Foaming Ability Research Articles

The effect of deamidation and lipids on the interfacial and foaming properties of ultrafiltered oat protein concentrates

The aim of this study was to investigate the air-water interfacial and foaming properties of oat protein concentrates produced by an enzyme-aided ultrafiltration method with and without deamidation. A further aim was to determine the role of polar and non-polar lipids at the air-water interface and in foams. The deamidated and ultrafiltered oat protein concentrate (DE-UF-OPC) exhibited higher surface tension compared to the ultrafiltered oat protein concentrate (UF-OPC). DE-UF-OPC had a significantly higher negative zeta potential value (−50 mV) compared to the UF-OPC (−38 mV) at pH 7.0. The higher net charge of the DE-UF-OPC may have decreased the equilibrium concentration of oat proteins at the interfacial layer due to higher repulsion between them. Both of the ethanol extracted OPCs exhibited higher surface tension values most likely due to the partial denaturation of albumins and/or globulins. Removal of the majority of non-polar lipids had no effect on the equilibrium surface tension of OPCs. DE-UF-OPC and UF-OPC exhibited some, but limited foaming ability. The removal of non-polar lipids significantly improved the foamability and stability of DE-UF-OPC and UF-OPC, but the removal of polar lipids only improved the foamability of DE-UF-OPC.

Light and strong poly (lactic acid)/ cellulose nanofiber nanocomposite foams with enhanced rheological and crystallization property

This work proposes a scalable and green foam injection molding technique to produce high-performance poly (lactic acid) (PLA) foams by adding biodegradable cellulose nanofibers (CNFs). The introduction of CNFs significantly improved the rheological properties and crystallization kinetics of PLA, resulting in improved foaming ability. Microcellular PLA/CNF composite foam containing modified CNFs was successfully obtained with minimum cell size of 5.4 µm and a void fraction of 50%. Furthermore, compared with the pure PLA, the yield stress and tensile modulus of both of solid and foamed PLA/CNF were obviously increased. The percentage increment in the yield stress and tensile modulus for composite foam were approximately 183% and 149%, respectively. This indicated that the added CNFs remarkably ameliorated the cellular morphologies of PLA as well as reinforced the PLA foams. This green strategy opens up new perspectives for developing fully-biobased, lightweight and high-performance PLA material.

ИССЛЕДОВАНИЯ ВЛИЯНИЯ ТЕРМИЧЕСКИХ ОБРАБОТОК НА ПОКАЗАТЕЛИ КАЧЕСТВА ИГРИСТЫХ ВИН

The article is devoted to a study aimed at identifying and developing technological techniques that ensure the intensification of enzymatic reactions in yeast biomass during the post-aging of sparkling wine and, as a result, a significant reduction in the aging time and improvement of the quality of the finished product. In order to study the mechanism of autolysis of yeast during the period of post-run exposure, the effects of temperature regimes of circulation treatments on changes in its physico-chemical and biochemical parameters in conditions excluding increased pressure and tightness of the medium were investigated. For this purpose, starting from the initial wine material and, operationally, in the circulation model, the activity of oxidative and hydrolytic enzymes was analyzed, the content of protein and amine nitrogen, as well as the foaming ability were determined.Despite a significant decrease in the foaming capacity with the use of cold treatment with long-range heat treatment, it was possible to increase its value from 8.7 c to 9.4 с. This value was achieved due to the breakdown of protein structures of the yeast cell and increased activity of hydrolytic enzymes, which contributed to an increase in the concentration of amine nitrogen from 157.5 to 161.0 mg/dm3, which are surfactants. It was also revealed that in order to carry out the secondary fermentation of the vi-nomaterial from the selection grape varieties, it is necessary to carry out the selection of yeast.Thus, the data obtained indicate the possibility of shortening the time of post-aging of the champagne cuvee and improving its foaming ability, as a result of the intensification of wine maturation processes due to increased enzymatic activity of yeast biomass during heat treatment.

