What is flame treatment in plastic?
Flame treatment is defined as a surface preparation technique in which the plastic is briefly exposed to a flame. Flame treatment oxidizes the surface through a free radical mechanism, introducing hydroxyl, carbonyl, carboxyl, and amide functional groups to a depth of ∼ 4–6 nm, and produces chain scissions and some cross-linking.
How do you test a sample with a flame?
Next, hold the sample to the edge of a flame until it ignites. If no flame is produced quickly, hold the sample in the flame for about 10 seconds. If the material burns, note the color of the flame, the nature of the smoke, the presence of soot in the air and whether, while burning, the sample drips.
What is the effect of flame treatment on the surface?
In general, flame treatment induces an increase in oxygen at the surface of polymers, which is dependent on the number of flame passes applied and/or the extent of exposure to flame. Figure 5.2. Principles of flame treatment.
Is it possible to do a burn test on plastic?
This can be a challenging task. Many plastics look and feel alike but we will take a closer look here at some of the ways using a burn test. Please note, this test should be done in an industrial setting and not at home since proper safety protocol must be observed. Burning plastics can give off toxic fumes and plastic drips are very hot.
How long does flame treatment last?
A Flame Treating process consists of exposing the surface to a suitable oxidizing flame for a period in the range 0.2 to 3.0 seconds.
How does flame treatment work?
Flame treatment uses a carefully controlled blend of natural gas and air to create a hot, oxygen rich plasma. First, the heat removes contaminants. Then, after contaminant removal, the oxygen rich plasma activates the surface by partial oxidation.
What is the effect of flame on plastics?
11.3. Flame treatment oxidizes the surface of polymeric materials to introduce polar reactive groups such as hydroxyl and carboxyl which improves surface free energy and consequently the wettability and adherability of their surfaces.
How do you fire plastic before painting?
Here's how to do it.Step 1: clean the surface. Use an alcohol wipe to clean the surface that you're going to flame-treat.Step 2: flame-treat the surface. To flame-treat the plastic, hold a propane torch about 15cm above the surface so that the flame just touches the plastic. ... Step 3: apply the mixed epoxy.
Why are bottles flame treated?
Flame Treating is the most commonly used means of rendering a molded bottle surface receptive to suitable inks, paints, etc. In this method, a hot oxidizing flame (2000 degrees to 5000 degrees) is applied directly to the intended label or decorated area.
What is flame plasma?
The part of a flame that possesses the well-known properties of electric plasma is called flame plasma. In order to explain the mechanism of ionization in flames, the gas temperature and its distribution has been studied extensively.
What plastics are flame retardant?
Flame retardants are added to polyolefins, polycarbonate, polyamides, polyester, and other polymers to increase resistance to ignition, reduce flame spread, suppress smoke formation, and prevent a polymer from dripping.
How do you make plastic fire retardant?
A: You can make fire-resistant plastic by adding hydrated magnesium oxide or aluminum oxide alone or with phosphorus or bromine compounds to low-density polyethylene. When there's a fire outbreak, the compounds decompose and absorb the fire energy, preventing the plastic from burning.
At what temperature is plastic flammable?
Forensic: Article 10 - PHYSICAL CONSTANTS FOR INVESTIGATORS....2. PHYSICAL CONSTANTS OF MATERIALS.Melting points and ignition temperaturesPlasticMelting Point RangeIgnition TemperatureNylons160°-275°424°-532°Polycarbonate140°-150°580°Polyesters220°-268°432°-488°14 more rows
What's the best primer for plastic?
1. Rust-Oleum Zinsser Bulls Eye Primer. From Rust-Oleum, this primer is ideal for prepping metal and plastic and will also seal porous surfaces like drywall, concrete, wood, and masonry.
What type of paint is best for plastic?
There are other paints other than acrylic paint for plastic available on the market that can be applied directly onto the roughened surface of the plastic item without having to apply the primer first. However, acrylic paint on plastic is the best option and for this, you will need to prime the plastic item.
How do you get acrylic paint to stick to plastic?
How do you get acrylic paint to stick to plastic? For acrylic paint to stick, you need to prime the plastic with a base coat that dries quickly. This will help the paint adhere to the plastic and give you a smooth finish. The primer must be specifically made for plastic surfaces.
Why use flame treatment?
Flame treatment improves the adhesion qualities of polymers prior to the application of coatings and adhesives. With flame treated surfaces, bond strength and durability is greatly improved. The attraction of using flame treatment as opposed to corona discharge or plasma treatment rests with the ease with which nonuniform shapes can be treated ...
