Manufacture Of Foams Research Articles

Shift from legacy to emerging per- and polyfluoroalkyl substances for watershed management along the coast of China

Per- and polyfluoroalkyl substances and their short-chain alternatives have attracted world-wide attention due to their widespread presence and persistence in the environment. However, the sources, environmental fate, and driving forces of PFAS in coastal ecosystems remain poorly understood. In this study, the spatial distribution, source apportionment, and driving mechanisms of PFAS were investigated through a comprehensive analysis of water samples collected along the China's coastline. The concentrations of Σ25PFAS in water samples followed a general pattern, with higher levels observed in northern coastal zones of China than the south, ranging from 0.72 to 1872.21 ng L−1. PFOA and PFBA were dominant. Emerging short-chain PFAS, such as PFBS, PFBA, F-53B and GenX, were frequently detected, with detection rates of 97%, 99%, 95% and 77%, respectively. This indicated a shift in coastal PFAS contamination from legacy compounds to emerging short-chain alternatives. Source apportionment using the Positive Matrix Factorization model identified key contributors to PFAS pollution, including textile production, volatile precursors, precious metal industries, aqueous film-forming foam, metal-plating, electrochemical fluorination, and fluoropolymer manufacturing. Additionally, PFAS concentrations were significantly positively correlated with cultivated land, urban area, and wastewater discharge, while negatively correlated with annual precipitation and woodland coverage (p < 0.05). Socio-economic development was identified as a major driver of PFAS emissions, while the hydrological factors and vegetation coverage can significantly enhance watershed resilience against PFAS pollution.

Waste-to-resource: Employing lime mud as a foaming agent in glass foam manufacturing

The paper industry globally releases vast amounts of lime mud waste annually, raising environmental concerns. Composed mainly of calcium carbonate, lime mud has been utilized in various research works, including catalyst synthesis, cement production, and ceramic fabrication. This study investigates the use of lime mud as an eco-friendly foaming additive in the production of glass foam. Glass foams were prepared through a simple sintering method, utilizing glass cullet collected from households and incorporating different lime mud contents (0.5–2.0 wt%). The effects of lime mud concentration on the density, porosity, and pore size distribution of the glass foams were examined. Additionally, the thermal conductivity, compressive strength, and Weibull modulus were investigated in relation to the average porosity. The results revealed that the pore size distribution was dependent on the amount of lime mud, exhibiting three distinct distributions: a positively skewed distribution, a non-symmetric bimodal distribution, and a positively skewed distribution with a wide range. The Weibull modulus markedly decreased with increasing pore size. The compressive strength of the prepared glass foams ranged from 5.53±0.40–12.73±0.46 MPa, while the bulk density and porosity fell within the ranges of 0.41±0.02–0.70±0.04 g/cm3 and 72.12±1.45–85.38±0.98 %, respectively. The thermal conductivity could be as low as 0.07 W/m·K, approaching the upper limit for commercial glass foams used in thermal energy storage systems and meeting the requirements for Type I cellular glass thermal insulation classified by ASTM C552–16.

A facile method to fabricate auxetic polymer foams

This paper presents a new efficient method for manufacturing auxetic foams, a subcategory of metamaterials with intriguing mechanical properties. Unlike previous methods that require two steps involving heating or the use of a chemical solvent, the present method involves compressing the foam during the manufacturing process after cells have been formed in the die, but while the material remains soft. This one-step process is more time-efficient, energy-efficient, and flexible; it also requires fewer facilities and materials. After the manufacturing process, various mechanical properties of the auxetic foams were evaluated by compression tests (energy absorption, mean force, and maximum force) and indentation tests (stiffness, absorbed energy, and hysteresis energy). The results confirmed that the auxetic foams exhibited superior behavior compared with conventional foam at the same density. To further investigate the foam microstructures and deformation mechanisms, in situ compression tests were conducted; the macro behaviors of the foams were explained based on these observations. Overall, this paper presents a promising approach for the manufacturing of auxetic foams with improved mechanical properties that can be used in applications typically dominated by conventional foams.

