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+---- Thread: Polymer Processing (/showthread.php?tid=57626)
Polymer Processing - ashish - 10-04-2017
Polymer Processing
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There are many processes for plastics. Selection of
a process depends on many factors including:
- Quantity and production rate
- Dimensional accuracy and surface finish
- Form and detail of the product
- Nature of material
- Size of final product
In general, plastics processes have three phases:
1. Heating - To soften or melt the plastic
2. Shaping / Forming - Under constraint of some kind
3. Cooling - So that it retains its shape
Thermoplastics start as regular pellets or
granules and can be remelted.
Thermosetting materials start as liquids/syrups,
often called "resins", as powders or partially
cured products ("preforms") which need heat for
the shaping phase. The shaping is accompanied
by a chemical reaction, which means that the
material does not soften on reheating. The
reaction may be exothermic (giving heat out), in
which case cooling is required.
-Food related applications
such as Meat Trays,
Microwave & Deep Freeze
Containers, Ice Cream and
Margarine Tubs, Snack
Tubs, Bakery and
Patisserie packaging,
Sandwich Packs and
Vending Drink Cups
-Manufacturing Collation
trays, Blister packaging
and Point of Sale display
trays.
Advantages of compression molding (compared
with injection molding)
-Low scrap arisings
-Low orientation in the moldings
-well distributed fibrous fillers
-low residual stress product
-retained mechanical and electrical properties
-low mold maintenance
-low capital and tooling costs
Disadvantages when compared with compression
-Give unwelcome orientation in the product
-Increase wear and maintenance costs
-Tooling is more complex and more expensive
-Runners owe scrap