroscopy was detected: new peaks related to oxygen-containing functional groups (hydroxyl and carbonyl) appeared. The developed UHMWPE/CaSiO3 materials have high wear resistance and can be used as triboengineering materials.

Production of high-density polyethylene biocomposites from rice husk biochar: Effects of varying pyrolysis temperature

The novelty of this study is to explore the effect of temperature varied biochar on the properties of biochar/polymers composites. Rice husk biochar (RB) samples were prepared at different pyrolysis temperatures and injection molding was used to prepare RB/high-density polyethylene (HDPE) composites. Additionally, ultimate analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), pore structure characteristics, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile properties, and dynamic mechanical analysis (DMA) were used to characterize these RB and RB/HDPE composites samples. The results validated that RB obtained at 600 °C showed the highest carbon content, the most complete pore structure, and the largest specific surface area. Moreover, the thermal studies revealed that the addition of RB improved the thermal stability of HDPE. The best tensile strength (26.25 MPa) and Young's modulus (1.87 GPa) were obtained in 500 °C RB/HDPE composites and 600 °C RB/HDPE composites due to their good physical/mechanical interlocking structures shown in SEM. DMA revealed that the stiffness, elasticity, creep resistance and stress relaxation of the composites were improved by the addition of RB. The utilization of temperature varied biochars in biocomposites is important to manage wastes and optimize the properties of biocomposites in terms of reducing production cost and ensuring environmental safety.

Thermal, morphological and structural characterization of a copolymer of starch and polyethylene

The objective of this paper was to perform a copolymerization between polyethylene and starch in order to obtain new environmentally friendly materials. The copolymer obtained was characterized thermally, morphologically and structurally, including its pasting profile. The starch-g-PE copolymer showed lower thermal stability compared to the control materials. FTIR analysis determined that the chemical bond signal between the starch and polyethylene in the copolymer overlaps with the native starch signals. The signal from this chemical bond was assigned by proton NMR spectroscopy at δ 4.45 ppm. X-ray studies of the copolymer showed a material with more amorphous characteristics compared to native starch. SEM analysis demonstrated the presence of cracks in the starch granules which favored the chemical interaction between the polymers. The pasting behavior of the copolymer was less pronounced compared to native starch. Therefore, the copolymerization of both polymers could be an alternative to recycle polyethylene and make biodegradable materials.

Structural Characterization and Analysis of High-Strength Laminated Composites from Recycled Newspaper and HDPE

Recycled newspaper (NP) shows excellent potential as a reinforcement for polymer composites. Herein, high-strength laminated composites were prepared by using NP laminas as reinforcement and high-density polyethylene (HDPE) films as matrix. Physical and mechanical properties of the laminated composites were measured. It was found that the flexural strength of the composites had a good linear relationship to its density, with R² = 0.9853. The flexural and tensile strength of the composites at the maximum density (1.40 g/cm³) reached up to 95.6 ± 2.4 MPa and 99.4 ± 0.8 MPa, respectively. SEM results showed that NP layer inside the composite became compact at the hot pressing time of 40 min, because the melted HDPE permeated into the NP layers to bond the NP fibers. Quantitative description of the composite porosity was conducted according to the density of the composite. The 24-h water absorption of the composite was highly related to its porosity, with R² = 0.8994. This study reveals that density of laminated composites is an important parameter, which could be used to forecast the mechanical strength, and its derived value, porosity of the composites, could be used to predict the water absorption behavior of the composite.

Frequency independent AC electrical conductivity and dielectric properties of polyaniline-based conductive thermosetting composite

Electrical impedance characteristics of polyaniline (PANI)-dodecylbenzenesulfonic acid (DBSA)/divinylbenzene (DVB) composite were evaluated as a function of PANI content in the frequency range of 102–108 Hz. Polymer composites were prepared by a one-step thermal process where doping of the PANI and curing of the polymer matrix DVB have occurred simultaneously in the presence of a strong protonic acid, i.e. DBSA. The alternating current (AC) conductivity value with respect to frequency of the PANI-DBSA/DVB composite shows a direct current (DC) plateau up to an extensive frequency range. Almost metal-like behavior is obtained with such highly conductive plastic material. In all frequency regions, composites with higher PANI concentration showed a frequency independent behavior, while in the case of neat composites without PANI, a frequency dependent behavior is observed. A plot of the real part of complex impedance vs. frequency and a plot of AC conductivity of the composites indicate that the high electrical conductivity in high PANI concentration composites is because of the direct contacts between filler PANI particles. In this work, AC conductivity behavior and dielectric properties of very highly conductive thermoset composites are presented, and it is shown that conductivity is frequency independent for a very high frequency range (up to 108 Hz).

