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IDENTIFICATION OF PLASTICS VISHAL VERMA Technical Officer

IDENTIFICATION OF PLASTICS VISHAL VERMA Technical Officer.

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IDENTIFICATION OF PLASTICS VISHAL VERMA Technical Officer

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  1. IDENTIFICATION OF PLASTICS VISHAL VERMA Technical Officer

  2. 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. IDENTIFICATION

  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 CONTENTS

  4. 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 Cut a small sliver off the sample. This tells you a lot about the type of plastic you are trying to identify IDENTIFICATION BY SIMPLE METHOD

  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.

  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.

  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.

  8. BENDING TESTS Some plastics will exhibit particular characteristics in the manner in which they respond to bending. The bending behaviour of some plastics are given in Table

  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

  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:

  11. Typical results of burning tests of polymers (thermoplastics)

  12. Typical results of burning tests of polymers (thermoplastics) cont.

  13. Typical results of burning tests of polymers (thermoplastics) cont.

  14. Typical results of burning tests of polymers (thermoset)

  15. Typical results of burning tests of polymers (Elastomer)

  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 BASIC: 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.

  17. 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.

  18. 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.

  19. 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 pressure 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 deg C below the melting point of sample. Then adjust the temperature ramp at 0.5 deg C/ min. observe the sample through microscope and note down the temperature where the material starts melting.

  20. Melting and softening point of polymer materials

  21. 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. CONFIRMATION TEST -Thermoplastics

  22. Test for Chlorine containing polymers CONFIRMATION TEST -Thermoplastics Cont. Copper wire test • Take the piece of copper wire about 5 mm long. Push on end of the wire in to a small cork. • 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. • 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.

  23. 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 5 gm. of basic bismuth nitrate and 25 gm. of potassium iodide in 10 ml. of 2% H2SO4). Precipitation of an orange red complex indicates the presence of caprolactum. CONFIRMATION TEST -Thermoplastics Cont.

  24. 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 violet colour confirms the presence of adipic acid. A yellowish green colour develops in the case of polyethylene-terephthalate and polybutylene-terephthalate confirming the presence of terephthalic acid. CONFIRMATION TEST -Thermoplastics Cont.

  25. 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) HCI. An intense red colour which is unaffected by methanol, indicates the presence of polycarbonate. CONFIRMATION TEST -Thermoplastics Cont.

  26. 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. CONFIRMATION TEST -Thermoplastics Cont.

  27. 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. CONFIRMATION TEST -Thermoplastics Cont.

  28. 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-nitrobenzaldehyde 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. CONFIRMATION TEST -Thermoplastics Cont.

  29. 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. CONFIRMATION TEST -Thermoplastics Cont.

  30. 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:

  31. Polyvinyl Alcohol A Sample (about 0.02g) is dissolved in water 5ml and iodine reagent described above (5 drops) added. The formation of Blue colour confirms the presence of Polyvinyl alcohol. CONFIRMATION TEST -Thermoplastics Cont.

  32. 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. CONFIRMATION TEST -Thermoplastics Cont.

  33. Shellac A sample (0.05g) is dissolved in ethanol (1ml) with warming. To the cooled solution is added water (about 1ml) to give an emulsion like precipitate. 5N aqueous NaOH 2 drops is added to the mixture. The colour change is reversed on acidification with 5N HCL. The formation of Violet - red colour confirms the presence of Shellac. CONFIRMATION TEST -Thermoplastics Cont.

  34. Test for formaldehyde A small amount of sample is boiled in water in presence of H2SO4and filtered. Few drops of 5% aqueous chromotropic acid solution (1,8-dihydroxynaphthalene-3, 6-disulphonic acid) and excess of cone. H2SO4are added to the filterate and heated at 1000 C for few minutes. In the presence of formaldehyde, the solution turns violet/dark violet. Poly (vinyl formal), polyoxymethylenes, PF, UF and MF resins contain formaldehyde. CONFIRMATION TEST -THERMOSET PLASTICS

  35. Test for Phenol in PF Million's Reagent: About 10 gm of Hg is dissolved in 10 ml. of HNO3 by gentle heating and then diluted with 15 ml. of distilled water. The sample is heated to boiling for two minutes with 1 ml. of clear million's reagent. Red colour indicates the presence of phenol in the sample. CONFIRMATION TEST -THERMOSET PLASTICS Cont.

  36. Test for Urea in UF About 0.5 gm. of sample is refluxed for 30 min. with 20% acetic acid (50 mI.). The mixture is cooled and filtered. To the filterate added a solution of (2 ml.) xanthydrol in methanol (1% solution) and boiled for 1-2 minutes. White bulky precipitate confirms the presence of urea. CONFIRMATION TEST -THERMOSET PLASTICS Cont.

  37. Test for Melamine in MF About 0.5 gm of sample is refluxed with 80% acetic acid (25 ml.) for 30 min., cooled and filtered. Then the filterate is evaporated to dryness and added 2 ml. of water, cooled and filtered. To the filtrate one drop of saturated aqueous picric acid is added. Yellow precipitate indicates the presence of melamine. CONFIRMATION TEST -THERMOSET PLASTICS Cont.

  38. Tests for Epoxy Resin Foucry Test: About 0.25 gm. of sample is dissolved in 98% H2SO4by slight warming. After cooling 1 ml. of 63% HNO3 is added. After shaking, the mixture is poured into 100 ml. of 5% aqueous NaOH. A bright red or orange red colour indicates the presence of epoxy resin. CONFIRMATION TEST -THERMOSET PLASTICS Cont.

  39. Rubber Testing: 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.

  40. Identification code of plastics

  41. THANK YOU

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