class23
TRANSCRIPT
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Shaping Processes of Polymer
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ElastomersIt contains long chain molecules that are cross linked. They owe their impressive elastic properties to combination of two features:(i) Long molecule tightly kinked when unstretched(ii) Degree of cross‐linking is substantially below that of thermosets
Curing is required to effect cross –linking in the elastomers. The term curing is known as VULCANIZATION involving the formation of chemical cross‐linking of polymer chains .
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Elastomers
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• ViscosityViscosity is defined as resistance to fluid flowMeasure of internal friction
• ViscoelasticityCombination of viscosity and elasticityStrain gradually increases under applied stress and also decays gradually whenthe stress is removed
Properties of polymer melts
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Elastomers
Natural Rubber ‐High molecular weight of ISOPRENE (C5H8)n‐ Sticky in hot weather‐Brittle in cold weather
VULCANIZATION leads to improvement of the property‐ High tensile strength‐Resilience‐Tear strength‐Resistance to wear and tear
Synthetic Rubber‐STYRENE –BUTADINE rubber : (C8H6)n(C4H6)m‐Predominant raw material is PETROLIUM
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Extrusion
Normal Extrusion
Polymer Extrusion
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Extruded Products
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Extruded Product
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Blown Film Extrusion
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Polymer Fibre: Melt Spinning
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Injection Moulding
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Injection Moulding
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Injection Moulding
Screw type
Plunger type
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Compression Moulding
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Compression Moulded Products
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Blow Moulding
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Stretch Blow Moulding
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Rotational Blow Moulding
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Rotational Blow Moulding
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Rotational Blow Moulding
Mobile Phone Shells
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Thermoforming
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Thermoforming
Semiconductor, consumer electronics and electrical, data storage, telecommunications, and medical industries.
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Polymer Sheet
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Chill Rolling
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Transfer Moulding
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Polymer Foams
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Polymer Foaming