Plastic Easy identification

Identification of plastics generally require a variety of instruments, such as infrared photometer, chromatography, and the like. At that time it does not have the general factory. For quick identification of plastic material, there are several ways to look at.

1, the proportion of law:

It can be heavier than water and specific gravity less than water distinguish two types of plastic materials. The proportion of various resins are listed in the following table.

2, the combustion method:

Combustion characteristics of various plastics in the following table.

Note: Also available from the gloss of the surface, transparency and flexibility to differentiate, for example: compared to HDPE and LDPE, HOPE poor transparency film, LDPE transparency, while LDPE compared with PP, LDPE film softness, The PP rigidity and so on.

3, solubility test method:

Test solution is to select a suitable solvent or mixture of solvents, in order to make the plastic resin and method for separating the other components. Solubility experiments in conjunction with other detection methods for identification knot plastic has important reference value. Due to the solubility of plastic grade products and whether it contains other ingredients which varies, and therefore can not serve as qualification tests solubility absolute criteria. When pure polymers also exhibit different solubility, because of the difficulty of dissolving or swelling the received length of the polymer molecules, arrangement, and other provisions and affect crystallinity and the like.

Many resin is insoluble in common solvents, such as polytetrafluoroethylene chloride, phenolic resin, melamine resin, nylon, polyethylene, and polypropylene. In addition to polyvinyl alcohol, methyl cellulose, etc. with a few exceptions, most polymers are not soluble in water. Under section shows the solubility of the resin.

NOTE: solubility experiments conducted in vitro generally. 10ml solvent was added at about 100mg powder sample, mix, sometimes shaking, observe a few hours. Before the polymer is completely dissolved often have swelling.

4, the qualitative element method:

Plastic, in addition to carbon, hydrogen, oxygen, also often contain sulfur, nitrogen, fluorine, phosphorus and other elements, to the detection of these elements, is one of the preliminary test identification of unknown polymer. In the system analysis by a combustion method and dissolution test method, the test often require the use of elements to be verified qualitatively.

These elements are usually qualitative sodium (or potassium) melting method. About 0.05g dry polymer placed in a small glass test tube, add a small pea-sized freshly cut sodium, heating and melting. Join 1mL ethanol trumpet of residual sodium cooled. Slowly heating of the tube was distilled to remove the ethanol, followed by heating with a strong fire to dark red, while hot tube containing 15mL of water thrown into a beaker, stirring with a glass rod broken tube, and then the solution was filtered off, the solution was Several Fengcheng subjected to the following tests:

① sulfur: about take 1mL filtrate, add acidification acetate, lead acetate plus 5% a few drops of the solution, if a black lead sulphide precipitate, indicating the presence of sulfur.

② Nitrogen: A small portion of the filtrate was added a 5% solution of ferrous sulfate few drops, a drop of 10% ferric chloride, acidified with dilute hydrochloric acid to dissolve the ferric hydroxide happens, if there is the presence of nitrogen, the resulting precipitate Prussian Blue s If yellow, it means that no nitrogen. If the degree of sample preparation is bad, there is no complete decomposition of sodium metal, will produce blue when the test nitrogen, but it does not precipitate.

③ chlorine: A small portion of the filtrate was acidified with dilute nitric acid, plus 4% silver nitrate solution was dropped a few, such as a white precipitate and soluble ammonium hydroxide, indicate the presence of chlorine.

④ fluorine: about filtrate 2mL, acidified with acetic acid added, heated to boiling, add 2 drops of a saturated calcium chloride solution was cooled, if there exists a fluorine generating colloidal precipitate was suspended in the solution. Another approach is to examine fluorine, take a drop of the above acetic acid acidification, boiling cooling treated solution placed on zirconium Qian paper, such as a yellow on red paper, then prove the presence of fluoride.

⑤ phosphorus: A small portion of the filtrate was acidified with nitric acid added, plus a few drops of ammonium molybdate solution, heated to boiling, if P is present, a yellow precipitate.

5, the color test identification method:

Color test is within the scope of micro or semi-micro qualitative identification tests using drip polymers, generally, plasticizers, fillers and modifiers are not involved in color reaction, then the presence of these substances reduces the color reaction sensitivity, so in most cases they should be separated from the polymer out. In order to avoid misinterpretation of test results, when necessary, can be known polymers for comparison testing.

① phenolic resin: Take a small sample into a test tube grinding degree, heating the decomposition was condensed at the upper end of the tube, and after cooling, add distilled water to a boil to dissolve. Take 1mL water, add a small amount of rice blue reagent, such as phenol red then prove the existence of the sample is a phenolic resin.

② Epoxy: Take a small sample in a test tube, adding to about 250 ℃ in the right-click on a silicone oil bath, on the mouth of the tube with a 5% sodium nitrite iron and 5% aqueous solution of morpholine moistened paper cover , if there is the appearance of the blue. It proved to be an epoxy resin. Also uses another detection method: Take a sample of about 0.5g, add diammonium terephthalate 30mg, water 8mL, boil 3min. Such as epoxy resin, the solution was pink.

③ polyamide: 0.1g sample taken in a small test tube, the tube mouth with cotton wool sese live, low heat, decomposition gas is cotton absorbed, remove the cotton, drops 1% methanol solution dimethylbenzaldehyde and concentrated hydrochloric acid solution, if it exists polyamide turns red.

④ polymethacrylimide polyacetal: 0.5g sample taken in a test tube, thermal decomposition, spout cover three pieces of paper to prevent monomer escape ml of concentrated nitric acid was added after cooling, the micro heat, after cooling plus nitric acid half amount of water, and then heated a little zinc particles, in the case of poly (methyl methacrylate), it appears blue.

⑤ poly alcohol acetal: take a little sample, adding sulfuric acid 2mL, then add a little chromic acid crystals hot bath heated at 60-70 ℃ in 10min, purple for formals, purple for acetal , red for butyral.

⑥ polyvinylidene chloride: take a sample 50mg, added 10mL morpholine, heated and dissolved in a water bath, dark brown as polyvinylidene chloride, polyvinyl chloride does not have this reaction.

⑦ polyvinyl fluoride: The sample was dissolved in a little pyridine solution, configured to sample an amount of 0.1% pyridine solution, 5ML of the solution in a test tube, adding 20% sodium hydroxide solution, 0.5ml, heated in boiling water, such as polyvinyl fluoride, the solution was red.

⑧ melamine resins: melamine resin available methods to generate chlorinated melamine and thiosulfate produce color reaction test. Put a small piece of the sample micro test tube, add one drop of concentrated hydrochloric acid. The mixture was gradually heated in a glycerin bath to 190-200 ℃, until the hydrogen chloride in time to make (with Congo red color change is no longer detected). About 50mg of sodium thiosulfate was added after cooling. A piece with 3% hydrogen peroxide wetting Congo red cap on the tube in the mouth, and heated 140 ℃, if the presence of melamine, but it was blue strip.

⑨ urea-formaldehyde resin: with an excess of phenylhydrazine with the sample heated urea is converted to Diphenylcarbazide be detected. The number of milligrams of sample into the micro test tube and treated with one drop of concentrated hydrochloric acid and evaporated to dryness at 110 ℃. After cooling, benzene was added one drop of hydrazine, and the mixture was heated to 195 ℃ in an oil bath for about 5min. After cooling, 3 drops of ammonia venues and 5 drops of 10% nickel sulfate solution, mixing special plus 10-12 drops of chloroform oscillation. If there purple Diphenylcarbazide gland in the chloroform layer, indicating the presence of urea-formaldehyde resin.