1. Elastomers
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Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion.
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2. Elastomers
Definition- materials capable of reversible change in length at operating temperatures, that is, once a load is removed the material returns to its original dimensions;
a rubbery compound;
Generally amorphous thermosets with Tg below room temperature to allow full chain mobility- the restoring force in entropic;
referred to as “memory”
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3. Types Natural and synthetic rubber-Thiokol, Buna, Neoprene
Polyurethanes
Silicone-polysiloxanes
Natural proteins-elastin
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4. Mechanical PropertiesF i b r e R g d P l a s t c x E o m S N / 2
Strain L D 1 3 4 5 6 B A

5. Elastomers have properties that can be explained by a model that shares characteristics of thermosets and thermoplastics -have all of the domains shown below
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6. Principles of Polyurethane Chemistry
High molecular weight polymers based isocyanate chemistry
Polyisocyanates have the following general formula:
R-(N=C=O)n, n= 2-4
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7. Addition of Nucleophilic Reactants
The most important reactions of isocyanates is the formation of carbamic acid derivatives (7) by the addition of components with an acidic H-atom (6) across the C=N double bond (1).
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8. OH group-containing compounds (8) are by far the most important reactants for isocyanates. They are added under mild conditions, forming carbamic esters (9). Primary alcohols, secondary alcohols, and phenols show decreasing reactivity in that order.
The trivial name urethane which is used for the compound ethyl carbamate, gave the whole polyurethane chemistry its name: polyisocyanates and polyols form polyurethanes.
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9. Intermolecular Bonds in Polymers
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10. The more nucleophilic primary and secondary amines react much more vigorously with isocyanates. In this reaction, ureas are formed (11).
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11. Important Building Blocks for Polyurethanes- Isocyanates
MDI or aromatic polyisocyanate O C N C H N C O 2 C H 3 C H 3 N C O O C N N C O
TDI-80 N C O 2 % 8 %
H12MDI O C N C H N C O 2
HDI
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12. Polyols

13. Synthetic Scheme of Polyurethanes
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14. Typical Chain-extenders

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16. Polyurethane Structural Model
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17. Schematic Model Domain Sturcture
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18. Hard Segment Interactions affect Mechanical Performance
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23. Effect of Polyurethane MW on Mechanical Properties
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