Foam Density Research Articles

Enhancing bioactive compounds retention in pomegranate juice powder through foam mat drying

AbstractThe effect of addition of whey protein isolate (WPI; 0%, 5%, 7.5% and 10%) and carboxy methyl cellulose (CMC; 0%, 0.25%, 0.5% and 0.75%) was studied for its foaming properties and stability in pomegranate juice (PJ). High‐quality powders can be produced from fruit juices and heat‐sensitive food items using foam mat drying (FMD). The PJ foam with 10% WPI, a foaming agent, and 0.25% CMC, a stabilizer had high foam expansion (FE) (455.28%) and low foam density (FD) (0.2030 g/cc) and foam drainage volume (FDV) (20.10 mL). The PJ foam was subjected to different drying temperatures (50, 60 and 70°C) and thickness (3 and 6 mm). The drying temperature of 60°C and foam thickness of 3 mm were found to be the acceptable drying conditions based on drying time (180 min) and retention of bioactive compounds. At optimum drying conditions, the retention of phenols, anthocyanin, ascorbic acid, and antioxidant capacity was 97.86%, 83.90%, 77.29%, and 87.11%, respectively. The sensory evaluation of the reconstituted foam mat dried pomegranate juice powder (FPJP) showed lower overall acceptability scores than fresh juice (FJ), but the overall acceptability of the powder dried at optimum drying conditions was within liking limits (>6). FPJP has an amorphous nature with a particle size of 3564 nm and a porous and irregular structure. Bioactive compounds in FPJP were studied after 8 months of storage, with higher retention of bioactive compounds in refrigerated conditions.Practical applicationThe studies revealed that foam mat drying is suitable for the pomegranate juice which has high moisture and sugar content. It requires shorter drying time of 180 min. for drying up to moisture content of 4% (db). The foam mat dried juice powder obtained at optimum drying conditions has retained higher bioactive compounds and has higher sensorial acceptability when compared with the other treatment combinations. This drying process requires low initial investment and can easily be scaled up to the commercial level thus making it profitable business venture. Further, higher storage stability up to 8 months, low volume and consequent low transport cost improves the technical and financial viability of the process in industrial application. The Foam mat dried pomegranate juice developed can be used in many food products such as reconstituted beverages, ice creams, confectioneries, etc.

Experimental investigation on the anti-detonation performance of composite structure containing foam geopolymer backfill material

The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts, reducing the vibration effect on the structure. Explosion tests were conducted using several composite structure models, including a concrete lining structure (CLS) without foam geopolymer and six foam geopolymer composite structures (FGCS) with different backfill parameters, to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading. Pressure, strain, and vibration responses at different locations were synchronously tested. The damage modes and dynamic responses of different models were compared, and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed. The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading, reducing the strain in the liner structure by 52% and increasing the pressure attenuation rate by 28%. Additionally, the foam geopolymer backfill reduced structural vibration and liner deformation, with the FGCS structure showing 35% less displacement and 70% less acceleration compared to the CLS. The FGCS model with thicker, less dense foam geopolymer backfill, having more pores and higher porosity, demonstrated better compression and energy absorption under dynamic impact, increasing stress wave attenuation efficiency. By analyzing the stress wave propagation and the compression characteristics of the porous medium, it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77% lower than that of CLS, and the transmitted wave energy was 90% lower. The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.

High strength microcellular thermoplastic polyimide/carbon fiber composite foams containing flexible ether amine, rigid diaminodiphenyl ether, and triaminopyrimidine moieties: Synthesis and fabrication

In this study, pyromellitic dianhydride (PMDA) and polyetheramine D230 were used as the primary polymerization monomers, with 2,4,6-triamino pyrimidine (TAP) as a chain extender. By introducing aromatic ring-containing 4,4′-diaminodiphenyl ether (ODA) and precisely controlling its molar ratio with D230, a highly branched, high-temperature-resistant thermoplastic polyimide (TPI), was successfully developed. The optimal thermal imidization temperature was determined to be 250 °C. Incorporating surface-modified short carbon fibers (SCF) via melt blending significantly improved the mechanical properties, with tensile and impact strengths increasing fourfold and sevenfold, respectively, at 10 phr of SCF. TPI foam prepared using supercritical carbon dioxide (scCO2) foaming technology exhibited excellent performance, achieving a regular hexagonal structure, cell sizes of 10.19 μm, and a cell density of 1.68 × 1010 cells/cm3 at an ODA to D230 molar ratio of 1:9. The TPI/SCF composite foam, with 3 phr SCF under 20 MPa saturation pressure and 120 °C foaming temperature, achieved a 90 % closed-cell ratio and a 300 % increase in compression strength at the same foam density. Compared to traditional thermoset PI foams, TPI/SCF foam offers smaller cell sizes and higher compression strength, demonstrating significant commercial potential. Backward differentiation shows that TPIF compression is constant at 0.035 ± 0.005 in the [0,0,1] lattice direction. This research provides theoretical and practical insights for preparing high-performance TPI foam for high-temperature applications.

