Poly master rheogram

The master rheogram for poly(ethylene terephthalate) (PEI) is shown in Fig. 4.21. cept for 4 data points taken from a research paper by Wu [61], the 169 data points were obtained from a single source, namely, the manufacturer [62]. All types of grades of PET (i.e., fiber, molding, tire cord, bottle) have been unified on the master rheogram [56]. in the case of nylon, the Newtonian plateau is very distinct and covers a wide range of shear rate. The deviation from the Newtonian behavior is also not too pronounced even at considerably higher shear rates. 

Tlie liquid-crystalline hydroxy benzoic acid/poly(ethylene terephthalate) (HBA/PET) copolymer master rheogram given in Fig. 4.37, however, is not amenable to a curve fit by any of the models discussed above. The reason is because the shape of the unified curve for this liquid-crystalline copolymer is radically different from those obtained for other thermoplastics. There are two shear-thinning regions separated by a short plateau as can be seen in Fig. 4.37. A new equation of the following form is thus suggested [12] ... 

For polyacetal (POM), viscosity versus shear rate data were obtained from two sources [57,58]. One source was the renowned book on polyacetals by Barker and Price [57], whereas the other source was a research paper by Pritchard and Wissbrun [58]. Only 24 data points were analyzed and the master rheograms as shown in Fig. 4.19 were generated [56]. Even with limited data, two distinct master rheograms were revealed—one for linear poly acetal and the other for branched polyacetal. This is not an unexpected situation and is similar to that observed earlier for polethylenes wherein HOPE (linear PE) and LDPE (branched PE) have two distinct master rheograms. 

Viscosity versus shear rate curves for two different compositions of a hydroxy benzoic acid/poly(ethylene terephthalate) copolymer (HBA/PET) at various temperatures were used [84] in the formation of the master rheogram for the liquid-crystalline polymer shown in Fig. 4.37. The data for 80 mole% of HBA at six different temperatures ranging from 275°C to 330 C were taken from Ref. 42. In order to eliminate operator and interlaboratory errors, the data on the same composition at one representative temperature of 275°C was also used from another source [85]. The other composition of HBA/PET chosen was 60 mole% and again from two different sources [42,86]. From one source [42], the viscosity data for 60 mole% of HBA at three different temperatures between 210°C and 300 C was used, where as from the other [86], three different temperatures between 260°C and 285 C was used. A total of 51 data points covering a shear-rate range from 2 to 8000/s have been included (Table B3 of Appendix B) in the unification process to form the master rheogram in Fig. 4.37. 

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