Polyethylene-terephthalate

Polyethylene terephthalate polyester is the leading man-made fiber in production volume and owes its popularity to its versatility alone or as a blended fiber in textile structures. When the term polyester is used, it refers to this generic type. It is used extensively in woven and knitted apparel, home furnishings, and industrial appl ications. Modification of the molecular structure of the fiber through texturizing and or chemical finishing extends its usefulness in various applications. Polyester is expected to surpass cotton as the major commodity fiber in the future. 

Polyethylene terephthalate becomes crosslinked and partly insoluble in o-chlorophenol [113] or trifluoracetic acid [114] when irradiated with 

PHOTOLYSIS OF POLYETHYLENE TEREPHTHALATE IN VACUO AT 313 nm (INITIAL QUANTUM YIELDS x 104) 

The mechanism proposed by Day and Wiles [115] to account for the main experimental results is 

On the basis of model compound studies and comparison with solution kinetic data, they conclude that the rates of reactions (18) and (19) should be comparable. However, since carboxyl groups are produced in significantly higher yield than carbon dioxide (see Table 4), another mechanism must be responsible for the formation of most carboxyl groups this is most 

Such a reaction has been shown to give 1-butene and carboxyl groups in equivalent yields (about 2 x 10-2) in the liquid-phase photolysis of undiluted di-n-butylterephthalate [116]. From Table 4 it can be seen that the quantum yields of chain scission and of carboxyl group formation are almost identical this suggests that reaction (22) is the main cause of chain scission in the photolysis of polyethylene terephthalate. It must also be pointed out that reactions (19) and (21) do not necessarily yield chain scission, since the probability of the macro-radicals escaping the cage is rather low in a rigid matrix. Indeed, the appearance of an absorption maximum near 775 cm-1 in the infrared spectrum of polyethylene terephthalate irradiated at 313 nm has been ascribed to 

Polyethylene terephthalate (PET) is a typical representative of comparatively thermally resistant aryl aliphatic polyesters its thermal decomposition begins at temperatures 

The thermal degradation of PET (250-320 C) in an inert atmosphere gives carbon dioxide, acetaldehyde and methane, benzene, acetylene, 2-methyldioxane and water as the basic gaseous products, and these are released in considerable amounts. Terephthalic acid and oligomeric products (dimers, trimers, cyclic, tetra- and pentamers) are found among the poorly volatile products of the thermal degradation of PET [45, 53]. The half-life temperature for PET is 450 °C. 

The following scheme has been proposed for the thermal degradation of PET  

The thermal conversions of the vinyl ester end-groups proceed at 400-500 C by the following schemes  

These schemes make it possible to elucidate the formation routes for acetylene, ketones and carbon dioxide detected among the thermal degradation products of PET. 

Polymerization of PET is different from the polyolefins described previously. It is formed by a condensation reaction between two monomers dimethyl terephthalate (DMT) and ethylene glycol (EG). The polymerization process involves a two-step process ester interchange (Eq. [2.3]) and polymerization (Eq. [2.4]). Weak basic catalysts, usually metal salts, are used to accelerate polymerization and control the molecular weight and stoichiometry of the polymer. The first step is carried out at temperatures from 150 to 200°C and the methanol is continuously distilled off. The reaction is a solution polymerization. The temperature in the second step is increased to 260—290°C, at which melt polymerization occurs (Odian, 1981). 

There are two types of processes batch and continuous (Pucetas, 1994). The batch process can produce 20 to 40 KN of polymer in 4 to 5 h. The ester exchange and polymerization steps take place separately at temperatures of 240 and 290°C, respectively. This process is not commonly used and is only for special cases. For the large production of PET, the continuous process is an effective method and can generate over 800 MN/year of resin. The more commercial process is to replace DMT by tereph-thalic acid with a paste form of EG to produce Z ri(2-hydroxy-ethyl)terephthalate, which is then polymerized as in Eq. [2.4]. 

Van Houwelingen [47] used coulometric bromination to determine vinyl ester end groups in polyethylene terephthalate (PET) formed by thermal chain scission  

The constant-current generation of bromine is carried out in a medium of dichloroacetic acid, water, potassium bromide and mercury(II)chloride. To this medium an amount of the polymer, previously dissolved in hexafluoroisopropanol and diluted with anhydrous dichloroacetic acid, is added and bromine generated. The end of the reaction is detected biamperometrically. The suitability of this method was tested against methyl vinyl terephthalate  

Additions of 14.2 pmol and 1.0 pmol of methyl vinyl terephthalate (corresponding to 30 mmol and 2 mmol of vinyl ester end groups per kilogram of polymer) were recovered quantitatively (recoveries of 99.8% and 98.5%, respectively). 

