Introduction
Polyurethane (PUR and PU) is any polymer composed of a chain of organic units linked via carbamate (urethane) links. Polyurethane polymers are shaped through step-growth polymerization, through reacting a monomer (by at least two isocyanate functional groups) through another monomer (by at least 2 hydroxyl or alcohol groups) in the presence of a catalyst.
n O=C=N-R-N=C=O + n HO-R1-OH [ C-NH-R-NH-C-O-R1- O ]n
diisocyanate diol O O
Route to the synthesis of polyurethane from diisocyanates
Properties of Polyurethane
Polyurethane is a unique substance that presents the elasticity of rubber joined through the toughness and durability of metal. Such polymers have elevated strength, good resistance to gas, oil, and aromatic hydrocarbons, elevated abrasion resistance and excellent resistance to oxygen and ozone, but are susceptible to microbial attack. Since urethane is available in an extremely broad hardness range (eraser-soft to bowling-ball-hard), it permits the engineer to replace rubber, plastic and metal through the ultimate in abrasion resistance and physical properties.
Advantages of Polyurethane
Abrasion resistant - Parts made of polyurethane will frequently outwear other substances via a margin of 5 to 50/one when severe abrasion is a factor. It has been proven to be greatly superior to rubber plastics and metal in many applications.
Tear resistant - Tear strength ranges between 500-100 Ibs./linear inch that is far superior to rubbers. As a consequence, urethane is frequently utilized as drive belts, diaphragms, roll covers, cutting pads, gaskets and chute liners. Oil and solvent resistant - Polyurethane has excellent resistance to oils, solvents, fats, greases and gasoline.
Excellent noise abatement properties - The solid urethanes are now being utilized as gears in products where engineers wish sound reduction. The soft urethanes are utilized to replace rubbers for progressed sound/vibration dampening. Load bearing capacity - Polyurethane has a higher load-bearing capacity than any conventional rubber. Since of this characteristic, it is an ideal substance for load wheels, heavy duty couplings, metal-forming pads, shock pads, growth joints and machine mounts.
Weather resistant - Polyurethane has outstanding resistance to oxygen, ozone, sunlight and common weather situations. Flex-Life - Most formulations offer tremendously elevated flex-life and can be expected to outlast other elastomer substances where this feature is a significant requirement. Dust boots, bellows, diaphragms, belts, couplings and similar products are made from urethane for this reason.
Electrical properties - Polyurethane have excellent electrical insulating properties and are used successfully in many moulded wire and cable harness assemblies. Heat and cold resistant - Continuous use above 225°F is not recommended nor is urethane recommended in hot water over 175°F. At low temperatures, polyurethane will remain flexible down to -90°F. Gradual stiffening will take place at 0°F, but won't become pronounced until much lower temperatures are attained.
Applications of Polymers
In metal forming pads, belts, wear strips, bumpers, gears, bellows, machinery mounts, cutting surfaces, sound-dampening pads, chute and hopper liners, prototype machined parts, gaskets, seals, rollers, roller covers, sandblast curtains, diaphragms.
The table below illustrates how polyurethanes are used (US data from 2004)
Table: Usage per application of polymer
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with an expert at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online chemistry tutoring. Chat with us or submit request at [email protected]
TutorsGlobe.com Chemical Kinetic-Collision Theory-Activation Energy Assignment Help-Homework Help by Online Access Chemistry Tutors
History of Ethology tutorial all along with the key concepts of Differences and similarities with comparative psychology, Scala naturae and Lamarck's theories, Theory of evolution by natural selection, Mating and supremacy
www.tutorsglobe.com offers Material Variances homework help, assignment help, case study, writing homework help, online tutoring assistance by accounting tutors.
theory and lecture notes of varieties of finite state machines all along with the key concepts of varieties of finite state machines, finite state machines, deterministic finite automaton, non-deterministic finite automaton. tutorsglobe offers homework help, assignment help and tutor’s assistance on varieties of finite state machines.
Emotion in Animals tutorial all along with the key concepts of Evidences, Various views on emotion in animals, Jeffrey Moussaieff Masson view and Illustrations of emotion in animal
Theory and lecture notes of Understanding the Growth Model all along with the key concepts of understanding the growth model, growing economy, Growth of Capital per Worker, Capital-Output Ratio, Steady State Growth Path. Tutorsglobe offers assignment help and tutor’s assistance on Understanding the Growth Model.
tutorsglobe.com factors included in brooding assignment help-homework help by online poultry tutors
Steel bands are laced on the front and back ends of the coils. Steel bands are up on the armature in a dissimilar way than in the cord bands.
Relativistic Energy tutorial all along with the key concepts of Relativistic Work and Energy, Mass-Energy Equivalence, Transformation of Momentum and Energy
Principles of Mass Spectrometry tutorial all along with the key concepts of The Mass Spectrometer, Molecular Ion, The Mass Spectrum and EI Mass Spectrum of Bromododecane
we assure impeccable and plagiarism free environmental philosophy assignment help service that ensure nothing but a++ grades!
The concepts of financial accounting - Separate Entity, Double Entry, Money Measurement Concept, Going Concern Concept, Matching Concept.
www.tutorsglobe.com offers quantity variances homework help, quantity variances assignment help, answering questions to accounting for quantity variances, online tutoring by accounting tutors.
Transformation of alkenes tutorial all along with the key concepts of Conversion of alkenes to Epoxides, Conversion of alkenes to syn-1,2-diols, hydroxylation, Ozonolysis of alkenes and oxidative cleavage
Reactions of Aldehydes and Ketones tutorial all along with the key concepts of Carbonyl Carbon consists of a nucleophilic site, Nucleophilic Addition, Condensation Reaction, Reactions of Aldehydes and Ketones, Cannizzaro Reaction, Uses of Aldehydes and Ketones
1956561
Questions Asked
3689
Tutors
1450597
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!