10. Extrusion Molding
Production of thermoplastic material into finished articles such as sheets, films and rod.
Done by using machine Extruders.
Raw materials in the form if thermoplastic pellets, granules, or powder, placed between the screw and extruder barrel.(feed zone)
The barrel is equipped with a screw . As screw rotates , the pellets are dragged forward and compressed (transition or compaction zone)
Heaters around the extruder’s barrels heats the pellets and liquefies them. (molten plastic) (metering zone).
Screw has 3-Zone
Feed zone
Melt or transition or compaction zone
Metering zone.

13. The screw depth is constant in both the feed and metering zones and varies in transition zone to begin generating pressure and to force the pellets to begin to melt.
Length of each zone in screws design varies according to type of plastic being processed. Example LDPE- melt gradually ,the overall length of the screw is roughly divided into three zone.
Nylon- have sharp melting point ,screw designed such that transition zone only consist of one turn of the screw flight.
PVC – Prone to thermal degradation and melt very gradually may be processed with screw whose entire length is composed of a compression zone.

15. Compression Molding Thermoplastic are molded by this method.
Known quantity of polymer (resin) which may in any form (powder or pellet) is placed in the lower portion of mold cavity.
IT is heated electrically or by passing steam to soften the material.
The mold cavity gets filled with fluidized plastic.
The melt is compressed by the upper mold.
compression mass gets cured and hardened and is open after cooling and the article removed.

17. Advantages and Applications
Low cost
Very low loss of materials
God surface finish
Fast setup time
Electrical parts
Cooker Handles
Electronic devices
Appliance housing and large container.

18. The surfaces may be metals , glasses, plastics, papers etc.
Adhesives
Adhesive is a polymeric material used to bind together two or more similar/dissimilar surfaces, so that the resulting material can be used as a single piece. Ex Fevicol,
The surfaces may be metals , glasses, plastics, papers etc.
-Process of binding two surface is known as bonding.
-surfaces joined are called Adherents.
Engineering Chemistry
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19. Classification of adhesives on basis of availability and composition of principal components
Natural
Adhesives which exist in nature. They have low bond strength
e.g. Gum, Glue, starch etc
Synthetic
Adhesives which do not exist in nature but synthesize in laboratory. They have high bond strength
e.g. Phenol-formaldehyde resin and urea-formaldehyde resin etc

20. Classification of adhesives on basis of Mechanism of adhesion
Solvent responsive
Heat sealing
Pressure sensitive

21. Classification of Adhesives:
Composition of principal components:
Natural ( gum, glue, starch, natural rubber) –low bond strength
Synthetic( PF, UF, Epoxy resins, etc.)-Superior Strength
Classification based on Mechanism of adhesion
Solvent responsive adhesives:
- Flow of the adhesives during application and adherence during bonding is caused by volatile liquid carrier. These adhesives are used in the form of solution ,pastes, gels and dispersions. Ex. Vegetable gums, starch, natural rubber.

22. Heat sealing adhesives: These adhesives solid at room temperature ,but they become sticky and undergoes fusion by the application heat and then they applied on the bonding surfaces. These adhesives are tougher , flexible, resistance to moisture ,solvent and chemicals. Ex. Waxes, cellulose , esters, polyvinyl alcohol, resins etc. Pressure sensitive adhesives: - Used as adhesives tapes, - should be capable of providing instanteous adhesion when applied with light pressure. -they should be capable of being removed from the surface with a very pull if not required. Ex- butyl rubber , neoprene , acrylic polymers , alkyl resins etc.

23. Application 1. epoxy resins used to join glass, metals, wood.
2. Used in Industrial flooring , skid resistance, highways surfacing, patching materials.
3. used as laminating materials in electrical equipments.
4. Molds made from epoxy resins are used in the production of aircraft and automobiles components.
5. Used as matrix in fiber reinforced plastics.

25. Organic Matrix composite (OMC’s) Metal Matrix composite (MMC’s)
Classification of composites on basis of Matrix
Organic Matrix composite (OMC’s)
Metal Matrix composite (MMC’s)
Ceramics Matrix composite (CMC’s)

27. Fiber reinforced composites Laminar composite Particulate composite
Classification of composites on basis of Reinforcement
Fiber reinforced composites
Laminar composite
Particulate composite

30. Uses of FRP - Light weight- used in making aircraft, cars
High strength(graphite epoxy) –used in making bridges
Resistance to corrosion- fiber glass used in making cars and boats.
Elastic in nature – used in car leaf springs.
High strength and insulation – used in making armors.
Fiber glass Used in thermal and sound absorption.
Non conductive nature , ladders made with fiberglass (power line)

32. Nematic phase
It is the most common LC phases. The word nematic comes from the Greek word nema, which means "thread". This term originates from the thread-like topological defects observed in nematics, which are formally called 'disclinations'. The nematic liquid crystal phase is characterized by molecules that have no positional order but tend to point in the same direction. In the following diagram, notice that the molecules point vertically but are arranged with no particular order.

33. Smectic Phases
The word "smectic" is derived from the Greek word for soap i.e. the thick, slippery substance often found at the bottom of a soap dish is actually a type of smectic liquid crystal.
The smectic phases, which are found at lower temperatures than the nematic, form well-defined layers that can slide over one another in a manner similar to that of soap. The smectics are thus positionally ordered along one direction. In the smectic state, the molecules maintain the general orientational order of nematics, but also tend to align themselves in layers or planes. Smectic state is more "solid-like" than the nematic.

34. Smectic A
Smectic C

35. Application
1. LCs used to detect Tumor, since tumor cell are at higher temperature than normal cell, these indicated by color change.
2. Used in electronic industry , a break in circuit increases the temperature , which is detected by change in color of LCs.
3. Used in thermostrips and disposable thermometers to read body temperature.
4. Used in Optical imaging and recording .
5. Used to detect radiation and pollution in atmosphere.
6. LCD screen used in watches ,calculator, laptops, television, sigh board.
7. used in non-destructive testing of materials under stress.
8. low molecular mass LCs used in erasable optical disks and light modulator for color electronic imaging.

36. Uses of Liquid Crystals
Flat screen television
Wristwatches
Laptop screens
Digital clocks
Thermometers
Switchable windows