Foam breaking by high speed rotors

The first part of this paper presents a relationship for the minimum velocity of rotating installations for foam breaking. The derivation is based on equilibrium of inertia and surface forces. Inertia forces occur during the acceleration of foam bubbles and act mainly at the plateau borders. High and definite acceleration can be obtained with a deformer composed of a rotor and a stator. The surface force is due to the dynamic surface tension because surface-active solutions react to a rapid change in surface area by altering their surface tension. The theoretical relationship is compared with experimental results of minimum velocities needed to break foams produced from aqueous solutions of detergents. The equation presented here explains why measured minimum velocities often range between 10 and 20 m/s. The second part of the paper deals with condensation of continuously generated foam in a closed system. In the process of condensation, foam is not completely separated into liquid and gas phase but turns into foam with small bubbles and high density. The collapse of this condensed foam must be considered for the control of persistent foams in a closed system. The collapse of foams made of aqueous solutions of different surface-active agents has been investigated. Different highly surface-active agents show small variations in times of coalescence. A relationship for the lifetime is given, which is based on laminar flow along plateau borders. Recommendations are made with respect to the geometry of the foam breaker, scale-up and operating variables such as rotational speed of the foam breaker and gas flow rate.     

Mechanical properties of urea–formaldehyde foam

The mechanical behavior of urea-formaldehyde foam was studied to evaluate its potential for energy absorption applications. The apparent elastic modulus (E_f) as a function of foam density was obtained from force-deformation tests. The values of energy absorption capacity were derived from a numerical integration technique. Poisson's ratio (v) was determined by a method of uniaxial compression of cylindrical samples. An increase in foam density results in an increase in the apparent elastic modulus of the material and therefore in its energy absorption capacity. Poisson's ratio is independent of the foam density. The mechanical properties' values obtained can be incorporated in various analyses for predicting desired characteristics for energy absorption applications.     

Fire-performance of a ventilated facade insulated with a B2–classified rigid polyurethane foam

A two-storey test rig was used to investigate how an insulated facade would react to the impingement of a simulated room fire. In particular, whether or not a facade insulated with polyurethane foam would promote vertical flame spread. Wooden cribs weighing 40 kg were used as fire sources. One set of tests was run without any steel cladding to study the behaviour of the polyurethane foam alone. In a wall-configuration test as well as under a conrner-configuration one limited vertical and horizontal flame propagation were found. The degree of damage was to some extent, greater under the corner-test conditions than with the wall tests. A ventilated facade construction with the profiled steel cladding fixed to vertical support-work was used for the second set of tests. In order to simulate repair conditions, the outer metal cladding was completely removed from the lower 1.5 m of the facade. In Both tests a strong chimney-effect behind the cladding was observed. This intensification of the flame impingement led to a flame spread up the top of the facade. The tests indicated that the vertical flame spread would continue unless the method of construction incorporated vertical fire stops.     

Fullerenes as a co-catalyst for high pressure – high temperature synthesis of diamonds

The paper reports on the effect of a fullerene co-catalyst on high pressure – high temperature (HPHT) synthesis of diamond from graphite. It is shown that the co-catalyst increases the diamond yield by a factor of 1.30–1.45 at relatively low pressure (4.5 GPa) and temperature (about 1200 °C).     

Foam application from a closed system – a study of machine and foam parameters

An attempt has been made to gain a greater insight into the interaction between foam and a moving textile substrate. The effects of changing wet pick–up, fabric velocity, liquid viscosity, foam density and mode of application on penetration have been studied. Application from a closed system makes it possible to apply an exact amount of liquid, and reflectance measurements revealed that between 10 and 60% wet pick–up the actual level of wet pick–up is of major importance. The amount of liquid available determines the likelihood of capillary transport. The results obtained in terms of fabric speed and foam density still leave questions to be answered on the mechanisms of foam flow and degradation in the textile.     

Foam breaking — key process in detoxification of kraft mill effluents by foam separation

A study was undertaken to demonstrate on pilot plant scale the performance of a turbine foam breaking system and to develop the design parameters for large scale application. Among various configurations a 3-blade vaned-disc turbine was found to be optimal for foam breaking. Major process variables controlling foam breaking were system design, tip velocity, rotation speed, and foam load. A foam breaking system with only restricted liquid draw-off performed 3 - 16 times better than a conventional flow through system. A 38 cm diameter turbine operating at 1800 τ/min (3600 cm/s tip velocity) collapsed up to 1.2 m³/min (42 ft³/min) of foam. Design equations developed for sizing of foam breakers suggest that a 61 cm (2-ft) diameter 21 kW turbine will collapse 4.7 m³/min of foam. For a 95 × 10³m³/d foam separation plant, approximately 12 foam breakers are required. Capital costs are estimated at $108,000.     