A novel alternative to free oil remediation and recovery: Foamy absorbents designed from low molecular paraffinic waste

This study focuses on preparing porous, hydrophobic, and oleophilic hydrocarbon-based foams applicable for removing free oils from water surfaces. Paraffinic waste material generated during industrial production of low-density polyethylene (Qatar Petrochemical Company) was used for the preparation of foamy, elastic structures through crosslinking of short aliphatic chains by dicumyl peroxide and foaming by 1,1′-azobiscarbamide. The porosity of the foam determined by computer microtomography was 58.9%, and the bulk density was 0.42 g.cm−3. The sorption ability of the foam was tested using diesel oil, motor oil, and heavy crude oil. The absorption capacity of foam was characterized as the ratio between the mass of oil absorbed by the foam and the mass of a neat foam (Sw) and as the ratio between the volume of oil absorbed by the foam and the volume of a neat foam (Sv). The absorption capacities of the new foam reported in this study (referred to here as Qwax foam) are 6.6 ± 0.3 g/g, or 3.3 ± 0.2 cm3/cm3 for diesel oil, 3.9 ± 0.4 g/g or 1.9 ± 0.3 cm3/cm3 for motor oil, and 3.4 ± 0.2 g/g or 1.4 ± 0.4 cm3/cm3 for crude oil. To compare the sorption ability of Qwax foam with some standard foams, the absorption capacities of highly porous commercial polyurethane (PU) and melamine (MA) foams were investigated under the same conditions. These foams showed much higher sorption capacity considering the Sw parameter as a reference; however, there was a lower sorption capacity compared to parameter Sv. In the last paragraph, the suitability and the relevancy of parameters Sw and Sv for a comparison of the absorption capacity of foams were theoretically analyzed.

The development of heat‐resistant and salt‐tolerant foam with betaine surfactants

AbstractA modified instrument was designed to evaluate foam properties under high temperature and pressure. The type and molar ratio of betaine surfactants were screened to develop the heat‐resistant and salt‐tolerant foam for Tahe oilfield (130°C, 220 g/L), and the effects of temperature and pressure on foam properties were also investigated. The synergism between surfactants and the enhanced oil recovery (EOR) mechanism of foam flooding in fractured‐vuggy reservoirs were studied. Experimental results showed the developed foam had excellent foaming ability and foam stability when the lauramidopropyl hydroxyl sulfobetaine (LHSB): erucic amide propyl betaine (EAB) molar ratio ranged from 1:1 to 1:2 (initial foam volume was 392 ml when the molar ratio was 1:1, drainage half‐time was 5.75 min and foam half‐time was 72 min when the molar ratio was 1:2 at 130°C and 2 MPa). The synergistic effect was found to reach its maximum when the LHSB:EAB molar ratio ranged from 1:1 to 1:2 according to interaction parameters, which agreed with the results of foam properties. Foam stability was found to considerably increase with increasing pressure, but decrease with increasing temperature. However, temperature and pressure were found to have consistent effects on foaming ability, that is, the foaming ability increased with increasing temperature and pressure. The flooding test showed foam flooding exhibited better sweep efficiency and higher recovery ratio in the fractured‐vuggy model than gas flooding and water flooding. This could be because injected foam did not channel through the top (or bottom) path due to its high viscosity and moderate density.

Remediation of Waste Engine Oil Contaminated Soil using Rhamnolipid based Detergent Formulation

The utilization of waste substrates for rhamnolipid synthesis is a worthy alternative to conventional substrates to reduce the production cost of rhamnolipids. Rhamnolipid produced by Pseudomonas aeruginosa gi |KP 163922| using waste engine oil as substrate was investigated in batch and semi-batch studies for soil bioremediation. Green liquid detergent formulations were prepared by using environment-friendly builder (sodium citrate) and filler (isopropyl alcohol). Rhamnolipid, a biosurfactant was utilized in place of chemical surfactant to prepare the liquid detergent formulation. The formulations at different rhamnolipid concentrations i.e., below critical micelle concentration (CMC), at CMC, and above CMC, were tested for soil remediation efficiency. Each detergent formulation was characterized based on emulsification index (EI24%), surface tension reduction, foam ability, and foam stability. The in-house rhamnolipid based formulations above CMC, recovered oil up to 82.02 ± 0.938 % from contaminated soil with maximum surface tension reduction and foam volume as 26.5 ± 0.412 mN/m and 51.10 ± 1.37 mL respectively. The proposed remediation strategy demonstrated that the recovery of oil is possible at room temperature conditions. The performance properties including detergency and foaming of rhamnolipid based liquid detergent formulations were also compared with commercial rhamnolipid and other detergents.

