To make a polyurethane, one reacts a polyol with a diisocyanate. A number of additional ingredients are required to achieve the desired properties in a polyurethane compound or coating. These additional ingredients are typically blended with the polyol to form what we call a polyol resin blend. These ingredients may include catalysts, surfactants, colorants (pigments or dyes), and flame-retardants.
Customers who purchase UPS polyurethane cable systems receive a two-part package, consisting of a diisocyanate and a polyol resin blend, when mixed together forms a flexible or rigid compound..
In physics, the term dielectric strength has the following meanings:
Of an insulating material, the maximum electric field strength that it can withstand intrinsically without breaking down, i.e., without experiencing failure of its insulating properties.
For a given configuration of dielectric material and electrodes, the minimum electric field that produces breakdown.
The maximum electric stress the dielectric material can withstand without breakdown.
The theoretical dielectric strength of a material is an intrinsic property of the bulk material and is dependent on the configuration of the material or the electrodes with which the field is applied. At breakdown, the electric field frees bound electrons.
If the applied electric field is sufficiently high, free electrons from Background radiation may become accelerated to velocities that can liberate additional electrons during collisions with neutral atoms or molecules in a process called avalanche breakdown.
Breakdown occurs quite abruptly (typically in nanoseconds)., resulting in the formation of an electrically conductive path and a disruptive discharge through the material.
For solid materials, a breakdown event severely degrades, or even destroys, its insulating capability.
Factors affecting dielectric strength
- It increases with the increase in thickness of the specimen. (Directly proportional)
- It decreases with the increase in operating temperature. (Inversely proportional)
- It decreases with the increase in frequency. (Inversely proportional)
- It decreases with the increase in humidity. (Inversely proportional)
For UPS compounds for cable, insulators and sealing, refer CABLE COMPOUNDS
A polyurethane (PUR and PU) is any polymer composed of a chain of organic units joined by carbamate (urethane) links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer (with at least two isocyanate functional groups) with another monomer (with at least two hydroxyl or alcohol groups) in the presence of a catalyst.
Polyurethanes are applied to the manufacture of electrical potting compounds; electrical cable coffins and joints; high performance adhesives; surface coatings and surface sealants; flexible, high-resilience foam seating; rigid foam insulation panels; microcellular foam seals and gaskets; durable elastomeric wheels and tires; automotive suspension bushings; synthetic fibers (e.g. Spandex); carpet underlay; and hard-plastic parts (i.e. for electronic instruments).
Polyurethane is an incredibly resilient, flexible, and durable manufactured material. Polyurethane is a unique material that offers the elasticity of rubber combined with the toughness and durability of metal. Because urethane is available in a very broad hardness range (soft & flexible to hard & rigid), it allows the engineer to replace rubber, plastic and metal with the ultimate in abrasion resistance and physical properties.
Urethanes have better abrasion and tear resistance than rubbers, while offering higher load bearing capacity.
Compared to plastics, urethanes offer superior impact resistance, while offering excellent wear properties and elastic memory.
For UPS Polyurethane products, refer CABLE COMPOUNDS
Epoxy is a copolymer; that is, it is formed from two different chemicals. These are referred to as the “resin” and the “hardener”. The resin consists of monomers or short chain polymers with an epoxide group at either end. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A, though the latter may be replaced by similar chemicals.
The hardener consists of polyamine monomers, for example Triethylenetetramine (TETA). When these compounds are mixed together, the amine groups react with the epoxide groups to form a covalent bond. Each NH group can react with an eproxide group, so that the resulting polymer is heavily crosslinked, and is thus rigid and strong.[1][2]
The process of polymerization is called “curing”, and can be controlled through temperature, choice of resin and hardener compounds, and the ratio of said compounds; the process can take minutes to hours. Some formulations benefit from heating during the cure period, whereas others simply require time, and ambient temperatures.
For Eproxy sealing and repair of concrete, refer UPS Thermo-Screed under COATINGS
High performance elastomers made with polyols can be used in a wide range of industries.
Polyols can form the soft segment of polyurethane, copolymer polyester and copolymer polyamide elastomers.
Elastomers can also be made by low pressure processes (casting or compression moulding) by filling a mould before the polymer viscosity increases from the curing reaction.
PROPERTIES
The composition of polyurethane elastomers can be formulated to produce hard to soft flexible materials.
UPS polyurethane elastomers are generally formulated from (MDI)
Description of chemical and product names refer Glossary