Seminar Topics & Project Ideas On Computer Science Electronics Electrical Mechanical Engineering Civil MBA Medicine Nursing Science Physics Mathematics Chemistry ppt pdf doc presentation downloads and Abstract

Polymer Processing
[attachment=17141]

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

Polymer Processing

[attachment=31328]

Back to the Beginning

Early in the course, we tried several ways to categorize polymers, such as condensation vs. addition, etc. From a processing point of view, the main classes are:

Thermoplastic: the resin is heated to make a viscous liquid and then processed into a usable object without much additional chemistry. Example: polyethylene, polystyrene.

Thermoset: upon heating, further reaction occurs to make molecules “set up” into a useful product. Chemistry occurs, so these are sometimes called “reactive polymers”. The resin may be provided as either small molecules or “prepregs”—partially polymerized stuff. Example: polyurethanes, phenol-formaldehyde, melamine-formaldehyde, epoxy glue.