Nissen and co-workers [48] described an ultraviolet (UV) spectroscopic method for carboxyl end groups in PET. Hydrazinolysis led to formation of terephthalomono-hydrazide from carboxylated terephthalyl residues to provide a selective analysis for carboxyl groups via UV absorbance at 240 nm. 

Other techniques that have been applied to end-gronp analysis of PET inclnde H-NMR, gel permeation chromatography-MALDI-time-of-flight (ToF) mass spectrometry [49] and MALDI-ToF combined with collision-induced dissociation (QD) [26]. 

When polyesters are processed, thermal degradation is caused by ester bond cleavage here, polyethylene terephthalate is more stable than polybutylene ter-ephthalate. Ester cleavage is influenced to various degrees by different trans-esterification and polycondensation catalysts. This is less significant in the thermai degradation of polybutylene terephthalate compared to polyethylene terephthalate. 

The acceleration of ester cleavage is attributed to the stronger polarization of the carbonyl group by a coordinative bond of the metal ion, which promotes proton cleavage in the cyclic transition state. Fig. 4.62 and Fig. 4.65. 

Although the technically relevant PET grades are relatively resistant, thermal (Fig. 4.65), thermal-oxidative (Fig. 4.64) and, in the presence of water, hydrolytic degradation reactions can occur during processing (270 to 300 °C), where the essential degradation process is hydrolysis. Hydrolysis proceeds 10,000 times faster than thermal degradation and 5,000 times faster than thermal-oxidative 

Influence of water content during Injection molding on degradation in polyethylene terephthalate Carboxyl groups and viscosity as a function of water content 

Because hydrolytic degradation is the decisive degradation mechanism in polyethylene terephthalate, it has to be kept as low as possible. This can be achieved by good pre-drying and - for non- pre-dried material - by means of process optimization, such as vacuum degasing and nitrogen superimposition [624]. 

Answers to these questions can be obtained if one performs small angle scattering measurements during isothermal crystallization. Such measurements have been performed on different materials. The results were observed to depend strongly on the material used. So, for example, with increasing crystallization time, the long period increased with polyethylene, it decreased with polyethylene terephthalate and it stayed constant with poly-P-hydroxybutyrate. 

The first measurements of the small angle scattering during crystallization have been performed on polyethylene terephthalate by Eisner, Zachmann, and Milch . Amorphous films were oriented by stretching at 92 °C and crystallized afterwards 

A model explaining this behavior is shown in Fig. 42. One has to assume bended lamella which flatten during annealing while the chain orientation does not change. The decrease of the long period is caused probably by this flattening. 

Studies were performed also with unoriented polyethylene terephthalate (Eisner, Koch, Bordas and Zachmann Also with unoriented samples the long period decreased with increasing time. Such a decrease has been observed already with samples quenched to room temperature (Zachmann and Schmidt The present results show that the decrease is not an artificial effect caused by quenching, but 

Measurements were performed up to now during isothermal crystallization at 117 °C of an initially amorphous film. Fig. 43 shows the scattering power Q = S I(s) ds of the small angle scattering as well as the degree of crystallinity obtained from wide angle scattering as a function of crystallization time. 

The level of crystallinity plays an important part in the level of heat stability of a PET bottle. Again, the evolution of preform designs and grades of material has increased the level of heat stability. In order to extend this stability to the temperatures used for hot-filling (typically 85°C), additional methods have 

When a product cools, it contracts. This distorts the normal shape of the PET bottle panel. Hot-fill bottles are made with panels in the body section and patented features in the bottle base that collapse in a consistent way so that the bottle can be handled and distributed when cold. 