Mechanical and Thermal Properties of R-High Density Polyethylene Composites Reinforced with Wheat Straw Particleboard Dust and Basalt Fiber

The effect of individual and combined particleboard dust (PB dust) and basalt fibers (BFs) on mechanical and thermal expansion performance of the filled virgin and recycled high density polyethylene (HDPE) composites was studied. It was shown that the use of PB dust had a positive effect on improving mechanical properties and on reducing linear coefficient of thermal expansion (LCTE) values of filled composites, because the adhesive of the particle board held the wheat straw fibers into bundles, which made PB dust have a certain aspect ratio and high strength. Compared with the commonly used commercial WPC products, the flexural strength of PB dust/VHDPE, PB dust/RHDPE, and PB dust/VHDPE/RHDEPE at 40 wt% loading level increased by 79.9%, 41.5%, and 53.9%, respectively. When 40 wt% PB dust was added, the crystallization degree of the composites based on three matrixes decreased to 72.5%, 45.7%, and 64.1%, respectively. The use of PB dust can help lower the composite costs and increase its recyclability. Mechanical properties and LCTE values of composites with combined BF and PB dust fillers varied with PB dust and BF ratio at a given total filler loading level. As the BF portion of the PB dust/BF fillers increased, the LCTE values decreased markedly, which was suggested to be able to achieve a desirable dimensional stability for composites. The process provides a useful route to further recycling of agricultural wastes.

Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylene-Co-Vinyl Acetate and Nano Clay Particles by Electron Beam

Surface modification of linear low-density-polyethylene (LLDPE), ethylene-co-vinyl acetate (EVA), and clay nanoparticles composite films was promoted by potassium permanganate solutions in HCl acidic medium using eight conditions by variation times and temperature, also concentrated oxidation solution of LLDPE and EVA blend films shows a very good clarity and tensile properties, this property can be improved by adding the clay nanoparticles as a filler in the composite. The influence of electron beams (EB) irradiation and amount of clay nanoparticles loading on the overall properties of linear low-density polyethylene (LLDPE) /ethylene-co-vinyl acetate blends was investigated. Samples were subjected to the EB irradiation with the dose values of 75 and 150kGy, afterwards mechanical and thermal properties of the LLDPE/EVA blends with and without clay nanoparticles at different irradiation dosages were utilized in order to analyze the characteristics of the final composite. These enhanced properties are due to the homogenize dispersion of Clay nanoparticles in LLDPE matrix. Moreover, in order to verify these characteristics and compare composite samples with and without Clay nanoparticles (Cloisites 30B), some tests such as DSC, TGA, PSA, SEM and Optical Micrographs (OM) were taken from the samples.

The Influence of Ziegler-Natta and Metallocene Catalysts on Polyolefin Structure, Properties, and Processing Ability

50 years ago, Karl Ziegler and Giulio Natta were awarded the Nobel Prize for their discovery of the catalytic polymerization of ethylene and propylene using titanium compounds and aluminum-alkyls as co-catalysts. Polyolefins have grown to become one of the biggest of all produced polymers. New metallocene/methylaluminoxane (MAO) catalysts open the possibility to synthesize polymers with highly defined microstructure, tacticity, and steroregularity, as well as long-chain branched, or blocky copolymers with excellent properties. This improvement in polymerization is possible due to the single active sites available on the metallocene catalysts in contrast to their traditional counterparts. Moreover, these catalysts, half titanocenes/MAO, zirconocenes, and other single site catalysts can control various important parameters, such as co-monomer distribution, molecular weight, molecular weight distribution, molecular architecture, stereo-specificity, degree of linearity, and branching of the polymer. However, in most cases research in this area has reduced academia as olefin polymerization has seen significant advancements in the industries. Therefore, this paper aims to further motivate interest in polyolefin research in academia by highlighting promising and open areas for the future.