Verification of Protection Performance of Concrete Blast-Proof Panels Against Internal Explosions

Recently, studies on blast-proof panels, which were attached to structures to protect facilities from local damage caused by explosions, have been actively performed. However, blast-proof panels are impractical yet due to the high installation cost and difficulty in construction, and protection performance for explosions inside a structure is not evaluated. In this study, a blast-proof panel consisting of concrete material was devised to ensure economic feasibility and constructability. Then, the protection performance of the concrete blast-proof panel for internal explosions was analyzed by numerical simulations and field experiments. First, field experiments on concrete explosion-proof panels were conducted for two cases, where panels without and with energy-absorbing foam were installed. As a result, the concrete blast-proof panel reduced the displacement of structures by up to 22% and the acceleration of structures by up to 86%. However, the reliability of the field experiment data was insufficient due to the shear failure of the test structure during experiments. Therefore, additional analysis was conducted by developing a numerical model. A series of numerical simulations was conducted according to the various densities of the energy-absorbing foam that was inserted between the panel and structure. Consequently, the optimum density of the impact-absorbing material differed depending on the type of structure damage to reduce (i.e., the displacement or acceleration of the structure).

High-performance lightweight foam concrete enabled by compositing ultra-stable hydrophobic aqueous foam

The major limitations of lightweight foam concrete are inferior mechanical properties and durability. This study designs a novel high-modulus hydrophobic foam to produce high-strength and durable foam concrete. Poly (methyl hydrogen)siloxane (PMHS) was employed to construct a hydrophobic boundary of hydroxypropyl methylcellulose (HPMC) foam. The produced hydrophobic foam bubbles exhibit a high modulus, fine bubble size, and exceptional thermodynamic stability. A dense foam wall of 8 μm in thickness functions as a structure for chemical loadings of inorganic-organic particles onto the viscoelastic bubble film. This facilitates their interaction effect of adsorption and chemical bonding, contributing to the hydrophobic nature of the foam wall. The resulting hydrophobic foam concrete shows low water adsorption and high mechanical strength. The hydrophobic foam concrete demonstrates superior chemical resistance and anti-chloride diffusion compared with normal concrete. This study might provide a practical strategy for designing high-performance lightweight foam concrete with significant potential as structural elements.

Experimental investigation and soft bond modelling analysis on mechanical behaviours of foamed polyurethane solidified ballast

Polyurethane solidified ballasted track (PSBT) offers a novel solution to the frequent maintenance requirements of ballasted track, delivering a high-quality track infrastructure. In this study, laboratory tests were carried out on polyurethane solidified ballast (PSB) specimens under compression, tensile and shear conditions to obtain stress-strain curves and deformation characteristics. The numerical model of the PSB specimens was developed based on the discrete element method (DEM). The effects of the parameters related to the bond elongation on the tensile and compressive properties of the PSB specimens were analysed, and the parameters were calibrated by the test results. The results showed that the compressive, tensile and shear strengths of the specimens increased with increasing polyurethane foam density. During uniaxial and split loading, the stress-strain curves of the PSB specimens gradually entered the stress softening stage after an elastic phase. The compressive-tensile strength ratio of the specimens was around 1.55. From the perspective of deformation, the PSB specimen is primarily strained by the highly compressible polyurethane materials, and the specimen generates a considerable residual strain at the initial stage of cyclic loading. Thus, it is necessary to pre-compress the PSB to achieve an optimal load-bearing condition. DEM simulations show that there is a strong correlation between the mesoscale bond elongation of particles and the macroscopic tensile and compressive strengths of the specimens. It is therefore possible to utilise a high value of bond elongation to simulate bonded granular materials with low compressive-tensile strength ratios. The results obtained from the simulation of the numerical method used in this study are in high agreement with the test, which provides a new idea for revealing the meso- and macro- mechanical properties of PSB and its application in PSBT.

