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IDENTIFICATION OF PLASTICS

IDENTIFICATION OF PLASTICS. IDENTIFICATION.

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IDENTIFICATION OF PLASTICS

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  1. IDENTIFICATION OF PLASTICS

  2. IDENTIFICATION When working with plastics there is often a need to identify which particular plastic material has been used for a given product. This is essential to get an idea of the cost and likely properties of the product. The identification of plastics is generally very difficult due to: • The wide range of basic polymers that is available for use. • The wide range of additives that can be used to modify the properties of the basic polymer. • The wide range of mixtures or compounds of polymers that can be manufactured to get the required properties. Despite this there are some simple tests that can be carried out to get a basic idea of the possible base polymer used for the manufacture of any given product. Corporate Training & Planning

  3. Introduction • Simple method • cutting test • hot wire penetration test • flotation test • bending test • dropping test • Burning test • Pyrolysis test • Specific gravity test • Solubility test • Softening and Melting point • Elemental Analysis • Confirmation test Corporate Training & Planning

  4. IDENTIFICATION BY SIMPLE METHOD • Stage 1: Look at the sample This will give you a lot of information. The colour of the plastic will give you some information. Some polymers have restricted colour ranges, particularly the thermosetting types. Others tend to be glossier in colour (polypropylene), whereas some are both glossy and glassy (the acrylics). • Stage 2: Feel the sample After you have carried out the tests in the is series a few times you will start to get the feel for various plastics. The polyolefins have a very distinctive feel and you can generally tell if it is one of them. The presence of glass fibre or other reinforcement materials can alter the feel and stiffness of the sample but you can sometimes tell by the feel if there is reinforcement present. • Stage 3: Cut a thin sliver from the edge of the sample. Follow the links to the appropriate page. The first test is to cut a small sliver off the sample. This tells you a lot about the type of plastic you are trying to identify Corporate Training & Planning

  5. CUTTING TESTS • If a shaving can be pared off with knife, it may be a thermoplastic. Note: PMMA and Polystyrene are brittle and difficult to pare • If the material is rigid and will not pare off instead flakes of powders, it may probably a thermoset plastic. • Scuff the sample with your fingernail. Results • Scuffs with fingernail - Urea formaldehyde resin. • Does not scuff with fingernail - Melamine formaldehyde resin. Corporate Training & Planning

  6. HOT ROD PENETRATION TEST • Heat an electronic soldering iron to red hot and press against the unknown sample. • If the plastic material softens, and the rod penetrates the sample is thermoplastic. • If the plastic material does not soften and the rod does not penetrate, the sample is thermoset plastic. Corporate Training & Planning 6

  7. FLOTATIONTEST This test will give the idea to distinguish the material according to their density. Note: Filled polyolefin’s and cellular foams are exceptional for this test. Corporate Training & Planning 7

  8. BENDING TESTS Some plastics will exhibit particular characteristics in the manner in which they respond to bending. The bending behaviour of some plastics of almost same cross-section is given in Table Corporate Training & Planning 8

  9. DROPPING TEST When a polymer moulded component is dropped on hard surface, it creates sound, which shall be either metallic sound or dull sound. On the basis of sound polymer is distinguished in two categories, which is tabulated in Table Corporate Training & Planning 9

  10. BURNING TEST A small sample is held in flame. If it ignites withdraw it from the flame a distance of flame. Make observations as listed below and record the observations, for example: Corporate Training & Planning 10

