Metal adsorption of tannin based rigid foams

Tannin based rigid foams are structures in which flavonoids are randomly cross-linked with furanic units throughout covalent bonds. The use of these aromatic substrates from natural materials to trap some heavy metal ions dissolved in water solutions is described. Interesting results have been achieved using different mimosa bark tannin (Acacia mearnsii formerly mollissima, De Wildt) and pine bark tannin (Pinus radiata) mixed foams. Capability to catch Pb²⁺ and Cu²⁺ ions at different concentrations has been verified throughout ICP-OES analysis of the foams. A reliable proportionality has been found between initial concentration and percentage of metal ions adsorbed. These foams were able to adsorb up to 12.5% of Cu(II) and 20.1% of Pb(II) with respect to the concentration of these ions in solution.     

Flexible natural tannin-based and protein-based biosourced foams

Flexible tannin foams as opposed to the rigid tannin foams already prepared, were obtained by the addition of an external (non-reacted) plasticizer, namely glycerol. Glycerol was chosen for its high boiling temperature and the lack of evaporation, coupled to its lack of toxicity. Flexible albumin protein foams were also prepared using glycerol as an external plasticizer. Flexibility and spring-back of these experimental foams when subjected to a cyclic compression force followed by spring-back and compression again was quantified by both thermomechanical analysis at different temperatures as well as by compression/spring back hysteresis cycle tests in a universal testing machine. Tannin foams containing formaldehyde and without glycerol have been shown to reach a stress plateau indicative of structure crushing. Tannin foams without formaldehyde but without glycerol too, becomes very fragile, brittle and rigid just two months after their preparation again presenting structure crushing with ageing. Instead, tannin foams without formaldehyde but with glycerol added do not show any change of flexibility with time and remain truly flexible. Albumin foams to which glycerol was added also do not show any change of flexibility with ageing. The glass transition temperature of the materials constituting the foams was measured by thermomechanical analysis.     

Characteristics of biodegradable Mater-Bi®-starch based foams as affected by ingredient formulations

Expanded polystyrene (EPS) foams are widely used to provide protection to merchandise during shipping and handling. The disposal of EPS foams, however, causes pollution to the environment. Starch based loose fill packaging foams are commercially available to replace the EPS foams. Starch foams dissolve readily in water, and do not possess satisfactory physical and mechanical properties. To improve the functional properties and water resistance of starch foams, regular (25% amylose) and waxy corn starches blended with Mater-Bi® ZF03U (MBI) were extruded into loose-fill packaging foams using a co-rotating twin screw extruder. MBI contents of 10, 25 and 40% and starch moisture contents of 19, 22 and 25% (d.b.) were used. Waxy starch produced foam with greater radial expansion and lower unit and bulk densities than regular starch. Higher levels of MBI reduced radial expansion and increased unit and bulk densities. Foam made with regular starch had a lower water solubility index than foam made with waxy starch. The addition of MBI improved the water solubility. Higher starch moisture contents increased foam water solubility indices. Foams made from both types of starch possessed acceptable mechanical properties. Regular starch produced more rigid foams than the waxy starch as indicated by the higher compressibility values based on both single-piece and bulk samples. Moisture content affected the compressibilities. Higher moisture contents produced more rigid foams. The spring indices of bulk samples were excellent (>95%) for all MBI contents.     

Insulation rigid and elastic foams based on albumin

Albumin-based rigid and elastic foams were prepared by mechanically beating water solutions of the protein mixed with formaldehyde and camphor. The resulting foams were cross-linked in a traditional or in a microwave oven. Formaldehyde was used as hardener of the protein and camphor as a plasticizer. Thermal conductivity was tested and found to be acceptable for thermal insulation but did not appear to be influenced by variations in foam density. Scanning electron microscopy of the different formulations showed some differences in cells structure. Formulations of different water content, formaldehyde hardener content, camphor content and oven curing time were tested. Within certain limits (a) increases in water proportion rendered the foam more elastic, (b) higher formaldehyde content increased foam rigidity and strength up to a value beyond which no further increase occurred, (c) the amount of camphor influences markedly the compression strength and foam elasticity/plasticity, (d) curing time improving foam strength up to 5 min in microwave curing, without any further effect for longer heating times. Only addition of glycerol, yielded truly soft elastic foams.     

