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EBB 2203 POLYMER ADDITIVES

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Title: EBB 2203 POLYMER ADDITIVES


1
EBB 220/3POLYMER ADDITIVES
  • DR AZURA A.RASHID
  • Room 2.19
  • School of Materials And Mineral Resources
    Engineering,
  • Universiti Sains Malaysia, 14300 Nibong Tebal, P.
    Pinang
  • Malaysia

2
Introduction
  • Most of polymers need to add with specific
    ingredients to obtain desirable properties.
  • Additives were used
  • 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
  • filler materials,
  • Plasticizer
  • stabilizers,
  • colorants
  • flame retardants.

3
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.

4
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
  • extender (large amount 20 pphr)? to make the
    end products cheaper
  • Processing aid (small amount 2-5 pphr)? to make
    the processing easier
  • Modifier ? to modifies some polymeric properties.

5
  • 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.

6
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.

7
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.

8
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 polytetrafluoroethyle
    ne (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.

9
Special purpose additives
10
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.

11
EBB 220/3MISCELLANEOUS APPLICATIONS
  • DR AZURA A.RASHID
  • Room 2.19
  • School of Materials And Mineral Resources
    Engineering,
  • Universiti Sains Malaysia, 14300 Nibong Tebal, P.
    Pinang
  • Malaysia

12
Coating
  • Coating are frequently applied to the surface of
    materials to serve one or more of the following
    function
  • to protect the item from the environment that may
    produce corrosive or deteriorative reactions
  • to improve the item's appearance
  • to provide electrical insulation.

13
  • Many of the ingredients in coating materials are
    polymers ? with majority are organic in origin
  • These organic coatings fall into several
    different classifications
  • paint,
  • varnish,
  • enamel,
  • lacquer, and
  • shellac

14
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.

15
  • 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 is the service temperature
    limitation.
  • Organic polymers maintain their mechanical
    integrity only at relatively low temperatures,
    and strength decreases rapidly with increasing
    temperature.

16
Some categories of adhesives
  • Natural adhesives
  • Adhesives based on vegetable (natural resin),
    food (animal hide and skin), and mineral sources
    (inorganic materials).
  • Synthetic adhesives
  • 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.
  • 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.

17
Adhesives failure
  • Adhesives may fail in one of two ways
  • 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).
  • 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.

18
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
  • 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
  • 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.

19
  • Some of the polymers that meet these criteria and
    are manufactured in film form are
  • 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.

20
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.

21
  • Some of commonly foamed polymers are
  • polyurethane,
  • rubber,
  • polystyrene, and
  • polyvinyl chloride.
  • Foams are commonly used as
  • cushions in automobiles and furniture
  • in packaging and
  • thermal insulation.

22
Example of the exams question
  • Discuss two of the various applications of
    polymeric materials.
  • What are the polymer characteristic to produced a
    film?

23
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