EBB 220/3
POLYMER ADDITIVES
DR AZURA A.RASHID
Room 2.19
School of Materials And Mineral Resources Engineering,
Universiti Sains Malaysia, 14300 Nibong Tebal, P. Pinang
Malaysia
Introduction

Most of polymers need to add with specific ingredients to obtain
desirable properties.

Additives were used:



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To improved or modify the mechanical, chemical, and physical
properties
To prevent degradation (both during fabrication and in service)
To reduce materials costs
To improve the processability

Each of the additives in formulation has specific functions either
during processing or end products applications

Typical additives include

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filler materials,
Plasticizer
stabilizers,
colorants
flame retardants.
Fillers
 Fillers normally add in polymeric materials for economical or
technical
 Filler materials are most often added to polymers to
improve tensile and compression strengths, abrasion
resistance, toughness, dimensional and thermal stability
and other properties.
 Materials used as particulate fillers  include wood flour
(finely powdered sawdust), silica flour and sand, glass, clay,
talc, limestone, and even some synthetic polymers.
 Particle sizes range all the way from 10 nm to macroscopic
dimensions
 Because these inexpensive materials replace some volume
of the more expensive polymer, the cost of the final
product is reduced.
Plasticizers

Can be in liquid, half solid or solid form.

It must be compatible with the polymeric
materials and other compounding ingredients 
incompatibility will results in poor processing
properties.

Plasticizer were used for:
1.
‘extender’ (large amount >20 pphr) to make the
end products cheaper
2.
Processing aid (small amount 2-5 pphr) to
make the processing easier
3.
Modifier  to modifies some polymeric
properties.


The aid of additives called plasticizers can :

improved the flexibility, ductility, and toughness

produces reductions in hardness and stiffness

lowers the glass transition temperature  at
ambient conditions the polymers may be used
in applications requiring some degree of
flexibility and ductility.
These applications include thin sheets or
films, tubing, raincoats, and curtains.
Stabilizers

Some polymeric materials under normal environmental
conditions are subject rapid deterioration in mechanical
properties.

Most often this deterioration is a result of exposure to light
 in particular ultraviolet radiation and oxidation

Ultraviolet radiation 




causes a severance of some of the covalent bonds along the
molecular chain
also result in some crosslinking.
Oxidation deterioration is a consequence of the chemical
interaction between oxygen atoms and the polymer
molecules.
Additives that counteract these deteriorative processes are
called stabilizers.
Colorants

Colorants impart a specific color to a polymer

They may be added in the form of:

dyes


The molecules in a dye actually dissolve and become part
of the molecular structure of the polymer.
pigments.

Pigments are filler materials that do not dissolve  but
remain as a separate phase;

have a small particle size, are transparent, and have a
refractive index near to that of the parent polymer.

Others may impart opacity as well as color to the polymer.
Flame retardants

The flammability of polymeric materials is a major concern,
especially in the manufacture of textiles and children's toys.

Most polymers are flammable in their pure form  exceptions
include those containing significant contents of chlorine and/or
fluorine
such as polyvinyl
chloride (PVC) and
polytetrafluoroethylene (PTFE).

The flammability resistance of the remaining combustible
polymers enhanced by additives called flame retardants.

These retardants may function by

interfering with the combustion process through the gas
phase, or

by initiating a chemical reaction that causes a cooling of the
combustion region and a termination of burning.
Special purpose additives
Additives
Function
Blowing agents
Gas generating chemicals that are necessary for
manufacturing sponge or micro porous products
Odorants
Strongly scented substances added in small amounts
that are capable of imparting a pleasant scent
Antistatic agents
Added to reduce the accumulated of dust or dirt on
surface and also to minimize possibility of sparking
resulting from the discharge of accumulated static
electricity
Retarders
Substances that used to reduce the tendency of
rubber mix to scorch  avoid premature
vulcanization during processing
Antioxidants
Protects products from oxidation of heat
Antiflex cracking
Agents that retard cracking caused by cyclic
deformations
Example of the exams question

What is the function of additives in
polymeric materials?

Discuss the used of fillers as one of
polymer compounding ingredients.
EBB 220/3
MISCELLANEOUS
APPLICATIONS
DR AZURA A.RASHID
Room 2.19
School of Materials And Mineral Resources Engineering,
Universiti Sains Malaysia, 14300 Nibong Tebal, P. Pinang
Malaysia
Coating

Coating are frequently applied to the surface
of materials to serve one or more of the
following function:
1.
to protect the item from the environment
that may produce corrosive or deteriorative
reactions;
2.
to improve the item's appearance
3.
to provide electrical insulation.