Development of a High Efficient Compound Surfactant for Foam Drainage in Gas Wells

In this study, the foaming properties of a compound surfactant formula containing cetyltrimethylammonium chloride (CTAC), cocamidopropyl betaine (CDAB), fatty alcohol polyoxyethylene ether-7 (AEO7) and sodium alpha-olefin sulfonate (AOST) were evaluated to meet the application requirements for foam generation and foam drainage in gas wells. The results exhibited that the foaming volume and the half-life of the compound surfactant solution (0.05 wt % CTAC + 0.7 wt % CDAB + 0.6 wt % AEO7 + 0.05 wt % AOST) can reach the values of 550 mL and 23 min, respectively, which suggested that the foaming ability and stability were improved in comparison with each solution containing a single surfactant. It showed that the surface tension can be lowered to 22.4 mN/m with the presence of the compound surfactants. Simultaneously, the microstructure of the foam was observed using a polarizing microscope, and it was found that there were almost no polyhedron structures in the foam within a certain range of formula concentrations. The results of the experiments also clarify that the formula has well properties of temperature resistance and salt resistance (measured using a high-speed agitator).

Investigation on the Stability of Janus SiO2-n Nanoparticle-Assisted Nonionic Surfactant-Stabilized Foam and Its Application in Enhanced Oil Recovery

The stability of the foam directly impacts the final efficiency of the foam flooding in enhanced oil recovery (EOR). In the present work, a series of Janus SiO2-n nanoparticles (JSn NPs) with various modification degrees were successfully prepared and employed to improve the stability of the nonionic surfactant polyethylene glycolmonoisodecylether (PMIE)-stabilized foam. The PMIE–JS3 system with a much low JS3 NP concentration (0.1 wt %) displayed extraordinary foamability and stabilizing foam ability via the foam volume, half-life, relative volume decay, and optical microscope photograph measurements. Then, the dynamic surface tension and dilatational viscoelasticity tests were conducted to explore the mechanism. It was found that the PMIE–JS3 system with great interfacial activity and intensive interfacial film highly facilitated the generation of the foam and improved the foam stability. Moreover, the PMIE–JS3-stabilized foam exhibited outstanding stability, even under the influence of crude oil. The sandpack flooding tests indicated that the PMIE–JS3-stabilized foam could effectively plug the high-permeability channels to modify the water injection profile and consequently greatly enhanced tertiary oil recovery (∼15.3% of the initial oil in place).

Synthesis and performance of a novel high-efficiency coal dust suppressant based on biopolysaccharide-xanthan gum

The coal production process produces a lot of dust, which pollutes the environment and threatens the occupational health of workers. Although many dust suppressants for coal dust control have been developed, the implementation of current dust suppressants does not meet the requirements due to their poor foaming, stability, and wettability effects. In our current study, the effect of xanthan gum (XG) on the properties and foaming ability of the composite surfactant ALAP has been investigated. The research shows that with the increase of CXG, the foaming volume of the solution increases by nearly 30% on average. The liquid-carrying capacity, the foaming delay period, and the liquid-draining half-life of the foam are also improved, while the performance of wetting coal dust decreases. Compared with traditional water-soluble polymers, XG molecules have a special double helix structure and plenty of polar functional groups, which can form a stable 3D network system with surfactant molecules. XG molecules could not only effectively improve the foaming performance of low-concentration ALAP, the liquid-carrying ability, and the stability of foam, but also reduce the burst rate of the bubbles. In our investigations, the dust reduction effect of the XG/ALAP systems have been comprehensively evaluated through the field application of the heading face. The dust reduction efficiency of total dust and respirable dust can reach nearly 90% and 85% respectively, which is 2.2 times and 2.5 times higher than that of water spraying. The XG/ALAP systems also effectively improve the visibility of the working surface. With the consideration of all the above-mentioned factors, the composition range of the high-efficiency dust suppressant is obtained as: 0.7‰≥CXG ≥ 0.5‰ and 4‰≥CALAP ≥ 3‰.

