Foaming Quality Research Articles

Study on foaming behavior of block copolymer/inorganic particles co‐construction of toughened epoxy resin foams

AbstractLow toughness and brittleness limit its application range of thermosetting epoxy resin (EP) based foams. In current research, inorganic particles are commonly utilized as heterogeneous nucleating agents to enhance foaming quality and EP toughness. However, the increasing inorganic particle content usually leads to particle agglomeration, which negatively impacts foaming quality and reduces EP performance. Block copolymers, which appear as liquid to effectively mitigate agglomeration, are employed as toughening materials for EP. In this study, a small number of modified calcium silicate particles (MCS) were used as anchor points to induce the distribution of block copolymers (P‐F68) to improve EP toughness and effectively enhance cell nucleation, thus, EP/MCS/P‐F68 foams performance was improved. The research results showed that EP foams obtained excellent cell structure and very small foam density (0.256 g/cm3) at the P‐F68 content of 10 wt%. The continuous increase of P‐F68 content would lead to the thickening of cell wall and the increase of cell size. Simultaneously, the core‐shell structure formed by P‐F68 in EP effectively enhanced the toughness of EP foams and mitigated its brittleness, offering crucial theoretical guidance for toughening and regulating the cell structure of EP foams.

High-Quality Foaming and Weight Reduction in Microcellular-Injection-Molded Polycarbonate Using Supercritical Fluid Carbon Dioxide under Gas Counter Pressure.

Microcellular injection molding (MuCell®) using supercritical fluid (SCF) as a foaming agent to achieve weight reduction has become popular in carbon emission reduction. In the typical MuCell® process, SCF N2 is commonly used. Although SCF CO2 exhibits high solubility and can achieve a high weight reduction, controlling the foaming is not easy, and its foaming cells are usually larger and less uniform, which limits its industrial application. Our previous studies have shown that gas counter pressure (GCP) can improve the foaming quality effectively. Here, we investigated whether or not the CO2 SCF foaming quality could be improved, and weight reduction was achieved for polycarbonate (PC) material. This is quite important for the electronics industry, in which most of the housing for devices is made of PC materials. MuCell® was subjected to molding experiments using the parameters of the SCF dosage, melt temperature, mold temperature, and injection speed. The results revealed that using CO2 gas for the PC material can reduce the size of microcellular cells to 40 µm and increase the cell densities to 3.97 × 106 cells/cm3. Using GCP significantly improved the microcellular injection-molded parts by reducing the cell size to 20.9 µm (a 45.41% improvement) and increasing the cell density to 8.04 × 106 cells/cm3 (a 102.48% improvement). However, implementing GCP may slightly decrease the target weight reduction. This study reveals that microcellular injection molding of PC parts using SCF CO2 can achieve high-quality foaming and reduce the weight by about 30%.

Effect of hardness on the foaming behavior, surface quality, and mechanical properties of thermoplastic polyurethane foams by chemical foaming injection molding

Effect of hardness on the foaming behavior, surface quality, and mechanical properties of thermoplastic polyurethane foams by chemical foaming injection molding

Effect of foaming behavior of polypropylene foams on flame retardant properties under different weight reduction methods

AbstractIn previous studies, the effect of cell structures of polypropylene (PP) foam materials on flammability behavior had been largely overlooked. In this work, ammonium polyphosphate and pentaerythritol were used as intumescent flame retardants (IFR) for PP, and then the PP‐IFR flame retardant foams were prepared by using injection foaming technology with two different weight reduction methods (same mold volume before foaming and after foaming). The results showed that the average cell size of all the PP‐IFR flame retardant foams in the 10% to 30% weight reduction was less than 100 μm. The PP‐IFR flame retardant foams with an average cell diameter of 26.22 μm and cell density of 7.88 × 106 cells/cm3 had the best limiting oxygen index (LOI) of 27.9%. In addition, the PP‐IFR flame retardant foams with better foaming quality had a higher LOI and a denser foam carbon layer whatever the weight reduction methods, resulting in better flame retardant properties. The escape of gases from the foamed and un‐foamed areas not only reduced the concentration of flammable gases but also led to the collapse and rupture of the foam carbon layer during the combustion process. Hence, it provides guidance for preparing PP foam materials with excellent flame retardancy.

