polymers: chemistry project

Chemistry Project

Atul Singh AroraClass: XII-D

Roll No.:

Synthesis and Property AnalysisPolymers

Teacher’s Signature

CAUTION: Some experiments require hazardous and/or potentially hazardous chemicals.* This refers to the level of caution required for each individual experiment.

CONTENTS

Acknowledgements iii

Aim of the Project 1

General Overview 1

1. Bakelite 3

2. Polystyrene 7

Result 15

References 16

Brief Theory, Synthesis and Analysis of

3. Epoxy Resin 11

*

Acknowledgments

I am very greatful to my chemistry teacher, Ms. Sadhana Bhargava, who has been a constant source of inspiration and guidance. She supported me with all my ideas and helped me to the maximum extend possible. She also gave me enough extra time to find all the required information to turn my ideas into a single project. Even though what I initially wanted to make (conductive Polymers) wasn’t possible to do with our existing lab apparatus, yet she encouraged me to search for something similar, yet interesting enough for me. This project would never have existed, if it wasn’t for her passion to teach.

I would also like to thank our lab assistant, Mr. Babu Lal for all the timely help he provided. Apart from this, I would like to thank all those people who’ve published their useful work on the internet, without which, I perhaps wouldn’t even have enough information to make even a single polymer.

Aim of the Project

Page 1

General Overview

The aim of this project is to find out the optimum conditions for synthesis of the following polymers, 1. Bakelite*2. Polystyrene**3. Epoxy Resin** and to study their physical properties like flexibility, strength, bounciness, color etc.

[* Synthesized using chemicals available in the school laboratory][** Synthesized using Industrial Reagents]

A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.


Due to the extraordinary range of properties accessible in polymeric materials, they have come to play an essential and ubiquitous role in everyday life - from plastics and elastomers on the one hand to natural biopolymers such as DNA and proteins that are essential for life on the other. A simple example is polyethylene, whose repeating unit is based on ethylene (IUPAC name ethene) monomer (Image 2.1). Most commonly, as in this example, the continuously linked backbone of a polymer consists mainly of carbon atoms. However, other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being silly putty and waterproof plumbing sealant. The backbone of DNA is in fact based on repeating units of polysaccharides (e.g. cellulose) which are joined together by glycosidic bonds via oxygen atoms.

Image 2.1

Natural polymers (from the Greek poly meaning “many” and meros meaning “parts”) are found in many forms such as horns of animals, tortoise shell, rosin (from pine trees), and from distillation of organic materials. One of the most useful of the natural polymers was rubber, obtained from the sap of the hevea tree. (Rubber was named by a chemist found that a piece of solidified latex gum was good for rubbing out pencil marks on paper. In Great Britain, erasers are still called “rubbers”.) Natural rubber had only limited use as it became brittle in the cold and melted when warmed. In 1839, Charles Goodyear discovered, through a lucky accident, that by heating the latex with sulfur, the properties were changed making the rubber more flexible and temperature stable. That process became known as vulcanization.

Image 2.2

Chemistry Project

Image 2.3

The first synthetic polymer, a phenol-formaldehyde polymer, was introduced under the name “Bakelite” (Image 2.2 & 2.3), by Leo Baekeland in 1909. Its original use was to make billiard balls. Rayon, the first synthetic fiber was developed as a replacement for silk in 1911. Although many polymers were made in the following years, the technology to mass produce them was not developed until World War II, when there was a need to develop synthetic rubber for tires and other wartime applications and nylon for parachutes. Since that time, the polymer industry has grown and diversified into one of the fastest growing industries in the world. Today, polymers are commonly used in thousands of products as plastics, elastomers, coatings, and adhesives. They make up about 80% of the organic chemical industry with products produced at approximately 150 kg of polymers per person annually in the United States.

Furthermore, conductive polymers are organic polymers that conduct electricity. Such compounds may be true metallic conductors or semiconductors. It is generally accepted that metals conduct electricity well and that organic compounds are insulating, but this class of materials combines the properties of both. The biggest advantage of conductive polymers is their processibility. Conductive polymers are also plastics (which are organic polymers) and therefore can combine the mechanical properties (flexibility, toughness, malleability, elasticity, etc.) of plastics with high electrical conductivities. Their properties can be fine-tuned using the exquisite methods of organic synthesis.