  11. TYPICAL RESULTS OF BURNING TESTS OF POLYMERS (THERMOPLASTICS) Corporate Training & Planning 11

  12. TYPICAL RESULTS OF BURNING TESTS OF POLYMERS (THERMOPLASTICS) Corporate Training & Planning 12

  13. TYPICAL RESULTS OF BURNING TESTS OF POLYMERS (THERMOPLASTICS) Corporate Training & Planning 13

  14. TYPICAL RESULTS OF BURNING TESTS OF POLYMERS (THERMOPLASTICS) Corporate Training & Planning 14

  15. TYPICAL RESULTS OF BURNING TESTS OF POLYMERS (ELASTOMER) Corporate Training & Planning 15

  16. PYROLYSIS TESTS • In this testing, heat few milligrams of the sample in an ignition tube and test the pyrolytic vapour with a moistened indicator paper. The behaviour of vapour to indicator paper is given as follows: • ACID: turns blue litmus to red • BASE: turns red litmus to blue. • ACID VAPOURS: may come from carbohydrate polymers & their derivatives. [e.g., cellulose acetate] • HIGH ACID VAPOURS: often indicates the presence of chlorine. e.g., PVC or rubber neutral vapors] evolved from hydro carbon polymers, silicones and some polyesters hydrochloride. • ALKALINE VAPOURS: indicate the presence of N2. e.g. polyamide, proteins & amino formaldehyde resins. Corporate Training & Planning

  17. RUBBER TESTING This scheme is useful for identification of CR, NBR, SBR, NR / IR, IIR type of rubbers Test Procedure: Heat strongly 0.5gm of sample in a test tube until sample begins to decompose and pass the fume in solution II and I and observe change in colour initially and after heating. (Refer the following table) • Solution - I : Dissolve one gram of p - dimethyl amino benzaldehyde in 5ml of HCl and add 10ml of ethylene glycol. Adjust the density to 0.851 gm /cc. by addition of methanol. • Solution - II : Dissolve 2gm sodium citrate , 200mg of citric acid , 300mg of bromo cresol green and 300mg of metanil yellow in 500ml of water. Corporate Training & Planning 17

  18. SPECIFIC GRAVITY TEST A simple test for differentiating between different types of plastics can be carried out by placing specimens in water. Some will sink and some will float depending on their specific gravity as shown in Table . Those with the higher specific gravities will sink as shown in the Table. Accurate specific gravity results can be obtained by the standard method of relating weight of the material to weight of water displaced. Corporate Training & Planning 18

  19. SOLUBILITY TESTS Solubility tests form a basis of some older identification schemes for main types of plastic materials. However, in many cases solubility varies considerably for different samples of the same resin and it is difficult to interpret the results Solubility of plastics may vary according to the grade or to the whether or not other constituents are present in the sample. The data in Table refer in principle to pure polymers, although even those polymers may exhibit differences in solubility. The solubility test should be carried out directly in a test tube. To about 100 mg of a powdered sample add 10ml of solvent, mix occasionally shake the contents of the test tube and observe for a few hours swelling may occur before complete dissolution of the polymer. Corporate Training & Planning

  20. SOLUBILITY TESTS Corporate Training & Planning

  21. SOFTENING AND MELTING POINTS The temperature range of softening and melting – point can be used to characterize/ identify the material. Procedure: Place the 2 to 3 mg portion on a clean glass slide and cover with No 1 cover glass. Heat the slide, sample and cover on a hot plate to slightly above the softening point of the polymer so that a thin film can be formed. By slightly pressor on the cover glass form a thin film 0.01 to 0.04 mm, and allow it to cool slowly by turning of the hot plate power to promote crystallization. Keep the slide on hot plate melting point apparatus. Adjust the hot plate temperature about 10 0 C below the melting point of sample. Then adjust the temperature ramp at 0.5 0 C/ min. observe the sample through microscope and note down the temperature where the material starts melting. Corporate Training & Planning

  22. MELTING & SOFTENING POINT OF POLYMER MATERIALS Corporate Training & Planning 22

  23. ELEMENTAL ANALYSIS • The results of test for the elements other than carbon, hydrogen and oxygen, namely nitrogen, sulphur, and halogens serve to indicate the possible nature of the unknown material • It should be noted that the compounding ingredients may contain elements which will also be detected and thus give rise to a positive result. They may interfere with the identification of the polymer. So additives free extracted purified polymer should be used for elemental analysis in order to identify exactly the nature of polymer. Corporate Training & Planning

  24. CARBON Experiment: 0.05 gm of material is mixed with 0.2 gm of potassium dichromate, 10 drops of phosphoric acid in a test tube. Exclude air present by blowing with CO2 with N2 or O2. Heat the solution in H2SO4 or glycerol bath at 200oC. Connect test tube to a U – tube containing clear BaCl2 solution. Observation: White precipitate of BaCo3 Inference: Carbon confirmed Corporate Training & Planning