Compressive viscoelastic properties of softwood kraft lignin-based flexible polyurethane foams

Softwood kraft lignin (SKL)-based water-blown flexible polyurethane foams were prepared using SKL as a crosslinking agent and a hard segment polyol. Polyethylene glycol (PEG) as a soft segment diol and 2,4-toluene diisocyanate (TDI) were used. While increasing hard segment content caused the increase in crosslink density in foams, the foams became more and more viscous with increasing hard segment content due to the distinctive phase heterogeneity in foams. In this case, the contributiveness of the filler-like behaviors of separated hard segments always overtook the crosslinking effects derived from SKL in terms of overall viscoelasticity, thus the resultant viscometric properties such as tanδ _max and hysteresis loss increased as hard segment content increased. Furthermore, increasing M _n,PEG caused the severer microphase separation and intensified the filler effects in foams, thus the foams became more viscous with increasing M _n,PEG. The 25 % and 65 % CFD values and Young’s moduli of foams increased with increasing hard segment content due to the increase in crosslink density for foams, and the properties also increased with increasing foam density. Most of foams showed the support factors in the range of 2–3, which are suitable values for cushioning use. Even though the microscopic deformation behaviors in foams are irrelevant to foam density, the cyclic compressive tests showed that the higher foam density possess the better shape recovery performances.     

Mechanical and physical properties of expanded starch, reinforced by natural fibres

Biodegradable foams made from potato starch and natural fibres were obtained by extrusion. The effects of varying origins of these fibres on foam properties were studied, as well the relationships between their properties and the foam microstructure. The addition of fibres increased the expansion index and led to a significant reduction in water adsorption of starch foams, generally improving foam properties. The mechanical properties of the foams were affected by both relative humidity (RH) of storage and foam formulation. In general, as the RH increased, the foam strength decreased. The formulation presenting the best mechanical properties contained 10 wt% hemp fibre and had a maximal resistance of 4.14 MPa and a modulus of 228 MPa, corresponding to a more compact and dense microstructure.     

Sound absorbent,flame retardant warp knitting spacer fabrics: Manufacturing techniques and characterization evaluations

This study proposes a combination for reciprocal reinforcement between warp knitting spacer fabrics and PU foams. PET/Kevlar nonwoven fabrics are made with an 80:20 ratio and an incorporation of various needle-punching speed of 100, 150, 200, 250, and 300 needles/min. Ascribing to having an optimal bursting strength, sound absorption coefficient, and limited oxygen index (LOI), the PET/Kevlar nonwoven fabric that is made by 200 needles/min are selected to be combined with a glass-fiber fabric by applying needle punch in order to form a surface layer. Next, warp knitting spacer fabrics and the nonwoven fabrics are laminated, followed by being combined with polyurethane (PU) foam that are featured with different densities of 200, 210, 220, 230, and 240 kg/m³ in order to form spacer fabric/PU foam composites with multiple functions. The composites are then tested with a drop-weight test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that all spacer fabric/PU foam composites reach a horizontal burning level of HF1, and their sound absorption coefficients at 2500-4000 Hz also suggest a satisfactory sound absorption. In particular, the optimal residual stress and compressive strength are present when the composites contain 210 kg/m³ PU foam. Similarly, the optimal bursting strength of the composites occurs when they are composed of 230 kg/m³ PU foam. The spacer fabric/PU foam composites are proven to have high strengths, sound absorption, and fire retardant, and thus have promising potentials for use as construction materials and light weight composite planks.     

Nonwoven fabric/spacer fabric/polyurethane foam composites: Physical and mechanical evaluations

In the first stage, polyethylene terephthalate (PET) fibers and Kevlar fibers are combined at a blending ratio of 80/ 20 wt% in order to form PET/Kevlar nonwoven fabrics. Two pieces of PET/Kevlar nonwoven fabrics that enclose a carbonfiber (CF) interlayer are then needle punched in order to form PET/Kevlar/CF (PKC) composites. In the second stage, the sandwiches compose PKC composites as the top and the bottom layers, as well as an interlayer that is composed of a spacer fabric and polyurethane (PU) foam. PU foams have different densities of 200, 210, 220, 230, and 240 kg/m³. These resulting nonwoven fabric/spacer fabric/PU foam sandwiches are then tested using a drop-weight impact test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that the optimal properties of sandwiches occur with their corresponding PU foam density as follows: an optimal residual stress (240 kg/m³), an optimal compressive strength (240 kg/m³), and an optimal bursting strength (220 kg/m³). In addition, the sandwiches reach the HF1 level according to the horizontal burning test results. They also have an average electromagnetic interference shielding effectiveness of -48 dB, as well as a sound absorption coefficient of 0.5 in a frequency between 1500-2500 Hz, which indicates a satisfactory sound absorption effect. The nonwoven fabric/spacer fabric/PU foam sandwiches proposed in this study are mechanically strong, sound absorbent, and fire retardant, and can be used in construction material and electromagnetic shielding composites.     

