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Poly(propylene terephthalate) Modified with 2,2‐Bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) Units: Thermal Behaviour, Crystallisation Kinetics and Morphology
Author(s) -
Berti Corrado,
Colonna Martino,
Finelli Lara,
Lorenzetti Cesare,
Lotti Nadia,
Vannini Micaela
Publication year - 2004
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200400246
Subject(s) - materials science , crystallinity , differential scanning calorimetry , polymer chemistry , crystallization , copolymer , propane , thermogravimetric analysis , phenylene , enthalpy of fusion , thermal stability , isothermal process , chemical engineering , analytical chemistry (journal) , melting point , composite material , thermodynamics , chemistry , polymer , organic chemistry , engineering , physics
Summary: The thermal behaviour of poly(propylene terephthalate) modified with 2,2‐bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) units (PPT/BHEEBT copolymers) was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and hot‐stage optical microscopy (MO). Good thermal stability was found for each sample. The thermal analysis carried out using the DSC technique showed that the T m of the copolymers decreased with the increment in BHEEBT unit content. This was different from the T g which, on the contrary, increased. Wide‐angle X‐ray diffraction measurements allowed the identification of the PPT crystalline structure in each semicrystalline sample. Multiple endotherms were shown in the PPT/BHEEBT samples, due to melting and recrystallisation processes, similarly to PPT. The $T_{\rm m}^ \circ $ of the copolymers was derived from the application of the Hoffman‐Weeks' method. The isothermal crystallisation kinetics were analysed according to Avrami's treatment. The introduction of BHEEBT units was found to decrease the crystallisation rate compared to pure PPT. Values of the Avrami's exponent n close to 3 were obtained for PPT/BHEEBT6 and PPT/BHEEBT12, regardless of T c , in agreement with a crystallisation process originating from pre‐determined nuclei and characterised by three‐dimensional spherulitic growth. As a matter of fact, for these two copolymers, space‐filling spherulites were observed through optical microscopy at all T c s. The heat of fusion (Δ H m ) was correlated to the specific heat increment (Δ c p ) for samples with different degrees of crystallinity, and the results were interpreted on the basis of the existence of an interphase, whose amount was found to depend mainly on composition, despite the thermal treatment applied to the polymer also playing an important role.Calorimetric curves of PPT, PBHEEBT homopolymers and their random copolymers after melt quenching.