PET (Polyethylene terephthalate)
Melamine (Melamine-formaldehyde)
Polyethylene terephthalate (PET or PETE) is a strong, rigid synthetic fiber and a member of the polyester family of resin and polymers. PET is cut into fibers for permanent-press clothing and blown into disposable beverage bottles.
PET is formed by polymerizofing ethylene glycol and terephthalic acid. Ethylene glycol is a colorless liquidobact from ethylene, and terphthalic acid is a crystalline solid derived from xylene. In chemical terms, ethylene glycol is a diol, an alcohol with a molecular structure consisting of two hydroxyl (OH) groups, and teripathic acid is a dicarboxylic aromatic acid, an acid with a molecular structure containing a large six-sided carbon. Is (or aromatic) ring and two carboxyl (CO2H) groups. Under the influence of heat and catalysts, the hydroxyl and carboxyl groups react to form ester (CO – O) groups, which work together in long-chain polymers to form chemical links that bind together in multiple PET units. Water is also produced as a by-product.
In this semicolon, PET is made into a high-strength textile fiber marketed under the trademarked name Dacron by the American company Invista. The hardness of PET fibers makes them highly resistant to deformation, so they provide excellent resistance to wrinkles in clothing.
PET is also made into insulated fabric and fiber filling for furniture and pillows. When made in very fine filaments, it is used in artificial silk, and in large-diameter filaments it is used in carpets. Industrial applications of PET include automobile tirevern, conveyor belts and drive belts, reinforcements for fire hoses and garden hoses, seat belts (an application in which it has been largely replaced by nylon), drains to stabilize drains, culverts And stabilizing railing beds. , And nonwoven for use as diaper tops and disposable medical clothing. PET is the most important of syntheticfibres in weight and value produced.
At slightly higher molecular weights, PET is made into a high-strength plastic that can be shaped by all the usual methods employed with other thermoplastics. PET films (often sold under the trademarks Mylar and Melinex) are manufactured by extrusion. Molten PET can be blown into transparent containers of high strength and hardness which are also impermeable to gas and liquid. In this form, PET is widely used for low-temperature processed food in carbonated-beverage bottles and jars. The low softening temperature of PET - about 70 ° C (160 ° F) - prevents it from being used as a container for hot foods.
PET is the most widely recycled plastic. However, in the United States, only 20 percent of the PET material is recycled. PET bottles and containers are usually melted and cut into fibers for fibrophils or carpets.
Was prepared by Dixon during a study of phthalic acid initiated in 1940. Due to wartime restrictions, the patent specifications of the new material were not immediately published. Production by Imperial Chemical of its Terlene-brand PET fiber did not begin until 1954. Meanwhile, by 1945, DuPont had developed a practical preparation process independently of terephthalic acid, and in 1953 the company began producing drone fibers. In the 1970s, better stretch-molding processes were devised that allowed PET to be made into durable crystal-clear beverage bottles - an application that soon became important for fiber production.
Melamine formaldehyde resins, due to their greater efficiency, have significantly different properties from urea formaldehyde resins, better chemical resistance, better color retention at elevated temperatures, better external durability, and shorter baking schedules in combination with hydroxy resins. It should be noted that their reactivity may be lower than that of stick causes. They are also more expensive. UF resins are highly satisfactory, however, for general-purpose industrial finishes, and are largely treated with acid-catalyzed room-temperature treated wood finishes. Benzoyangamine resins are used for container coatings.
While the strong acid catalysts of mixtures containing UF resin proceed satisfactorily, with MF resins it may be self-reacting rather than co-reacting. Consequently treated with MF resin blends for low bakes or room temperatures, where high acid catalyst levels may be indispensable with alkade resins, for example, sometimes it is necessary to prepare a prefabricated form with MF resin.
Alkylated melamine resins will be selected by their reactivity where high reactivity can mean high viscosity and rapid curing, but low mineral spirit tolerance and such poor compatibility with alkade resins. While the commonly used resins are butyl, other alcohols are used. Secondary and tertiary alcohol-modified resins typically recover at a slower rate, but can result in harder films.
Special mention should be made of hexamethoxymethyl melamine (HMMM) resins, which have secured their own location in the coating. Although available as pure materials as a waxy solid, they are most widely used in slightly modified or condensed form when they are more readily accumulated liquids. They are soluble in water and are in all common organic solvents, except for aliphatic hydrocarbons, and are compatible with practically all resin media. They are usually available in 100% solids. They are significantly more stable in contrast to other alkylated MFs. Their preparation as other alkylated MFs requires a higher alcohol during the reaction to ensure complete reaction; Preparation problems include the removal of methanol containing distillates.
The attaining of better adhesion and ductility can be attributed to a lower tendency of self-condensation and a more satisfactory film structure. However, for the best properties there is a fast optimum for the amount of HMMM required in any composition. The resin finds special use in highly solid and water-borne compositions. It should be noted that HMMM is also more effective in that only 18% of solids are lost on stoving compared to 29% with a butylated counterpart.
HMMM has the disadvantage of increasing surface tension in paint, resulting in application and film defects, and mixed methyl / butyl ether resins overcome these defects. Adequate water misunderstanding is maintained when the methyl / butyl equilibrium is correct, while hydrolytic stability and water resistance are improved. These mixed ether resins are finding increasing applications.
0 Comments