What is the meaning of the word foam?
Jul 27, 2010 · A foam is a substance made by trapping air or gas bubbles inside a solid or liquid. Typically, the volume of gas is much larger than that of the liquid or solid, with thin films separating gas pockets. Another definition of foam is a bubbly liquid, particularly if the bubbles, or froth, are undesirable.
What is chemical foam made of?
Foam, in physical chemistry, a colloidal system (i.e., a dispersion of particles in a continuous medium) in which the particles are gas bubbles and the medium is a liquid. The term also is applied to material in a lightweight cellular spongy or rigid form.
What is the difference between gas and foam?
foam, in physical chemistry, a colloidal system ( i.e., a dispersion of particles in a continuous medium) in which the particles are gas bubbles and the medium is a liquid. The term also is applied to material in a lightweight cellular spongy or rigid form.
What is soap foam?
What is Chemical Foam ? Chemical foam is formed by mixing together a solution of an alkali (usually sodium bicarbonate), an acid (usually aluminum sulfate), water and a stabilizer. The stabilizer is added to make the foam tenacious and long-lived. When these chemicals react, they form a foam or froth of bubbles filled with carbon dioxide gas.
What is foam in chemistry with example?
Foam is a dispersion of a gas in a liquid (liquid foams). Examples froth, whipped cream, soap lather.Jun 21, 2016
What is foam in chemistry class 9?
Foam- A foam is a colloid in which a gas is dispersed in a liquid medium. Examples are soap bubbles and shaving cream.
What are chemical foams?
Chemical foam is formed by mixing together a solution of an alkali (usually sodium bicarbonate), an acid (usually aluminum sulfate), water and a stabilizer. The stabilizer is added to make the foam tenacious and long-lived. When these chemicals react, they form a foam or froth of bubbles filled with carbon dioxide gas.
What is foam in simple words?
1 : a light frothy mass of fine bubbles formed in or on the surface of a liquid or from a liquid: such as. a : a frothy mass formed in salivating or sweating.
What is foam in chemistry class 12?
In physical chemistry, foam or foam spray is defined as a colloidal system (it means a dispersion of particles in the continuous medium), where the particles are given as gas bubbles and the medium as a liquid.
What is foam Class 12?
Foam is a type of colloid in which gas is the dispersed phase and solid is the dispersed medium.
What is all foam?
Company Description: Allfoam Industries, Inc. is located in Elmhurst, IL, United States and is part of the Miscellaneous Nondurable Goods Merchant Wholesalers Industry. Allfoam Industries, Inc. has 2 total employees across all of its locations and generates $460,274 in sales (USD).
Why is foam called foam?
It's called FOAM, short for Foam Optics and Mechanics. "One way to understand the basic physics of any material is to explore its 'critical point'--the threshold where the material changes phases, for instance, from a solid to a liquid," says Durian. "Exploring the critical point of foams is what FOAM will do."Jun 9, 2003
What produces foam?
How is a foam produced? A foam is produced by trapping millions of tiny gas bubbles in a liquid (whipped egg white) or a solid (marshmallow). Whisking water and air produces hundreds of bubbles but they soon 'pop', leaving only water and air again.
What is the function of foam?
Foam is bunch of tiny bubbles created by foaming agents. But you also need water and air to make foam. The true purpose of foam is to provide contact time on a soiled surface to allow the wetting agents, detergents and degreasers enough time to do their jobs.Jun 3, 2016
Is foam a colloid?
Foams are a special kind of colloidal dispersion: one in which a gas is dispersed in a continuous liquid phase.
What is cell foam?
Open cell foam is a rubber-like product made by incorporating an inflating agent, such as sodium bicarbonate, into the rubber compound; this agent gives off a gas, which expands the rubber during vulcanization. Foam is usually classified as “open cell” when more than half of its cells are open.May 31, 2017
What is solid foam?
Typically, these particular foams are classified into two types according to their pore structure: open-cell-structured fo ams (which is also called reticulated foams) and closed-cell foams. At the high enough cell resolutions, any type can be treated either as continuous or "continuum" materials, and they are called cellular solids with predictable mechanical properties.
What are the conditions required to make foam?
Many conditions are required to produce foam: there should be mechanical work, surface active components (or the surfactants), which reduce the surface tension, and the foam formation faster than its breakdown. To create the foam, work (W) is required to increase the surface area (ΔA):
What is syntactic foam?
Answer: The syntactic foams advantage is that they contain a very high strength-to-weight ratio, making them ideal materials for several applications, including space and deep-sea applications. One of the specific syntactic foam employs the shape memory polymer as its matrix by enabling the foam to take on the characteristics of composite materials and shape memory resins; it means it has the ability to be repeatedly reshaped when heated more than a certain temperature and cooled.
