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Polymers Engineering Fundamentals
PE-2102
Lecture 19-21
Polymer Processing into product
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Polymer Compounding
• Few polymers are used in pure form since they often require chemical
modification to achieve optimum properties and promote non-inherent
performance.
• The process of adding essential ingredients to polymers to achieve these results
is termed compounding.
• Compounds must behave as a system, consisting of the base polymer and
additives, selected to achieve a set of final properties.
• During compounding, mixing must occur at two fundamental levels; dispersive
mixing and distributive mixing.
Polymer Compounding
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Polymer Compounding
Polymer Blends
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Polymer Blends
• A polymer blend, or polymer mixture, is a member of a
class of materials analogous to metal alloys, in which at least
two polymers are blended together to create a new material
with different physical properties.
• Polymer blends are physical mixtures of two or more polymers
with/without any chemical bonding between them.
• The objective of polymer blending is a practical one of
achieving commercially viable products through either unique
properties or lower cost than some other means might provide.
• When two or more polymers are mixed, the phase structure of
the resulting material can be either miscible or immiscible.
Polymer Blends
Polymer Blend is a combination of two or more polymers, which are mixed
at molecular scale to obtain a single phase.
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Polymer Blends
Examples of Polymer Miscible blends
Examples of Polymer Immiscible blends
Polymer Blends
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Compatibilizers & Blend Morphology
Polymer Blends
• Plastic materials have a wide application range
- Automotive industry
- Electronic sector
- Packaging industry
- Manufacturing of consumer goods
• All these industries are attributed to the incorporation of additives
- Additives are added into
❑Virgin
❑ Processed/Recycled polymers
▪ Polymer industry is impossible without additives
Additives
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Any Substance that is added generally in small concentration to polymers
in order to :
• Improve their properties
• Facilitate processing
• Change the physical, chemical or electrical properties of end products.
• Reduce the cost
Additives
Requirements of Additives
• Effectiveness in their function
• Stable under processing conditions
• Stable under service conditions
• Economic
• Compatibility with Polymer Matrix
– At molecular level
• Neither Volatile nor extrude to the surface
• Neither bleed nor bloom
• Must have low vapour pressure at high temperature
• Non-Hazardous, not impart taste & odour
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Functions of Additives
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Additives in Polymer Industry
• Additives in plastics provide the means to overcome
- Processing problems
- Property performance limitations
- Restricted environmental stability
• Additives can be main ingredients for plastics, but they play a crucial role in
other materials such as
- Coatings
- Lacquers
- Paints
- Printing inks
- Photographic films
- Papers
Additives in Plastics
• Plastic additives are a diverse group of specialty chemicals that are
either incorporated into the plastic
- Before processing
- During processing
- Applied to the surface of the product when the processing is completed.
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Additives in Rubbers
• Rubber is a thermosetting polymer which requires curing (peroxides) in
a reaction. The reaction must be controlled by
- Initiators (e.g. sulphur compounds)
- Accelerators (e.g. aniline)
- Retarders, etc.
• The whole compounding and moulding process is to be controlled by
- Antioxidants
- Antiscorch agents to prevent decomposition
• Plasticizers are added to improve processability
• Adhesion promoters may be added to improve the bonding with
reinforcement
Additives in Rubbers
• To protect cured rubber products during lifetime other additives are
added to provide the resistance from
- Ozone
- Ultraviolet
- Internal heat build-up as the compound is stressed
• Other vital components of a final rubber compound are
- Fillers as reinforcing agents
- Pigments
- Extenders (Low-cost fillers)
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Fillers
• Fillers are used to extend a material and to reduce its
cost
• Few inexpensive fillers are still being used purely for
filling purpose such as
- Walnut shells
- Fly ash
- Wood flour
- Wood cellulose
• • Basic low-performance materials such as clays and
chalks are still used very widely
• Modern market demands that fillers should give some
additional value such as improvement in the mechanical
properties beside extending
Function of Fillers
• The basic purpose is to fill a compound:
- Increase bulk at low cost
- To do this the mix must be homogenous
- Should have good filler-polymer adhesion
- The filler also improves the physical and mechanical properties of
polymers
• By using the low-density filler as compared to polymer specific weight of
polymer can be reduced.
• Adhesion properties are influenced by
• Filler geometry
• Surface texture
- Adhesion can be improved by surface treatment
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Classification of Fillers
Fillers Materials/Characteristics
• Fillers that have a reinforcing effect are
- Clays
- Calcium carbonates
- Talc
- Silicates
- Pigments such as
• Titanium dioxide
• Carbon black
• Fillers that offer good properties are
- Glass
- Ceramic microspheres
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Fillers For Commercial Polymer
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