By showing knowledge this chapter for pharmacy student

1. Material of construction

2. A number of equipment are used in the manufacture of
pharmaceuticals , bulk drugs , antibiotics, biological products , etc
. A wide variety of materials are used .

3. Factors affecting the selection of materials of
construction.
The selection of a material for the construction of equipment
depends on the following properties:-
1. Physical properties
A. Strength F. Ease of fabrication
B. Mass. G. Cleaning
C. Wear properties. H. Sterilization
D. Thermal conductivity. I. Transparency
E. Thermal expansion

4. 2. Chemical factors
A. Contamination of the product
B. Corrosion of material of construction
3. Economic factors
1. Physical factors
A. Strength
The material should have sufficient physical strength to withstand
the required pressure and stress .
• Tablet punching machine ; upper and lower punch sets are
made up of stainless steel to withstand very high pressure .

5. • Glass has strength but are brittle .
• Plastics are weak . So, they are used in packaging materials like
blister packs
B. Mass
For the transportation, light weight packaging materials are used .
Plastic, aluminium and paper packaging materials are used for
packing pharmaceutical products.

6. C . Wear properties
When , there is a possibility of friction between two surfaces, the softer
surface wears off. These materials contaminate the product. For eg;
during grinding , the grinding surfaces wears off & contaminate the
product.
Ceramic & iron grinding surfaces are not used , when pharmaceutical
products of very high purity is required.
D. Thermal conductivity
In evaporation, dryers and heat exchangers , the material employed
have very good thermal conductivity. In such cases , iron, copper or
graphite tubes are used for effective heat transfer .

7. E. Thermal expansion
If the material has very high thermal expansion coefficient , then as temperature
increases, the shape of the equipment changes . This produces uneven stress
and may cause fractures . So, such materials should be used which are able to
maintain the shape and dimension of the equipment at the working temperatures.
F. Ease of fabrication
During fabrication of an equipment, the materials undergo various processes
such as casting, welding, forging, etc. For eg:- glass & plastics may be easily
moulded into containers of different shapes& sizes . Glass may be used as lining
material for reaction vessels.

8. G . Cleaning
Smooth & polished surfaces make cleaning easy . After an operation is
completed, the equipment should be cleaned thoroughly. So that the
previous product cannot contaminate the next product. Glass and stainless
steel can be smooth and polished. Hence easy to clean .
H. Sterilization
In the production of parenteral, opthalmic & bulk drugs products, all the
products should be sterilized. It is generally done by the steam under the
high pressure. If rubber materials are there, it should be vulcanised to
withstand the high temperature

9. I . Transparency
In reactors & fermenters, a visual port is provided to observe the
progress of process going on inside the chamber. In this case ,
borosilicate glass is often used .
In parenteral & opthalmic containers the particles, if any are observed
from the polarised light . The walls of the container should be
transparent to see through. Hence glass is preferred material.
2. Chemical factors
Whenever a chemical substance is placed in a container or equipment,
due to the direct contact of material of construction and product, the
material of construction may contaminate the product (contamination)
or the product may destroy the material of construction (corrosion).

10. A. Contamination of the product
Iron contamination may change the colour of the product (like gelatin
capsule shells) , catalyse some reactions that may enhance the rate of
decomposition of the product.
Leeching of glass may make aqueous products alkaline . This alkaline
medium may catalyse the decomposition of the product
Hence metals such as lead inactivate penicillin

11. B. Corrosion of material of construction
The products may be corrosive in nature . They may react with the material of
construction & may destroy it . The life of equipment is reduced.
Extreme PH , strong acids , strong alkali , powerful oxidizing agents , tannins, etc
react with the materials. Hence alloys having special chemical resistance is used .
3. Economic factors:
Initial costs and maintenance of the plant must be economical. Here the main
concern is not simply to obtain the least cost material. Low wearing qualities and
lower maintenance may well mean that a higher initial cost is more economical in
long run.