1. Bakelite

Page 3


Brief Description

Level of Caution

Bakelite is a material based on the thermosetting phenol formaldehyde resin, developed in 1907–1909 by Belgian Dr. Leo Baekeland. Formed by the reaction under heat and pressure of phenol (a toxic, colourless crystalline solid) and formaldehyde (a simple organic compound), generally with a wood flour filler, it was the first plastic made from synthetic components. It was used for its electrically nonconductive and heat-resistant properties in radio and telephone casings and electrical insulators, and was also used in such diverse products as kitchenware, jewellery, pipe stems, and children's toys. In 1993 Bakelite was designated an ACS National Historical Chemical Landmark in recognition of its significance as the world's first synthetic plastic.The retro appeal of old Bakelite products and labor intensive manufacturing has made them quite collectible in recent years.Image 6.1 shows the structure of bakelite.

Ima

ge

3.1

Chemistry Project

Precautions

Materials Needed

Procedure

First make the Phenol-formaldehyde reaction mixture by mixing 25 g 36-40% formaldehyde + 20 g phenol + 55 mL glacial acetic acid.Under a hood, measure 25 mL of the phenol-formaldehyde reaction mixture into a 150-mL beaker.Place the beaker on a white paper towel.Add 10 mL of concentrated hydrochloric acid, slowly, with stirring.Add additional hydrochloric acid, dropwise, with stirring. (You will need approximately 2 mL of HCl.) As the polymerization point is reached, a white precipitate will form and dissolve. At the point where polymerization begins, the white precipitate will not dissolve.Continue to stir as the plastic forms and becomes pink in color.Wash the plastic well before handling.

1. Wear safety goggles at all times in the laboratory.

2. Formalin is an irritant to the skin, eyes, and mucous membranes.

3. Phenol is toxic via skin contact. It is listed as a carcinogen.

4. Glacial acetic acid is an irritant and can cause burns on contact.

5. Work under a hood and wear gloves and protective clothing when working with these materials.

Chemicals:1. 25g 40% formaldehyde 2. 20 g phenol 3. 55 mL glacial acetic acid4. conc Hydrochloric acid

Apparatus:1. 150-mL beaker2. stirring rod


What actually happened

I was slightly nervous to try out something absolutely new and was uncertain of its results. I took the chemicals given to me by Baboolal sir and followed the instructions. I took the phenol-formaldehyde reaction mixture in a beaker, placed it over a sheet of paper. Took a test tube full of HCl, and added it to the beaker slowly with constant stirring. And by slowly I mean I almost emptied the test tube in about two minutes. I couldn’t figure the polymerization point as no precipitate appeared. Thinking there’s something wrong with the procedure, I went to ask for ma’ams advice. She asked me to indirectly heat it. Due to certain reasons, I didn’t hear indirectly and heated the beaker over the flame for about 30 seconds. Nothing happened. Depressed, I walked away from it wondering what to do next. And then suddenly there was this loud noise of some kind of explosion. It was the beaker. All the contents had poured out like foam, except solid. It was light pink in color. It had lots of pours in it and kind of looked like pumice stone. Ma’am said it happened because I’d supplied a lot of heat by direct heating, and it seemed the most plausible explanation to it and so to obtain a proper polymer, I modified the experimental setup after discussing it with ma’am.I set up a large water filled beaker on a tripod stand with wire gauze and in a boiling tube took the reaction mixture. I fixed this boiling tube using a clamp stand, half dipped in the beaker so that the contents were evenly heated. I added the same amount HCl as before, except this time, I added a few drops after every 30 seconds. This time, after 3 minutes, I could see something suddenly happen in the boiling tube. I alerted ma’am but again it exploded. The sudden reaction broke the boiling tube, and caused a crack in the beaker. I collected the polymer and washed it. Its physical appearance was the same as before.

Both these experiments suggested that the reaction was extremely fast, but its activation energy was fairly high. So no matter if its directly heated, or indirectly, the moment it gains sufficient energy, the polymerization starts rapidly.

High AE

reactant

product

intermediate

energ

y

reaction progress

Chemistry Project

Property Analysis

Test Result

Flexibility Brittle

Strength Low

Bounciness Negligible

Color Dark Pink

Inertness Stable in air at room temp.

Slightly PorousTexture

Chemistry Behind it

For determining the optimum conditions for the synthesis of Bakelite, I decided to take a reaction mixture in a beaker, heat it to a certain temperature (indirectly), and then add HCl to find out the optimum temperature. I chose beaker over boiling tube, because as was apparent by the pores, greater the surface area, safer it would be to carry out the reaction.