What are the different types of experiments that can be used to study foam?
Considering various scales, the experimental techniques are diffraction ones, primarily the light scattering techniques (static and dynamic light scattering, DWS, neutron, and X rays scattering) at either the sub-micrometre scales or the microscopic ones.
What is azodicarbonamide used for?
Answer: One of the examples of the use of azodicarbonamide as a blowing agent can be found in the manufacture of EVA-PE and vinyl (PVC) foams, where it plays an important role in the formation of air bubbles, breaking down into the gas at high temperature.
What is RIM in manufacturing?
The closed-mould process, which is more commonly called reaction injection moulding (RIM), injects the mixed components into the closed mould at high pressures.
What is the most widely used technique to monitor the product's dispersion state?
Answer: A typical light scattering (which is also called diffusion) optical technique, multiple light scattering that is coupled with vertical scanning, is given as the most widely used technique to monitor the product’s dispersion state, thus identifying and quantifying the phenomena of destabilization. It works on any of the concentrated dispersions, including foams, without dilution. When light is sent via sample, it is backscattered by the bubbles.
How is foam made?
Foam is manufactured by adding water, which reacts with the terminal isocyanate groups to increase the molecular weight… . plastic: Foaming. Foam s, also called expanded plastics, possess inherent features that make them suitable for certain applications.
What is beer foam made of?
The foam used to combat oil fires consists of bubbles of carbon dioxide (liberated from sodium bicarbonate and aluminum sulfate) stabilized by dried blood, glue, or other cheap protein-containing materials. Beer foam is believed to be stabilized by the colloidal constituents present, which include proteins and carbohydrates.
What is the largest segment of the market for polyurethanes?
The largest segment of the market for polyurethanes is in rigid and flexible foams. Flexible foams are usually made with polyols and an excess of TDI. Foam is manufactured by adding water, which reacts with the terminal isocyanate groups to increase the molecular weight…
What are foam stabilizers?
Of the great variety of substances that act as foam stabilizers, the best known are soaps, detergents, and proteins. Proteins, because they are edible, find wide use as foaming agents in foodstuffs such as whipped cream, marshmallow (made from gelatin and sugar), and meringue (from egg white).
What is an encyclopedia editor?
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. ...
What is foam in a bath?
Soap foam bubbles. Foam is an object formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Soap foams are also known as suds .
What is skin foam?
Integral skin foam, also known as self-skin foam, is a type of foam with a high-density skin and a low-density core. It can be formed in an open-mold process or a closed-mold process. In the open-mold process, two reactive components are mixed and poured into an open mold. The mold is then closed and the mixture is allowed to expand and cure. Examples of items produced using this process include arm rests, baby seats, shoe soles, and mattresses. The closed-mold process, more commonly known as reaction injection molding (RIM), injects the mixed components into a closed mold under high pressures.
What is the Marangoni effect?
Marangoni effect of a film (2) The stabilization of a foam is caused by van der Waals forces between the molecules in the foam, electrical double layers created by dipolar surfactants, and the Marangoni effect, which acts as a restoring force to the lamellae.
What are the conditions needed to make foam?
Several conditions are needed to produce foam: there must be mechanical work, surface active components (surfactants) that reduce the surface tension, and the formation of foam faster than its breakdown. To create foam, work (W) is needed to increase the surface area (ΔA):
What is one scale of foam?
One scale is the bubble: material foams are typically disordered and have a variety of bubble sizes. At larger sizes, the study of idealized foams is closely linked to the mathematical problems of minimal surfaces and three-dimensional tessellations, also called honeycombs.
What is an example of open cell foam?
A bath sponge is an example of an open-cell foam: water easily flows through the entire structure, displacing the air. A camping mat is an example of a closed-cell foam: gas pockets are sealed from each other so the mat cannot soak up water. Foams are examples of dispersed media.
Is soap foam open or closed cell?
Soap foams are also known as suds . Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms discrete pockets, each completely surrounded by the solid material. In open-cell foam, gas pockets connect to each other. A bath sponge is an example of an open-cell foam: water easily flows through the entire structure, ...
What is polyurethane foam?
Polyurethane is another synthetic resin-type varnish. Polyurethane foam are formulated in different ways for different uses. A urethane is a carbonyl containing functional group in which the carbonyl carbon is bonded to both an -OR group and an -NR 2 group. A polyurethane is formed by reacting a hydroxyl terminated polyether or polyester ...
What is polymer used for?
Used in technical fibre ropes, fishing lines, and some agricultural products. Used in cars and household furnishings, the polymer is used in the construction industry and in the manufacture of footwear and for coating and adhesives as well as textiles.
What is the first stream of polyurethane?