12. Corrosion
Corrosion is defined as the reaction of metallic material with it’s
environment which causes measurable changes to the material and can
result in an functional failure of the metallic component or of a complete
system
Factors influencing corrosion
1. PH of the solution
• Iron dissolves rapidly in acidic PH.
• Aluminium and zinc dissolve in both acidic and alkaline PH .
• Noble metals ( gold and platinum) are not affected by PH.

13. 2. Oxidizing agents:
• Oxidizing agents may accelerate the corrosion of one class of
materials whereas retard another class
• oxidizing agents form a surface oxide (like aluminium oxide ) &
makes the surface more resistant to chemical attack.
3. Velocity :
• When the corrosive medium moves at high velocity along the metallic
surfaces , the rate of corrosion increases due to
• corrosion products are formed rapidly and washed away rapidly to
expose new surface for corrosion reactions.
• Accumulation of insoluble films on the surface is prevented.

14. 4. Surface films :
• Thin oxide films are formed on the surface of stainless (rusting) . These
film absorbs moisture and increase the rate of corrosion.
• Grease films protect the surface from direct contact with corrosive
substances.

15. FERROUS METALS
1. Carbon steel
 It is the most common, cheapest and most versatile metal used in
industry.
 It has excellent ductility, permitting many cold forming operations.
 It is also the most weldable of all commercial metals.
 The corrosion resistance of steel depends upon the formation of an
oxide surface film.
 Many large water tanks are fabricated from carbon steel as well as
storage tanks for organic solvents and similar chemicals.
 Carbon steel should be used in contact with dilute acids.

16. 2.Wrought iron
 Ferrous metal that includes about 3% of a minutely and evenly
distributed quantity of iron silicate (slag) in the form of fibers with a few
trace elements like C, Si, Mn, P and S is called Wrought iron.
 It is tough and ductile with excellent fatigue and shock resistance.
 Wrought iron can be worked easily by hot and cold forming technique.
 It has excellent resistance to atmospheric corrosion.
 It can handle alkalis and alkaline solution but dilute acid cause rapid
failure.

17. 3.Low alloy steels
Alloy steels contains one or more alloying reagents to improve
mechanical and resistant properties over those of carbon steel.
A typical low alloy grade contains
0.4% C 0.7% Mn 1.85% Ni 0.8% Cr 0.25% Mo.
Many other alloying agents are used to produce special grades.

18. 4. Cast iron
 Generally case iron is not a particularly strong or tough structural material , although
it is one of the most economical materials which is widely used industrially.
Types of cast iron:
a. Gray cast iron
 It is low in cost and easy to cast into intricate shapes, contains C, Si, Mn and Se.
 It has outstanding ability to absorb vibration and wood resistance.
 However, it is brittle ,with poor resistance to impact and shock.
b. Malleable iron
 It is made from white cast iron.
 It is easily machined, withstands bending and cold working without cracking.

19. c. White cast iron
 It is made by controlling the composition and rate of solidification of the molten
iron.
 It is very abrasive and weal resistant.
 It is used as liners, for grinding balls and pump impellents.
d. Ductile cast iron
 It is also known as ductile iron, nodular cast iron, spheroidal graphite iron which
is a type as graphite rich cast iron.
 It is durable, fatigue - resistant metal due to its spherical graphite structure.

20. 5. Stainless steel
 There are more than 70 standard types of stainless steels and many special
alloys. Generally all are iron based with 12-30 % Cr, 0-2 % Ni, minor
amounts of C, Cu, Mo, Se, Columbium, Tantalum and Titanium.
 They are very popular in the process industries. They are heat and corrosion
resistant, non contaminating and easily fabricated into complex shapes.
 There are 3 groups of stainless alloys :-
1) Martensitic
2) Ferritic
3) Austenitic

21.  The first group i.e martensitic contains 12-20 % Cr with controlled amount of
C content and others . Type 410 is a typical member of this group.
 The second group i.e ferritic contains 15-30% Cr with low C content (0.1%).
The higher Cr contents improves its corrosion resistance. Type 430 is a
typical example.
 The third group i.e austenitic are the most corrosion resistant of the three
groups. They contain 10-26% Cr and 6-22% Ni and C is kept low (0-0.8%).
They are tough and ductile.
 Austenitic stainless steels have excellent resistance to Nitric acid at
practically all concentrations and temperatures. Most nitric acid plants are
constructed with Type 304.
 Cast stainless alloys are widely used in pumps, valves and fittings.