Foam density mapping via THz imaging

Plastic foams, near-ubiquitous in everyday life and industry, show properties that depend primarily on density. Density measurement, although straightforward in principle, is not always easy. As such, while several methods are available, plastic foam industry is not yet supported with a standard technique that effectively enables to control density maps. To overcome this issue, this paper proposes Terahertz (THz) time-of-flight imaging using normal reflection measurements as a fast, relatively cheap, contactless, non-destructive and non-dangerous way to map plastic foam density, based on the expected relationship between density and refractive index. The approach is demonstrated in the case of polypropylene foams. First, the relationship between the estimated effective refractive index and the polypropylene foam density is derived by characterizing a set of carefully crafted samples having uniform density in the range 70–900 kg/m3. The obtained calibration curve subtends a linear relationship between the density and the refractive index in the range of interest. This relationship is validated against a set of test samples, whose estimated average densities are consistent with the nominal ones, with an absolute error lower than 10 kg/m3 and a percentage error on the estimate of 5%. Exploiting the calibration curve, it is possible to build quantitative images depicting the spatial distribution of the sample density. THz images are able to reveal the non-uniform density distribution of some samples, which cannot be appreciated from visual inspection. Finally, the complex spatial density pattern of a graded foam sample is characterized and quantitatively compared with the density map obtained via X-ray microscopy. The comparison confirms that the proposed THz approach successfully determines the density pattern with an accuracy and a spatial scale variability compliant with those commonly required for plastic foam density estimate.

Functionally graded foam materials for head impact protection

Head injuries commonly result from impact accidents, underscoring the urgent requirement for enhanced helmet protection. Functionally graded foam (FGF) materials present promising avenues for augmenting the design of impact-attenuating liners in helmets, thereby mitigating head injuries. This study aims to investigate the performance of the FGF materials in protecting against head impact and provide an effective optimization methodology to support the efficient and reliable design of the FGF materials. The foam finite element model was developed and coupled with a highly biofidelic head model to simulate the FGF-head frontal impact scenarios. A parametric study based on the coupled FGF-head model was conducted to explore the effects of the configuration parameters on the protection performance of the FGF materials. The study demonstrated that the negative-gradient FGF materials provide better head impact protection than the uniform density foam (UDF) and positive-gradient FGF materials, despite the potential disadvantage in energy absorption. A discrete optimization method based on the FGF-head model was developed and illustrated to efficiently achieve an optimized design for FGF protectability, thereby reducing the risk of head injuries. The optimized FGF design reduced the Head Injury Criterion (HIC) value by 40.4 % compared to the conventional UDF design, from 1660 to 990. Therefore, this study provides a further understanding and a new optimization insight into designing FGF materials to improve head impact protection.

Brazing of Copper Foam Using Cu-4.0Sn-9.9Ni-7.8P Filler Foil: Effect of Brazing Temperature and Copper Foam Pore Density

Copper (Cu) foam is a promising material that owns a high surface area that can be utilized in a thermal application. In this research, the brazing of Cu substrate to Cu foam in the sandwich configuration using Cu alloy filler foil was carried out. The foam at different pore per inch (PPI) of 15, 25 and 50 are brazed at different brazing temperatures. Mechanical and microstructure analysis were conducted to investigate a suitable brazing temperature and the best pore density of foam. The compressive strength of brazed 50 PPI foam has yielded the highest due to the highly dense interconnected branches. While the highest shear strength of brazed interface using 15 PPI foam has been recorded. The large branch size of 15 PPI foam has contributed to the sound joint between the brazed joint interface of Cu substrate and foam. Both mechanicals analysis above exhibits a highest strength at 660 °C as a brazing temperature The shear stress-strain curve of Cu substrate and foam brazed joint interface shows a brittle behaviour which accordance with the discoverable brittle phases of Cu3P and Ni3P using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) have presented the formation of Cu3P and Ni3P at the brazed joint interface of Cu substrate and foam.