  25. HYDROGEN Experiment: Place little of the sample in a micro test tube with few o-g- of pure sulphur cover mouth strain with led-acetate paper. Heat the solution in glycerol bath for 2 min. Observation: Brown black strain Inference: Hydrogen Confirmed Corporate Training & Planning

  26. OXYGEN Experiment: Reagent preparation: Dissolve 1 gm of ferric chloride and 1gm of potassium thiocyanate separately in 10 ml of methanol. Mix the two solutions and after standing for few hours filter of the KCl precipitate. Dip strips of filter paper in methanol solution. Dry it is air, Prepare fresh strips before test. Several drops of liquid polymer or its solution are placed on the paper prepared above (conduct a blank also) Observation: Deep wine red colour Inference: Oxygen confirmed Corporate Training & Planning

  27. NITROGEN Experiment: 2 ml of the sodium fusion extract is boiled with 3 drops of freshly prepared aqueous ferrous sulphate (approx 5%) & then cooled, after acidification with acid, a drop of 0.5N aqueous ferric chloride is added Observation: Blue precipitate Inference: Nitrogen confirmed Corporate Training & Planning

  28. SULPHUR Experiment: Three drops of freshly prepared aqueous sodium nitroprusside (approx 5%) are added to the test portion. Observation: Violet colour Inference: Sulphur confirmed Corporate Training & Planning

  29. CHLORINE & BROMINE Experiment: The test portion is acidified with 5N Nitric acid; the solution is boiled for 2 min. 0.1 N aqueous silver nitrate is then added. Observation & Inference: A white precipitate which is soluble in ammonia, Chlorine confirmed. A yellow precipitate which is insoluble in ammonia, Bromine confirmed. Corporate Training & Planning

  30. FLUORINE Experiment: • An aqueous solution of Zirconium nitrate (0.1%) and alizarin reds (0.1%) is prepared. • Filter paper is immersed in the solution and then allowed to dry. When required, a small piece of the paper is moisturened with aqueous acetic acid (50%). • The solution to be tested is neutralized with 5N HCL and a drop placed on the moistened test paper. Observation: Red spot turns Yellow Inference: Fluorine Confirmed. Corporate Training & Planning

  31. HALOGEN: COPPER WIRE TEST • Take the piece of copper wire about 5 mm long. Push on end of the wire in to a small cork. (The cork is used as a handle so you are not touching a hot wire. • Place one pellet or plastics sample near your Bunsen burner. This is the sample you will be testing. • Hold the free end of the copper wire in the burner flame until it is red-hot and the flame no longer has a green colour. • Remove the wire from the flame and torch the hot wire to the plastics pellet or sample you will be testing. A small amount of the plastics should melt onto the wire. If the wire sticks to the plastic sample, use a pair of tongs to remove it. • Place the end of the wire, with small amount of plastic on it, into the flame. You should see a slight flash of a luminous flame (a yellow- orange colour). If the flame turns green in colour, then the sample contains chlorine. Corporate Training & Planning

  32. CONFIRMATION TEST -THERMOPLASTICS Tests for Polyolefins A piece of dry sample is pyrolysed in a tube closed with a filter paper which is drenched with a solution of 0.5 g yellow mercury (II) oxide in sulphuric acid (1.5 ml conc. Sulphuric acid added to 8 ml. Water). If the vapour gives a golden yellow spot, indicates polyisobutylene, butyl rubber and polypropylene (the latter only after a few minutes). Polyethylene does not react. Natural and nitrile rubber, as well as polybutadiene yield a brown spot. Corporate Training & Planning

  33. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Chlorine containing polymers • Heat a small amount of polymer in pyridine and make a solution. • Add few drops of 5% alcoholic (Methanol) NaOH to a portion of boiling solution and a portion of solution in cool condition. • Observe the change of colour taking place in the solutions. • Table 6 is the list of colours observed in various chlorine containing polymers. Corporate Training & Planning