22.  The main resistance to corrosion of stainless steels lies in a tenacious
passive oxide film which is readily formed and not easily dissolved or
destroyed even under severe operating conditions.
Grade level of stainless steel
1. Grade 202L
 Grade 202L is chromium-manganese-nickel stainless steel with high
toughness at low temperature. In comparison, grade 202 has less nickel
content unlike grade 304. Hence , it offers low corrosion resistance and lower
toughness.202L stainless steel is one of the most common stainless steel
alloys used in construction, fabrication.
 Grade 202 stainless steel has a low amount of chromium and nickel, which
makes it more prone to rushing.

23. 2. Grade 304L
 Grade 304L represents 50% of the produced around the world due to its excellent
corrosion resistance and value.
 Grade 304L 18% chromium and 8% nickel, which makes it pleasing as well as
durable.
 Its one weakness is saline, so grade 304 can pit or crevice when used near salt
water.
 Stainless steel sheet, stainless steel pipe, stainless steel bar, stainless steel coil all
are grade 304.
 Grade 304L is particularly rust proof because of its high nickel content therefore it
is used for variety of household and industrial applications such as food handling,
machinery parts, utensils, etc.
3. Grade 316L
 The second most commonly produced steel, grade 316 contains 2-3%
molybdenum.
 Consequently, its more resistant to saline and thus better for coastal environment.

24.  Many surgical supplies also get made from grade 316 stainless steel.
 It is available in 316L stainless steel sheet, 316L stainless steel plate, 316L
stainless bar and 316L stainless steel tube.
4. Grade 317L
 Grade 317L is a low carbon corrosion resistant austenitic chromium-nickel-
molybdenum stainless steel.
 This grade provides high tensile strength at elevated temperature.
 It is more resistant to corrosion and pitting than either grade 304 or grade 316
stainless steel.
 It is used to handle sulphur, pulp liquor, acid dyestuffs, acetylating and nitrating
mixtures, bleaching solutions, severe coal and oil, and many chemical
compounds.

25. • Definition:-it is the mixture of two or more metal when a material is needed which
required certain properties and this does not exist in pure metal.
Non ferrous metal
• Aluminum
• Aluminum is cheap , light in weight and offers adequate mechanical strength. Also ,
aluminum equipment can be easily fabricated and the maintenance and cleaning is also
easy.
ADVANTAGES:-
1. High resistance to atmospheric conditions , industrial fumes , vapor and fresh or salt
waters . It can be used with concentrated nitric acid and acetic acid.
Alloys

26. 2. Thermal conductivity of aluminum is 60% of pure copper.
• Melting point =660.3
DISADVANTAGE:-
1.The mechanical strength decreases greatly above 150 degree Celsius.
2.Aluminium can’t be used with strong caustic solution .
3.Many minerals acids attacks aluminum .
4.Oxide and hydroxide films are formed rapidly , when it’s surface is
exposed. Normally this films is thickened by chemicals and electrolyte
means.

27. USES
1. A super grade is preferred for many heat transfer applications .
2. Aluminium is non toxic to organism thus has considerable use in bio-synthesis
processes such as production of citric acid , gluconic acid and streptomycin by
deep culture methods.
3. Aluminium alloys with improved qualities are used for construction of equipment
haldling salts.