What is the principle of flame treatment?
Principles of flame treatment. The oxygen concentration reduces as a function of depth, and although the initial oxygen concentrations increase with the extent of flame treatment, all decay to a plateau value approaching zero over the same depth.
What are the factors that affect the adhesion of polypropylene?
Key factors include the gas type, gas-to-air ratio, burner type, gas flow rate, flame distance, and flame passage speed (treatment time). Excessive treatment of the surface results in degradation of the polypropylene, therefore poor adhesion.
What is the gas flame?
Gas flame contains excited fragments and species such as atomic oxygen (O), NO, OH, and others that can abstract hydrogen from the surface of the polymer that is replaced by oxygenated functional groups (most ly – C O and – OH). This method is not effective in the adhesion treatment of perfluoroplastics. Figure 17.22.
How much tension does polyethylene have?
Polyethylene and polypropylene have a surface tension of 30 dynes/cm that must be raised to a minimum of 38 dynes/cm (preferably to 42 dynes/cm) to render their surfaces adherable. Flame treatment is the most widely used method of pretreatment. It is flexible and reliable if carefully controlled.
Does flame treatment increase oxygen?
In general, flame treatment induces an increase in oxygen at the surface of polymers, which is dependent on the number of flame passes applied and/or the extent of exposure to flame. Figure 5.2. Principles of flame treatment.
How to flame treat plastic?
To flame-treat the plastic, hold a propane torch about 15cm above the surface so that the flame just touches the plastic. Move it across the surface very quickly, at a rate of about 30-40cm per second. Keep the torch moving and make sure you work your way up and down the plastic carefully in sections, each time slightly overlapping ...
How to test if flame treatment works?
If you’re not sure whether your flame treatment has worked, you can perform a simple test. Apply two water droplets – one to an untreated area of plastic and one to a treated area. On untreated plastic, the droplet should be very spherical.
Can you heat plastic before applying epoxy?
If your plastic is PVC, HDPE or ABS, the simple answer is to flame-treat it before you apply the epoxy. By flame-treating, I don’t mean heating. In fact, this is really important: you’re not looking to change the surface in any visible way whatsoever.
Does epoxy affect plastic?
Well, in their basic state, certain plastics behave in exactly the same way. Whatever liquid you apply will typically bead up and roll off. That liquid can include epoxy. This ‘hydrophobic’ tendency of plastic can affect adhesion of plastic surfaces with epoxy, which ultimately affects the strength of the bond.
Can you use flame treating on plastic?
On the face of it, ‘flame-treating’ a flammable material like plastic may seem like a strange thing to do. However, this useful technique is vital for creating a better bond between epoxy and plastic. Technical expert Hamish Cook is on hand to guide you through the process.
What is PTFE in hair?
PTFE. PTFE is a fluorocarbon. It is very white and has a waxy feel. It is also fairly soft. You can mar it with your thumb nail. A piece of PTFE with no flame applied gives off the faint smell of burned hair. When a flame is applied, the material does not drip.
What is 6/6 plastic?
Nylon 6/6. Nylon 6/6 is an off-white plastic material. It is fairly hard and cannot be marred with a fingernail. When burned it gives off the odor of burnt wool or hair. The flame is blue with a yellowish tip. Additionally, the material drips when flame is applied.
What does polycarbonate smell like?
Polycarbonate gives off a faint, sweet aromatic ester smell. The flame is orange in color and PC will drip when a flame is applied. The smoke is black and gives off soot into the air.
Is polyester flame retardant?
There are no drips. Polyesters are flame retardant. When the flame source is removed the material will continue to burn. The smell is nondescript but the flame is a yellow color with blue edges. Again. there are no drips and the material burns slowly. Polyesters will crack and break when flame is applied.
Does PP float in water?
It will continue to burn after the flame source is removed giving off a sweet smell. The flame at this point is blue with a yellow tip. PP produces drips as it continues to burn slowly. When bent, polypropylene sheet will turn white on the crease line. Interestingly, PP floats in water.
What is the burn test for plastic?
Naturally, the burn test should be used only for tentative identification. Many complex plastic compounds require a rigorous spectral or destructive chemical analysis for a positive identification. To initially determine whether a material is thermoplastic (meltable) or thermoset (non-meltable) type, heat a metal or glass stirring rod ...
How often should you repeat a flame test?
Once you have made a tentative identification, it is usually desirable to repeat the flame test once or twice to confirm the results of the original identification. Remember that additives may affect results. For example: flame retardants can mask the polymer material's normal flame & smoke burning characteristics.
