Drying polyester

The glass-transition temperature, T, of dry polyester is approximately 70°C and is slightly reduced ia water. The glass-transitioa temperatures of copolyesters are affected by both the amouat and chemical nature of the comonomer (32,47). Other thermal properties, including heat capacity and thermal conductivity, depend on the state of the polymer and are summarized ia Table 2. 

The batch process consists of adding the requisite amount of NDI to the hot dried polyester contained in a stainless steel beaker and reacting in a heated vessel under vacuum. The reaction is exothermic and the initial fall in temperature caused by adding the solid NDI to the hot polyester is followed by a gradual rise until the reaction is complete when it levels out and eventually falls. This is of the order of 10 min. The beaker can then be removed from the vacuum vessel and the material is ready for the addition... 

Clean rooms have to be wet cleaned with the aid of polyester or microfibre swabs or mops. Polyester is used for light cleaning and disinfecting. The polyester fibres adsorb dirt and if wetted with a disinfectant the disinfectant will be evenly spread out on the surface. Microfibre swabs and mops are used for cleaning only. The microfibres ensure that particles are not only removed from the cleaned surface but are firmly captured within the fibres. Dry polyester swabs or mops are only used for removing wet product or other wet waste. 

As mentioned, the most adopted bioresorbable polymers to synthesize NPs for medical and pharmaceutical applications are polyesters such as PLA, PGA, poly(lactic-co-glycolic acid) (PLG A), and PCL. However, such polymers are generally synthesized in bulk phase via ROP and obtained as solids. Therefore, for producing biodegradable polymeric NPs, physical processes are required that allow for obtaining a stable suspension starting from the dry polyesters. Several methods have been proposed to synthesize NPs by dispersing a preformed polymer, but the most widely adopted methods are emulsification-evaporation and nanoprecipitation (Fig. 12.3) [5,6]. 

The dried polyester polymer is transported to extruders where it is melted, and piunped to spinning packs held in a spin manifold. The spin packs contain spiimeiets with a large number of fine holes through which the melted polymer flows to form filaments. Any contaminants in the polymer are removed by filtration prior to the spinneret. Different spinneret designs enable a wide range of fibre cross-sections to be produced including solid round, hollow and trilobal. 

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

Dry chlorine has a great affinity for absorbing moisture, and wet chlorine is extremely corrosive, attacking most common materials except HasteUoy C, titanium, and tantalum. These metals are protected from attack by the acids formed by chlorine hydrolysis because of surface oxide films on the metal. Tantalum is the preferred constmction material for service with wet and dry chlorine. Wet chlorine gas is handled under pressure using fiberglass-reinforced plastics. Rubber-lined steel is suitable for wet chlorine gas handling up to 100°C. At low pressures and low temperatures PVC, chlorinated PVC, and reinforced polyester resins are also used. Polytetrafluoroethylene (PTFE), poly(vinyhdene fluoride) (PVDE), and... 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

THPC—Amide—PoIy(vinyI bromide) Finish. A flame retardant based on THPC—amide plus poly(vinyl bromide) [25951-54-6] (143) has been reported suitable for use on 35/65, and perhaps on 50/50, polyester—cotton blends. It is appUed by the pad-dry-cure process, with curing at 150°C for about 3 min. A typical formulation contains 20% THPC, 3% disodium hydrogen phosphate, 6% urea, 3% trimethylolglycouril [496-46-8] and 12% poly(vinyl bromide) soUds. Approximately 20% add-on is required to impart flame retardancy to a 168 g/m 35/65 polyester—cotton fabric. Treated fabrics passed the FF 3-71 test. However, as far as can be determined, poly(vinyl bromide) is no longer commercially available. 

LRC-100Finish. The use of LRC-100 flame retardant for 50/50 polyester cotton blends has been reported (144). It is a condensation product of tetrakis(hydroxymethyl)-phosphonium salt (THP salt) and A/A7,A7 -trimethylphosphoramide [6326-72-3] (TMPA). The precondensate is prepared by heating the THP salt and TMPA in a 2.3-to-l.0-mole ratio for one hour at 60—65°C. It is appUed in conjunction with urea and trimethylolmelamine in a pad-dry-cure oxidation wash procedure. Phosphoms contents of 3.5—4.0% are needed to enable blends to pass the FF 3-71 Test. 

Preformed Two-Piece Metal Containers. Ink vehicles for letterset printing of two-piece aluminum or steel containers are mainly based on special polyester vehicles used in conjunction with melamine cross-linkers. Short cycle ovens which dry inks in 1—5 seconds are now used and operate at temperatures as high as 350 °C. The rheology of these inks must be adjusted to the unique geometry of the press. Desired rheological properties are achieved by the use of additives as weU as extender pigments. 

Plastics. Vehicles in offset inks for plastics (polyethylene, polystyrene, vinyl) are based on hard drying oleoresinous varnishes which sometimes are diluted with hydrocarbon solvents. Letterset inks for polystyrene employ vehicles of somewhat more polar nature. Polyester or other synthetic resins (acryhc) dissolved in glycol ethers and/or esters are used in some of the older inks. Uv inks are widely used for decoration of these preformed plastic containers. 

In the case of some types of polyesters, the dried treated sheet is very tacky, and must be interleaved with a plastic release film to prevent blocking in the roU prior to use. Certain polyesters and acryhcs can be converted to a gelled state by exposure to actinic radiation. 

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

The polymer is then dried thoroughly and stored for subsequent processing. Whenever a polyester is made by melt polycondensation, a small amount of cycHc oligomer is formed which is in equiHbrium with the polymer. This can be extracted with solvents from soHd polymer but when the... 

Other minor raw materials are used for specific needs. Eumaric acid [110-17-8] the geometric isomer of maleic acid, is selected to maximize thermal or corrosion performance and is the sole acid esterified with bisphenol A diol derivatives to obtain optimum polymer performance. CycloaUphatics such as hydrogenated bisphenol A (HBPA) and cyclohexanedimethanol (CHDM) are used in selective formulations for electrical apphcations. TetrahydrophthaUc anhydride [85-43-8] (THPA) can be used to improve resiUence and impart useful air-drying properties to polyester resins intended for coating or lining apphcations. 

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