Current Trends in the Use of Biomass in the Manufacture of Rigid Polyurethane Foams: A Review

This paper discusses methods of using biomass from the agriculture, forestry, food and aquaculture industries as potential raw materials for bio-polyols and as fillers in the production of rigid polyurethane (RPUR) foams. Various aspects of obtaining bio-polyols are discussed, as well as the impact of replacing petrochemical polyols with bio-polyols on the properties of foams. Special attention is paid to the conversion of vegetable oils and lignin. Another important aspect of the research is the use of biomass as foam fillers. Chemical and physical modifications are discussed, and important factors, such as the type and origin of biomass, particle size and amount, affecting the foaming process, microstructure and properties of RPUR foams are identified. The advantages and disadvantages of using biomass in foam production are described. It is found that bio-polyols can replace (at least partially) petrochemical polyols while maintaining the high insulation and strength of foams. In the case of the use of biomass as fillers, it is found that the shaping of their properties is largely dependent on the specific characteristics of the filler particles. This requires further research into process optimization but allows for the fine-tuning of RPUR foam properties to meet specific requirements.

A Split-Plot Experimentation Strategy for Making Causal Inferences in Advanced Materials: Auxetic Polyurethane Foam Manufacturing and Processing Analysis.

Development of advanced materials is often time consuming and expensive because of the large number of variables involved and experiments needed. An effective experimentation strategy would accelerate development by reducing the required amount of experiments without sacrificing the obtainable information. In this paper, the development of auxetic polyurethane (PU) foams was discussed as a case study. Auxetic materials are materials with a negative Poisson's ratio and have potential in many structural and functional applications. Auxetic PU foams are the most studied auxetic materials, and their manufacturing and properties are affected by many processing and environmental factors. This paper introduces a sophisticated design of experimental methodology to help reduce the experimental effort while effectively screening these factors. This methodology is then applied in an experiment to illustrate its utility and distinct advantages that greatly facilitate material development.

Wire Arc Additive Manufacturing of Aluminum Foams Using TiH2-Laced Welding Wires.

Composite materials made from aluminum foam are increasingly used in aerospace and automotive industries due to their low density, high energy absorption capacity, and corrosion resistance. Additive manufacturing processes offer several advantages over conventional manufacturing methods, such as the ability to produce significantly more geometrically complex components without the need for expensive tooling. Direct Energy Deposition processes like Wire Arc Additive Manufacturing (WAAM) enable the additive production of near-net-shape components at high build rates. This paper presents a technology for producing aluminum foam structures using WAAM. This paper's focus is on the development of welding wires that are mixed with a foaming agent (TiH2) and produce a foamed weld metal as well as their processing using MIG welding technology.

Multi-Scale MXene/Silver Nanowire Composite Foams with Double Conductive Networks for Multifunctional Integration.

With the onset of the 5G era, wearable flexible electronic devices have developed rapidly and gradually entered the daily life of people. However, the vast majority of research focuses on the integration of functions and performance improvement, while ignoring electromagnetic hazards caused by devices. Herein, the 3D double conductive networks are constructed through a repetitive vacuum-assisted dip-coating technique to decorate the 2D MXene and 1D silver nanowires on the melamine foam. Benefiting from the unique porous structure and multi-scale interconnected frame, the resultant composite foam exhibited high electrical conductivity, low density, superb electromagnetic interference shielding (48.32dB), and Joule heating performance (up to 90.8°C under 0.8V). Furthermore, a single-electrode triboelectric nanogenerator (TENG) with powerful energy harvesting capability is assembled by combining the composite foam with an ultra-thin Ecoflex film and a polyvinylidene fluoride film. Simultaneously, the foam-based TENG can also be considered a reliable wearable sensor for monitoring activity patterns in different parts of the human body. The versatility and scalable manufacturing of high-performance composite foams will provide new design ideas for the development of next-generation flexible wearable devices.