The vacuum that creates the bottle panel has to be contained by the closure, and so hot-filled bottles have a specific closure design and applicator that are different from standard carbonated closure designs (see Section 9.5) 

The chemical resistance of PC is poor and hydrolysis of aliphatic PC s is more prominent than that of bis-phenol A PC s. There is resistance to dilute (25%) mineral acids and dilute alkaline solutions other than caustic soda and caustic potash. Where the resin comes into contact with organophilic hydrolysing agents such as ammonia and the amines, the benzene rings give little protection and reaction is quite rapid. The absence of both secondary and tertiary C-H bonds leads to a high measure of oxidative stability. Oxidation takes place only when thin films are heated in air to temperatures above 300°C. 

The main disadvantages are a. processing requires care, b. limited chemical resistance, c. notch sensitivity and susceptibility to stress cracking. 

Polyethylene terephthalate, PET, is a thermoplastic polyester made by condensation reaction of ethylene glycol with either terephthalic acid or dimethyl terephthalate (Margolis, 1985). By the end of the 1920s J.R. Whinfield and J.T. Dickson discovered PET (BP 578079). It was first commercialized by Du Pont in 1930 (Brydson, 1982) as Dacron , followed by ICI with Terylene Films and blow-molded articles have become very important commercially. 

The permeability of water vapor through PET is higher than that of polyolefins but lower than that of polycarbonate, polyamide, and polyacetal. Antioxidants are necessary to prevent to the oxidation of polyether segments in thermoplastic polyester elastomer. Chemical resistance of PET is generally good to acids, alkalis, and organic solvents. 

Typical properties for partially crystalline PET include, a. high strength and stiffness, b. favorable creep characteristics in comparison with POM, c. hard surface capable of being polished, d. high dimensional stability, e. good electrical, mediocre dielectric properties, and f. high chemical resistance except to strong acid and alkaline solution. 

Koh and co-workers [29], investigated the mechanical and thermal properties of glass reinforced PET used as printer parts. This study emphasised the importance of the moulding processes in achieving optimised mechanical properties. 

The styrenics are a family of low to medium price, rigid, easily processed plastics with good gloss and optical properties. ABS and HIPS are more tough, due to the acrylonitrile ruhher content, which has either been incorporated into the plastic or copolymerised with the styrene monomer, respectively. Fillers have been looked at by several producers 

Polyphenylene sulfide is a high temperature, stiff, fire-resistant, chemically resistant plastic, which has a very low melt viscosity and accepts fillers and reinforcing agents very well. Talc, china clay, dolomite, quartz and glass fibre filled grades are all available but volumes are very small and the situation changes very rapidly. 

The properties of particulate fillers in a number of other thermoplastics are being investigated by plastics producers and academic institutions but usually with a low priority rating. This activity has been growing less and less in recent years as companies, in particular, have been reducing the staffing levels in the research and development departments. 

Thermoplastic composites are all around us and their use is increasing every year. The reason for this is that thermoplastics have an excellent combination of cost and performance. The performance can often he further enhanced by addition of fillers while maintaining a favourable cost. The recycleahility of thermoplastic composites is an advantage compared to rubbers and thermosetting polymers because the latter two types cannot be melted and reshaped. This favours the continued growth of the thermoplastics and their composites at the expense of other polymeric materials. 

To understand and optimise composites, one must have an overview of all the different economic, chemical, surface and physical aspects. Furthermore, one must have a clear goal, and be able to correctly prioritise the properties of most import for the intended application. The best composite is the one that makes the best compromise between the multitude of properties, at the lowest cost. 

Dimitra Fragidou, Kyriaki Galiou, Ina Keridou, Zoe-Anastasia Papakonstantinou and Dimitris S. Achilias 

PET is formed from the monomers terephthalic acid and ethylene glycol, which are both derived from oil feedstock. PET was originally patented and exploited by DuPont during the search for new fibre-forming polymers polyester fibre applications have 

Most of the physical and mechanical properties of PET improve as the molecnlar weight increases. The molecnlar weight required is dictated by the end nse of 

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Condensation polymerization differs from addition polymerization in that the polymer is formed by reaction of monomers, each step in the process resulting in the elimination of some easily removed molecule (often water). E.g. the polyester polyethylene terephthalate (Terylene) is formed by the condensation polymerization (polycondensation) of ethylene glycol with terephthalic acid ... 

Those polymers which are the condensation product of two different monomers are named by applying the preceding rules to the repeat unit. For example, the polyester formed by the condensation of ethylene glycol and terephthalic acid is called poly(oxyethylene oxyterphthaloyl) according to the lUPAC system, as well as poly (ethylene terephthalate) or polyethylene terephthalate. 

