PET Polymer

Polymerization. Commercial productioa of PET polymer is a two-step process carried out through a series of coatiauous staged reactioa vessels. Eirst, monomer is formed by transesterificatioa of DMT or by direct esterificatioa of TA with 2G ... 

Cyclohexanedimethanol (47) starts from dimethyl terephthalate. The aromatic ring is hydrogenated in methanol to dimethyl cyclohexane-l,4-dicarboxylate (hexahydro-DMT) and the ester groups are further reduced under high pressure to the bis primary alcohol, usually as a 68/32 mixture of trans and cis forms. The mixed diol is a sticky low melting soHd, mp 45—50°C. It is of interest that waste PET polymer maybe direcdy hydrogenated in methanol to cyclohexanedimethanol (48). 

We (fl) have reported the photophysical processes of a series of model esters of PET, and tentatively assigned the fluorescence and phosphorescence of the aromatic esters as (n, tt ) transitions, respectively. We (9) also performed an extensive study of the photophysical processes available to dimethyl terephthalate (DMT) in order to relate this monomeric species to the PET polymer. In 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) (Table I), DMT has three major,absorptions which are according to Platt, s notation 191 nm, A- B, e = 40,620 1 mole" cm"1 244 nm, A-dLaT e = 23,880 1 mole-) cm" 289 nm, A U, e = 1780 1 mole")cm. ... 

Fluorescence Analysis of Irradiated PET and PET-4,41-SD Yarns. As we noted above, the fluorescence emission at 460 nm in irradiated PET polymer has been attributed to the hydroxyterephthaloyl component (2). The fluorescence spectra of irradiated (100 hours) PET homopolymer yarns and PET-4,4 -SD copolymer yarns are identical and agree with that obtained by Day and Wiles for PET film (2). 

Figure 5.12 Density as a function of temperature and time during SSP [26]. From Wick, G., Characterization of PET polymer for bottle manufacturing, presentation given at the Society of Plastics Engineers Benelux Seminar, 20-21 May, 1980, Amsterdam, and reproduced with permission of KoSa GmbH Co. KG...

Wick, G., Characteristics of PET polymer for bottle manufacturing, presentation given at the Society of Plastics Engineers Benelux Seminar, Amsterdam, 20- 21 May, 1980. 

The PET polymer structure can also be generated from the reaction of ethylene glycol and dimethyl terephthalate, with methyl alcohol as the byproduct. A few producers still use this route. The aromatic rings coupled with short aliphatic chains are responsible for a relatively stiff polymer molecule, as compared with more aliphatic structures such as polyolefin or polyamide. The lack of segment mobility in the polymer chains results in relatively high thermal stability, as will be discussed later. 

Solid PET polymer is relatively hard and brittle. It must be formed into very fine fibers in order to exhibit a bending stiffness that is low enough for textile materials. Most commercial PET fibers are produced in a diameter range of about 10-50 pm, considerably smaller than a human hair. Within this range lie large differences in the softness, drape and feel of fabrics formed from the fibers, since the bending stiffness of a cylindrical fiber depends on the 4th power of its diameter. 

Some efforts have been made to incorporate sites into PET that accept acid dyes, but most of these alkaline-containing additives cause degradation and discoloration of the polymer. No acid-dye PET polymer has yet been commercially successful. 

Figure 13.3 also shows the orientation factors of the crystalline and amorphous regions as a function of take-up speed, which is pronounced in the case of a branched PET polymer. The shift towards increased freezing temperatures in branched polymer samples seems to be an indicator of higher elasticity (Figure 13.4). 

Figure 13.7 A UO2 agglomerate in PET polymer [9], Optical micrographs provided by W. Goltner...

Bishydroxyethyl terephthalate (BHET) is the monomer used to make the PET polymer. BHET can be made either by the esterification of terephthalic acid (TPA) with ethylene glycol (EG) ... 

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