Temperature Observations

40-35 *C No observable changes

50-45 *C Turbidity started apearing

60-55 *C Roughly Polymerization started

75-60 *C Semi Solid appeared at the bottom of the beaker

At long standing, the color changed to dark pink30-25 *C

Phenol and Formaldehyde react in the following manner to make the polymer.


The structure below shows the growing molecule of BAKELITE.

2. POLYSTYRENE

Polystyrene (pronounced /ˌpɒliˈstaɪriːn/) (IUPAC Poly(1-phenylethane-1,2-diyl)), sometimes abbreviated PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used kinds of plastic.Polystyrene is a thermoplastic substance, which is in solid (glassy) state at room temperature, but flows if heated above its glass transition temperature (for molding or extrusion), and becoming solid again when cooling off. Pure solid polystyrene is a colorless, hard plastic with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be transparent or can be made to take on various colors.Solid polystyrene is used, for example, in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. Products made from foamed polystyrene are nearly ubiquitous, for example packing materials, insulation, and foam drink cups.Polystyrene can be recycled, and has the number "6" as its recycling symbol. Polystyrene does not biodegrade, and is often abundant as a form of pollution in the outdoor environment, particularly along shores and waterways.

Brief Description

Level of Caution

+ +

Chemistry Project

Precautions

Materials Needed

Procedure

Take 4 clean, numbered test tubes and to each add 3mL of Vinyl Benzene. Fill the syringe with methyl ethyl ketone.Start the stop watch.Make the volume of Vinyl Benzene in test tube one equal to 5 mL.Now note the time as you add 5 divisions of the syringe, i.e. 0.5 mL to test tube one and stir it well.Repeat the above 2 steps with 4.5 mL of Vinyl Benzene and 1.0 mL of methyl ethyl ketone, in the second test tube and so one.Place these in the thermostat with temperature set to 40 *C.


2. Styrene may pose health risks if it comes in contact with the body.

3. Styrene resin is sticky, so use gloves.


Chemicals:1. Vinyl Benzene (Styrene Casting Resin)2. Methyl ethyl ketone (Casting resin catalyst)

Apparatus:1. Test tubes2. Stirring rod3. Thermostat4. Measuring Cylinder5. a 5 mL Syringe6. Stop Watch


Concentration of catalyst Time taken to cure

0.5 3 hours 14 minutes





0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5

Time

Concentration

Chemistry Project

Test Result

Flexibility Low

Strength Medium


Color Yellowish, Transparent

Inertness Stable in air at room temp.

SmoothTexture

Property Analysis

Chemistry Behind it

The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon connected to a phenyl group (the name given to the aromatic ring benzene, when bonded to complex carbon substituents). Polystyrene's chemical formula is (C8H8)n; it contains the chemical elements carbon and hydrogen. Because it is an aromatic hydrocarbon, it burns with an orange-yellow flame, giving off soot, as opposed to non-aromatic hydrocarbon polymers such as polyethylene, which burn with a light yellow flame (often with a blue tinge) and no soot. Complete oxidation of polystyrene produces only carbon dioxide and water vapor.This addition polymer of styrene results when vinyl benzene styrene monomers (which contain double bonds between carbon atoms) attach to form a polystyrene chain (with each carbon attached with a single bond to two other carbons and a phenyl group).


3. EPOXY RESIN

Epoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.Credit for the first synthesis of bisphenol-A-based epoxy resins is shared by Dr. Pierre Castan of Switzerland and Dr. S.O. Greenlee of the United States in 1936. The applications for epoxy-based materials are extensive and include coatings, adhesives and composite materials such as those using carbon fiber and fiberglass reinforcements (although polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic). The chemistry of epoxies and the range of commercially available variations allows cure polymers to be produced with a very broad range of properties. In general, epoxies are known for their excellent adhesion, chemical and heat resistance, good-to-excellent mechanical properties and very good electrical insulating properties. Many properties of epoxies can be modified (for example silver-filled epoxies with good electrical conductivity are available, although epoxies are typically electrically insulating). Variations offering high thermal insulation, or thermal conductivity combined with high electrical resistance for electronics applications, are available.

