Aim: The aim of this project is to find out the optimum conditions for synthesis of the following polymer, Bakelite and to study its physical properties like flexibility, strength, bounciness, color etc.

Theory: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. 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 of 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 Glycosdic bonds via oxygen atoms.

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 heave 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.

The first synthetic polymer, a phenol-formaldehyde polymer, was introduced under the name ‘Bakelite’, 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

Bakelite

following years, the technology to mass produce them was not developed until World War II, when there was a need to develop a synthetic rubber for tires and other wartime applications and nylon parachutes. Since that time, the polymer industry had 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 150kg 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 semiconductor. 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 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-tunes using the exquisite methods of organic synthesis.

Brief Description: BakeliteBakelite or Polyoxybenzylmethylenglycolanhydride, is an early plastic. It is a thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde. It was developed by Belgian-born chemist Leo Baekeland in New York in 1907.

One of the first plastics made from synthetic components, Bakelite was used for its electrical nonconductivity and heat-resistant properties in electrical insulators, radio and telephone casings, and such diverse products as kitchenware, jewelry, pipe stems, children's toys, and firearms. The "retro" appeal of old Bakelite products has made them collectible.

Bakelite was designated a National Historic Chemical Landmark on November 9, 1993 by the American Chemical Society in recognition of its significance as the world's first synthetic plastic.

Materials Needed:Chemicals-

1.) 2.5g of 40% Formaldehyde

2.) 2g of Phenol

3.) 5mL Glacial Acetic Acid

4.) Concentrated Hydrochloric Acid

Apparatus-1.) 150mL beaker2.) Stirring rod

Procedure:First make the Phenol-formaldehyde reaction mixture by mixing 2.5mL formaldehyde, 2g phenol and 5mL glacial acetic acid. Under a hood, pour the phenol-formaldehyde reaction mixture into a beaker. Place the beaker on a white paper towel. Add a few drops of concentrated hydrochloric acid, slowly, with stirring. Add additional hydrochloric acid, drop wise, with stirring. 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.

Observations:

Temperature

Observations

40-35o C No observable changes

50-45o C Turbidity started appearing

60-55oC Roughly polymerization started

75-60oC Semi solid appeared at the bottom of the beaker

30-25oC At long standing, the color changed to dark pink

Property Analysis:

Test Result

Flexibility Brittle

Strength Low

Bounciness Negligible

Color Dark pink

Texture Slightly porous

Inertness Stable in air at room temperature

Chemistry Behind It:Phenol and Formaldehyde react in the following manner to make the polymer.

The first step in forming a polymer chain involves substitution of methanal in the phenol ring in the 2- or 4- position:

The product then undergoes a condensation reaction:

When methanal and phenol, in the proportion of 0.5:1, are reacted under acidic conditions, a resin (often known as a novalac resin) is produced, where n = 0 to 6;

With higher proportions of methanal and with the 4-position vacant, branching is possible, the methanal providing additional -CH2- links. On heating a resin is produced. Part of the 3-

dimensional cross-linked structure is illustrated:

Result:Its optimum synthesis temperature range was found to be 70-80oC. Its synthesis requires high activation energy but the reaction is kinetically very fast.

Uses:The polymers with giant three-dimensional, cross-linked structures form resins that cannot be melted and reshaped.  On heating to high temperatures, they begin to decompose and char.  They are also insoluble

in a wide range of solvents and are non-reactive.  Their high electrical and heat resistance means that they are used as an electrical insulator and for the manufacture of brake and clutch linings for vehicles.  When they are used with fillers such as wood flour (wood that has been pulverized roughly to the size of a rice grain) or mica, they have major applications in the construction of worktops and printed circuit board insulation.  They are also widely used as adhesives, for example in producing plywood and hardboard.

Precautions:1.) Use heat-resistant gloves and/or tongs

when handling hot glassware, chinaware, etc.

2.) Use plastic gloves when handling any hazardous materials to prevent skin contact.

3.) When diluting acids, pour the acid into the water, NOT water into acid as this may cause spattering of the acid.

4.) Do not store basic solutions in glass containers with glass stoppers, use plastic or rubber stoppers.

5.) Dispose of all used solutions in an approved manner as directed by the instructor.

6.) Use the right amount of chemicals as instructed.

7.) Use clean apparatus.8.) Handle Phenol carefully as it is a very

strong acid.

Bibliography:- https://en.wikipedia.org/Polystyrene- https://en.wikipedia.org/wiki/Bakelite- https://www.google.co.in/- http://www.americanchemisrty.com/- http://

www.essentialchemicalindustry.org/polymers/methanal-plastics.html

- Material provided by Vikram A. Sarabhai Community Science Centre.