Polyurethane

Introduction

Polyurethane (PUR and PU) is a polymer composed of a chain of organic units joined by carbamate (urethane) links.

Most of the polyurethanes are thermosetting polymers that they don't melt when heated, but thermoplastic polymers are also available.

Polyurethanes are used in the manufacture of nonflexible, high-resilience foam seating; microcellular foam seals and gaskets; durable elastomeric wheels and tires (such as roller coaster, escalator and skateboard wheels);;; high performance adhesives; surface coatings and surface sealants; synthetic fibers ; hard-plastic parts (e.g., for electronic instruments); and hoses.

Preparation Polyurethane polymers are traditionally and most

commonly formed by reacting a di- or polyisocyanate with a polyol. 

Physical properties

Hardness Tensile strength Compression strength Impact resistance Abrasion resistance  Tear strength

Applications

When scientists discovered that polyurethanes could be made into fine threads, they were combined with nylon to make more lightweight, stretchable garments.

 The most common use for polyurethanes in major appliances is rigid foams for refrigerator and freezer thermal insulation systems.

The good thermal insulating properties of rigid polyurethane foams result from the combination of a fine, closed-cell foam structure and cell gases that resist heat transfer.

Polyurethanes play a major role in modern materials, such as composite wood.

Polyurethanes based binders are used in composite wood products to permanently glue organic materials into oriented strand board, medium-density fiberboard, long-strand lumber, laminated-veneer lumber.

Non-foam polyurethanes are frequently used in the electrical and electronics industries to encapsulate, seal and insulate fragile, pressure-sensitive, microelectronic components, underwater cables and printed circuit boards. Which are oftenly referred as “potting compounds”.

Polyurethane, mostly in the form of flexible foam, is one of the most popular materials used in home furnishings such as furniture, bedding and carpet underlay.

 As a cushioning material for upholstered furniture, flexible polyurethane foam works to make furniture more durable, comfortable and supportive.

Polyurethane epoxy resins seal boat hulls from water, weather, corrosion and elements that increase drag, affect hydrodynamics and reduce durability. 

Polyurethane packaging foam is widely used to safely protect and transport many items, such as electronic and medical diagnostic equipment, delicate glassware and large industrial parts.

Biodegradation Two species of the Ecuadorian fungus Pestalotiopsis

are capable of biodegrading Polyurethane in aerobic and anaerobic conditions

Polyester type polyurethanes are more easily biodegraded by fungus than polyether type.

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