Brief Description

Level of Caution

Precautions


2. The hardner, Triethylenetetramine may cause allergic reactions. Wear gloves at all times.

3. Both the chemicals are sticky so avoid contact with bare hands.


Chemistry Project

Materials Needed

Procedure

Take 4 clean, numbered test tubes and to each add 3mL of Resin. Fill the syringe with Triethylenetetramine .Start the stop watch.Make the volume of Resin in test tube one equal to 5 mL.Now note the time as you add 5 divisions of the syringe, i.e. 0.5 mL to test tube one and stir it well.Repeat the above 2 steps with 4.5 mL of Resin and 1.0 mL of Triethylenetetramine , in the second test tube and so one.Place these in the thermostat with temperature set to 40 *C.Repeat all the steps and keep this set at room temperature. (7 *C)

Chemicals:1. Epoxy Resin (formed by reaction between epichlorohydrin and bisphenol-A)

2. Hardener (Triethylenetetramine)

Apparatus:1. Test tubes2. Stirring rod3. Thermostat4. Measuring Cylinder5. a 5 mL Syringe6. Stop Watch



0.5 28 minutes

1.0 20 minutes

1.5 12 minutes

2.0 10 minutes

at 40 *C

Appearance

almost clear, yellowish

slightly frothy, yellowish

frothy, yellowish

very frothy, yellowish

+


0

5

10

15

20

25

30

0 0.5 1 1.5 2 2.5

Time (min)

Concentration

0

20

40

60

80

100

120

140

160

180

0 0.5 1 1.5 2 2.5

Time (min)

Concentration

at 40 *C

at 7 *C


0.5 170 minutes

1.0 150 minutes

1.5 130 minutes

2.0 95 minutes

at 7 *C

Appearance

almost clear

almost clear, ‘starry’

fewer bubbles, transparent

bubbles, almost transparent

Chemistry Project

Page 14

Chemistry Behind it

Epoxy is a copolymer; that is, it is formed from two different chemicals. These are referred to as the "resin" and the "hardener". The resin consists of monomers or short chain polymers with an epoxide group at either end. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A, though the latter may be replaced by similar chemicals. The hardener consists of polyamine monomers, for example Triethylenetetramine (TETA). When these compounds are mixed together, the amine groups react with the epoxide groups to form a covalent bond. Each NH group can react with an epoxide group, so that the resulting polymer is heavily crosslinked, and is thus rigid and strong.The process of polymerization is called "curing", and can be controlled through temperature and choice of resin and hardener compounds; the process can take minutes to hours. Some formulations benefit from heating during the cure period, whereas others simply require time, and ambient temperatures.

Test Result

Flexibility Low

Strength High


Color Transparent

Inertness Stable in air at room temp.Unreactive to Acids

SmoothTexture

Property Analysis


BakeliteIt’s optimum synthesis temperature range was found to be 70-80 *C. Its synthesis requires high

activation energy but the reaction is kinetically very fast.

PolystyreneIt cures faster at higher concentrations of the catalyst. The strength of the polymer was independent of

the concentration ratio of the resin and catalyst. Its kinetics are complex as its concentration v/s curing time graph was found to be irregular. The optimum temperature range for synthesis of this polymer was found to be over 40 *C at the tested concentrations of the catalyst.

Epoxy ResinIt cures faster at high concentrations of its catalyst. It also cures faster at higher temperature. The

strength of the polymer was independent of the concentration ratio of the resin and catalyst. The reaction may be following first order kinetics as the concentration v/s curing time graph was found to be close to linear. The optimum temperature range for synthesis of this polymer was found to be 5-10 *C at the tested concentrations of the catalyst.

RESULT

+ +

Chemistry Project

Page 16

REFERENCES

http://www.google.co.in/webhp?hl=enhttp://en.wikipedia.org/wiki/Polystyrenehttp://en.wikipedia.org/wiki/Styrenehttp://en.wikipedia.org/wiki/Epoxyhttp://en.wikipedia.org/wiki/Bakelitehttp://papers.ssrn.com/sol3/papers.cfm?abstract_id=1420502http://answers.yahoo.com/question/index?qid=20090717144012AAKmCybhttp://inventors.about.com/od/pstartinventions/a/plastics.htmhttp://www.barrule.com/workshop/images/info/foams/index.htmhttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC2430229/http://www.pslc.ws/mactest/styrene.htmhttp://www.americanchemistry.com/s_plastics/sec_pfpg.asp?CID=1421&DID=5213

for any further details or clarification, suggestions etc., contact meEmail: ~ Cell: +91 9818055646 ~ Landline: +91 011 [email protected]

Chemistry Project


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polymers: chemistry project

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