Microwave-assisted foam mat drying of red beet pulp: influence of milk protein concentrate (MPC) and maltodextrin as a foaming agent, optimization and quality attribute

Microwave-assisted foam mat drying of red beet pulp: influence of milk protein concentrate (MPC) and maltodextrin as a foaming agent, optimization and quality attribute

Enhancing the foaming properties of polypropylene/basalt fiber composites by altering their rheological and crystallization behavior via polyethylene–octene blending modification

AbstractThe quality of foam in polypropylene/basalt fiber (PP/BF) composite materials is currently unsatisfactory, which restricts their use in industrial applications. To address this limitation, the objective of this study is to improve the foaming properties of PP/BF composite foam by modifying their rheological and crystallization behavior using polyethylene–octene (POE) blending modification. The results demonstrate that the inclusion of POE has a beneficial impact on the rheological and crystallization characteristics of PP/BF composites. Consequently, this creates favorable conditions for the foaming process of PP/BF composite foam. It is conducive to obtaining high foaming quality PP/BF composite foam. The results demonstrate that a 5 wt% POE content yields the best foaming performance for the PP/BF composite foam, with the most uniform cell distribution, a cell size of 54 μm and a cell density is measured at 3.43 × 107 cells/cm3. The optimal temperature range for foaming is between 180 and 200°C. The introduction of POE in PP/BF composite foam may lead to a decrease in its tensile and flexural strength. However, this drawback is offset by a significant improvement in the notch impact strength of the foam. This study's findings will enhance our understanding of the production and application of PP/BF composite foam, making it a valuable material for applications that require exceptional toughness.Highlights Improved the crystallization and rheological properties of PP/BF composites. Significantly improve the foaming quality of PP/BF composites. Make PP/BF composite foam has excellent impact toughness.

Effect of viscosity on foaming behavior and surface quality of foamed Polyamide 6

AbstractAlthough a large body of literature has reported that PA6 modification enhances melt strength and improves foam quality, the relationship between melt viscosity and foaming quality remains ambiguous. This paper aims to select four PA6 with different viscosities to explore the effect of the viscosity of the material on foaming quality. First, the foamed materials of four PA6 were prepared by core‐back injection foaming technology. In addition, the crystallization properties and rheological behavior of four PA6 were systematically studied by rotational rheometer and differential scanning calorimetry. The morphologies of composite foams with different viscosities were analyzed using scanning electron microscopy. It was found that the cell size and cell density of M2400 with low viscosity were 114 μm and 1.87 × 105 cells/cm3, respectively. With the increase of viscosity, the cell size and cell density of M2500I decreased to 98.3 μm and 2.66 × 105 cells/cm3, respectively. However, as the viscosity continues to increase, the cell size increases, and the cell density decreases. The findings indicate that the secret to good foaming is rheological behavior. The lower viscosity is challenging to prevent cell growth and easy to break, while high viscosity causes poor fluidity which deteriorates foaming quality and surface quality. It provides guidance for preparing foaming materials with excellent performance and surface through a modification that enhances melt strength.

Hybrid reinforced effect of long carbon fiber and short glass fiber on polycarbonate foams

AbstractBecause of advantages such as remarkable mechanical properties and the ease of recycling, fiber‐reinforced thermoplastic polymer composites have been increasing in importance in industrial, transport, and sporting potential extraordinary applications. To fabricate polycarbonate (PC) components with lightweight and high mechanical properties, short glass fiber (SGF), long carbon fiber (LCF) reinforcement, and foaming technology were used in this study. The effects of SGF, LCF, and SGF/LCF on the mechanical properties and foaming quality of PC samples were carefully investigated and compared. The results show that SGF has a better foaming nucleation effect than LCF, and the mechanical enhancement effect of LCF is more significant than that of SGF. The combination of SGF and LCF can effectively improve the cell quality of foam samples and significantly enhance their mechanical properties. Therefore, a comprehensive application of the fiber‐reinforcement effect of PC resin is proposed.Highlights LCF and SGF reinforced PC foams have been successfully fabricated. Hybrid reinforced effect of LCF and SGF on PC foams was verified.

Influence of temperature distribution on the foaming quality of foamed polypropylene composites

Abstract The foamed polypropylene (PP) composites were prepared by injection molding process. Fourier’s law and software were used to calculate and simulate the internal temperature distribution of PP composites, respectively, and the influence of the temperature distribution on the foaming quality of foamed PP composites was further analyzed. The result showed that the calculative and simulated results of temperature distribution in different thermal transfer directions had great reproducibility. In different isothermal planes, the temperature from the nozzle to the dynamic mold gradually decreased. The isothermal plane with a temperature of 370.36 K had a better foaming quality, average diameter of cell and cell density were 28.46 µm and 3.7 × 1010 cells·cm−3, respectively. In different regions of the same isothermal plane, the temperature gradually decreased from the center to the edge. The foaming quality in the region (c) at a temperature of 335.86 K was ideal, and the average diameter of cell and the cell density were 26.5 µm and 2.39 × 1010 cells·cm−3, respectively. This work could provide prediction for improving the foaming quality of foamed polyolefin composites.