28. Aluminum alloy
They are alloys in which aluminum (Al) is the predominant metal. The typical
alloying elements are copper, magnesium, manganese, silicon, and zinc.
There are two principal classifications, namely casting alloys and wrought alloys,
both of which are further subdivided into the categories heat-treatable and non-
heat-treatable.
Alloys composed mostly of the two light weight metals aluminum and magnesium
have been very important in aerospace manufacturing since somewhat before
1940

29. Lead
Lead is highly malleable , ductile and relatively poor conductor of electricity . lead has the lowest
cost but has little use, because of the risk of contamination even in traces produces toxicity . Yet
because of its density and ability to absorbed vibrations , and as an excellent shield against
different type of harmful radiation it is frequently preferred . ( m.p. -327.5 )
Advantages
1. It is the most dense (non-radioactive) common metal, which makes it invaluable for
applications requiring high weight with small volumes.
2. Is highly ductile and malleable.
3. Has a relatively low melting point compared to most metals.
4. Can absorb and dampen sound vibrations.

30. 5. Has good resistance to corrosion, especially in non-acidic environments.
6. Excellent material for radiation shielding in medical and nuclear
applications due to its massive nucleus and resultant high density.
7. Relatively abundant and easy to refine, making it cost-effective compared to
many other metals.
Disadvantages
1. Lead has low melting point and hence possess poor structural qualities .
2. It has high coefficient of expansion, therefore temperature strain results in
permanent deformation .

31. • Uses
Lead alloy with superior performance qualities have been established . Silver and
copper , improves corrosion resistance .
Antimony , tin , arsenic: hardens (still melting point is low)
Lead- lined steels are used in constructions of pipes , valves and vessels .

32. Copper
• Introduction
Copper is preferred when good thermal and electrical conductivity is required. It
is relatively inexpensive and possesses fair mechanical strength. It can be
fabricated easily into wide variety of shapes. Copper is resistant to atmospheric
moisture and oxygen, because a protective coating (Cuo) is formed on the
surface. (MP-1085°C) Copper exhibits good corrosion resistance to strong
alkalis, with the exception of ammonium hydroxide. It resists most organic
solvents and aqueous solutions of organic acids.

33. Disadvantage
Soluble in most acids and hence not suitable material for construction. Many
components of formulation react with copper. Hence, copper is protected by the lining
of tin in pharmaceutical plants.
Uses
Copper is used for evaporators, pans (for sugar coating), stills and fractionating
columns. However for reasons of corrosion, it is largely replaced by SS.
Copper piping is used for piping of cold water, gas, vacuum and flow pressure steam.
Copper alloys, such as brass (copper-zinc alloy) and bronze(copper-tin alloy), can
exhibit better corrosion resistance and better mechanical properties than pure copper.
Brass is used for tube plates, condenser, valves and in making of nuts, bolts, rods etc.
Bronze is used for filter gauges, stirrer, pipes, autoclaves and special tablet punches
and dies.

34. Tin
Introduction
• Tin has high resistance to a variety of substances and is highly used as
containers alone and in combination with other metals. Being chemically inert,
steel sheet coated with tin is used for condenser tubes and containers. Brass
and copper are also coated with tin for protective non-reacting lining. (MP-
231.9 °C)
Advantage of tin
• Tin is a silver-white metal that is soft, ductile and malleable. Due to this
flexibility, tin can be molded and stretched into a variety of shapes without
cracking. Tin is also considered to be non-toxic, conductive and resistant to
corrosion

35. Disadvantage of tin
• The main disadvantage of tin can packaging is that it cannot be used for
packaging extremely acidic products just like any other metallic can. It is due to
the fact that tin is corrosive and the packaging of the acidic products would
certainly cause a reaction which would destroy both the can and the product
Uses of tin
Most tin is utilized as an alloy with other metals like lead or zinc or as a protective
coating. Tin is used in glass production, bearing alloys, coatings for steel
containers, solders for connecting pipes or electrical/electronic circuits, and other
tin chemical use.

36. INORGANIC NON –METALS
GLASS
Glass is a hard, brittle substance, typically transparent or translucent, made by
fusing sand with soda and lime and cooling rapidly.
It is chemically inert to a large extent and available in a variety of sizes, shapes,
and colors. It is economical and shows good protective qualities.
Glass containers practically offer excellent barriers against every element and light.
UV rays and sunlight are harmful to certain ingredients and bring out chemical
deterioration.
Protective action against glass can be done by amber-coloured glass. Protection
against IR rays can be obtained by using green glass.

