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Term |
Definition |
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UF
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Urea-formaldehyde resin
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UF
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Urea-formaldehyde
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UHM
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Ultra-high-modulus
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UHMW
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Ultra-high molecular weight
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UHMW-HDPE
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Ultra high molecular weight HDPE
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UHMWPE
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Ultra high molecular weight polyethylene
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UL
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Underwriter's Laboratories
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UL Temperature Index
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The maximum temperature below which a material maintains its electrical and mechanical integrity over a reasonable period.
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Ultimate Elongation
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The elongation that the body exhibits before breaking at the maximum amount of force; specified as a percentage of the starting length
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Ultimate Strength
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Term used to describe the maximum unit stress a material will withstand when subjected to an applied load in a compression, tension, or shear test.
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Ultrasonic Sealing
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A film sealing method in which sealing is accomplished through the application of vibratory mechanical pressure at ultrasonic frequencies (20 to 40 kc.). Electrical energy is converted to ultrasonic vibrations through the use of either a magnetostrictive or piezoelectric transdeucer. The vibratory pressures at the film interface in the sealing area develop localized heat losses which melt the plastic surfaces effecting the seal.
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Ultraviolet
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Zone of invisible radiations beyond the violet end of the spectrum of visible radiations. Since UV wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.
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Undercut
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Having a protuberance or indentation that impedes withdrawal from a two-piece, rigid mould. Flexible materials can be ejected intact even with slight undercuts. Any such protuberance or indentation; depends also on design of mould.
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Unicellular
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With foamed plastics, each cell an isolated unit. Equals closed-cell.
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Unidirectional
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Aligned in one direction
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Unit Mould
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A simple mould which comprises only a single cavity without further mould devices to be used for the production of sample containers having a shape which is difficult to blow.
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Unsaturated Compounds
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Any compound having more than one bond between two adjacent atoms, usually carbon atom, and capable of adding other atoms at that point to reduce it to a single bond.
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Unsaturated Polyester
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While this family of plastics goes under the name of "polyesters," they are quite distinct from the polyesters described above. In fact, they are thermosets, and are probably most familiar to the public for their role in fiberglass reinforced plastics. These materials were introduced to military use (i.e., naval craft) in 1942. After World War II, their characteristics proved extremely appealing to such non-military markets as automotive, marine, corrosion-resistant structures, building, electrical applications, and consumers goods such as luggage, fishing poles and cases and housings of every type and description. These thermosetting resins are made by the condensation reaction between difunctional acids and glycols. The resulting polymer is then dissolved in styrene [C6H5CHCH2] or other vinyl unsaturated monomer. The structures of the acids and glycols used and their proportions, especially the ratio of the unsaturated versus the saturated acid, and the type and amount of monomer used, are all tailored for each resin to balance economy, processing characteristics, and performance properties. One common formulation is the reaction of maleic anhydride [(COCH)2O], phthalic anhydride [C6H4(CO)2O], and propylene glycol [CH3CHOHCH2OH]. Both dicyclopentadiene [C10H12] and isophthalic acid [C6H4(COOH)2] can be substituted for phthalic anhydride. Vinyl ester resins are linear reaction products of bisphenol A [(CH3)2C(C6H4OH)2] and epichlorohydrin [CH2OCHCH2Cl] that are terminated with an unsaturated acid such as methacrylic acid [CH2C(CH3)COOH].
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UP
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Unsaturated polyester
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Urea Plastics
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Plastics based on resins made by the condensation of urea an aldehydes.
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What does that mean?!