Influence of chemical foaming agent on the physical, mechanical, and morphological properties of HDPE/wood flour/nanoclay composites

Kord, Behzad; Varshoei, Ali; Chamany, Vahid

doi:10.1177/0731684411417200

Cited by 18 publications

(22 citation statements)

References 37 publications

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“…This transition can be mechanically interesting as creating a density/composition gradient that can remove stress concentration point and properties discontinuities as reported for density gradient materials (DGM) [19]. growth in the outer layer (close to the mold wall) from the heterogeneous nucleating effect of the fibers acting as nucleating agents [8,33,34]. The presence of bubbles in the first layer when using ACA also explains the thickness increase as reported in Figure 5.…”

Section: Morphologymentioning

confidence: 89%

“…These voids, as well as the natural porosity of AF promote the migration of gas molecules to regions having higher temperature and void content [32]. This structure also helps bubble nucleation and growth in the outer layer (close to the mold wall) from the heterogeneous nucleating effect of the fibers acting as nucleating agents [8,33,34]. The presence of bubbles in the first layer when using ACA also explains the thickness increase as reported in Figure 5.…”

Section: Morphologymentioning

confidence: 97%

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Morphological and Mechanical Properties of Bilayers Wood-Plastic Composites and Foams Obtained by Rotational Molding

et al. 2020

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In this work, the suitability for the production of sustainable and lightweight materials with specific mechanical properties and potentially lower costs was studied. Agave fiber (AF), an agro-industrial waste, was used as a reinforcement and azodicarbonamide (ACA) as a chemical blowing agent (CBA) in the production of bilayer materials via rotational molding. The external layer was a composite of linear medium density polyethylene (LMDPE) with different AF contents (0–15 wt %), while the internal layer was foamed LMDPE (using 0–0.75 wt % ACA). The samples were characterized in terms of thermal, morphological and mechanical properties to obtain a complete understanding of the structure-properties relationships. Increases in the thicknesses of the parts (up to 127%) and a bulk density reduction were obtained by using ACA (0.75 wt %) and AF (15 wt %). Further, the addition of AF increased the tensile (23%) and flexural (29%) moduli compared to the neat LMDPE, but when ACA was used, lower values (75% and 56% for the tensile and flexural moduli, respectively) were obtained. Based on these results, a balance between mechanical properties and lightweight can be achieved by selecting the AF and ACA contents, as well as the performance and aesthetics properties of the rotomolded parts.

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Section: Morphologymentioning

confidence: 89%

Section: Morphologymentioning

confidence: 97%

Morphological and Mechanical Properties of Bilayers Wood-Plastic Composites and Foams Obtained by Rotational Molding

et al. 2020

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“…This is due to the extremely fine dimensions and large surface area of GNPs that help create more nucleation centers in the polymer and at the polymer/wood interface; consequently, there is less amount of gas available for bubble growth which leads to cell size reduction and cell density enhancement. 28–31 Besides, heterogeneous nucleation due to the existence of nanoparticles, which reduces the activation energy barrier to the nucleation process. 13 As a result, the GNPs provide more nucleation sites.…”

Section: Resultsmentioning

confidence: 99%

“…It can be concluded that more bubble nucleation originates from the nanoparticles, which caused the increase of cells and the decrease of composite density. 13,14,29–31…”

Section: Resultsmentioning

confidence: 99%

Preparation, characterization and performance evaluation of wood flour/HDPE foamed composites reinforced with graphene nanoplatelets

