Polyester melt viscosity

Thermoplastic, linear and saturated polyester give, depending on their chemical composition, hard or elastic and tacky bond lines they have relatively high melting viscosities bond lines are resistant against moisture, water and UV. 

Fig. 5.—The partial degradation of decamethylene adipate polyester with small percentages of decamethylene glycol (experiments 8, 13, and 17), or with lauryl alcohol (experiment 19), at 109°C, catalyzed with 0.1 equivalent percent of p-toluenesulfonic acid. The fraction of added glycol, or alcohol, unassimilated has been calculated indirectly from melt viscosity measurements and is plotted on the logarithmic ordinate scale.2 ...

P.R.149 also lends color to cast resins made from materials such as unsaturated polyester or methacrylic acid methylester, which are polymerized with peroxide catalysts. P.R.149 is equally lightfast in these media. In polycarbonate, the pigment tolerates exposure to more than 320°C. This is an asset in view of the fact that polycarbonate shows high melt viscosity and is thus processed at up to 340°C. The list of applications also includes other media, such as PUR foams and elastomers, for which P.R.149 is recommended because of its good heat stability and its coloristic properties. 

Japon, S., Leterrier, Y. and Manson, J.-A., Increasing the melt viscosities of a polyester resin, World Patent WO 00 29 470, 1999. 

Polycondensation of highly viscous polyesters in the melt phase is limited. The removal of the volatile by-products becomes more difficult due to diffusion inhibited by the increased viscosity of higher-IV polyesters. In addition, undesirable side reactions due to thermal degradation impede the growth of the molecular chains. As a consequence, the reaction rate decreases and decomposition reactions dominate, thus resulting in a decrease in the melt viscosity [2], As it is able to address these limitations, SSP has become the method of choice and is therefore so popular. 

This article is an overview of the novel technology of self-reinforced LCPs with polyesters, poly(ethylene terephthalate) (PET) and poly(ethylene naphtha-late) (PEN) [10-13, 21, 23], LCP/polyester blends in a polyester matrix form in situ fibrils which improve the mechanical properties. LCPs have an inherently low melt viscosity, and provide LCP/polyester blends that effectively lower the melt viscosity during melt spinning [24], and fast injection-molding cycles. The miscibility between the LCP and polyesters can be controlled by the degree of transesterification [25] in the reactive extrusion step, and fibril formation in LCP-reinforced polyester fibers has been studied. 

Fig. 11. Melt viscosity at 85 °C vs molar mass for hydroxy-functional hyperbranched aliphatic polyesters based on bismethylol propionic acid. Theoretical molar mass based on core bis-MPA ratio ( ) and Mn determined with SEC relative to linear polystyrene standards (O) [117]...

The flexibility of amorphous polymers above the glassy state, where segmental mobility is possible, is governed by the same forces as melt viscosity and is dependent on a wriggling type of segment motion in the polymer chains. This flexibility is increased when many methylene groups (—CH2—) or oxygen atoms (—O—) are present. Thus, the flexibility of aliphatic polyesters usually increases as m is increased ... 

Star-branched polyesters exhibit unique properties such as lower melt viscosities, lower crystallinity, and smaller hydrodynamic volume in solution by comparison with their linear counterparts. Two general strategies are possible for their... 

A series of different hydroxyfunctional hyperbranched polyesters (H1-H6) with increasing ratio TMP bis-MPA was studied. The tests were made on samples quenched from melt. As discussed previously, the molar masses for these polymers are difficult to determine and the results ate therefore presented as a function of the ratio bis-MPA TMP, which can be directly related to the theoretical molar mass. The complex dynamic viscosity (r ) of hyperbranched polyesters show an increase in viscosity with size which levels out at a certain value (Figure 11). The corresponding linear polymers would exhibit a linear relationship q versus log molar mass and hence have a higher melt viscosity. The hydroxyfunctional polyesters exhibit a Newtonian behavior within a medium shear range (10 -10 rad s ). 

Gibson and coworkers also found that the melt viscosity of a polymer is also altered by the formation of a polyrotaxane [19], Poly(ester rotaxane) 60 containing 42C14 as the cyclic component had a melt viscosity equivalent to that of the parent polyester with 2.5-fold higher molecular weight. This result clearly indicates that there is less chain entanglement in the polyrotaxane than in the backbone polymer by itself. 

Preparation of Carboxylated Polyesters. Hydroxyl-terminated polyester segments were prepared by conventional procedures and extended with an equimolar amount of dianhydride (2). To avoid the possibility of crosslintdng the polymer, reaction1 with the dianhydride was carried out at 175 °C. Depending upon the size of the reaction mixture, about 1 to 3 hours were required for all of the dianhydride to react and for a medium-to-high melt viscosity to be obtained. Inherent viscosities were 0.3 to 0.4. 

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