Environmentally-friendly solvent pulping and grafting strategies for better foamability of poly(lactic acid)/agricultural waste biocomposites

In this study, the foamability of poly (lactic acid) (PLA) through a continuous extrusion process was enhanced by using an agricultural waste, environmentally friendly pulping methods, and reactive compatibilization of the lignocellulosic filler with matrix in the extrusion flow field. Both applied solvent-pulping methods by using chemicals with low safety and toxicity risks were considerably successful in purifying the micron-sized cellulosic fibers of rice straw (RS). The interface of PLA matrix with RS pulp fibers was modified by applying reactive compatibilizers containing maleic anhydride (MA) and epoxy functional groups. Both compatibilizers had the ability to simultaneously react with the hydroxyl groups of RS pulp fibers and end groups of PLA chains during the melt-compounding process. As a result of RS pulping and PLA/RS pulp compatibilizing reactions, the processability of PLA in an extrusion foaming process was substantially enhanced, in a way that the void fraction and cell density of PLA foam increased more than seven and two times, respectively. The extruded lightweight all-green biocomposite foams can be applied in construction and packaging applications.

Optimization design of crashworthiness of polyurethane foam filled Origami thin wall square tube based on an surrogate model

Rigid polyurethane foam, due to its low density, light weight and effective energy absorption, can be used as a new filling material to improve the energy absorption capacity of pipe fittings, thus improving the overall crashworthiness of automobiles. In this paper, numerical simulations on rigid polyurethane foam-filled origami thin-walled pipe fittings are carried out. The effects of interlayer dihedral angle, number of layers of creased pipe, and filling of foam with different densities on the crashworthiness of the pipe fittings are compared and analyzed. Additionally, an surrogate model is established to predict the correlation between the above three factors and the model. Taking the specific absorption energy (SEA) and the initial peak force (PCF) as optimization objectives, the NSGA-II algorithm and the CHC algorithm were used for optimization analysis respectively. Simulation experiments were conducted to validate the accuracy of the optimized structural parameters. The results show that the CHC algorithm provides more accurate optimization results compared to the NSGA-II algorithm. The optimized optimal interlayer dihedral angle is 150°, the number of creased tube layers is 8, and the foam density is 0.3 g/cm3. Consequently, the tubing’s specific absorption energy is enhanced by 10.3 % compared to ordinary straight tubing, demonstrating the significant improvement in crashworthiness achieved through foam filling. This study proves that the filling of tubing with foam has excellent impact resistance, and the results provide a certain reference value for future research.

Evaluating how citrus fiber affects the cell structure and functions of starch-based foam

This work used a proper content of citrus fiber (10 wt% ∼ 30 wt%, dry starch base) to improve the cell structures and functions of starch foam. The insoluble fiber promoted cell nucleation in the starch melt, whereas the soluble pectin improved the starch matrix's strength by forming ester bonding with starches as confirmed by FTIR results. This effectively modified the starch foaming process and endowed the obtained foams with an increased cell density (from 83.37 to 123.44 cell/cm3×104) and a reduced foam density (from 0.457 to 0.142 g/cm3). The foam containing 20 wt% citrus fiber exhibited the highest expansion ratio of 5.20. Due to the improved structures and the tortuous path effect of cellulose crystals, the prepared foams significantly presented a strengthened compression performance and improved moisture resistance. Meanwhile, the fiber-loaded foams displayed a high free radical-scavenging activity (60.30 % ∼ 85.75 %), showing good antioxidant activity. It is therefore believed that this study could provide a facile and green way for producing starch-based foams with desirable functions.

Flexural behavior of singly curved GFRP sandwich panel with polyurethane foam core

Curvilinear architecture and structures are becoming a worldwide trend for its streamlined appearance and synchronicity with the surroundings. Nonetheless, the conventional construction materials might not be able to achieve the desired curvilinear geometries in an effective and economic manner. In this regard, glass fiber-reinforced polymer (GFRP) curved sandwich panel with polyurethane foam core is able to meet the requirement of the construction efficiency and economy as well as satisfy the need for a lower energy consumption. However, few studies are available on the mechanical behavior of such panels. In this regard, this work was to conduct an experimental and numerical investigation on the singly curved GFRP sandwich panels to evaluate the flexural performance. In particular, the effect of the foam density, inclined angle, core thickness and stacking sequence of face sheet on the load-carrying capacity and failure mode was addressed. Four failure modes were identified. The singly curved GFRP sandwich panel showed an improved stiffness when compared to the flat panel, but showed more complicated failure mechanism. The stiffness of the curved panel with inclined angle 30° was 250 % higher than that of the flat panel in the test results. It was shown that the strength and stiffness increased as the density and thickness of the foam core increased. In addition, a finite element analysis was conducted via MSC.Marc and validated by the experimental results. A parametric study was performed to address the design parameters. It was found that the specimens with inclined angles of 30° and 45° showed the greatest stiffness.