  34. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Caprolactum in Nylon 6 • About 0.5 gm of sample is heated in 5.0 ml of distilled water and allowed to boil for 10 to 15 min. • After cooling, 2-3 drops of con. H2SO4 is added to 0.5 ml of the above solution followed by addition of 2 ml. of potassium iodo bismuthate (a solution of 5gm of basic bismuth nitrate and 25gm. of potassium iodide in 10ml. of 2% H2SO4 ). • Precipitation of an orange red complex indicates the presence of caprolactum. Corporate Training & Planning

  35. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Adipic acid in Nylon 6,6 • About 0.2 gm of sample is heated in low flame in a test tube and the vapour coming out of the tube is passed over a filter paper moistened with a saturated solution of O-nitrobenzaldehyde in 2N aqueous NaOH. • A deep mauve (violet) colour confirms the presence of adipic acid. • A yellowish green colour develops in the case of polyethylenete rephthalate and polybutyleneterephthalate confirming the presence of terephthalic acid. Corporate Training & Planning

  36. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Polycarbonate • About 1.0 gm of sample is pyrolysed in an ignition tube, which is plugged with cotton. • The cotton is removed and immersed in 1% methanolic solution of p-dimethylamino benzaldehyde and then one drop of 5 N-Hydrochloric acid is added. • A dark blue colour appears in the case of polycarbonates. • A red colour that does not change to blue is observed in the case of polyamides. • The cotton floak in which the prolysed vapours of the sample absorbed is treated with dilute (1:1) HCL. • An intense red colour which is unaffected by methanol indicates the presence of polycarbonate. Corporate Training & Planning

  37. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for PMMA • About 1 gm of sample is heated in an ignition tube and the pyrolysate is collected in a test tube wrapped with a wet filter paper. • To the distillate, 1 ml. of conc. HNO3 is added and heated just to boiling. • After cooling, 5 ml. of water is added an then sodium nitrite (0.1 gm) is added. • A blueish green colour confirms the presence of polymethylmethacrylate. Corporate Training & Planning

  38. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Polyacetals • Polyacetals produce formaldehyde on heating. • A small amount of sample is heated with 2 ml. conc. Sulphuric acid and a few crystals of chromotropic acid for about 10 min at 60 -70C. • A strong violet colour indicates formaldehyde. Corporate Training & Planning

  39. CONFIRMATION TEST -THERMOPLASTICS Cont. Tests for PET and PBT • PET and PBT are soluble in nitrobenzene. • A small sample is pyrolysed in a glass tube covered with filter paper. • The filter paper is drenched with a saturated solution of O-nitroben zaldehyde in dilute sodium hydroxide. • A blue-green colour, which is stable against dilute hydrochloric acid, indicates terephthalic acid. • Then PET and PBT are differentiated based on melting points. Corporate Training & Planning

  40. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for polyurethane • About 0.5 gm of sample is dissolved in 10 ml of glacial acetic acid and 0.1 gm of p-dimethylamino benzaldehyde is added. • The solution turning yellow after several minutes shows the presence of polyurethane. Corporate Training & Planning

  41. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for polyurethane • About 0.5 gm of sample is dissolved in 10 ml of glacial acetic acid and 0.1 gm of p-dimethylamino benzaldehyde is added. • The solution turning yellow after several minutes shows the presence of polyurethane. Corporate Training & Planning

  42. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Cellulose in Cellulosics (Molisch Reaction) Sample is dissolved in acetone, reacted with 2 to 3 drops of 2% ethanolic solution of 1-napthol and a few drops of conc. H2S04. is allowed to flow down the wall of the test tube. Red to Reddish brown ring at the interface indicates cellulose. Corporate Training & Planning

  43. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for acetates and propionates • The sample (about 0.2 gm) and few ml of Hydrochloric acid are heated for 10 minutes and dilute ammonia is added to make alkaline. • One ml of this solution is reacted with 1":2 drops of a 5% lanthanom nitrate solution and 1 drop of 0.1 N Iodine solutions. • A fast colour change to blue confirms the presence of acetates and a brown colour indicates the presence of propionate. • For differentiation between cellulose acetate and cellulose acetate-butyrate, it is usually sufficient to examine the vapour produced by dry heating of the sample. • The acetate smells like acetic acid, the acetatebutryate has the smell of both acetic acid and butyric acid (like rancid butter). Corporate Training & Planning

