What polyfoams happen?
In modern assortment of polyfoams fiendish difficulty. How not to be deceived by advertizing and to choose polyfoam necessary to you, you learn from this article.
Practically all types of polyfoams possess one valuable property - low heat conductivity. Only mineral wools can compete with them on heat-insulating properties - the layer of low-density polyfoam 10 cm thick replaces 40 cm of a pine, 60 cm of a gas concrete, 1 meter of a constructive keramzitobeton, 1. 5th meter of a hollow ceramic brick and 4 meters of heavy concrete.
Acoustic properties of polyfoams depend, first of all, on their structure, and more precisely, from that what porosity - the closed type or open prevails. The majority of polyfoams has mainly closed porosity, for example all types of polystyrene foam polyfoams, extrusive polyethylene, polyvinylchloride polyfoams. Such polyfoams well absorb the sound having frequency only more than 1600 - 2000 hertz, for example, poorly absorb sounds of steps of the person, and well noise of the fan, but polyfoams with the closed porosity well reflect sounds of any frequency and therefore are good sound-proof stuff.
Polyfoams of mainly open structure, such as polyurethane foam rubber, well absorb everything sound frequencies, at the same time badly reflecting a sound therefore they can be applied to creation of good acoustics in rooms.
Bespressovy and press it is easy for b to measure polystyrene polyfoams by eye even not to the expert - polyfoam consists of small stseplyonny balls, as if honeycombs in a beehive. Remember how polyfoam into which your TV was packed looks, the refrigerator, a microwave and other household appliances, is besspresovy polyfoam.
Press externally and on heat-insulating properties practically what does not differ in, but from - for the fact that its granules are linked a little stronger, is slightly more difficult to crumb or break it. From - for bigger difficulties of production this type of polyfoam is widespread less than bespressovy.
Still can meet so-called extruded expanded polystyrene is practically the same, as bespressovy expanded polystyrene.
Brands of domestic press polyfoams begin on letters PS, for example PS - 1, PS - 4. Polyfoam is designated by Bespressova as PSB, through a dash there can be other letters and figures designating various modifications, for example PSB - With (the polyfoam self-fading), and import bespressovy polyfoam, for example BASF firms, has to be designated, in principle, as PPS.
Bespressovy and press polyfoams have one unpleasant feature - between granules of which they consist, there are smallest cavities through which water vapor from the room can get, and at a negative temperature of couple of water are condensed in polyfoam, increasing its humidity, from - for what approximately for 5 - 10% its heat-insulating ability worsens. Not much, polyfoam and so very good heat insulator would seem, but, unfortunately, the water giving life can give and destructions. The freezing water extends from what even steel pipes sometimes burst, in the same way when freezing water extends between granules of polyfoam and slowly but surely destroys it.
Extrusive polyfoam (not to confuse to extruded), which is uniform in appearance is relieved of similar shortcomings. For certain you already met him, make disposable tableware and packing for foodstuff of such polyfoam.
Extrusive polyfoam is designated as EPPS and depending on the producer has the company name, for example Penopleks.
Disputes and fights concerning toxicity of polystyrene polyfoams do not cease.
Though polystyrene in itself is not toxic, but at it there is always a so-called residual styrene which is strongly toxic substance.
On the one hand, still was proved by the Soviet scientists that expanded polystyrene under adverse conditions can slowly allocate the styrene remains in air and long influence of small concentration of styrene leads to deterioration in health of the person.
is Also scandalous examples of constructions with use of expanded polystyrene at which operation in air of premises excess of maximum permissible concentration of harmful substances was recorded.
With another, there are laboratory researches confirming that they at use of qualitative polystyrene foam polyfoams of release of styrene should not exceed admissible level and therefore cannot lead to deterioration in health.
Anyway, it is necessary to try to buy expanded polystyrene of the producers having everything necessary sanitarno - hygienic certificates on products, and the content of residual styrene in them has to be as little as possible, at the level of 0. 01 - 0. 05%, at least, should not exceed 0. 1%.
The durability of polystyrene polyfoams very strongly depends on their quality, so according to different data polyfoams of brands of PSB, PSB - With do not change significantly the properties from 10 to 40 years, extrusive polyfoam is more durable and at high quality can be operated without considerable change of properties till 80 years.
But the biggest problem of polystyrene polyfoams is a high combustibility. Without special additives styrene polyfoams easily light up from a flame or a spark, quickly burning down with the smoking flame, at the same time melting and allocating a toxic smoke.
Trying to lower combustibility of polyfoams, entered nonflammable and plamyagasyashchy additives into them, thus there was a self-fading type of polyfoams, for example brands of PSB - S.
Such polyfoam is similar to a coal block - in any way not to set fire to it from a match or a spark, but in a fire it burns very well. Therefore any type of polystyrene polyfoams for reduction of fire danger is recommended to be applied to external isolation.
Polyurethane polyfoams (PPU).
The most widespread example of polyurethane foam is well-known foam rubber in life.
This type of polyfoams is very elastic and has an open time, that is can well pass air and water vapor, it is usually applied in production of furniture and household various household things, also do construction foams of polyurethane foam.
Polystyrene foam polyfoams are short-lived, at action of sunshine they turn yellow, at the same time the top layer collapses.
Polyfoams on the basis of polyurethane are also strongly flammable and can be self-fading, but unlike polystyrene foam, their smoke is more toxic as it contains large amounts of very poisonous hydrocianic acid.
Polyethylene polyfoams (PPE).
Polyfoams from a penopolietilen are elastic. Quite perhaps, you held it already once in hand because in thin elastic sheets from such polyfoam quite often wrap fragile and fragile goods.
It is most of all widespread extrusive penopolietilen which is designated by PPE and has a set of company names. Products of their such polyfoam let out in the form of translucent flexible sheets of the most various thickness - from several millimeters to tens of centimeters.
Extrusive penopolietilen it is durable and is in this regard almost equivalent to extrusive expanded polystyrene, but unlike it does not incorporate residual toxic substances and therefore is much more eco-friendly.
Though penopolietilen burns a little more slowly than expanded polystyrene and with a little smaller allocation of a toxic smoke, but it is also flammable material.
Polyvinylchloride polyfoams (PVC).
This polyvinylchloride polyfoam very much reminds on properties extrusive pennopolietilen - elastic, does not contain highly toxic substances, but at the same time, in itself, is the self-fading material, that is it can burn only surrounded with a flame from a foreign source, but if burns, then emits chloride hydrogen which with water forms hydrochloric acid, from - for what the smoke from the burning polyvinylchloride is very suffocating.
It is not the full list of all types of polyfoams and furthermore their properties, but I sincerely hope that this article though will a little dispel fog of doubt in a question of the choice of polyfoam.]