Elastomers 02/13/20 1 Elastomers Definition- materials capable of
Elastomers 02/13/20 1 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 02/13/20 2
6 3 2 Elastomers have properties that can be explained by a model that shares characteristics of thermosets and thermoplastics -have all of the domains shown below 02/13/20 5
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 02/13/20 6 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). 02/13/20 7 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. 02/13/20 8 Intermolecular Bonds in Polymers
02/13/20 9 The more nucleophilic primary and secondary amines react much more vigorously with isocyanates. In this reaction, ureas are formed (11). 02/13/20 10
Important Building Blocks for Polyurethanes- Isocyanates OCN CH2 MDI or aromatic polyisocyanate NCO CH3 NCO OCN
John Stuart Mill (author of Utilitarianism) writes that "the Greatest Happiness Principle" is:. An existence exempt as far as possible from pain, and as rich as possible in enjoyments, both in point of quantity and quality; the test of quality,...
family consists of a married couple and their children = extended . family . h as parents, their son and his wife and children. = The . joint family . M ay contain 3 or more generations within one household.
mini dipper doodle bar w/ fruit . NEW goldfish colors w/ fruit . sunflower seeds w/ fruit . salsa fresca rumbles w/ fruit . cheddar goldfish crackers . educational snacks w/ fruit . cinnamon skeeters w/ fruit . goldfish pretzels...
INSERTING AND DELETING CELLS. After creating a worksheet, you might decide to add more data or delete unnecessary data. Although you can insert or delete entire rows and columns, sometimes you just need to work with a single cell or...
Positional Diagnosis. If the rotation is found in seated flexion, it is an ERS- the segment is stuck in Extension, Rotation, and Sidebending. The dysfunctional facet is on the side that the vertebra has rotated towards
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