Structural Regulation of Microcellular Thermotropic Liquid Crystalline Polymer with Low‐Dielectric Properties During Supercritical Fluid Foaming Process

With the development of radio technology, 5G electronic equipment has higher requirements for materials. This has become an imperative matter to realize the controllable preparation of Thermotropic liquid crystal polyester (TLCP) foams with homogeneous microcellular. Accordingly, the foaming behavior of TLCP in isotropic state is investigated. TLCP foams are prepared by a one‐step rapid depressurization foaming method at different temperature pressures, with cell diameter in the range of 67.5–283.9 μm and the material density in the range of 0.37–0.25 g/cm3. In order to broaden the distribution of cell diameter and the density of TLCP foams, the mixture foaming agent of N2 and CO2 is used in foaming process. When mixture foaming agents are used, the cell diameter is widened to the range of 40.5–283.9 μm, and the material density is widened to the range of 0.70–0.25 g/cm3, which realizes the controllable preparation of cell diameter and material density of TLCP. The dielectric constant and dielectric loss of TLCP foams can be as low as 1.35‰ and 0.85‰ at 10 GHz, respectively. The structural regulation of low‐dielectric TLCP microcellular materials is achieved for the first time by way of varying the temperature, pressure, and co‐blowing agent ratio.

Extrusion foaming of Poly(lactic acid)/Rice straw composites: Opposing effects of eco-friendly physical/chemical treatment and compatibilization methods

In this study, the effects of two environmentally-friendly pulping methods along with two different reactive compatibilization methods on the foamability of poly (lactic acid) (PLA)/rice straw (RS) biocomposites have been investigated. RS as an annually renewable agricultural waste is low-cost and available. Melt-compounding and melt-foaming processes were performed through a twin-screw extrusion processing. The correlations between processing and microstructure were studied. The findings show that the RS pulping with sodium bicarbonate (SB) solution leads to the lignocellulosic particles with a porous structure. The structure causes the filler/matrix mechanical engagement and improves the interfacial adhesion and rheological properties, hence forming smaller cells with the narrowest cell size distribution. In contrast, applying ultrasound waves on the RS pulp brings the particles to very smooth surfaces. These surfaces have the highest activity at the cell nucleation stage and considerably increase the foam’s cell density. The reactive compatibilizers based on epoxy and maleic anhydride groups show opposing effects on the biocomposite microstructure, depending on the RS pulp type. The use of the reactive compatibilizers in the PLA/RS pulp treated with SB led to lighter foams with larger cells and higher cell densities and void fractions. Whereas the incorporation of the compatibilizers into the biocomposites containing RS pulp treated with SB and ultrasonic waves resulted in noticeably lower cell density and larger foam density. The extruded biocomposite foams with closed-cell microstructure can be used in insulation and packaging applications.

Liquid foaming of TPU with Methylal

This work investigates the peculiarities of using a liquid blowing agent, namely dimethoxymethane (Methylal) to foam a thermoplastic polyurethane (TPU) in the laboratory practice of batch foaming equipment. We preliminarily measured thermodynamic properties of the polymer/gas system relevant to foaming, namely the vapor-liquid pressures at the TPU foaming temperatures. Three different paths were then explored for foaming. First, we used Methylal under its liquid-vapor equilibrium condition, in which both liquid and vapor are present. Secondly, we used Methylal in the liquid state to experiment with liquid foaming strategies. We have observed specific aspects, details, and issues related to the use of liquid blowing agents and devised strategies to deal with them. Finally, we used Methylal as a co-blowing agent together with CO2. In all cases, we examined the impact of pressure, pressure drop rate, and temperature on foam density and morphology.Overall, liquid foaming has proven to be a viable technique and Methylal an effective blowing agent, especially in cooperation with other gaseous blowing agents, where it significantly improves the expansion ratio of the final product.