Water solubility,thermal characteristics and biodegradability of extruded starch acetate foams

Starch based foams have been studied as replacements for non-degradable expanded polystyrene (EPS) as loose-fill packaging material because of starch’s total degradation and low cost. However, starch’s hydrophilicity, poor mechanical properties and dimensional stability limited their applications. Acetylated starch with a high degree of substitution (DS) is an alternative. Starch acetates with DS 1.11, 1.68, and 2.23 were extruded with either water or ethanol as solvents. The effects of DS and type of solvent on the starch acetate foam’s water absorption index (WAI), water solubility index (WSI), thermal behavior (glass transition temperature [T_g], melting temperature [T_m], and thermal decomposition temperature), and biodegradability were investigated. There was a significant interaction (P < 0.05) between solvent type and DS on WAI and WSI of the foams. As DS increased from 1.11 to 2.23, WAI and WSI increased when ethanol was used as solvent and decreased when water was used as solvent. The T_g values of starch decreased with acetylation and with increasing DS, but increased with extrusion. Acetylation and extrusion increased the thermal stability of the foams. The rate of biodegradation of the foams decreased with increasing DS. The foams, extruded with ethanol, had higher degradation rates than those with water.     

The preparation of polyurethane foam combined with pH-sensitive alginate/bentonite hydrogel for wound dressings

Polyurethane (PU) foam was combined with protein drug-loaded pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a linear copolymer composed of 1–4-linked β-D-mannuronic acid (M) and its c-5-epimer α-Lguluronic acid (G). The amount of (M) and (G) and their sequential distribution are varied depending on the alginate source. Soluble sodium alginate can become a hydrogel when cross-linked with divalent cations and has widespread applications in the food, drink, pharmaceutical and bioengineering industries. Recently, it has been also proposed as a biomaterial for drug delivery systems. Bentonites are the natural inorganic polymers consisting of a large proportion of expandable clay minerals with a three-layer structure such as montmorillonite, beidellite, nontronite, etc. They are important adjutants and supports for medical products, and they have many useful physicochemical, mechanical, and biological properties such as absence of toxicity, indifference to other raw materials, sorption, swelling, and complex formation properties. Alginate-bentonite hydrogels were prepared at concentration ratios of 10/0, 7/3, 5/5, 3/7. PU foams were prepared using hydrophilic polyols. We investigated the controlled release of a protein drug from PU foam combined with alginate-bentonite hydrogel at different pH values of 4.2, 5.2, 7.2, 8.2. The mechanical properties and cytotoxicity tests of this foam were also studied.     

Tannin contents and protein digestibility of black grams (Vigna mungo) after soaking and cooking

The objective of this research was to ascertain the effects of soaking black grams (Cultivar AARI-5732)in different salt solutions at different temperatures and different timeperiods, and different methods of cooking on the tannin content and proteindigestibility. Tannin content of black grams was reduced to variousextents by soaking at 30^° and 100 ^°C for different timeperiods. However, soaking at 100 ^°C increased the rate ofextraction and reduced the extraction time of tannins. Soaking black gramsin water at 100 ^°C reduced tannins by 22.14% in 45 minuteswhereas about 2.5 times more tannin was reduced after soaking in sodiumbicarbonate solution with or without sodium chloride. Maximumimprovement in protein digestibility was also observed after soaking blackgrams in sodium bicarbonate solution. Tannin contents were furtherreduced along with improvement in protein digestibility as a result ofcooking.     

Foaming properties of gluten and acetylated gluten: Studies of the mathematical models to describe liquid drainage

The foaming properties of gluten and acetylated gluten were studied at various concentration values (1%, 5%, 10% and 20%). Acetylated gluten was prepared by acetylation of gluten with acetic anhydride in presence of sodium hydroxide as catalyst. The foaming properties were characterised by measuring foam stability and drainage. It was found that foam made from acetylated gluten is more abundant and stable than the foam made from gluten studied in the whole range of concentration, i.e. 1–20%.     