Fracture mechanics parameters for polystyrene under high speed impact

A series of commercial polystyrenes was tested using an instrumented impact tester to determine the fracture toughness K_c and critical strain energy release rate G_c. Over the range of M_w, 201,000 to 336,000, K_c increased from 1.38 MN/m^3/2 to 1.76 MN/m^3/2and G_c from 0.92 kJ/m² to 1.60 kJ/m². A linear correlation for K_c and G_c was seen with melt index, and an inverse relationship was obtained against molecular weight. Examination of the fracture surfaces revealed the presence of crack growth bands corresponding to the crack tip plastic zone size. It is suggested that these bands are the consequence of variations in crack growth along crazes that form in the crack tip stress field. As the crack propagates, the stress is relaxed locally, decreasing the growth rate allowing a new bundle of crazes to nucleate along which the crack advances. The spacing of these bands corresponds to the craze length formed in the plastic zone, and the band spacing increases with molecular weight.     

Glycols in polyurethane foam formulations with a starch–oil composite

A dry starch–oil composite was blended with each of three glycols; ethylene, polyethylene, and propylene, and then reacted with isocyanate to produce polyurethane foams. The liquid glycols permitted the dry composite to blend well with the other ingredients in the foam formulations. Infrared spectra confirmed the presence of urethane structures in the composite–glycol foams. Polyethylene glycol provided a slightly less dense foam than the other glycols in the composite–glycol products. Microscopy showed a greater number of larger cells in the composite–polyurethane glycol foams. Infrared spectra indicated essentially no qualitative differences in the composite–glycol foams with the three glycols. By prestaining starch with toluidene blue and oil with sudan red, the location of the starch and oil components of the milled composite were observed in the composite–propylene glycol foam. Intact flakes of the composite were observed in the foam. An apparent loss of mobility of oil in the composite–polyurethane foam, as evidenced by NMR analysis, is probably due to crosslinking by isocyanate diffusing into the flakes. Both the cell structure and uniformity of blending were improved by using these glycols rather than the polyester polyol described previously. J Appl Polym Sci 69: 957–964, 1998. Published 1998 John Wiley & Sons, Inc.     

Mechanical properties of a particle‐strengthened polyurethane foam

Quasi‐static compression tests have been performed on polyurethane foam specimens. The modulus of the foam exhibited a power‐law dependence with respect to density of the form: E* ∝ (ρ*)ⁿ, where n = 1.7. The modulus data are described well by a simple geometric model (based on the work of Gibson and Ashby) for a closed‐cell foam in which the stiffness of the foam is governed by the flexure of the cell struts and cell walls. The compressive strength of the foam is also found to follow a power‐law behavior with respect to foam density. In this instance, Euler buckling is used to explain the density dependence. The modulus of the foam was modified by addition of gas‐atomized, spherical, aluminum powder. Additions of 30 and 50 wt % Al measurably increased the foam modulus, but without a change in the density dependence. However, there was no observable increase in modulus with 5 and 10 wt % additions of the metal powder. Strength was also increased at high loading fractions of powder. The increase in modulus and strength could be predicted by combining the Gibson–Ashby model, referred to above, with a well‐known model describing the effect on modulus of a rigid dispersoid in a compliant matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2724–2736, 1999     

4–Hydroxy–3–arylamino–l, 8–naphthalimides and 3–(and 4–) hydroxy–2–(and 5–) arylamino–7H–bcnzimidazo–(2, l–a)benz(d,e)isoquinolin–7–ones. Red dyes for synthetic–polymer fibres

4–Hydroxy–1, 8–naphthalimides and the isomer mixtures of'3–and 4–hydroxy–7 H–benzimidazo–(2, l–a)–benz(d, e)–isoquinolin–7–ones were coupled with diazotised arylamines to yield orange–red to bluish–red dyes having good coloration properties and excellent fastness to light on polyester fibres. Structure–property relationships in the dyes are discussed with respect to the nature of the substituents in the imide, imidazole and arylazo moieties.     