Strategy to Enhance Geological CO2 Storage Capacity in Saline Aquifer

AbstractGeological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly accepted sense, considered as the most promising and powerful approach to mitigate the global carbon emissions during the transition to net‐zero. Of the geological media which initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts, up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, two tandem papers propose novel strategies for the first time, by synthesizing and utilizing new high‐dryness CO2 foam, to enhance geological CO2 storage capacity in saline aquifer and oil and gas reservoirs. In this paper, a new high‐dryness CO2 foam is synthesized and injected into the saline aquifers to explore the storage capacity enhancement, with the unique foam‐induced advantages of sweep area expansion and storage efficiency improvement. Such a new idea is specifically evaluated and validated through a series of static analytical and dynamic performance experiments. With the optimum surfactant concentration of 0.5 wt%, the foaming volume and quality are determined to be 521 mL and 80.81%, respectively, which also shows excellent salt tolerance with 45,000 ppm Na+, 25,000 ppm Ca2+, and 25,000 ppm Mg2+. Moreover, the water consumption for CO2 storage decreases from 464.31 g/mol at 25% foam quality to 67.38 g/mol at 85% foam quality by using the new CO2 foam. Overall, the newly synthesized CO2 foam could effectively enhance geological CO2 storage capacity and concurrently diminish water consumption, therefore realizing the win‐win environment and economic benefits.

Time-dependent rheological behavior of pineapple pulp foam and its relationship with foaming properties and quality attributes of dried powder

The time-dependent rheological characteristics of pineapple pulp foam (PPF), prepared by whipping the pulp with varying concentrations (2–6%) of skim milk powder (SMP), were investigated at different shear rates (1, 10, and 50 s−1). The PPF showed time-dependent shear-thinning behavior that could be explained by the Hahn and Figoni-Shoemaker models (|r|≤0.997). The time and shear-rate-dependent structural breakdown coefficients (B- and M-values) varied due to foam properties (stability, expansion, and drainage volume) and SMP concentration. These coefficients could be suitable indices to judge the stability of the foam. The effective moisture diffusivity during foam drying increased significantly with SMP (p ≤ 0.05); the physical properties of powder were also influenced. A strong correlation existed between SMP, foaming, and rheological properties. The principal component analysis (PCA) indicated a good interrelation among rheological properties, foam, and powder characteristics.

Effects of paste resins on the foaming properties of PVC plastisols

AbstractThis article studies the foaming properties of PVC plastisols prepared from six different types of PVC paste resins with different degrees of polymerization that were produced through two methods, a seed emulsion method and a micro‐suspension method. The underlying mechanisms that result in differences in the foaming properties are discussed as well. The results indicate that formulation S5 has the best foaming quality using past resins produced with the seed emulsion method, and formulation S6 made the best plastisol samples from paste resins produced through the micro‐suspension method. Seed emulsion‐produced paste resins with low degrees of polymerization are more suitable for preparing high‐quality foam materials. The parameters used to judge the foam quality are the initial decomposition temperature Tf (5%), Tf − Tηmax and Tf (5%) − Tηmax. The greater the value of these three parameters, the better the foaming effect. The degree of polymerization of the paste resin and the particle morphology directly affect the rheological parameters, namely Tηmax, of PVC plastisol, and subsequently affect the magnitude of Tf − Tηmax and Tf (5%) − Tηmax, which in turn affect the quality of the foam.

Processing Effects on the Through-Plane Electrical Conductivities and Tensile Strengths of Microcellular-Injection-Molded Polypropylene Composites with Carbon Fibers.