Structural,thermal, and mechanical properties of polyurethane foams prepared with starch as the main component of polyols

In this study, rigid polyurethane foams were prepared using starch as the main component of polyols and their structural, thermal, and mechanical properties were investigated. The starch content in polyols was 30∼50 wt.%. The prepared polyurethane foams had a cell structure. When the starch content and -NCO/-OH molar ratio (TS4-05, TS3-07, and TS3-05) was low, polyurethane foams were not formed. To confirm the formation of a urethane linkage between -OH of the starch and -NCO of the 2,4-TDI, FT-IR spectroscopic analysis was performed. The thermal properties of polyurethane foams were analyzed by DSC and TGA. DSC thermograms showed two endothermic peaks: a sharp peak at a lower temperature and a broad peak at a higher temperature. Both peaks were shifted to higher temperature with starch content in polyols and -NCO/-OH molar ratio. Thermal degradation of polyurethane foams began at a lower temperature and ended at a higher temperature than that of starch. The impact resistance, compressive stress and modulus of polyurethane foams increased with -NCO/-OH molar ratio and starch content.     

Preparation and property evaluation of sound-absorbing/thermal-insulating PU composite boards with cushion protection

This study used recycled fibers and inflaming retarding fibers to form composite nonwoven and then compounded with PU foam preparing composite board with sound-absorbing, thermal-insulating and cushion properties. Effects of foam density and composite nonwoven on three properties of PU composite board have studied. Result shows that, with increase of foam density, composite boards had higher sound absorbing coefficient at medium and high frequencies, lower thermal insulation as well as firstly improved and then decreased cushion property. After assessment, the optimal foam density was 60 kg/m³. For diverse requirements, PU foam matches with different kinds of composite nonwoven to achieve excellent cushion property. The resulting composite board can effectively ease hurts from rigid wall, and could be applied in kindergarten, music hall, audio-visual room, pub and recreational centre etc in the future.     

Comparison of the effect of acylation and phosphorylation on surface pressure,surface potential and foaming properties of protein isolates from rapeseed (Brassica napus)

A protein isolate from rapeseed was exhaustively modified by acetylation, succinylation and phosphorylation. Changes in protein solubility, adsorption kinetics, surface pressure and surface potential of monolayer, wetting and foaming properties due to chemical modification were studied. Chemical modification distinctly increased the solubility of the rapeseed protein in the alkaline pH range. Acylation increased the reduction of the surface tension. An overall improved pressure transformation and increase in surface potential in monolayer after modification was observed whereby the highest changes were achieved after succinylation. The wettability with water of protein coated hydrophobic glass substrates could be improved by succinylation and phosphorylation. Chemical modification increased the foam capacity and foam expansion of the protein. A higher foam stability was only measured after acetylation and phosphorylation. Adsorption kinetics and surface potential could be related well to the properties of protein films on hydrophobic substrates as well as in foams.     

An evaluation of the three-dimensional geometric shape of moulded bra cups

Bra cup moulding is currently a remarkable process in the production of seamless intimate apparel. The process is highly complex, time-consuming and error-prone due to the large variations of foam and lamination properties, cup styles and sizes, and geometric features of graduated padding. In particular, the three-dimensional (3D) geometric shape of foam cups is difficult to assess accurately because they are very soft and readily deform. In cases that involve fitting problems, shape modifications of the mould head and determination of the optimal moulding conditions have undergone repeated trials and errors. There is limited knowledge about the effects of foam properties and cup parameters in the controlling of moulding conditions. This study adopts a parameterization-based remesh algorithm method to evaluate the 3D shapes of the convex surface of scanned cup samples. The shape conformity of the cup is quantified in accordance to the corresponding mould head. In this respect, the moulding conditions that would achieve the most desirable geometric shapes of bra cups can be accurately and objectively demonstrated. Based on moulding experiments with 6 types of polyurethane (PU) foam materials, empirical equations that associate the cup shape conformity and the shape deviations from selected cup sectional curves are established. Through the use of non-linear regression models, the shape conformity of the moulded cups can be predicted by moulding conditions with reasonable accuracy. The shape conformity provides effective guidelines for quality assurance and improves production efficiency of bra cup moulding. Moreover, thermal-mechanical properties, such as compressive strain and softening temperature obtained from thermomechanical analysis (TMA) scans, provide a good understanding of cup shape conformity and determine the lowest moulding temperature at initial trails of the bra cup moulding process. Surprisingly, in pliable foams, the cup size does not have an apparent effect on the moulding conditions to achieve optimal cup shape conformity. The results reveal that the moulding conditions for sizes 34B and 34D could remain the same for pliable foam materials. Nevertheless, in the case of more rigid foams, a higher moulding temperature is required to achieve a desirable cup shape for size 34D as more energy is required for the heat-setting of foam materials with higher proportions of hard segments at the moulding of a larger cup size in anticipation of larger deformations.     