Heat transfer and flow characteristics of a plate-fin heat sink equipped with copper foam and twisted tapes

The objective of this paper is to present new heat transfer enhancement approaches in plate-fin heat sinks (PFHS) using copper foam and twisted tapes. The motivation behind these concepts is to reduce pressure drop while enhancing heat transfer compared to PFHSs fully inserted with copper foam. The impact of twisted tape type, twist ratio, and Reynolds number (Re) on the heat and flow behaviors inside the PFHS equipped with copper foam (PFHSCF) is investigated. Copper foam has a porosity of 0.932 and a pore density of 40 pores per inch. Stationary and rotating twisted tapes with twist ratios between 2.7 and 4 are tested at Re between 3000 and 6000. The experimental results indicated that the pressure drop of the airflow inside a PFHS equipped with copper foam and a stationary twisted tape (PFHSCF_STT) as well as a PFHS equipped with copper foam and rotating twisted tapes (PFHSCF_RTT) decreased by an average of 34.8 % and 37.9 %, respectively, compared to a PFHSCF. When the twist ratio is decreased from 4 to 2.7, the thermal resistances of PFHSCF_STT and PFHSCF_RTT are reduced by 14.2 and 14.8 %, respectively. Based on assessment, the thermal-hydraulic performance of a PFHSCF_RTT with twist ratios of 2.7 and 3.3 is higher than that of a PFHSCF. To facilitate practical applications, correlations are proposed to predict the Nusselt number and friction factor. Additionally, considering the outcomes of the current study, conducting numerical investigations on the thermal performance of PFHS under different pore densities of copper foam and wider twist ratios of twisted tapes is recommended to determine optimal working conditions for future research.

On the Crush Behavior and Energy Absorption of Sustainable Beverage Cans and Their Polyurethane Foam-Filled Structures: An Experimental Study.

In the pursuit of global energy conservation and emissions reductions, utilizing beverage cans as energy-absorbing components offers potential for a sustainable economy. This study examines the impact of foam filling on the crushing behaviors and energy absorption of various types of beverage cans. Quasi-static compression tests were conducted on five geometrically sized cans filled with three densities of polyurethane foam to study their deformation modes and calculate crashworthiness parameters within the effective stroke. Results show that empty beverage cans have lower energy absorption capacities, and deformation modes become less consistent as can size increases. Higher foam density leads to increased total energy absorption, a slight reduction in the effective compression stroke, and a tendency for specific energy absorption to initially increase and then decrease. Regarding crush behavior, smaller cans transition from a diamond mode to a concertina mode, while larger cans exhibit a columnar bending mode. Next, the coupling effect of energy absorption between foam and cans was analyzed so as to reveal the design method of energy-absorbing components. The specific energy absorption of smaller cans filled with polyurethane foam is superior to that of similar empty cans. These findings provide valuable insights for selecting next-generation sustainable energy absorption structures.

Effects of Mixing Techniques and Material Compositions on the Compressive Strength and Thermal Conductivity of Ultra-Lightweight Foam Concrete.

The research focuses on ultra-lightweight foam concrete with a dry density below 200 kg/m3, primarily used as insulation material. Factors that may affect material properties are categorized into mixing techniques and material composition, and experimental investigations were conducted on the impact of these factors on the rheological properties of cement slurry, density at different time intervals, compressive strength, and thermal conductivity of foam concrete samples. The experimental results indicate the influence of mixing speed and mixing duration on the instrument during the cement slurry production and mixing process with foam. Additionally, variations in foam concrete sample properties are observed due to the water-to-cement ratio, foam content, and foam density in the selected material compositions. By analyzing the material density at different time intervals, the relationship between the ambient air trapped during the mixing process and the viscosity of the material can be indirectly observed. This analysis can also reveal the correlation between the unplanned air content and the properties of the material.

Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

Rigid polylactic acid (PLA) foams fabricated via thermally induced phase separation (TIPS) utilizing a ternary solution of PLA, Tetrahydrofuran (THF), and water. The PLA gels were stabilized mechanically by the substituting of the THF/water solvent mixture with ethanol as non-solvent and subsequently vacuum dried. A comprehensive characterization of PLA foams was achieved by Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Brunauer–Emmett–Teller (BET) analyses. The BET area obtained in the PLA foam is up to 18.76 m2/g. The Response Surface Methodology (RSM) was utilized to assess the impacts of four independent variables (polymer concentration, solvent composition, quench temperature, and aging time) on the pore size and density of PLA foam. The experimental findings demonstrated that the fabrication parameters could be fine-tuned to govern the morphology of the pores, comprising their size and density. The optimal values of parameters for cell size were identified by RSM to be 8.96 (wt%), 91.60 (w/w), 5.50 °C, and 3.86 h for the optimum cell size of 37.96 µm (37.78 by Genetic Algorithm). Optimum density by RSM 88.88 mgr/cm3 (88.38 mgr/cm3 by Genetic Algorithm) was obtained at 5.00 (wt%), 89.33 (w/w), 14.40 °C and 2.65 h.