  44. CONFIRMATION TEST -THERMOPLASTICS Cont. Test for Cellulose Ethers: The important cellulose ethers are Methyl cellulose, Ethyl. Cellulose and Benzyl cellulose. Reaction to Heating and Burning: Cellulose ethers melt and char after heating and continuously burn after ignition. Nature of flame and smell of the cellulose ethers are as follows: Corporate Training & Planning 44

  45. CONFIRMATION TEST -THERMOPLASTICS Cont. Detection of Methyl Cellulose • The sample is treated with a 10% tannic acid solution. • A flaky (flocculent) precipitate confirms the presence of methyl cellulose. • A sample is treated with Iodine - Potassium Iodide solution. • A colour change from violet brown to brown, which disappears on the addition of strong NaOH confirms the presence of methyl cellulose. Corporate Training & Planning

  46. CONFIRMATION TEST -THERMOPLASTICS Cont. Detection of Ethyl Cellulose: • The sample is treated with one drop of dichromate solution (1.09 of potassium dichromate K2Cr207 + 60 ml water + 7.5 ml of con. H2S04) and then heated to 100° C. • The mouth of the tube is covered with a filter paper moistened with a mixture of equal volumes of 20% aqueous morpholine solution and 5% aqueous sodium nitroprusside. • A blue colour indicates the presence of Ethyl Cellulose. Corporate Training & Planning

  47. CONFIRMATION TEST -THERMOPLASTICS Cont. Cellulose Nitrate • 1 ml of water is added to a test tube containing about 1mg of the sample & 2 ml of freshly prepared 0.2% solution of enthrone in conc. H2S04. A green colour changing to dark blue is confirmed cellulose. • 20ml of diphenylamine is dissolved in 1ml of conc H2S04. Few drops of this are poured on to a small piece of the sample on a spotting plate. Immediate development of intense blue colour is confirmed Nitrate. • Wash the sample with hot water dissolve in conc. H2S04. Add a small amount of resorcinol. A purple blue colour development is confirmed Nitrate. Corporate Training & Planning

  48. CONFIRMATION TEST -THERMOPLASTICS Cont. Acrylonitrile – Butadiene Styrene The polymer (about 1 g) is refluxed with concentrated nitric acid (20 ml) for 1 hr using a long air condenser in a fume cupboard. The mixture is poured into water (100ml) and extracted with ether (2 x 25 ml) and the aqueous extracts rejected. The ethereal layer is extracted with in aqueous NaOH (2x25ml). The ethereal layer is rejected. The alkaline extracts are combined and just acidified with concentrated HCl & then excess of acid (20 ml) is added. Granulated zinc (5g) is added & the mixture heated on a steam, bath for 20 min. The mixture is cooled freshly prepared sodium nitrate (approx. 0.1g in 2 ml) added. The resulting solution is poured into freshly prepared alkaline - Napthol solution (approx.0.05g in 10 ml SN aqueous NaOH). The formation of vivid scarlet colour confirms the presence of styrene. Corporate Training & Planning

  49. CONFIRMATION TEST -THERMOPLASTICS Cont. Casein • A sample about (0.02g) is dissolved in concentrated HNO3 (2ml) by boiling for about 5mn. • The solution is cooled and excess 5N ammonium hydroxide added. • The formation of orange colour confirms the presence of casein. Corporate Training & Planning

  50. CONFIRMATION TEST -THERMOPLASTICS Cont. Polyisobutylene • Filter paper is immersed in freshly prepared mercuric sulphate solution (prepared by dissolving yellow mercuric oxide (1g) in boiling 5N H2SO4 (20ml) and cooling before use and used without drying. • The paper is inserted in the mouth of an ignition tube containing the polymer (about 0.2g). The tube is gently heated. The formation of Bright yellow colour confirms the presence of Polyisobutylene. Corporate Training & Planning

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