Recycling coal overburden waste to fabricate functionally graded SiC foam with gradient microstructure via one step thermo-foaming process

An economical and efficient thermo-foaming method, coupled with an in-situ reaction bonding technique, was employed to produce mullite-bonded functionally graded silicon carbide (SiC) foams with gradient microstructures using coal mine overburden waste (CMW). The foaming process utilized sucrose dehydration with sulphuric acid, allowing for tailored porosity in SiC foams. Mullite bonding material was in situ developed during sintering, facilitated by silica and alumina from CMW, promoting mullite phase formation. Alumina incorporation further enhanced mullitization. The use of CMW as a low-cost precursor for mullite conversion facilitated SiC particle bonding through mullite, reducing sintering temperature and overall production cost. Varied sucrose content and sintering temperature influenced foaming behavior, porosity, microstructural gradient, and mechanical properties. Mullitization process, reaction bonding behavior, and mechanical properties were analyzed based on CMW and alumina content, and sintering temperature. The resulting SiC foams exhibited bulk density and porosity in the range of 0.6–1.2 g/cm3, 60–80 % respectively. This study introduces an eco-friendly approach for repurposing CMW waste and cost reduction in SiC foam manufacturing.

Revolutionizing Foam Cutting Efficiency in Indonesia with AutoCAD

Foam set machines are essential for cutting foam sheets in various industries, including furniture, textiles, and foam manufacturing. PT. Amangriya, using a custom foam set machine for two years, identified the need for efficiency improvements. This research aimed to enhance the foam set machine's design using AutoCAD software. Key improvements included an automatic top clamp, a flexible side clamp, and reduced machine dimensions. These modifications resulted in a more efficient and compact machine, facilitating easier manufacturing and assembly processes. The study highlights the potential for significant efficiency gains in the foam manufacturing industry through design enhancements. Highlight: Enhanced machine design with AutoCAD software improves efficiency and functionality. Key modifications include automatic top clamp and flexible side clamp. Reduced machine dimensions facilitate easier manufacturing and assembly. Keywoard: Foam set machine, design enhancement, efficiency, AutoCAD, manufacturing

Experimental and numerical study on the pressure drop and flow pattern of liquid foam in a foam generator

In the present study, a comprehensive analysis of the pressure drop, flow pattern, and foam structural properties of vertical upward two-phase flow in a Kenics static foam generator of a compressed air foam system was carried out. A liquid with an extremely low surface tension (16.5 mN/m) was used for making the foam. The effects of the number of elements (number of individual elements combined into the mixer), aspect ratio (the ratio of length to diameter of each element), and transition angle (transition angle between elements) of the Kenics mixers on the pressure loss during foam generation were studied in detail over a wide range of Reynolds numbers through experiments and numerical simulation. A new pressure drop correlation was successfully obtained by scaling analysis and the modified Lockhart–Martinelli correlation was proposed to describe the pressure drop during foam generation. Furthermore, the experimental results validated the proposed correlation and exhibited good reliability and predictive accuracy. Finally, four flow patterns for foam generation in vertical pipes that were different from the classical gas–liquid two-phase flow patterns were proposed, and the relationships among the pressure drop, flow pattern, and foam structural properties were explored. This research expands the study of foam generation in vertical tubes containing a built-in spiral structure with low flow resistance. It provides new insights and guidance for developing continuous foam manufacturing.

Facile Preparation of Lightweight Natural Rubber Nanocomposite Foams with High Wear Resistance.

The light weight and excellent mechanical properties of rubber foam means that it is widely applied in the aerospace, automobile, and military industries. However, its poor wear resistance contributes directly to a short service life and a waste of resources. Therefore, the design and development of high-wear-resistance rubber foam are of great importance. In this work, some nanoclay/rubber composite foams were prepared by blending NR/EPDM with different kinds of nanoclays containing layered double hydroxide (LDH), montmorillonite (MMT), and attapulgite (ATP) to indicate the effects of the kinds of nanoclays on the wear resistance and mechanical properties of nanoclay/rubber composite foams. The kinds of nanoclay/rubber composite foams were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The results showed that nanoclay has heterogeneous nucleation in composite foamed materials. The wear resistance of the composite foam materials with added nanoclay was significantly improved, and the MMT of the lamellar structure (increased by 43.35%) and LDH (increased by 38.57%) were significantly higher than the ATP of the rod-like structure (increased by 13.04%). The improvement in the wear resistance of the matrix was even higher. Compared with other foams, the wear resistance of the OMMT-NR/EPDM foam (increased by 58.89%) with a lamellar structure had the best wear resistance. Due to the increase in the lamellar spacing of the modified OMMT, the exfoliation of worn rubber molecular chains has little effect on the adjacent molecular chains, which prevents the occurrence of crimp wear and further improves the wear resistance of composite foaming materials. Therefore, this work lays the foundation for the manufacturing of rubber foams for wear-resistant applications.