Polymers reinforced with conducting fibers to achieve electrical conductivity have attracted remarkable attention in several engineering applications, and injection molding provides a cost-effective way for mass production. However, the electrical performance usually varies with the molding conditions. Moreover, high added content of conducting fibers usually results in molding difficulties. In this study, we propose using microcellular (MuCell) injection molding for polypropylene (PP)/carbon fiber (CF, 20, and 30 wt%) composites and hope that the MuCell injection molding process can improve both electrical and mechanical performance as compared with conventional injection molded (CIM) parts under the same CF content. Both molding techniques were also employed with and without gas counter pressure (GCP), and the overall fiber orientation, through-plane electrical conductivity (TPEC), and tensile strength (TS) of the composites were characterized. Based on the various processing technologies, the results can be described in four aspects: (1) Compared with CIM, microcellular foaming significantly influenced the fiber orientation, and the TPECs of the samples with 20 and 30 wt% CF were 18–78 and 5–8 times higher than those of the corresponding samples molded by CIM, respectively; (2) when GCP was employed in the CIM process, the TPEC of the samples with 20 and 30 wt% CF increased by 3 and 2 times, respectively. Similar results were obtained in the case of microcellular injection molding—the TPEC of the 20 and 30 wt% composites increased by 7–74 and 18–32 times, respectively; (3) although microcellular injection molding alone (i.e., without GCP) showed the greatest influence on the randomness of the fiber orientation and the TPEC, the TS of the samples was the lowest due to the uncontrollable foaming cell size and cell size uniformity; (4) in contrast, when GCP was employed in the microcellular foaming process, high TS was obtained, and the TPEC was significantly enhanced. The high foaming quality owing to the GCP implementation improved the randomness of fiber orientation, as well as the electrical and mechanical properties of the composites. Generally speaking, microcellular injection combined with gas counter pressure does provide a promising way to achieve high electrical and mechanical performance for carbon-fiber-added polypropylene composites.

Study on improving the quality of high content recycled PE foamed board by enhancing screw elongational effect in mixing process

AbstractThis paper focused on improving the content of recycled PE in the foaming board and the compatibility of recycled PE with other materials and fillers, reducing the unmelted recycled PE particles in the recycled PE foaming board, and enhancing the foaming density and quality of the recycled PE foamed board. In this paper, the elongational mechanism was applied to the design of the screw mixing section, and a new type of elongational screw was designed to improve the mixing effect of PE and LDPE and fillers by strengthening the elongational effect of the screw. Through simulation analysis and experimental comparison, it was found that the mixing capacity of the strong elongational mixing section was 1.3 times higher than that of the ordinary mixing section. The mixing quality of pre‐foaming compound and the foam quality and density of foamed board were studied by macroscopic and microscopic showed that the unmelted particles and filler aggregates in the extruded preform prepared by the new elongational screw were significantly reduced, while the foaming density and extrusion production capacity were significantly increased, especially the formula of pure recycled PE foamed board. It could be seen that increasing the elongational effect played a crucial role in improving the melting of the blends in the extruder, the crushing and refinement of the filler aggregate, and improving the fluidity of the blend foaming materials in the molding foaming machine to avoid the lack of materials in the cavity.

The Effect of Soaking Layer Eggs into Boiled Water of Melinjo (Ggnetum gnemon l.) Leaves against Oxidation, Foaming, and Internal Quality of Eggs

This study aimed to evaluate the effect of soaking layer eggs into boiled water of melinjo leaves on oxidation, foaming, and internal quality of eggs. The experimental design was a Completely Randomized Design with 4 treatments namely without any soaked (P0), soaked for 24 h into boiled water of melinjo leaves 15% (P1), 30% (P2), and 45% (P4) with 4 replications. The measurements were on the 14th and 21st days. The data were analyzed using ANOVA and DMRT multiple comparisons by significance of 0.05. The observed variables included peroxide value, moisture content, foam, albumen and yolk (weight, volume, and index), air sac, and haugh unit. The results showed that the immersion into the boiled water of melinjo leaves had an effect on water content, oxidation rate, foam stability and internal quality of eggs with the best concentration was 30% (P2) and 45% (P3), but had no effect on foam formation. It was concluded that the immersion of chicken eggs at concentrations of 30% (P2) and 45% (P3) was able to prevent the acceleration of the changes in moisture content, suppress oxidation, improve the foam stability, and maintain the internal quality of eggs until the 21st day.

Designer petals shape ZnO nanoparticles as nucleating agents: Verification the mechanism of cavity nucleation in the polymer for foaming

The morphology, size and surface roughness of the nucleating agent significantly affect the nucleation effect for foaming in the polymer. In this work, four nucleating agents with different morphologies, namely DE, MS, OMMT and β- CD as heterogeneous nucleation agents were selected for a polypropylene (PP) foaming injection molding process to explore nucleation mechanism. A theoretical assumption (cavity nucleation) in polymer foaming had been put forward about how to enhance the efficiency of bubble nucleation based on classical nucleation theory (CNT). Subsequently, the cavity nucleation was validated by chemical core-back injection foaming molding and in-situ visualization and elaborated by establishing a formula. Finally, designed petals shape particles as nucleating agents to further test this theory. The confirmation of this theory effectively improved the nucleation efficiency and foaming quality, which has important guiding significance to the development of lightweight products.

