Reactive Blending of Aromatic Polyesters: Thermal Behaviour of Co‐precipitated Mixtures PTT/PET

Abstract

Summary: Due to its unique combination of properties, PTT is a promising material for textile fibre and engineering thermoplastic applications, both as neat polymer and in formulated products. To bring down the cost yet keeping some of its advantageous properties it seems interesting to apply PTT in blends and particularly with PET. We consider here the effect of composition and reaction time on co‐precipitated mixtures PTT/PET, in terms of melting and crystallization behaviour, solution properties and morphology. Blends of various compositions were prepared from mixed solutions, kept in the DSC at 280 °C for different times (0–120 min) and analysed during a successive cooling‐heating cycle. A single Tg was detected for each composition, indicative of miscibility in the glassy state. Melting temperatures, at fixed composition, decrease with increasing treatment time. Mixtures rich in one component show a single Tm, whereas two distinct peaks were observed for the 50/50 blend; on increasing the treatment time some transesterification takes place, evidenced by the melting peak broadening and merging together. The overall crystallinity developed when transesterification plays a role strongly depends on composition: it is inhibited for the 50/50 mixture on cooling, though it can be induced to some extent by reheating or holding during cooling, whereas in one component‐rich blends the main effect is a reduction of the crystallization temperature. Isothermal crystallizations were also carried out as a function of the composition and of the residence time in the molten state; crystallization rate decreases with increasing holding time in the melt. Morphology of PTT and PTT‐rich mixtures under the adopted crystallization conditions exhibits typical banded spherulites, whose growth rate and band spacing vary with melt holding time; moreover, less regular concentric circles develop on increasing residence time at 280 °C.Spherulitic texture developed at 198 °C after 60 min storage at 280 °C by a PTT/PET 90/10 mixture.magnified imageSpherulitic texture developed at 198 °C after 60 min storage at 280 °C by a PTT/PET 90/10 mixture.

The New Measurement Method of Blending Ratio of PTT/PET Fiber Blends by Centrifugal Separation

“…1.36 g/cm 3 1.37 g/cm 3 1.38 g/cm 3 10 mm 5 mm 2 mm fiber power Fig. 2 Liquid density on separation effect Fig.…”

“…The effect of liquid density on centrifugal separation Three mixed solutions with density of 1.36 g/cm 3 , 1.37 g/cm 3 , 1.38 g/cm 3 were respectively prepared using xylene and carbon tetrachloride. Fifteen milliliters of each solution was added into three centrifuge tubes, respectively.…”

“…The preparation of mixed solutions with densities between 1.33 ~ 1.38 g/cm 3 were obtained by mixing of different ratio of xylene (0.857 g/cm 3 ) and carbon tetrachloride (1.572 g/cm 3 ). The mixed fiber samples were degassed to be sufficient wet in the mixed solution, and then were added into the centrifuge tubes, which were filled with a certain amount of centrifugal liquid.…”

“…The PTT (polytrimethylene-tereph-thalate) fiber is one of the new polyester fibers. The densities of PET and PTT are 1.38 and 1.33 g/cm 3 , respectively. The latter has good acid and alkali resistance just like the former, and also good flexibility like polyamide fiber, and good elasticity like spandex.…”

“…So the PTT fiber has been more and more applied in the textile and garment industry. [2][3] Fig. 1 showed that the difference of these two fibers is only one methylene group in the structural unit of PTT molecular than PET molecular.…”