Influence of seawater on interfacial Properties, foam performance and aggregation behaviour of Fluorocarbon/Hydrocarbon surfactant mixtures

• Adding seawater lowers surface activity and adsorption kinetics of SDS/FS-50 mixtures. • Ca 2+ , Mg 2+ and K + have greater adverse effects on foaming ability than Na + in seawater. • Dual effects of salts on foam stability are observed at different surfactant concentrations. • Spontaneous transition from vesicle to micelle is observed after mixing SDS and FS-50. In this work, the influence of seawater on interfacial properties, foam performance and aggregation behaviour of fluorocarbon/hydrocarbon surfactant mixtures was systematically investigated. Two model foaming solutions containing different surfactants (nonionic APG, anionic SDS, and amphoteric FS-50) were prepared by deionized water and seawater, respectively. Multi-scale methods including surface tension measurements, foam ageing tests and cryogenic-transmission electron microscopy (cryo-TEM) were used. The results show that the addition of seawater reduces the equilibrium surface tension, foaming ability and adsorption kinetics of SDS/FS-50 mixtures. Among the counterions in seawater, Na + can lower the surface tension and slightly improve the foaming ability, while the presence of Ca 2+ , Mg 2+ and K + allows the formation of surfactant precipitate to weaken the foaming ability of the solution. It turns out that seawater has dual effects on foam stability and the defoaming/stabilizing effects of seawater are related to ionic surfactant concentrations. Besides, it is confirmed that the spontaneous transition from single-lamellar vesicle to rod-like micelle occurs after mixing FS-50 with SDS in the deionized water, while only multi-lamellar vesicles and surfactant crystals can be observed in the seawater. The aggregation behaviour strongly affects solution viscosity as well as foam performance. At high SDS concentrations, the surfactant precipitate/aggregate can inhibit the liquid drainage process and improve foam stability.

Synthesis of branched surfactant via ethoxylation of oleic acid derivative and its surface properties

A class of bio-based nonionic surfactants with double hydrophilic head groups (DMOE n ) was obtained from the waste cooking oil. • A new strategy for the preparation of branched surfactants from renewable oleic acid in waste cooking oil was proposed, and a class of bio-based nonionic surfactants with double hydrophilic head groups (DMOE n ) was obtained. • The ethoxylation reaction process of DMO and its reaction kinetic were both systematically optimized and studied. • The surface activities, aggregation and adsorption behaviors of DMOE n were investigated, and it was discovered that DMOE n had the characteristics of typical branched surfactant with good wetting performance, low foaming and strong defoaming ability. A new series of bio-based branched nonionic surfactants (ethoxylated dihydroxy stearic acid methyl ester, DMOE n ) was synthesized and characterized. DMOE n was based on a hydroxyoctadecanoic acid methyl ester, which was obtained from renewable oleic acid in waste cooking oil. These new polyoxyethylene surfactants contained double hydrophilic and hydrophobic chains, which shows the surface properties of the branched surfactant. The synthesis rules and reaction kinetics were studied in detail. The physicochemical properties and surface properties of the DMOE n with different degrees of ethoxylation at various concentrations were investigated. Furthermore, the surface tension results indicate that DMOE n reduced the surface tension reduction and increased the diffusion rate in an aqueous solution. The dynamic contact angle, wettability, foaming properties, and emulsifying capacity tests showed that DMOE n exhibited good wetting performance, low foaming, fast defoaming, and excellent emulsifying ability, which shows that the surfactant has potential application in industrial cleaning.

