THERMOFORMING

THERMOFORMING

Thermoforming is the process of heating a
plastic material in sheet form to its particular
processing temperature and forming the hot and
flexible material against the contours of a mold
by mechanical means (e.g., tools, plugs, solid
molds, etc.) or pneumatic means (e.g., differentials
in air pressure created by pulling a vacuum
or using the pressures of compressed air).
When held to the shape of the mold and allowed
to cool, the plastic retains the shape and
detail of the mold. Because softening by heat
and curing by the removal of heat are involved,
the technique is applicable only to thermoplastic
materials and not to thermosets.
Advantages of thermoforming over most
other methods of processing plastics include
lower tooling and machinery costs, high output
rates, the ability to use predecorated plastic
sheet, and good-quality physical properties in
finished parts.
Its disadvantages include the need to begin
with sheet or film rather than less costly basic
resins, trimming material used to clamp sheet
for forming, and the problem of trim scrap reclamation.

ROTATIONAL MOLDING

Rotational molding

Rotational molding (also popularly known as
rotomolding) is best suited for large, hollow
products requiring stress-free strength, complicated
curves, a good finish, a variety of colors,
a comparatively short (or very long) production
run, and uniform wall thickness. It has been
used for products such as fuel tanks, furniture,
tilt trucks, industrial containers, storage tanks,
portable outhouses, modular bathrooms, telephone
booths, boat hulls, garbage cans, light
andRotational molding offers a number of advantages

1.Virtually unlimited design possibilities(parts as

small as a golf ball to a 22,500-gallon agricultural tank).

2.Relatively low machinery cost.

3. Low tooling costs.
4. Economical prototyping

5 . Strong outside comers in virtually stress-
6. Part finish from matte to high gloss.
7, Simultaneous processing of multiple
8. Simultaneous processing of different
9. Quick mold changes.
10. Possibility of molding in metal inserts.
11. Molded-in multicolor graphics.
12. Multilayer molding for chemical resis-
13. Double-walled parts molding for addi-
14. Possibility of minor undercuts.

MASTICATION AND MIXING

MASTICATION AND MIXING

Rubber Processing is a general term which includes all the operations which are carried out on the rubber and which alter its physical shape or chemical composition.
The raw polymer, natural or synthetic can be softened either by mechanical work, termed action, by heat or by chemicals known as peptisers. The increase of plasticity or decrease of viscosity brought about by mastication and peptisers is permanent; by heat it may be permanent or temporary, depending on the nature of the polymer. When the rubber contains all the ingredients needed it is known as a compound or preferably a mix. If some ingredients have been withheld deliberately, the partially completed compound becomes a master batch. The master batch is converted to the compound by the addition of the withheld ingredients, which are usually the vulcanising or curing ingredients.

POLYMER BLEND

POLYMER BLEND

Polymer blend refer to intimate mixture of two monomers of two or more polymers. The individual polymers may be melt mixed, solution blended and co-precipitated, or lattices may be blended and coagulated before final processing.
Blending of polymers is carried out
1. To reduce the cost of expensive engineering thermoplastic.
2. To increase the process ability of a high temperature heat sensitive thermoplastic
3. To improve the impact strength of a brittle polymer
4. To expand temperature range of applications of a polymer

BLOWING AGENT

BLOWING AGENT

Blowing agent are substances stable at room temperature and decomposes at high temperature by liberating gas.They are classified as follows
1-organic blowing agent
2-inorganic blowing agent
A good blowing agent must be filled following requirement
- Must contain large amount of releasing gas
-Must be non toxic 
-Should not produce bad smell 
-Should disperse well in rubber
-Should not influences vulcanization or Aging properties

CARBONBLACK

CARBON BLACK

Among the reinforcing fillers used in rubber industry, a lion's share is constituted by different types of carbon blacks. They are essentially elemental carbon prepared by converting liquid or gaseous hydrocarbons into elemental carbon by partial combustion or thermal decomposition. Depending on the process adopted for the preparation, carbon blacks and lampblack. The furnance blacks, channel blacks and lamp blacks. The furnace blacks are produced by incomplete combustion of natural gas or heavy aromatic residue oils from the petroleum industries, in refractory lined steel furnaces and separating the carbon formed by means of cyclones and filter bags. Finally, they are pelleted and packed, In the thermal process, natural gas or oil is thermally decomposed at about 1300°C in the absence of free air, in cylindrical furnaces filled with an open checker work of slice bricks. The channel blacks are produced by feeding the natural gas or oil into thousands of small burner tips where the small flames inpinge either on to a large rotating drum or on to reciprocating channel irons. The black deposited is scraped out and collected. Lamp black is made by burning oil and allowing the black formed to settle out by gravity in a series of chambers.

EXTENDERS

Extenders

These are substances which are added to rubber compounds in lage quantities so that the cost of the compound can be reduced, without seriously affecting the final properties. Important among the commercially used extenders are the following.