The first stream, known as the polyol stream, usually contains surfactants and catalysts. This stream is also known to contain blowing agents. The other streams contain other important additives that determine the type of polyurethane that is produced as the final product.
Is polyurethane foam flame retardant?
The combustion of this compound is also known to produce large quantities of hydrogen cyanide, another highly toxic substance. This is one of the reasons why polyurethane foams are usually treated with flame retardant substances during the production process. Test Your Knowledge On Polyurethane Foam! Q 5.
Is polyurethane a combustible substance?
However, this compound is classified as a combustible substance and must be kept away from open flames (since it may spontaneously ignite). Moreover, the decomposition reaction undergone by polyurethane can result in the formation of carbon monoxide gas, which is highly toxic to human beings.
Is polyurethane foam recyclable?
This variant of polyurethane foam is also used in the manufacture of automobile seats and also in the manufacture of carpet cushions. The cores and the paddings of certain solid-core mattresses also employ flexible polyurethane foam as a component. Since this polymer is recyclable , these products are considered by many to be moderately ...
How are air bubbles determined?
As the air bubbles ascend, their velocities are principally determined by their sizes, the difference in the viscosities of the liquid and gas phases and the properties of the gas/liquid interface. However, as the bubbles grow in size, they may collide and in cases where only weak foaming agents are present in solution, ...
What is disproportionation in chemistry?
Although the term “disproportionation” is commonly used by chemists to describe inter-bubble gas diffusion within foams, it is often referred to as Oswald ripening, which was originally used to define the evaporation–condensation mechanism in two-phase separation of binary alloys.
What is a polymer that is a composition of organic units and joined by carbamate links called?
A polymer which is a composition of organic units and joined by carbamate links is called polyurethane foam. Most of the polyurethanes do not melt on heating and hence are thermosetting polymers, but thermoplastic polyurethanes also exist. These polymers are commonly and traditionally created by a reaction of di- or tri-isocyanate with one polyol.
What is the raw material used to make polyurethane?
The widely used isocyanates to make polyurethane are aromatic diisocyanates, methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI). MDI and TDI are cheaper compared to other isocyanates and much more reactive.
What are the properties of polyurethane?
Polyurethane properties can be classified into physical and chemical ones, and they are as follows: Physical properties of polyurethane foam. Resilience. Between the polyether and polyester foams, the latter ones have high tensile strength, hardness and elongation at break.
What are surfactants used for?
Surfactants. These compounds are utilised for the characteristic modification of non-foam and foam polyurethane polymers. In polyurethane foam, the surfactants regulate the size of the cell, emulsify liquid elements, stabilise the structure of the cell to prevent subsurface voids and to collapse. After learning the raw materials, let us proceed ...
What is the weight of polyols?
These compounds can be further categorised depending on their end-use. The polyols which have high weight (molecular weight ranging from 2000 to 10000) are utilised to create flexible polyurethane foam and the ones with low weight are used to make rigid products.
What is a chain extender?
Chain extenders (f=2) and crosslinkers (f>=3) are amine-terminated and hydroxyl compounds that play a major role in polymer morphology of elastomers, polyurethane fibres, adhesives and specific microcellular and skin foams.
What are the two types of catalysts for polyurethane?
The catalysts of polyurethane can be divided into two wide categories – acid amine and basic amine. Tertiary amine catalysts work by improving the diol component’s nucleophilicity. Oxides, alkyl tin carboxylates and mercaptides oxides work as mild Lewis acids to accelerate polyurethane formation.
How does defoaming work?
Defoaming additives work by bringing controlled incompatibility into the system.
What is the purpose of hydrophobic defoamer?
Hydrophobic particles have a rough surface. They help to lower the entry barrier of the defoamer droplet.
What is the third factor in choosing a defoamer?
The third factor in choosing a defoamer is the shear needed to incorporate the defoamer for optimal performance. The shear used to make the coating will incorporate the defoamer and compatibilize it over time. Figure 5 shows what can happen if the incorporation of the defoamer is not correct. If too much shear is used in processing, the defoamer will be fully compatibilized and the defoaming effect will be lost. If too little shear is used, the defoamer will not be dispersed and will cause cratering. Defoamer concentrates will need more shear to compatibilize than emulsified defoamers but will also need a lower loading of defoamer in the coating to see an effect.
Why do defoamers lose their effectiveness?
As coatings sit on the shelf, defoamers can lose their effectiveness as the active ingredients become solubilized into the resin. Hydrophobic particles (silica, urea or polymeric) will not undergo this process as readily and can help retain the activity of the defoamer over time.
What is the pH range of polymeric defoamers?
The acceptable pH range for polymeric defoamers is wider (3-12) than what is acceptable for silicone defoamers. Additionally, processing polymeric defoamers can be easier for incorporation than silicone defoamers. As formulations continue to become more complex so too does the defoamer portfolio.