The hydrate-based separation of hydrogen and ethylene from fluid catalytic cracking dry gas in presence of n-octyl-β-d-glucopyranoside

Hydrate-based gas separation (HBGS) needs a kinetic promoter to increase its economic value. The kinetic promoters for HBGS should have low foaming ability, high performance on increasing the conversion rate of the water into hydrate (RWH) and little thermodynamic inhibition on hydrate formation. However, no reported kinetic promoter meets all above requirements at same time. According to the experimental results in this work, n-octyl-β-d-glucopyranoside (OGP) met all those requirements of HBGS. For that reason, OGP was proposed as a new kinetic promoter for HBGS, and its effects on HBGS were revealed by investigating the HBGS of hydrogen and ethylene from fluid catalytic cracking dry gas in presence of OGP in this work. OGP enhanced the HBGS performance by increasing RWH from less than 64% to higher than 84%. By one-step separation, the hydrogen concentration was increased from 26.0 mol% to about 46.8 mol% while the ethylene concentration was increased from 52.0 mol% to about 74.4 mol%. The effect of the initial OGP concentration in liquid phase (wp,0) on HBGS increased with the increase in RWH, and the optimum wp,0 was 0.20 mass%. The processing capacity of the OGP solution in the HBGS was about 350 NL feed gas/L. OGP enhanced the promotion of increasing pressure on the HBGS performance. A new model was proposed to predict the thermodynamic equilibrium hydrate formation pressures of the experimental systems: the maximum relative deviation is 5.08% and the average relative deviation is 2.61%.

The formation of soy protein fibrils-chitin nanowhisker complex coacervates: Relationship to mixed foam stability

The effects of protein fibrillation modifications on foam properties and the foaming and stabilization ability of soy protein fibrils (SPF) and chitin nanowhisker (CNW) complex systems were investigated and evaluated. The results showed that the structure of SPF stretched significantly with the increase of heating time, probably due to the unfolding and rearrangement of protein structure. The foaming ability and stability of SPF were significantly higher than those of natural protein. The SPF and CNW coacervates effectively increased the foam strength, probably due to the interaction between the "worm-like" SPF structure and the short crystal structure of CNW. In addition, the samples containing salt had higher foaming ability, stability and viscosity compared to those without salt, resulting in a significant improvement in foaming properties. This study provided a new idea for studying the functional properties of modified protein-modified polysaccharides complex coacervates.

Antibacterial and biodegradable keratin-based quaternary ammonium salt surfactant potential as hair care additive

Biomass-based surfactants have excellent surface activities, showing the common characteristics of natural biomass including biocompatibility, biodegradability and non-toxicity, which are environmental-friendly and accord with the green development direction. In this study, a keratin based quaternary ammonium salt surfactant (denoted as E-K) was prepared by cationic modification of keratin with epoxypropyldodecyldimethylammonium chloride (EPDDMAC). The characterization of E-K by FTIR and the conversion rate of -NH2 in keratin confirmed the successful preparation of E-K. Subsequently, surface activity such as surface tension (γcmc) and critical micelle concentration (cmc), physicochemical properties such as HLB value, isoelectric point, foaming property and emulsifying property, as well as antibacterial activity and biodegradability were investigated. The results show that E-K possesses good surface activity, acceptable emulsifying and foaming ability. The HLB of E-K is 14-15, and it has excellent compatibility with commercial surfactants commonly used in hair care products. Particularly, E-K is a betaine zwitterionic surfactant, and its isoelectric point increases from 3.8 to 9.2 due to cationization. This means that the quaternized keratin hydrolysate is easily adsorbed on the hair surface, and makes the hair surface smoother and denser, which was proved by the adsorption test and SEM observation. Furthermore, E-K has outstanding antibacterial activity against E. coli and S. aureus, and the BOD5/CODCr value indicated that it is easily biodegradable. Therefore, the prepared biomass-based surfactant (E-K) has great potential application in hair care products and other products related to antibacterial and biodegradable surfactants.

