Polyethylene terephthalate stabilization

Chapter 661 of the USP provides criteria for the interchangeability of low- and high-density polyethylene for dry, oral dosage forms. In addition, there are standards for polyethylene terephthalate bottles and polyethylene terephthalate G bottles. USP criteria for interchangeability are listed in Table 17. These criteria allow usage of alternate materials in the same plastic class to be used prior to obtaining prior stability data. 

All of these intermolecular forces influence several properties of polymers. Dispersion forces contribute to the factors that result in increased viscosity as molecular weight increases. Crystalline domains arise in polyethylene because of dispersion forces. As you will learn later in the text, there are other things that influence both viscosity and crystallization, but intermolecular forces play an important role. In polar polymers, such as polymethylmethacrylate, polyethylene terephthalate and nylon 6, the presence of the polar groups influences crystallization. The polar groups increase the intensity of the interactions, thereby increasing the rate at which crystalline domains form and their thermal stability. Polar interactions increase the viscosity of such polymers compared to polymers of similar length and molecular weight that exhibit low levels of interaction. 

Edge, M., Wiles, R., Allen, N. S., McDonald, W. A. and Mortlock, S. V., Characterisation of the species responsible for yellowing in melt degraded aromatic polyesters - I. Yellowing of polyethylene terephthalate), Polym. Degrad. Stabil, 53, 141-151 (1996). 

The first method used a Pauling-Erdeli-Pauling thermobalance at temperature intervals between 20° and 700°C in an inert medium. The temperature was raised 12.4°C per minute, the results being compared with those of the standard polymer. With a Fe3+ complex synthesized for 96 hours, the polychelate reached a maximum loss of only 28 at 440°C and often showed a constant thermal stability. Unmodified polyethylene terephthalate continually lost weight showing a loss of 95.9 at 577°C. 

Note-. 2 - sufficient thermal stability and limited reactivity with polymer allows broad use, 1 = marginal thermal stability or potential reactivity with polymer restricts use, 0 = generally unsuitable for use. FPVC, Flexible Polyvinyl Chloride RPVC, Rigid Polyvinyl Chloride PS, Polystyrene LDPE, Low Density Polyethylene HDPE, High Density Polyethylene PP, Polypropylene ABS, Acrylonitrile-butadiene-styrene copolymer PET, Polyethylene terephthalate PA, Polyamide PC, Polycarbonate... 

To estimate thermal stability of obtained polyethylene-terephthalate/layered silieate nanoeomposites the following well-known methods were used thermal gravimetrie analysis (TGA), differential scanning calorimetry (DSC) and melt thermal stability coefficient determination. Results of thermal stability researeh for polyethyleneterephthalate/layered silieate are shown in Table 2. 

The melt stability of step-growth polymers is affected by water absorption prior to processing, which can reverse the polymerisation equilibrium reaction in the melt. For example, polyethylene terephthalate (PET) has an... 

The high impact strength, dimensional stability and optical clarity (low crystallinity) of bisphenol-A polycarbonate (PC) together with its low dielectric loss have led to a range of applications embracing optical components, CD-ROMs, film capacitors and safety-related products Subsequent market demands for enhanced physical properties has stimulated the development of a range of commercial blends of which rubber-modified bisphenol-A polycarbonate (PC) with polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) are amongst the more successful ... 

Polyethylene terephthalate (PET) is susceptible to deterioration by UV at wavelengths below 315 nm, causing embrittlement, crazing and yellowing of thin films and sheeting [40], Both PET and polybutylene terephthalate (PBT) bulk polymers, however, are used in stabilized form for exterior mouldings, sometimes in admixture with other polymers such as acrylonitrile styrene acrylate. 

Blends of polyethylene terephthalate and linear low-density polyethylene were compatibilised using diethylmaleate grafted polyethylene, and characterised using Fourier transform infra-red spectroscopy, thermogravimetric analysis and scanning electron microscopy. Interactions between the components in the blends were observed, which affected the glycol sequences of the polyester and also improved the thermal oxidative stability of the blends. The introduction of the compatibiliser resulted in a particle size reduction of the dispersed phase and better adhesion between the phase and the matrix. 15 refs. 

The fibre must also be able to withstand prolonged exposure to sunlight, specifically irradiation by UV light. The twin considerations of thermomechanical stability up to 200 °C and resistance to UV radiation do rule out several types of commodity fibre. These fibres include most natural fibres, as well as commercial polyolefin and acrylic fibres, all of which melt or begin to decompose below 200 °C. Nevertheless, polyethylene terephthalate (PET) fibres are potentially suitable substrates they melt at 260-270 °C and exhibit good stability to UV radiation [6]. They are also commercially... 

Polyesters UV absorbers have been used as efficient stabilizers of the linear polyesters, polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) as well as for improving the lightfasmess of dyes in polyester fibers during outdoor exposure. Effective stabilization of high-molecular-weight PET fibers by a UV absorber was shown [106] to depend on the level of uptake and its uniform distribution throughout the fiber cross section. A benzophenone-type stabilizer provided considerably better protection than the benzotriazole- and benzotriazine-type stabilizers because it diffused throughout the fiber whereas the other two... 

PDBS-80 was the first in the series. This material is a homopolymer of dibromostyrene that contains 59-60% bromine. Its primary applications are in high-temperature polyamides and polyethylene terephthalate (PET) because it has excellent flow characteristics and very good thermal stability. In addition, there are benefits of excellent colour retention. The main weakness of this approach is the bromine content relative to the competitive material. Today s competition contains around 68% bromine. This can translate into a 2-3 parts difference in the load level needed in the protected polymer to give equivalent flame retardancy. 

Saturated polyester, polyethylene terephthalate (PET) 15-25 Appliance panels automotive body panels power tool housings Improved strength Improved heat deformation temperature Improved dimensional stability... 

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