New Intermediates and Dyes for Synthetic–polymer Fibres 4–(4–Methoxyanilino)–3–nitro–l, 8–naphthalimides

The synthesis of a series of 4–(4–methoxyanilinoj–3–nitro–1, 8–naphthalimides by condensation of amines with 4–(4–methoxyanilino)–3–nitronaphthalene–l, 8–dicarboxylic anhydride, and also by condensation of 4–halogeno–3–nitro–1, 8–naphthalimides with 4–methoxyaniline is described. They dye synthetic–polymer fibres, particularly polyesters, deep orange of excellent fastness properties. In presence of strong bases, e. g. 3–aminopropan–l–ol, the 4–arylamino group is replaced, giving a series of yellow dyes. A method is described for preparing the dyes without isolation of intermediate stages.     

A low sintering temperature glass based on SiO2–P2O5–ZnO–B2O3–R2O system for white LEDs with high color rendering index

A low sintering temperature glass based on the SiO₂–P₂O₅–ZnO–B₂O₃–R₂O (R=K and Na) system was studied as a matrix for embedding phosphors to fabricate color tunable white LEDs. The proposed system, which uses no heavy‐metal elements and can be sintered at 500°C, incorporates thermally weak commercial phosphors such as CaAlSiN₃:Eu²⁺ to produce phosphor‐in‐glasses (PiGs). Changing the mixing ratio of glass to phosphors affected the photo‐luminescence spectra and color coordinates of the PiGs when mounted on a blue LED. The color rendering index (CRI) and color correlated temperature (CCT) of the LEDs were also varied with the mixing ratio, providing color tunable white LEDs. A high CRI, up to 93, as well as highly improved thermal stability were obtained, along with a low sintering temperature compared to other glass systems, suggesting the practical feasibility of the proposed system.     

Mechanical Characterization of Annealed ZrB2–SiC Composites

Composites consisting of 70 vol% ZrB₂ and 30 vol% α‐SiC particles were hot pressed to near full density and subsequently annealed at temperatures ranging from 1000°C to 2000°C. Strength, elastic modulus, and hardness were measured for as‐processed and annealed composites. Raman spectroscopy was employed to measure the thermal residual stresses within the silicon carbide (SiC) phase of the composites. Elastic modulus and hardness were unaffected by annealing conditions. Strength was not affected by annealing at 1400°C or above; however, strength increased for samples annealed below 1400°C. Annealing under uniaxial pressure was found to be more effective than annealing without applied pressure. The average strength of materials annealed at 1400°C or above was ~700 MPa, whereas that of materials annealed at 1000°C, under a 100 MPa applied pressure, averaged ~910 MPa. Raman stress measurements revealed that the distribution of stresses in the composites was altered for samples annealed below 1400°C resulting in increased strength.     

Phenolic antioxidants – radical‐scavenging and chain‐breaking activity: A comparative study

Fifty phenolic antioxidants (AH) (42 individual compounds and 8 binary mixtures of two antioxidants) were chosen for a comparative analysis of their radical‐scavenging (H‐donating) and chain‐breaking (antioxidant) activity. Correlations between experimental (antiradical and antioxidant) and predictable (theoretical) activities of 15 flavonoids, 15 hydroxy cinnamic acid derivatives, 5 hydroxy chalcones, 4 dihydroxy coumarins and 3 standard antioxidants (butylated hydroxytoluene, hydroquinone, DL ‐α‐tocopherol) were summarized and discussed. The following models were applied to explain the structure‐activity relationships of phenolic antioxidants of natural origin: (a) model 1, a DPPH assay used for the determination of the radical‐scavenging capacity (AH + DPPH? → A? + DPPH‐H); (b) model 2, chemiluminescence of a model substrate RH (cumene or diphenylmethane) used for the determination of the rate constant of a reaction with model peroxyl radicals (AH + RO₂? → ROOH + A?); (c) model 3, lipid autoxidation used for the determination of the chain‐breaking antioxidant efficiency and reactivity (AH + LO₂? → LOOH + A?; A? + LH (+O₂) → AH + LO₂?); and (d) model 4, theoretical methods used for predicting the activity (predictable activity). The highest lipid oxidation stability was found for antioxidants with a catecholic structure and for their binary mixtures with DL ‐α‐tocopherol, as a result of synergism between them.     