Physicochemical properties of saponin containing Acanthophyllum laxiusculum extract: example application in foam stability and qualitative parameters for malt beverage industry.

Aqueous Extract of Acanthophyllum laxiusculum root (AE) exhibited remarkable foaming profile, emulsification properties and antifungal activity due to the presence of high concentration of total saponins. Total phenolic compounds, another main component, accounted for the AE antioxidant activity. Spray drying of AE, as a thermal process, did not affect the foaming indices of A. laxiusculum Spray-dried Extract (SE) and is a recommended alternate for convenient application in food industry. Addition of SE to the malt extract at accepted levels of total saponin daily intake (below 50mg/kg) showed positive attribution of malt and carbonation on the foaming quality of SE. Meanwhile, antioxidant activity of commercial malt beverage was enhanced by addition of phenolic compounds containing SE. The 20-60% antifungal inhibitory ratio of the SE developed here is within the applied range of total saponin that supports its application to inhibit the growth of Saccharomyces cerevisiae after malt beverage production. The bitter taste of SE was not sensed in malt beverage at 30mg/kg total saponin content and suggested A. laxiusculum root extract as a natural additive in malt industry.

Modification of sodium bicarbonate and its effect on foaming behavior of polypropylene

Abstract As a potential physical blowing agent, sodium bicarbonate (SB) is environmentally friendly and low in cost, but its low decomposition temperature cannot meet the requirements of polyolefin foam materials. Herein, for enhancing the thermal properties of SB, a modified way was offered to fabricate various SB-based capsules via suspension polymerization. As the modified SB-based capsules, epoxy resin (EP) accompanied with several organic acids was successfully coated on the surface of SB, serving as heat-insulation layer of SB. Various physicochemical characterizations provided reliable evidences for the good coating effect, and the thermal performance of the modified SB was improved. Further, the composite SB capsules were applied for the foaming of polypropylene (PP), and the foaming behavior of the SB-based capsules in PP was significantly improved, with more uniform distribution, smaller cell diameter, and higher cell density. In all, this work fully proved that the coated shells enhanced the thermal properties of SB, and the modified SB capsules significantly improved the foaming quality of foamed PP.

In-Situ Visualization of the Cell Formation Process of Foamed Polypropylene under Different Foaming Environments.

In this paper, the dynamic foaming process of micro-foaming polypropylene (PP) in different foaming environments in real time was obtained via a visualization device. The relationship curve between cell number (n) and foaming time (t) was plotted, and then the nucleation kinetics of foam cells was analyzed. Results showed that the formation rate of cells changed obviously with the variation of melt temperature and the content of the foaming agent. The n-t curves presented a typical “S” shape, which indicated that the appearance of the cell number increased slowly in the initial foaming period, then increased rapidly in a short time, and finally maintained a certain value. When a certain pressure was applied to the PP melt, the external force had a great influence on the n-t curve. With the increasing external force, the rate of cell formation increased rapidly, and the shape of the n-t curve changed from “S” to “semi-S” without an obvious slow increase. The investigation of the n-t relationship in the PP dynamic foaming process under different foaming environments could provide effective bases for improving the foaming quality of injection molding foaming materials.

Mechanical and Adsorptive Properties of Foamed EVA-Modified Polypropylene/Bamboo Charcoal Composites.

Due to its excellent adsorption and humidity control function, bamboo charcoal (BC) has often been mixed with polypropylene (PP) to produce PP/BC composites for interior paneling applications. However, due to the poor foaming quality of PP, PP/BC composites suffer as a result of their high density, which limits their scope of use. Here, to improve its foaming quality, PP was modified with ethylene vinyl acetate (EVA), and then the EVA-modified PP (E-PP) was mixed with different contents of BC (0 wt.%–50 wt.%), as well as foaming agent (Azodicarbonamide, AC) and its auxiliaries (ZnO, Znst), in a twin-screw extruder, followed by hot-pressing at high temperature to obtain foamed E-PP/BC composites. The resulting composites showed good porosity and pore distribution with an increase of BC content by up to 20%. Further increase in the BC content seemed to cause the foaming performance to decrease significantly. The product density and adsorption rate increased, while the mechanical strength decreased with increasing BC content. At a BC content of 40 wt.%, the foamed E-PP/BC composite showed the best combined performance, with a density of 0.90 g/cm3, 24-h formaldehyde adsorption rate of 0.48, and bending strength of 11.59 MPa.