Evaluation of Sodium and Potassium Soaps Prepared from Beeswax: Adding Value to Material

This study investigated the potential of producing quality soaps from beeswax with a view to widening its applications and providing alternative to the high demanding fats and oils. Its potassium and sodium soaps were prepared by hot method and their properties examined. The FTIR spectroscopy indicated carboxylate band at 1560.46 cm−1 for both soaps, which is, however, absent in the original beeswax, showing that metal ions associated with the COO− ions in monodendate structures. The soaps have good qualities with respect to pH, foam ability, longevity, hardness, free alkali and total fatty matter, with the potassium soap having higher qualities. The foam ability and stability of the potassium soap were comparable to those of some commercial toilet and laundry soaps. The sodium soap, however, has better lubricating properties due to its unstable foam and low water solubility. Both prepared soaps showed lower antibacterial activity than tested antiseptic soaps but displayed almost the same activity with those of tested toilet soaps. The results showed that beeswax has the potential to serve as a good alternative to the conventional fats and oils in soap industry.

Underlying synergistic collection mechanism of an emerging mixed reagent scheme in chalcopyrite flotation

Effective collectors are essential for the flotation of copper sulphide resources. In this work, we prepared a novel surfactant containing C-O-C groups, O,O'-bis(2-butoxyethyl) ammonium dithiophosphate (BEAT), and mixed it with O-isopropyl-N-ethyl thionocarbamate (IPETC) as an emerging reagent scheme for efficiently improving the flotation recovery of chalcopyrite. Foaming performance tests revealed that BEAT possessed a stronger foaming ability and foam stability than methyl isobutyl carbinol (MIBC). Micro-flotation results indicated that a significant improvement of chalcopyrite flotation recovery of 92.43% was achieved when mixed IPETC/BEAT collectors (BEAT optimal molar fraction of 60%) of 4 × 10−5 mol/L at pH 7.0–7.5 were employed. Bench-flotation results of copper sulphide ores showed that compared with IPETC + MIBC (30 g/t + 36 g/t) or BEAT (30 g/t) alone reagent system, a smaller amount of mixed IPETC/BEAT collectors (only 20 g/t) scheme was able to obtain higher Cu recovery and Cu grade. Surface tension results implied that the mixtures provided higher surface activity than individual IPETC, thus exhibiting superior foaming properties and better water solubility. Wettability results suggested that mixed collectors possessed stronger hydrophobicity and superior selectivity towards chalcopyrite against pyrite than single collector. FTIR results demonstrated that mixed collectors were chemically involved with the chalcopyrite surface through co-adsorption. Intermolecular interaction parameter computation confirmed the positive synergistic effect of mixed collectors.

Unsteady-state CO2 foam injection for increasing enhanced oil recovery and carbon storage potential

The efficiency of CO2 injection for enhanced oil recovery and carbon storage is limited by severe viscosity and density differences between CO2 and reservoir fluids and reservoir heterogeneity. In-situ generation of CO2 foam can improve the mobility ratio to increase oil displacement and CO2 storage capacity in geological formations. The aim of this work was to investigate the ability of CO2 foam to increase oil production and associated CO2 storage potential, compared to other CO2 injection methods, in experiments that deploy field-scale injection strategies. Additionally, the effect of oil on CO2 foam generation and stability was investigated. Three different injection strategies were implemented in the CO2 enhanced oil recovery and associated CO2 storage experiments: pure CO2 injection, water-alternating-gas and surfactant-alternating-gas. Foam generation during surfactantalternating-gas experiments showed reduced CO2 mobility compared to water-alternatinggas and pure CO2 injections indicated by the increase in apparent viscosity. CO2 foam increased oil recovery by 50% compared to pure CO2 injection and 25% compared to water-alternating-gas. In addition, CO2 storage capacity increased from 12% during pure CO2 injection up to 70% during surfactant-alternating-gas injections. Experiments performed at high oil saturations revealed a delay in foam generation until a critical oil saturation of 30% was reached. Oil/water emulsions in addition to CO2 foam generation contributed to CO2 mobility reduction resulting in increased CO2 storage capacity with foam. Cited as: Sæle, A., Graue, A., Alcorn, Z. P. Unsteady-state CO2 foam injection for increasing enhanced oil recovery and carbon storage potential. Advances in Geo-Energy Research, 2022, 6(6): 472-481. https://doi.org/10.46690/ager.2022.06.04

