EBB 2203 POLYMER ADDITIVES

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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

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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.

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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.

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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.

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• 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.

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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.

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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.

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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.

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Special purpose additives
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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.

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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

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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.

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• 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

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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.

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• 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.

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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.

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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.

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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.

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• 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.

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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.
  

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• 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.

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Example of the exams question

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

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