Nucleation of crystallization of polyester by catalyst remnants—a review

Abstract

The antimony catalyst content of poly(ethylene terephthalate) has an appreciable effect on the tendency of the polymer to crystallize upon cooling from the melt. Nucleation density increases significantly as antimony catalyst concentration increases. The crystallization tendency of the polymer at a given molecular weight correlates strongly with both the antimony content and the diethylene glycol comonomer content. The behavioral patterns of nucleation by catalyst remnants are similar in polyester prepared from terephthalic acid or dimethyl terephthalate. The antimony catalyst is deposited in the polyester matrix in a form suitable to nucleate quiescent crystallization. The differences in tendency to crystallize that correlate with catalyst and diethylene glycol comonomer content are reflected in the crystallinity of injection molded samples.

Poly(ethyene terephthalate)–solvent interaction: Gelation and melting point depression

“…Bier, et al (191, reported a linear relationship between the crystallization temperature T, and the cube root of cooling rate for the crystallization of pure PET. While no explanation was offered, the Bier relationship was shown to hold true in another work on PET crystallization (20). Such a Bier plot for the pure PET used in this study isdepicted in Flg.…”

“…The crystallization temperature of pure PET extrap olated to zero cooling rate on the Bier plot is desig nated as intrinsic crystallization temperature, TZ,,,, which is known to vary with PET molar mass, diethylene glycol content, and additives (e.g., [20][21][22]. Similarly, the gelation temperature of PET solution extrapolated to zero cooling rate on the Bier plot is designated as intrinsic gelation temperature, T:ep It is the upper temperature limit for gel formation in the quiescent state.…”

Nucleation and crystallization of PET droplets dispersed in an amorphous PC matrix

“…22 This phenomenon of a higher quantity of nuclei present during the heating run could explain why, even in dispersed PET droplets, the polymer shows a greater tendency to crystallize at lower temperatures (cold crystallization) during the heating run and therefore exhibits a small fusion endotherm in the heating scan.…”

“…As a matter of fact, the number of dispersed particles (10 9 -10 10 particles/cm 3 ) is very high (see Table I) as compared with the usual number of type A heterogeneities in molten PET (10 6 heterogeneities/cm 3 ; see Ref. 22). This means that many PET droplets will not contain any type A heterogeneity; therefore, the polymer inside the droplet cannot crystallize at the same undercooling, and will crystallize at larger undercoolings only if another type of heterogeneity (say, "type B," active at larger undercoolings) is present or by creating its own nuclei in a homogeneous crystallization process that usually occurs at the largest possible undercooling.…”

Synthesis of copoly(ethylene terephthalate /imide)s and crystallization kinetics

“…The plot of the nonisothermal cooling crystallization function (or,(T)) vs. temperature for PETI copolymers shown in Ag. 9 exhibited a trend similar to the isothermal Avrami rate constant vs. temperature plot Nonisothermal crystallization data were also analyzed according to the plot suggested by Lawton (18). In this method, the crystallization peak temperatures are plotted against the cube root of cooling rates (2.5,5, 10,20"C/min).…”