Many of the ingredients in coating
materials are polymers  with majority
are organic in origin

These organic coatings fall into several
different classifications:
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paint,
varnish,
enamel,
lacquer, and
shellac :
Adhesives

An adhesive  substance used to join together the surfaces of
two solid material (termed "adherends") to produce a joint with a
high shear strength

Adhesives may come from either natural or synthetic sources.

Some modern adhesives are extremely strong, and becoming
increasingly important in modern construction and industry

The bond forces between the adhesive and adherend surfaces
are electrostatic similar to the secondary bonding forces
between the molecular chains in thermoplastic polymers

A strong joint may be produced if the adhesive layer is thin and
continuous.

If a good joint is formed, the adherend material may fracture or
rupture before the adhesive.

Polymeric materials that fall within the
classifications of thermoplastics, them setting
resins, elastomeric compounds, and natural
adhesives (animal glue, cast starch, and resin)
may serve adhesive functions.

Polymer adhesives may be used to join a large
variety of material combinations: metal-metal,
metal-plastic, metal-ceramic, and so on.

The primary drawback
temperature limitation.

Organic polymers maintain their mechanical
integrity only at relatively low temperatures,
and strength decreases rapidly with increasing
temperature.
is
the
service
Some categories of adhesives

Natural adhesives

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Synthetic adhesives

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Adhesives based on vegetable (natural resin), food (animal hide and
skin), and mineral sources (inorganic materials).
Adhesives based on elastomers, thermoplastic, and thermosetting
adhesives.
Drying adhesives
These adhesives are a mixture of ingredients  polymer dissolved in a
solvent e.g. glues and rubber cements
 As the solvent evaporates  the adhesive hardens and they will adhere
to different materials to greater or lesser degrees.
 These adhesives are typically weak and are used for household
applications. Some intended for small children are now made non-toxic.

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Hot adhesives (thermoplastic adhesives)



Also known as "hot melt" adhesives
they are applied hot and simply allowed to harden as they cool.
These adhesives have become popular for crafts because of their ease
of use and the wide range of common materials to which they can
adhere.
Adhesives failure


Adhesives may fail in one of two ways:
1.
Adhesive failure is the failure of the adhesive to stick or bond with
the material to be adhered (also known as the substrate or
adherend).
2.
Cohesive failure is structural failure of the adhesive. Adhesive
remains on both substrate surfaces, but the two items separate.
Two substrates can also separate through structural failure of one of
the substrates 


this is not a failure of the adhesive. In this case the adhesive remains
intact and is still bonded to one substrate and the remnants of the other.
For example,

when one removes a price label, adhesive usually remains on the label
and the surface  this is cohesive failure.

If, however, a layer of paper remains stuck to the surface  the
adhesive has not failed.

when someone tries to pull apart oreo cookies with the filling all on one
side. The goal is an adhesive failure, rather than a cohesive failure.
Films

Polymeric materials have found widespread use the
form of thin films.

Films having thicknesses between 0.001-0.0005 in
(0.025 -0.125 mm)

Used extensively as
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bags for packaging food products and other merchandise,
as textile products, and a host of other uses.
Important characteristics of the materials produced and
used as films include:
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Low density,
high degree of flexibility,
high tensile and tear strengths,
resistance attack by moisture and other chemicals,
low permeability to some gases, especially water vapor.

Some of the polymers that meet these criteria and are
manufactured in film form are:
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polyethylene,
polypropylene,
cellophane, and
cellulose etate.
There are several forming methods:

simply extruded through a thin die slit followed by a rolling
operation that serves to reduce thickness and improve strength.

Blown moulding

continuous tubing is extruded through an annular die; and
maintaining a controlled positive gas pressure inside the
tube,


wall thickness may be continuously reduced( to produce a
thin cylindrical film, which may be cut and laid flat.
Some of the newer films  produce using co extrusion that is,
multi layers of more than one polymer type are extruded
simultaneously.
Foams

Very porous plastic materials  produced in a
process called foaming

Both thermoplastic and thermosetting materials
may be foamed by  including in the batch a
blowing agent


upon heating decomposes with the liberation of a
gas.

gas bubbles are generated throughout the now-fluid
mass remain as pores up cooling and give rise to
a sponge-like structure.
The same effect is produced bubbling an inert
gas through a material while it is in a molten
state.
Some of commonly foamed polymers are :

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polyurethane,
rubber,
polystyrene, and
polyvinyl chloride.
Foams are commonly used as:

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cushions in automobiles and furniture
in packaging and
thermal insulation.
Example of the exams question

Discuss two of the various applications of
polymeric materials.

What are the polymer characteristic to
produced a film?