Polyethylene terephthalate [25038-59-9] (8) is a polyester produced by the condensation polymerization of dimethyl terephthalate and ethylene glycol. Polyethylene terephthalate sutures are available white (undyed), or dyed green with D C Green No. 6, or blue with D C Blue No. 6. These may be coated with polybutylene adipate (polybutilate), polyydimethylsiloxane, or polytetrafiuoroethylene [9002-84-0]. The sutures are distributed under the trade names Ethibond Exel, Mersdene, Polydek, Silky II Polydek, Surgidac, Tevdek II, Polyester, and Tl.Cron. 

Nylon-6 [25038-54-4] (9) is made by the bulk addition polymerization of caprolactam. Monofilament Nylon-6 sutures are avadable undyed (clear), or in post-dyed black (with logwood extract), blue (ED C Blue No. 2), or green (D C Green No. 5). Monofilament nylon-6 sutures are sold under the trade names Ethilon and Monosof monofilament nylon-6,6 sutures, under the trade names Dermalon and Ophthalon and monofilament polyethylene terephthalate sutures, under the trade name Surgidac. 

The primary substrates or support iaclude many types of paper and paperboard, polymer films such as polyethylene terephthalate, metal foils, woven and nonwoven fabrics, fibers, and metal cods. Although the coating process is better suited to continuous webs than to short iadividual sheets, it does work very well for intermittent coating, such as ia the printing process. In general, there is an ideal coater arrangement for any given product. 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

Polycarbonate-polyethylene terephthalate (PC-PET) alloys have also recently been announced by DSM. 

Friedrich et al. also used XPS to investigate the mechanisms responsible for adhesion between evaporated metal films and polymer substrates [28]. They suggested that the products formed at the metal/polymer interface were determined by redox reactions occurring between the metal and polymer. In particular, it was shown that carbonyl groups in polymers could react with chromium. Thus, a layer of chromium that was 0.4 nm in thickness decreased the carbonyl content on the surface of polyethylene terephthalate (PET) or polymethylmethacrylate (PMMA) by about 8% but decreased the carbonyl content on the surface of polycarbonate (PC) by 77%. The C(ls) and 0(ls) spectra of PC before and after evaporation of chromium onto the surface are shown in Fig. 22. Before evaporation of chromium, the C(ls) spectra consisted of two components near 284.6 eV that were assigned to carbon atoms in the benzene rings and in the methyl groups. Two additional... 

In studying contact between films of polyethylene (PE) and polyethylene terephthalate (PET) bonded to quartz cylinders, they observed an increase in adhesion energy with contact time for a PE/PE pair, but not for PE/PET or PET/PET combinations. They interpreted this as evidence for the development of nanoscale roughness due to the interdiffusion of chains across the PE/PE interface [84],... 

The Shodex GPC HFIP series is packed with a hexafluoroisopropanol (HFIP) solvent. Engineered plastics, such as polyamides (nylon) and polyethylene terephthalate, were analyzed previously at a high temperature of about 140°C. Using FIFIP as an eluent, such engineered plastics can be analyzed at ordinary temperatures (Table 6.4). 

Figures 6.18—6.20 show the chromatograms of engineered plastics such as polyamide (nylon) and polyethylene terephthalate at ordinary temperature.

FIGURE 6.20 Polyethylene terephthalate. Column Shodex GPC HFIP-806M, 8 mm i.d. x 300 mm. Eluent S mM CFaCOONa/HFIP. Flow rate O.S mL/min. Detector Shodex Rl. Column temp. 40°C. Sample 0.05%, SOO /iL. PET. 

FIGURE 9.26 Room temperature analysis of polyethylene terephthalate. Columns PSS PEG 100 + 1000. Eluent HFIP + 0.1 /VI NatFat. Temp 2S°C. Detection UV 2S4 nm, Rl. Calibration PSS PET standards (broad). 

Melamine-Formaldehyde Nylon (all types) Polybstylene-Terephthalate Polyethylene-Terephthalate... 

PBT - polybutylene terephthalate PDMS - polydimethyl siloxane rubber PE - polyethylene PET - polyethylene terephthalate PHB - poly[D(-)]-3-hydroxy butyrate PP - polypropylene... 

As mentioned earlier, polyethylene terephthalate is an important thermoplastic. However, most PET is consumed in the production of fibers. 

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