Melting temperature versus crystallinity: new way for identification and analysis of multiple endotherms of poly(ethylene terephthalate)

Abstract

Poly(ethylene terephthalate) (PET) materials with different molecular weights were isothermally crystallized from melt by systematically varying the temperature and duration of the treatment performed in the differential scanning calorimeter (DSC). Multiple endotherm peaks were observed on the subsequent heating thermograms that were separated from each other on the basis of their melting temperature versus crystallization temperature and melting temperature versus crystallinity function. By this new approach five sub-peak sets were identified and then comprehensively characterised. Wide-Angle X-Ray Diffraction (WAXD) analyses revealed that the identified sub-peak sets do not differ in crystalline forms. By analysing the crystallinity and the melting temperature of the sub-peak sets as a function of crystallization time, crystallization temperature and intrinsic viscosity, it was concluded that below the crystallization temperature of 460 K the sub-peak sets that were formed during primary or secondary crystallization transform partially or completely to a third sub-peak set during the heating run of the measurement, while above this temperature, the sub-peak set formed during primary crystallization gradually transforms to a more stable structure, with higher melting temperature. These formations and transformations are described with mathematically defined parameters as well.

Investigation of physico‐mechanical, thermal, morphological, optical and biodegradation properties of polyvinyl alcohol films reinforced with alkali treated Limonia acidissima shell powder

“…The hydrophilic nature of LASP was diminished by alkali treatment, and more holes were found on the treated LASP surface. [ 41 ] Figure 7B showed the SEM images of alkali‐treated LASP, after alkali treatment, the LASP surface becomes rough, and these rough surfaces have additional advantages in particulate composite fabrication because they enable effective interfacial bonding between the polymer matrixes. [ 42 ]…”

“…DSC, differential scanning calorimetry; LASP, Limonia acidissima shell powder; PVA, polyvinyl alcohol LASP surface. [41] Figure 7B showed the SEM images of alkali-treated LASP, after alkali treatment, the LASP surface becomes rough, and these rough surfaces have additional advantages in particulate composite fabrication because they enable effective interfacial bonding between the polymer matrixes. [42] The SEM images of PVA/(5-25 wt.%) alkali-treated LASP biofilms shown in Figure 7C-H.…”

Effect of the Sequence Distribution and Internal Structure on the Hydrophilicity of Poly(ethylene terephthalate-co-aliphatic amide) Copolymers

“…The six peaks appear at approximately 16.3, 17.5, 21.6, 22.9, 26.1, and 32.6°, which are designated to the six crystal planes including (01̅1), (010), (11̅1), (11̅0), (100), and (111̅), respectively. Moreover, the copolymers (PAT/APs and PET/APA) possess similar characteristic diffraction peaks to those of PET and are classified as triclinic crystal structures. , This phenomenon reveals that the incorporation of modified monomers does not form a new crystal form but is only arranged in the amorphous region of the copolymers.…”

Flame retardancy of PET foams manufactured from bottle waste

“…2). The crystallisation ability of polymers is strongly related to their structure [37]. DSC measurements were performed on the FR-containing rPET foams to indirectly analyse the structural changes in the polymer chains that occurred during processing.…”