37. The main disadvantages are its fragility and weight.
Glass is considered a super-cooled liquid, though it is seen in the solid state.
Glass is composed of:
• Sand as a base material (silicon dioxide, SiO2 ),
• soda ash (sodium carbonate, Na2CO3 ),
• lime stone (calcium carbonate) and
• cullet( broken gas as fusion agent).

38. • Silicon dioxide has a tetrahedron structure. The glass prepared by silicon dioxide
alone is the most resistant, but relatively brittle. It can be melted and molded in
high temperatures. Therefore, cations such as sodium, potassium, calcium,
magnesium, aluminum, boron, iron, etc., are added.
• These cations (available as oxides) modify the physiochemical properties of glass
so that it is suitable for the manufacture of glass with desired characteristics.
However, this glass has low chemical resistance. It is because most alkali oxides
Na2O, K2O, MgO, and CaO enter the spaces within the structures and reduce the
strength of inter-atomic forces between silicon and oxygen. It decreases the
melting point of glass.

39. Varieties of glass
Types of glass Composition Advantages or uses
Soft glass Sodium silicate
Calcium silicate
Making bulb and windows glasses.
Hard glass Potassium silicate
Calcium silicate
Glass apparatus which resists the action of
acid
flint glass Lead silicate
Potassium silicate
Optical instrument because of the refractive
index
Jena glass Zinc silicate
Barium borosilicate
Laboratory glassware because of its resistant
of acids and alkali
Pyrex glass Silicon dioxide
Boron oxide
sodium oxide
Laboratory glassware and reactor vessels
because of the resistant to head
Quartz glass Pure silica Silica crucibles, distilled water stills ( for high
purity) because of their low coefficient of
expansion

40. Glass used in pharmaceutical
industry
Type
s
General
description
Properties uses
I Highly resistant
borosilicate
Resistant to alkali leaching,
less brittle,low thermal
expansion
Contained for buffered and
unbuffered, aqueous solutions
and injectables
Ii Treated soda lime
glass
Surface alkali is neutralized
by sulphur dioxide apours.
Resistant to water.
Contained for buffered solution
having pH below 7,Dry powder,
oleaginous solution
Iii Soda lime glass Release alkali, moderate
hydrolytic resistance
Dry powder, oleaginous solution
iv General purpose
sodalime glass
Not for parentral used as
containers for tablets
oralsuspension,ointment and
liquid for external use

41. Glassed steel:
• Glassed steel is an inorganic product of fusion, which is cooled to a rigid
condition without crystallizing. It requires special considerations in its design
and use. These surfaces are applied to heavy vessels. Normally, several
coatings are fused in a furnace. Glassed steel combines the corrosion
resistance of glass with the working strength of steel.
Properties:
1. It has excellent resistance to all acids except hydrofluoric acid and hot
concentrated sulphuric acid.
2. It can be attacked by a hot alkaline solution. Particularly suitable for piping
when transparency is desirable.
3. It is brittle and gets damaged by thermal shock. Hence it is protected using
glass lined with epoxy polyester fibre glass.

42. 4.Glass linings are resistant to:
i. All concentrations of hydrochloric acids upto 120°C.
ii. Dil. Concentration of sulphuric acid upto boiling point.
iii. All concentration of nitric acid upto boiling point.
iv. Acid resistant glass with improved alkali resistance (up to pH 12).
Uses:
Glass lined steel is used for handeling of strong acids, alkalis and saline
solution. For small-scale manufacture and pilot plant work, glassed steel
vessel are used.

43. ORGANIC NON-METAL
• Rubber:
Rubber is a tough elastic polymeric substance made from the latex of a tropical
plant or made synthetically. It is used as lining materials for construction of plants.
There are two types of on the basis of source. They are:
1. Natural rubber
2. Synthetic rubber

44. Natural rubber:
Naturally occurring polymer, which is obtained as latex from rubber trees. It is
common example of elastomer. Elastomer is a substance that can be stretched
readily and when released, rapidly regains its original form.
Synthetic rubber:
• Synthetic rubber has taken greater importance over natural rubber due to its
superiority in properties such as resistance to oxidation, solvents, oils and other
chemicals.
• Synthetic rubber when mixed with Sulphur, warmed and set into a given shape
retains its form.