Technological aspects of whey by-products use in the production of zephyr of improved quality

The research in the field of sugar-free zephyr production with the use of milk whey by-products - whey permeate powder and whey protein dry concentrate - is presented. The quality indicators of the ingredients used are investigated, their characteristics and nutritional value are presented. The foaming properties of dry whey protein concentrate were evaluated in order to establish the optimal content of dry substances of the protein solution for its further use in the production of confectionery masses of foamy structure. The greatest maximum value of the foaming ability (403%) was observed when using solution with a mass fraction of dry substances (24%) with the addition of citric acid in the amount of 0.8% (pH of the solution - 4.1). When replacing white sugar with permeate in zephyr production and using molasses in greater amount than in the control sample, the viscosity of zephyr mass decreases to a greater extent, the volume of foam, its stability and dispersion increase. The developed samples of zephyr, in comparison with the control sample, have a lower density 1.2-1.3 times. Also, they do not contain white sugar, have a reduced total carbohydrate content 1.2-1.3 times. The content of easily digestible carbohydrates is reduced 1.5-1.7 times, which in turn made it possible to obtain products of moderate sweetness, increased protein content 1.1-1.6 times, reduced calorie content 1.5-1.6 times, decreased glycemic index 1.5-1.6 times.

Microscopic testing of carbon fiber laminates with shape memory epoxy interlayer

For the first time, microscopic testing has been performed on shape memory polymer composites (SMPCs) which were manufactured by commercial materials already used in aerospace. Results from micro-tests have been compared with those from conventional memory-recovery cycling on macro-scale. Two shape memory polymer composite (SMPC) laminates were fabricated with different shape memory (SM) interlayer: one in the form of an uncured epoxy powder and the other in the form of a thin epoxy foam. The latter, in particular has been studied to evaluate lightweight and stiff sandwich structures with SM properties. The assessment of the manufacturing process by a hot press moulding technique was assessed through micro scale analysis using SEM and MicroCT analysis. DMA analyses were carried out to understand the interaction mechanisms between raw constituents. A Vickers micro-indentation examination before and after heating was able to assess the shape recovery behaviour at the micro-scale level. A nano-instrumental indentation was used to characterise the shape memory response under different loads at elevated temperatures. Whilst an instrumented thermo-mechanical test allowed to investigate the shape memory behaviour at macro-scale level. Results allow identifying the recovery mechanisms at the micro-scale which are responsible for the shape memory performances at the macro-scale. The higher recovery ability of the SM foam is confirmed in comparison with bulk interlayers.

Microcellular injection molded lightweight and tough poly (L-lactic acid)/in-situ polytetrafluoroethylene nanocomposite foams with enhanced surface quality and thermally-insulating performance

High-performance microcellular polymer foams have been widely used all over the world, while the excessive usage of petroleum-based polymers caused serious environmental problems. As the eco-friendly awareness is increasing significantly, poly (L-lactic acid) (PLLA), as a typical biomass polymer, has gradually attracted widespread attention. However, the slow crystallization and poor melt strength of PLLA lead to low foaming ability and thus limiting its industrial applications. Herein, a novel and scalable strategy by coupling in-situ fibrillation and mold-opening microcellular injection molding (MOMIM) was developed to fabricate lightweight and tough PLLA/polytetrafluoroethylene (PTFE) foams. Thanks to the reticulated in-situ PTFE nanofibrils with a diameter of 100–200 nm, the crystallization and viscoelasticity of PLLA were dramatically promoted, and further contributing to its foaming ability. The expansion ratio of the MOMIM PLLA/PTFE foam was increased by 86 % compared with the regular microcellular injection molded (RMIM) PLLA foam. Moreover, the lower foam density and the toughening effect of PTFE nanofibrils resulted in the outstanding ductility of the PLLA/PTFE foams, whose tensile elongation, flexural strength, and impact strength were maximally increased by 52 %, 28 %, and 48 %, compared with PLLA foams. More importantly, the thermally-insulating performance and surface quality of PLLA/PTFE foams were also greatly improved.