Direct numerical simulation of a single contaminated droplet microextraction in a yield-stress fluid

The present work investigates the extraction of solute from the contaminated micro-droplet suspended in non-Newtonain viscoplastic fluids (Herschel Bulkley). The fluid flow dynamics and interfacial mass transfer phenomena near a contaminated micro-droplet have been investigated prior to the estimation of extraction efficiency. The stagnant-cap model is employed to depict the droplet that has been contaminated. Dispersed droplet systems are commonly observed in diverse facets of our everyday encounters. These systems are found in various industries, encompassing flotation, energy storage, biofuels, printing, airlift reactors, and foam manufacture, among others. The study has focused on a linear thermodynamic equilibrium relationship that exists at the interface between two fluid phases. The momentum and species transport have been solved for a range of dimensionless parameters. These parameters include θcap, which varies between 120∘ and 150∘, the Reynolds number (1≤Re≤100), the Bingham number (0≤Bn≤5), the dispersed to continuous fluid viscosity ratio (0.5≤μratio≤4), and the shear-thinning index (0.4≤n≤1). The results have been conveyed in the form of streamlines, contours, and by delineating the regions of deformation and non-deformation. The size of the zone that undergoes yielding tends to diminish as a result of the impact of the yield stress, while the presence of inertia promotes the enlargement of the zone that remains unyielded. The extraction efficiency and Sherwood number were estimated to be a function of θcap, Bingham number, Reynolds number, and shear-thinning index.

Estimation of cutting forces in CNC slot-milling of low-cost clay reinforced syntactic metal foams by artificial neural network modeling

PurposeThis study aims to elucidate the machining properties of low-cost expanded clay-reinforced syntactic foams by using different neural network models for the first time in the literature. The main goal of this endeavor is to create a casting machining-neural network modeling flow-line for real-time foam manufacturing in the industry.Design/methodology/approachSamples were manufactured via an industry-based die-casting technology. For the slot milling tests performed with different cutting speeds, depth of cut and lubrication conditions, a 3-axis computer numerical control (CNC) machine was used and the force data were collected through a digital dynamometer. These signals were used as input parameters in neural network modelings.FindingsAmong the algorithms, the scaled-conjugated-gradient (SCG) methodology was the weakest average results, whereas the Levenberg–Marquard (LM) approach was highly successful in foreseeing the cutting forces. As for the input variables, an increase in the depth of cut entailed the cutting forces, and this circumstance was more obvious at the higher cutting speeds.Research limitations/implicationsThe effect of milling parameters on the cutting forces of low-cost clay-filled metallic syntactics was examined, and the correct detection of these impacts is considerably prominent in this paper. On the other side, tool life and wear analyses can be studied in future investigations.Practical implicationsIt was indicated that the milling forces of the clay-added AA7075 syntactic foams, depending on the cutting parameters, can be anticipated through artificial neural network modeling.Social implicationsIt is hoped that analyzing the influence of the cutting parameters using neural network models on the slot milling forces of metallic syntactic foams (MSFs) will be notably useful for research and development (R&D) researchers and design engineers.Originality/valueThis work is the first investigation that focuses on the estimation of slot milling forces of the expanded clay-added AA7075 syntactic foams by using different artificial neural network modeling approaches.