Processing of polyurethane/polystyrene hybrid foam and numerical simulation

Polyurethane foams were produced by using a homogenizer as a mixing equipment. Effects of stirring speed on the foam structure were investigated with SEM observations. Variation of the bubble size, density of the foam, compressive strength, and thermal conductivity were studied. A hybrid foam consisting of polyurethane foam and commercial polystyrene foam is produced. Mechanical and thermal properties of the hybrid foam were compared with those of pure polyurethane foam. Advancement of flow front during mold filling was observed by using a digital camcorder. Four types of mold geometry were used for mold filling experiments. Flow during mold filling was analyzed by using a two-dimensional control volume finite element method. Variation of foam density with respect to time was experimentally measured. Creeping flow, uniform density, uniform conversion, and uniform temperature were assumed for the numerical simulation. It was assumed for the numerical analysis that the cavity has thin planar geometry and the viscosity is constant. The theoretical predictions were compared with the experimental results and showed good agreement.     

Esparto wool as reinforcement in hybrid polyurethane composite foams

In the present work polyurethane foams containing variable concentrations of nano-sized clay and esparto wool were prepared and studied, with the objective of developing new multi-scalar rigid foams. The addition of montmorillonite clay favoured foaming and the formation of finer and homogeneous cellular structures, resulting in foams with compressive elastic moduli and collapse stresses lower than that of the polyurethane foams. Nevertheless, a comparative analysis versus the foams’ relative density demonstrated that both properties follow one single trend for the two materials. The combination of esparto and montmorillonite further reduced the cell size of foams, at the same time promoting higher open cell contents, resulting in the foams with the lowest mechanical properties. Although no important differences in thermal conductivity were found with adding montmorillonite, its value decreasing with reducing the relative density, the incorporation of esparto led to higher thermal conductivities, independently of the relative density. The combination of esparto and montmorillonite resulted in foams with thermal conductivities halfway between the esparto-reinforced and the montmorillonite-reinforced foams, related to a higher open cell content.     

Plant species richness, functional type and soil properties of grasslands and allied vegetation in English Environmentally Sensitive Areas

To facilitate the maintenance and restoration of semi‐natural grasslands, it is important to understand their relationships with soil properties. Semi‐natural grasslands typically have a high incidence of stress‐tolerant species (measured here by high stress radius values), but not all have high species richness. Species richness and stress radius values were related to soil pH, Olsen extractable phosphorus (P), extractable potassium (K) and magnesium (Mg), total nitrogen (N) and organic matter (OM) at 571 sites representing a wide range oftemperate grasslands. Highest species richness (>30 m^?2) occurred at pH > 6 and 4–15 mg l^?1 P, but species richness was also highly variable at 4–15 mg l^?1 P. At pH < 5, species richness was low (<20 m^?2). Stress radius values were highest (mainly calcareous and heath grasslands and mires) at pH c. 8·0 and < 5·0, and at the lowest soil P levels (<5 mg l^?1). A wide range of stress radius values occurred at low soil P levels because appropriate management is also needed to maintain semi‐natural grasslands. Reducing soil P is difficult in practice, so grassland restoration in the presence of elevated soil‐extractable P levels merits re‐assessment.     

Biodegradable foam tray from cassava starch blended with natural fiber and chitosan

This work developed biodegradable foam trays from cassava starch blended with the natural polymers of fiber and chitosan. The kraft fiber at 0, 10, 20, 30 and 40% (w/w of starch) was mixed with cassava starch solution. Chitosan solution at 0, 2, 4 and 6% (w/v) was added into starch/fiber batter with 1:1. Hot mold baking was used to develop the cassava starch-based foam by using an oven machine with controlled temperature at 250 °C for 5 min. Results showed that foam produced from cassava starch with 30% kraft fiber and 4% chitosan had properties similar to polystyrene foam. Color as L^*, a^* and b^* value of starch foam tray was slightly increased. Density, tensile strength and elongation of the starch-based foam were 0.14 g/cm³, 944.40 kPa and 2.43%, respectively, but water absorption index (WAI) and water solubility index (WSI) were greater than the polystyrene foam.