45. • Vulcanization is a chemical process in which the rubber is heated
with Sulphur, accelerator and activator at 140–160°C.
• The process involves the formation of cross-links between long
rubber molecules so as to achieve improved elasticity, resilience,
tensile strength, viscosity, hardness and weather resistance.
• Vulcanization process make gloves, bands and tubes, caps for vials
etc.

46. Soft rubber:
• The naturally occurring polymer is known as soft rubber. It is a polymer of
monomeric isoprene (C5H8).
• Thus, rubber is polyisoprene with a formula (C5H8)n.
• Soft rubber has the advantages of being resistant to dilute mineral acids,
dilute alkalis and salts.
• The disadvantage is that soft rubber can be attacked by oxidizing media, oils
and organic solvents.
• Soft rubber is used as lining materials for plants, as it can bond easily to the
steel.

47. Hard rubber:
• When soft rubber is mixed with Sulphur, warmed and set into a given shape, it
retains its form.
• The Sulphur combines with the polymeric chains of rubber and cross-links
between them.
• This process is called vulcanization. Soft rubber with 25% or more Sulphur is
known as hard rubber.
• Hard rubber has the advantages of hardness and strength thus used for making
gloves, bands, tubes and stoppers.
• Rubber is soft material, but can be hardened by addition of carbon black.
• Hardened rubber is used for making tyres , tubes and conveyer belts.

48. Plastics:
• Plastic materials are light in weight so transportation is easy and cheap.
• These are available in variety of shapes implying that it can be easily
fabricated.
• Plastic containers are used for storing a number of substances such as
inorganic salts and weak mineral acid.
• In machines, plastic materials are preferred wherever moving parts are
present indicating that it offer less friction.
• These has better resistance to environmental factors.
• Plastic are synthetic resins containing long chain of atoms linked to form
giant or
macromolecules (polymers). They have high molecular weight (103 to
107gm/mol).

49. Advantages:
1. Low thermal and electrical resistance.
2. Excellent resistance to weak mineral acids.
3. Unaffected by inorganic salts.
4. Resistance to slight changes in Ph.
Disadvantages:
1. Low mechanical strength
2. High expansion rates.

50. Two types of plastics are used in pharmaceutical industry:
1.Thermosetting plastics:
• They are formed under heat and pressure.
• These cannot be softened or remoulded , once hardened. Some thermosetting plastics
are made of phenolic and urea resin.
2.Thermoplastic plastics:
• They are also formed by application of heat and pressure but can be softened and
remolded.
• Recycling of this type of plastic is major advantage.
• Major thermoplastics are used for polyethylene (cables, bucket, pipes) , polypropylene
(ropes), polyvinyl chloride (gloves, water proof garments), Teflon (gaskets, coating), etc.

51. TYPES OF PLASTICS
Polyethylene Terephthalate (PETE or PET):
• It is the most common thermoplastic polymer resin of the polyester family and is
used in fibers for clothing, containers for liquids and foods, thermoforming for
manufacturing, and in combination with glass fiber for engineering resins.
(C10H804)n.
• They are used in making of vials, diagnostic devices, petri dishes, bottles,
cleaning cloths, clothing.
• They are thermoformed to make blister pack.

52. Polyethylene:
• Polyethylene (C2H4)n is a lightweight, durable thermoplastic with variable crystalline
structure.
• It is one of the most widely produced plastics in the world (tens of millions of tons
are produced worldwide each year).
• Polyethylene is used in applications ranging for films, tubes, plastic parts, laminates,
etc. in several markets (packaging, automotive, electrical, etc.)
• Cost effective, ease in fabrication, High tensile strength.