Spontaneous room temperature reaction of titanium and its alloys with hydrogen during self-shearing reactive milling

Surface wear-activated spontaneous reactions of titanium and its alloys with hydrogen at room temperature are shown in this work. Titanium powder, intensively mixed under hydrogen pressure in a planetary mill, without any grinding media, reacts readily with hydrogen gas with the formation of stoichiometric titanium dihydride. The reaction, once initiated, proceeds spontaneously even without movement of the milling vial with a similar reaction rate. The moment of initiation of the reaction seems to be related to the removal of oxide impurities from the surface of the titanium particles and is strongly correlated with milling velocity. According to thermogravimetric measurements and X-ray diffraction (XRD) phase analysis, titanium is fully converted to TiH2. Titanium alloys were found to react in the same manner. Ti-5553 (β) reacts more easily than grade 5 Ti (Ti-Gd5) (α’), which is more reactive than grade 2 Ti (Ti-Gd2). The titanium alloy particles maintain their shape and coherency after hydrogenation. The method seems to be extremely cost-effective in the synthesis of titanium hydride and also allows the production of hydrogenated alloyed powders in spherical form, which can potentially be applied in the additive manufacturing of titanium foams. The results also show a significant risk of using titanium alloys in a hydrogen atmosphere at room temperature. It seems that after losing the protective oxide layer, parts made of pure titanium or its alloys may undergo catastrophic destruction after losing strength and ductility upon full conversion to hydride.

Variable pressure foaming on functionality and structural properties correlation in flexible polyurethane foam

The production cost of flexible polyurethane foam is significantly dependent on the cost of polyol, which constitutes the largest percentage of materials used in foam production with the characteristics to induce superior mechanical properties. Suitable fillers that are relatively cheap can be introduced in the foam as replacement for polyol. Certain compositions of filler have deleterious effect on some relevant mechanical properties of the foam. This paper investigates the Effects of Variable Pressure Foaming on functionality and structure property correlation in polyurethane foam using different percentage of inorganic fillers at different pressure in flexible polyurethane foam for the dual purposes of achieving sustained mechanical properties of polyurethane foam and reduction in the production cost by using the VPF Technique. Government restricts the use of certain auxiliary blowing agents like chlorofluorocarbon, trichloroethane, carbon dioxide, methylene chloride, acetone, pentane and water. VPF machine, in which we can make different densities of foam without adding auxiliary blowing agents which are banned in the Europe and other countries. These blowing agents are highly carcinogenic and ozone depletors, which are also harmful for human beings’ health and greenhouse effect. Water is a natural blowing agent, producers have tried to raise the water level substantially as an ABA agent, With the high exotherm associated with high water level formulations, there is so much urea formation that it is difficult to make flexible PU foams and inferior foam quality and durability, scorching in the foam and pose a fire hazard during foam manufacturing. For the rapid cooling process, it required excess Toluene Diisocyanate usage and allowed excess TDI vapour to be released into the atmosphere. In VPF, enclosed chamber and the exhaust is vented through carbon beds, it filters the TDI fumes which are very harmful for human beings’ health and for the environment. Foams can be achieved by foaming under vacuum, thus substantially reducing the water level and TDI usage. VPF technique offers a unique combination of environmental friendliness, superior product consistency and unique foam properties. It provides us with a platform for new product technology and a reliable process to meet the increasingly stringent environmental regulations.

Emerging and legacy per- and polyfluoroalkyl substances in Daling River and its estuary, Northern China

Strict restriction on legacy per- and polyfluoroalkyl substances (PFASs) has caused a dramatic increase in production and usage of emerging PFASs over the last decades. However, the environmental behaviors of emerging PFASs is largely unknown in Daling River, Northern China. In this study, the potential sources, sediment-water partitioning and substitution trends of PFASs were investigated in overlying water and sediments from Daling River and its estuary. Perfluorooctane sulfonate and 6:2 fluorotelomer sulfonic acid were major compounds, and sodium p-perfluorous nonenoxybenzene sulfonate was first detected. Firefighting foam manufacturing and fluoropolymer production were the main sources of PFASs. Compared to legacy PFASs (C8), the emerging PFASs (C6 - C9) were more incline to distribute into overlying water. Substitution trends indicated 6:2 fluorotelomer sulfonic acid and hexafluoropropylene oxide trimer acid as the important alternatives of perfluorooctane sulfonate and perfluorooctanoic acid, respectively. The results were meaningful for understanding the environmental behaviors of emerging PFASs.