Ghalehno

Kord²

2020

Journal of Composite Materials

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This research explores the effects of nanographene on the cell morphology, mechanical strength, and water uptake behavior in the extrusion foaming of wood polymer composites. Composite materials containing high-density polyethylene, wood flour, coupling agent, graphene nanoplatelets (GNPs), and azodicarbonamide as a foaming agent were melt compounded using a twin-screw extruder. Finally, the samples were foamed via a batch process using a compression molding machine. Thereafter, the morphological aspects of the specimens including cell size and cell density were characterized using a scanning electron microscope. Further, the density, flexural strength, tensile strength, water absorption, and thickness swelling of the specimens were evaluated. Results indicated that the cell size of the specimens was found to decrease with the incorporation of GNPs while the cell density increased, owing to the reinforcing effect of the GNPs in the composites. The cell nucleation efficiency of the samples using GNPs was significantly enhanced when compared to that without nanoparticles. The density of composite foams decreased with the addition of GNPs due to more bubble nucleation originating from nanoparticles. Mechanical properties of the specimens improved when using GNPs in comparison to those of foams without GNPs as a result of better interaction with the polymeric matrix. The highest flexural and tensile values were observed for the composite foams containing 1 phr GNPs. Furthermore, the water absorption and thickness swelling of the samples were remarkably reduced with the addition of GNPs. The specimen foams produced with 4 phr GNPs exhibited superior water resistance and dimensional stability.

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“…To reduce manufacturing costs, improve light weighting, and allow easy installation of screw fasteners in crossties, chemical blowing agents (CBA) such as azodicarbonamide (ADC) are introduced into the extrusion process [10]. Kord et al [11] studied the effect of the blowing agent ADC on composites made from High-Density Polyethylene (HDPE), wood flour, and nanoclay. They observed that the increase of ADC content resulted in increased cell size and average cell density, which decreased the overall density of the structure and also reduced the tensile modulus.…”

Section: Introductionmentioning

confidence: 99%

Strength Prediction Sensitivity of Foamed Recycled Polymer Composite Structures due to the Localized Variability of the Cell Density Distribution

Pulipati

Jack

2020

J. Compos. Sci.

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The need for novel methods for the reuse of post-industrial/post-consumer polymer solid wastes (PSW) is of increasing societal importance. Unfortunately, this objective is often limited due to material stream variability or insufficient load-carrying capacity of the fabricated goods. This study investigates a large format fiber-reinforced structural member that contains spatially varying material properties, specifically density. The application is focused on the unique features of closed-cell foamed composite structures made from recycled post-industrial/post-consumer PSW composed of High-Density Polyethylene (HDPE) and Glass Fiber Polypropylene (GFPP). The structures in this research are manufactured using a hybrid extrusion process, which involves foaming enabled by chemical blowing agents that form a fully consolidated solid outer shell and a closed-cell core. The cell distribution is inhomogeneous, in size distribution and spatial distribution, leading to significant spatial variations of the local effective stiffness. To understand the correlation between density variations and effective stiffness and strength, a low-cost method using digital imaging is introduced and integrated into a finite element subroutine. The imaging approach includes sectioning the structural member and analyzing the resulting image using various custom imaging processing techniques in the MATLAB environment. The accuracy of the imaging technique was experimentally verified using a Keyence digital microscope, and the error was found to be 3% in any given spatial feature. The processed image is then correlated to a localized density map of the cross-section using a weighted spatial averaging technique, and the local effective material properties of the foamed region are predicted using the presented micromechanical approach. The local stiffness is a function of void density, local fiber orientation, constitutive behavior of both the fiber and the matrix blend, and the non-linear response of the matrix blend. The spatially varying stiffness and nonlinear strength response at each spatial location are then integrated into a finite element subroutine within the COMSOL multiphysics environment, and results are presented for the deflection and internal stress state of the composite structure. Results indicate that the internal microstructural variations have a nominal impact on the bulk deflection profile. Conversely, results show the peak of the internal stress is increased by ∼11% as compared to the uniform core assumption, thus safe designs must consider core density spatial variations in the final product design.

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Influence of chemical foaming agent on the physical, mechanical, and morphological properties of HDPE/wood flour/nanoclay composites

Cited by 18 publications

References 37 publications

Morphological and Mechanical Properties of Bilayers Wood-Plastic Composites and Foams Obtained by Rotational Molding

Morphological and Mechanical Properties of Bilayers Wood-Plastic Composites and Foams Obtained by Rotational Molding

Preparation, characterization and performance evaluation of wood flour/HDPE foamed composites reinforced with graphene nanoplatelets

Strength Prediction Sensitivity of Foamed Recycled Polymer Composite Structures due to the Localized Variability of the Cell Density Distribution

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