Modification of EPDM with Alkylphenol Polysulfide for Use in Tire Sidewalls, 1 – Mechanical Properties

APPS has been used to modify EPDM in order to solve the cure incompatibility and heterogeneous filler distribution of NR/BR/EPDM blends for tire sidewall applications. The physical properties of the NR/BR/APPS‐EPDM blends are compared with an NR/BR/EPDM blend and a conventional NR/BR tire sidewall. It is demonstrated that the application of APPS‐EPDM leads to a significant improvement of the tensile properties, tear strength, and fatigue properties. The properties of the NR/BR/APPS‐EPDM blends are equivalent or even superior to those of conventional NR/BR tire sidewall compounds. The dynamic viscoelastic properties of the NR/BR/APPS‐EPDM blends are not quite comparable with the conventional NR/BR sidewall blend, but still greatly improved, compared to using virgin EPDM.

     

Mechanical properties and morphology of impact modified polypropylene–wood flour composites

The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene–ethylene/butylene–styrene triblock copolymer (SEBS–MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM–MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1–1 μm. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1503–1513, 1998     

Mechanical and processing requirements for a shock mitigating phenolic foam

A high load-bearing shock-mitigating phenolic foam was developed to meet specific compression-deflection and gas permeability requirements. It was required that the foam display an almost constant compressive stress within the limits of 50–68 psi at strains ranging from 10% to 60%. Furthermore, the foam had to possess a highly open-celled structure so that its resistance to gas flow would be minimal. These properties were obtained from a chemical formulation utilizing a combination of two phenolic resins, a phosphoric-sulfuric acid catalyst system, a surfactant combination that included both a hydrophilic and a lipophilic surfactant, and a fluorocarbon blowing agent.     

Compositional effects on the crosslink density of Ca–(Mg)–(Y)–Si–Al–oxyfluoronitride glasses

The effects of fluorine and nitrogen substitution for oxygen in aluminosilicate glasses, effectively oxyfluoronitride (OFN) glasses, modified by calcium, calcium–yttrium or calcium–magnesium on thermal and physical/mechanical properties have been compared. Thus, 42 glasses in the Ca–(Mg)–(Y)–Si–Al–O–(N)–(F) system have been prepared and characterized with respect to density (ρ), molar volume (MV), compactness (C), free volume (FV), glass transition temperatures measured by DTA (T_g,DTA) and dilatometry (T_g,dil), dilatometric softening point (T_DS), microhardness (μHv) and Young's modulus (E). Gradients of property variation with nitrogen or fluorine substitutions for oxygen are similar for all three different oxyfluoronitride glass systems and are comparable with those reported for other OFN glasses, again indicating independent and additive effects of nitrogen and fluorine. In attempting to further understand how fluorine affects the cross‐link density (CLD) in OFN glasses, it becomes apparent that it is necessary to allow for a greater contribution by aluminum in a modifier role as fluorine content is increased. This modified calculation of CLD values results in good linear fits between T_g and CLD values. This analysis clearly demonstrates and endorses the concepts that thermal properties are related to CLD while physical/mechanical properties are dependent on glass compactness.     

Preparation and characterization of a foam regulator with ultra‐high molecular weight

Multistage emulsion polymerization was used to prepare ultra‐high molecular weight foam regulator of low cost, with methyl methacrylate (MMA), butyl acrylate (BA), styrene (St) as main raw materials. Ubbelohde viscometer, dynamic light scattering, infrared and raman spectra, TEM, DSC, TGA, and GPC were all used to characterize constituent and structure, morphology, and molecular weight. As a result, when the ratio of soft monomer (BA) and hard monomer (St + MMA) is 1:3, MMA:St = 4:1, potassium persulfate (KPS): 0.15%, sodium hydrogen sulfite (SHS): 0.05%, azodiisobutyronitrile (AIBN): 0.15%, divinyl benzene (DVB): 0.3%, the final product terpolymer has obvious core‐shell structure and ultra‐high molecular weight (M_w = 1,400,000). This kind of foam regulator showed improvements in the melt strength, prevention of bubble coalescence and reduction on cost when compared with the traditional. Finally, the coefficients of poly (methyl methacrylate‐butyl acrylate‐styrene) terpolymer's Mark‐Houwink equation were calculated with tetrahydrofuran (THF) solvent at 25 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44479.