Defect Detection Model Using CNN and Image Augmentation for Seat Foaming Process

In the manufacturing industry, which is facing the 4th Industrial Revolution, various process data are being collected from various sensors, and efforts are being made to construct more efficient processes using these data. Many studies have demonstrated high accuracy in predicting defect rates through image data collected during the process using two-dimensional (2D) convolutional neural network (CNN) algorithms, which are effective in image analysis. However, in an environment where numerous process data are recorded as numerical values, the application of 2D CNN algorithms is limited. Thus, to perform defect prediction through the application of a 2D CNN algorithm in a process wherein image data cannot be collected, this study attempted to develop a defect prediction technique that can visualize the data collected in numerical form. The polyurethane foam manufacturing process was selected as a case study to verify the proposed method, which confirmed that the defect rate could be predicted with an average accuracy of 97.32%. Consequently, highly accurate defect rate prediction and verification of the basis of judgment can be facilitated in environments wherein image data cannot be collected, rendering the proposed technique applicable to processes other than those in this case study.

Investigation of an optimized hot press process design for manufacturing structural polyethersulfone foams

Semi-finished thermoplastic foam panels can be transformed into structural foams—a sandwich-like structure with high-density skins—through thermoforming. This transformation enables the production of mono material sandwich panels, which allow a significant increase in bending properties without increasing the part weight. This study describes the effect of process parameters on skin formation in thermoplastic structural foams manufactured in a two-step isochoric and isothermal hot press process. Process data recorded during foam manufacturing was analyzed and compared to foam behavior in quasi-static isothermal compression tests performed at different levels of temperature and crosshead speeds. The effect of skin-core structure on bending properties is compared to theoretical models from the established literature. It was found that a rule of linear mixture that considers the relative skin thickness allows adequate prediction of both bending modulus and strength. Preferable process design—especially combinations of tool temperature and maximum compaction speed—is described based on the comparison of measured and predicted performance.

THE EFFECT OF AL2O3 AND STIRRING TIME ON DENSITY AND POROSITY OF ALUMINUM ADC12 FOAM

The instability of the foam forming during metallic foam manufacture commonly occurs, which will cause undesirable pores. The stability of the foam structure is one of the important factors. A stabilizer can maintain the foam cell during the melting process. In this study, the metal used is ADC12 with a 12 wt.% of Si element content, and the foaming agent is CaCO3. CaCO3 will produce gas to form bubbles in the melt during the solidification process and use a stabilizer to strengthen cell walls so that foam does not easily fall off or collapse. The stabilizer uses Al2O3 with the variation of Al2O3 are 1 to 3 wt.%. The stirring time is as variable as well. A stirring process is conducted to distribute foaming agents so that the foam distribution is more homogeny throughout the aluminum foam. The variation of the stirring time is carried out for 60, 120, and 180 seconds. The results show that as the time of stirring and the addition of stabilizer increases, the porosity will rise, but the density decrease. Compressive strength results show it has no significant relation with increasing the stabilizer and stirring time. The highest compressive strength is obtained in the sample with a stirring time of 120 seconds with an Al2O3 content of 1 wt.%.

Controlling size and shape of pores during metal solidification for manufacturing of functionally graded metal foams

Manufacturing of metal foams by solidification processing involves numerous challenges related to achieving localized control of porosity with a limited material selection. The objective of this work is to control the size and shape of pores during metal solidification in a casting process by harnessing the thermal decomposition of discrete polymer features upon their interaction with molten metal. The influence of geometrical parameters and physical properties of these features on the evolution of pores generated from their interaction with molten metal was studied in detail. We firstly used an analytical model to evaluate the thermal response of such features in a model molten metal medium to determine the process window within which pores can be generated and captured in place during metal solidification. Systematic experiments were conducted to demonstrate the influence of the feature geometry on the evolution of the size and shape of captured pores. We further demonstrate that the relative separation of these features can exert a strong influence on the interaction of adjacently generated pores during metal solidification. This work essentially exhibits the potential of exploiting a lattice of discrete features that can enable the spatial control of pore capture during a metal solidification process.