53. High Density Polyethylene (HDPE)
• It is a cost-effective thermoplastic with linear structure and no or low
degree of branching.
• It is manufactured at low temperature (70-300°C) and pressure (10-80
bar) & derived from either: Modifying natural gas (a methane, ethane,
propane mix) or catalytic cracking of crude oil into gasoline.
• Used as packaging material, drums, bulk containers, garbage
container, ropes, piping, wiring and cables.

54. Low Density Polyethylene (LDPE)
• It is a semi-rigid and translucent polymer.
• Compared to HDPE, it has a higher degree of short and long side-chain branching.
It is produced at high pressure (1000-3000 bar; 80-300°C) via free radical
polymerization process.
• The LDPE is composed of 4,000-40,000 carbon atoms, with many short branches.
• Mainly used in packaging, pipes and fitting due to its plasticity and low water
absorption.

55. Polyvinyl Chloride (PVC):
• PVC is a thermoplastic that is formed when vinyl chloride (CH2=CH-Cl)
polymerizes.
• When made, it's brittle, so manufacturers add a plasticizer liquid to make it soft
and moldable.
• PVC is commonly used for pipes and plumbing because it's durable, can't be
corroded and is cheaper than metal pipes.
• Over long periods of time, however, the plasticizer may leach out of it, rendering it
brittle and breakable.

56. Polypropylene (PP)
• Also known as polypropene, is a thermoplastic polymer.
• Used in packaging, automotive and instrument in battery cases, bumpers, trays,
vials, diagnostic devices, petri dishes, intravenous bottles, specimen bottles,
food trays, pans.
• Used in industrial sector to produce acid and chemical tanks, sheets, pipes,
transport packaging.
• It is produced via chain-growth polymerization from the monomer
propylene(C3H6)n

57. Polystyrene (PS):
• Polystyrene is formed by styrene molecules.
• The double bond between the CH2 and CH parts of the molecule
rearranges to form a bond with adjacent styrene molecules, thereby
producing polystyrene.
• It can form a hard impact-resistant plastic for furniture, computer cabinet,
glasses and utensils.
• When polystyrene is heated and air blown through the mixture, it forms
Styrofoam.
• Styrofoam is lightweight, moldable and an excellent insulator

58. Nylon:
• Nylon is a generic designation for a family of synthetic polymers, based
on aliphatic or semi-aromatic polyamides.
• Nylon is a thermoplastic silky material that can be melt-processed into fibers,
films, or shapes. It is made of repeating units (C12H22N2O2)n linked by amide
links similar to the peptide bonds in proteins.
• Nylon fibers are exceptionally strong and elastic and stronger than polyester
fibers.
• The fibers have excellent toughness, abrasion resistance, and are easy to wash,
and to dye in a wide range of colors. The filament yarns provide a smooth, soft,
and lightweight fabric of high resilience.
• Nylon polymers have found significant commercial applications in fabric and
fibers
(apparel, flooring and rubber reinforcement), in shapes (molded parts for cars,
electrical
equipment, etc.), and in films (mostly for food packaging)

59. Polytetrafluoroethylene (Teflon):
• Teflon is made by polymerization of tetrafluoroethylene molecules (CF2=CF2).
• The polymer is stable, heat-resistant, strong, resistant to many chemicals and has a
nearly frictionless surface.
• Teflon is used in plumbing tape, cookware, tubing, waterproof coatings, films and
bearings.
Cellulose based plastics:
• Cellulose-based plastics also called bio-plastics are made of cellulose, the main
component in plant tissues.
• Cellulose bio-plastics are mainly the cellulose esters, (including cellulose acetate and
nitrocellulose) and their derivatives, including celluloid.
• Cellulose can become thermoplastic when extensively modified.

60. • An example of this is cellulose acetate, which is expensive and therefore rarely
used for
packaging.
• However, cellulosic fibers added to starches can improve mechanical properties,
permeability to gas, and water resistance due to being less hydrophilic than
starch.
• Bio-plastics can be used for disposable items, such as packaging, crockery,
cutlery, pots,
bowls, and straws.
• Few commercial applications exist for bio-plastics as cost and performance
remain problematic.