What is a flame treater?
For 3D objects, the plant typically consists of ( Fig. 5 a ):#N#(1)#N#a conveyor belt, which allows a continuous loop of material, i.e., the polyolefin objects, which are normally mounted on heat-resistant holders;#N#(2)#N#a cleaning device, such as a stream of compressed air or a brush-like system. This is normally placed a few centimetres in front of the burners to assure the removal of all small particles (e.g., dust) that might negatively affect successful flame treatment; and#N#(3)#N#a burner, i.e., the basic part of the equipment that produces the oxidising flame.
What is a laminar flame?
A laminar flame (which is ordinarily employed by flame treaters) is defined as a mixture of a fuel and an oxidiser, thoroughly premixed before combustion. The term ‘premixed laminar flame’ is interchangeable with the term ‘deflagration’ to indicate the propagation of the combustion process accompanied by a decrease in both density and pressure together with an increase in velocity (contrary to the propagation known as ‘detonation’). Within a laminar flame profile, three main zones can be observed ( Fig. 2 ), which correspond to specific reactions. As a consequence, different thermal gradients and reactive species can be encountered. These zones are briefly described here.
What is the molar ratio of a gas to an oxidizer?
The molar ratio of the fuel to the oxidiser is probably the most important parameter within the flame treatment process. For this reason, particular care must be paid to setting it adequately before the flame treatment is started. For each gas there exists a specific and well-defined amount of oxidiser at which the fuel is completely burnt. This precise ratio is known as the stoichiometric ratio, which relies on the chemical structure of the gas. For example, the stoichiometric ratio methane/air by mass is equal to 1:17.2, whereas for a propane/air flame it is 1:15.5, i.e., 15.5 kg of air is needed for the complete combustion of 1 kg of propane. However, in practical applications it is unlikely that the stoichiometric ratio can be verified. Most probably, the flame obtained will be below or above this value. Therefore, the concept of the equivalence ratio ( ϕ ), defined as the actual mass gas/air ratio used during treatment divided the stoichiometric fuel-to-oxidiser ratio [43], is widely accepted: (28) ϕ = m fuel / m oxidizer ( m fuel / m oxidizer) stoichiometric where m is the mass. The most common parameter is the reciprocal of the equivalence ratio, which is called the lambda factor and is expressed by the formula: (29) λ = ϕ − 1
What is the gap between a flame and a web surface?
It is widely recognised that the gap between the flame and web surface (i.e., the distance between the tips of the luminous flame cones and polyolefin surface) is a key factor in determining the extent of activation accomplished by the treatment. As a general trend, it has been observed that when the film passes through the flame, a rapid depletion in the wettability of the treated surface occurs. As the distance between the cone of the flame and film surface increases, surface activation decreases, although a beneficial effect arising from the treatment is still appreciable up to approximately 20 mm.
What is the formula for polyolefins?
The term polyolefin encompasses all those polymers produced by an olefin as a starting monomer, whose general formula is C n H 2n. Most common polyolefins in the packaging field are polyethylene (PE) and PP. Although they have different specific properties, it is recognised that both polymers are inherently hydrophobic, which is in turn responsible for their typical poor wettability, especially to waterborne systems. For this reason, polyolefins generally need to be surface-activated before the deposition of inks, paints, adhesives, metals, and coatings. Flame treatment is a valuable technique to improve the surface energy of polyolefins, although it has been exploited to a minor extent with respect to corona treatment so far. However, because of improvements in safety conditions as well as in some technical aspects, it is receiving renewed attention, especially by those sectors (e.g., packaging) that historically lagged behind in the exploitation of the technique.
What is the coldest region of a flame?
This region, also called the ‘dark zone’, has a typical dark bluish colour. It is the coldest region of a flame because even though some of the hydrogen formed is oxidised to water the combustion process has not yet reached the explosion condition, and thereby the amount of net energy released is negligible. In this region, the only abundant free radical is the hydrogen atom, which reacts quickly with hydrocarbons and oxygen, thereby impeding the formation of the radical pool. For this reason, this zone is also known as the ‘reducing zone’. This is an ineffective and unimportant region for surface activation purposes, since it in no way contributes to the oxidation of the plastic substrate.
Can a flame propagate spontaneously?
This means that if the air/hydrocarbon mix is within its flammability limits (i.e., it has a suitable composition) and within its explosive conditions (i.e., within adequate pressure/temperature boundaries for the same composition), the flame is generated and can spontaneously propagate.