What are the benefits of using a defoamer?
Using the right defoamer will lead to many desired effects in the final coating performance. First and foremost, the foam will be eliminated and the appearance will be at its best. There are also additional benefits. For instance, durability of a coating can be improved with the elimination of foam.
What is the most cost effective defoamer?
Mineral oil defoamers are often the most cost efficient. These defoamers make up a large segment of the market and can provide sufficient defoaming. There are, however, some undesirable impacts on a coating that can occur with using a mineral oil defoamer.
Types of Foams
Foam Structure
- In many cases, foam is a multiscale system. One scale is given as the bubble, where the material foams are typically disordered and contain a wide range of bubble sizes. Whereas, at larger sizes, the idealized foam’s study is closely linked to the three-dimensional tessellations, mathematical problems of the minimal surfaces, and also known as hone...
Mechanical Properties of Solid Foams
- Often, the solid foams have lower nodal connectivity to that of the other cellular structures such as truss lattices and honeycombs, and therefore, their failure mechanism can be dominated by the bending of members. Ultimately, the low nodal connectivity and the resulting failure mechanism lead to their strength of lower mechanical and stiffness compared to the truss lattices and hone…
Experiments
- Foam can be studied using many different techniques, being a multiscale system involving several phenomena and a versatile medium. Considering various scales, the experimental techniques are diffraction ones, primarily the light scattering techniques (static and dynamic light scattering, DWS, neutron, and X rays scattering) at either the sub-micrometre scales or the micro…
Characterizations
- Considering this system as the continuous one, its bulk properties may be characterized by light transmittance but also conductimetry. In particular, the correlation between bulk and structure is evidenced more accurately by acoustics. The organization between the bubbles has been numerically studied using sequential attempts of the evolution of the minimum surface energy e…
Foam Formation
- Many conditions are required to produce foam: there should be mechanical work, surface active components (or the surfactants), which reduce the surface tension, and the foam formation faster than its breakdown. To create the foam, work (W) is required to increase the surface area (ΔA): W = γΔA where γ is given as the surface tension. One of the ways that foam creates is via dispersi…
Overview
Foam is an object formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Soap foams are also known as suds.
Solid foams can be closed-cell or open-cell. In closed-cell foam, the gas forms …
Structure
A foam is, in many cases, a multi-scale system.
One scale is the bubble: material foams are typically disordered and have a variety of bubble sizes. At larger sizes, the study of idealized foams is closely linked to the mathematical problems of minimal surfaces and three-dimensional tessellations, also called honeycombs. The Weaire–Phelan structureis conside…
Mechanical properties of solid foams
Solid foams, both open-cell and closed-cell, are considered as a sub-class of cellular structures. They often have lower nodal connectivity as compared to other cellular structures like honeycombs and truss lattices, and thus, their failure mechanism is dominated by bending of members. Low nodal connectivity and the resulting failure mechanism ultimately lead to their lower mechanical strength and stiffness compared to honeycombs and truss lattices.
Formation
Several conditions are needed to produce foam: there must be mechanical work, surface active components (surfactants) that reduce the surface tension, and the formation of foam faster than its breakdown. To create foam, work (W) is needed to increase the surface area (ΔA):
where γ is the surface tension.
Stability
The stabilization of a foam is caused by van der Waals forces between the molecules in the foam, electrical double layers created by dipolar surfactants, and the Marangoni effect, which acts as a restoring force to the lamellae.
The Marangoni effect depends on the liquid that is foaming being impure. Generally, surfactants in the solution decrease the surface tension. The surfac…
Experiments and characterizations
Being a multiscale system involving many phenomena, and a versatile medium, foam can be studied using many different techniques. Considering the different scales, experimental techniques are diffraction ones, mainly light scattering techniques (DWS, see below, static and dynamic light scattering, X rays and neutron scattering) at sub-micrometer scales, or microscopic ones. Consideri…
Applications
Liquid foams can be used in fire retardant foam, such as those that are used in extinguishing fires, especially oil fires.
In some ways, leavened bread is a foam, as the yeast causes the bread to rise by producing tiny bubbles of gas in the dough. The dough has traditionally been understood as a closed-cell foam, in which the poresdo not connect with each other. Cutting the dough releases the gas in the bub…
Defoaming
Foam, in this case meaning "bubbly liquid", is also produced as an often-unwanted by-product in the manufacture of various substances. For example, foam is a serious problem in the chemical industry, especially for biochemical processes. Many biological substances, for example proteins, easily create foam on agitation or aeration. Foam is a problem because it alters the liquid flow and blocks oxygen transfer from air (thereby preventing microbial respiration in aerobic fermentationprocesses). …