Microstructure of Thermally Crosslinkable Poly(Ethylene Terephthalate) (Pet-co-Xta) Benzocyclobutene Functionalized Copolymers

1996 ◽  
Vol 461 ◽  
Author(s):  
Brendan J. Foran ◽  
Elizabeth Pingel ◽  
Gary E. Spilman ◽  
Larry J. Markoski ◽  
Tao Jiang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Degree Of Crystallinity ◽  
Limiting Oxygen Index ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Poly Ethylene Terephthalate ◽  
Stable Flame ◽  
Poly Ethylene ◽  
Crystalline Domains ◽  
The Degree Of Crystallinity

ABSTRACTThe microstructure and thermal properties of copolymers of polyethylene terephthalate (PET) containing a crosslinkable terephthalic acid, 1,2-dihydrocyc Iobutabenzene 3,6 dicarboxylic acid (XTA) are reported. Wide angle x-ray scattering (WAXS) show that the addition of XTA does not alter the PET crystal structure in copolymers at low XTA contents. However, the degree of crystallinity drops for higher XTA levels. WAXS profiles show that PET-co-XTA 50% is amorphous, and that PEXTA homopolymer has a different crystal structure. Thermal data from DSC and TGA show that crosslinking of the benzocyclobutene groups (∼350°C) occurs at temperatures between melting (∼250°C) and degradation (∼400°C), making it possible to melt process the copolymers into fibers before the onset of crosslinking. Limiting oxygen index (LOI) measurements show that increased oxygen concentrations are required to sustain a stable flame in PET-co-XTA copolymers; whereas unmodified PET had an LOI value of -18%, the copolymers had LOI values near 32%. Further, while unmodified PET melts and drips as it burns, XTA copolymers formed a stable char that inhibiting flame propagation. An increased char was observed in optical micrographs for XTA containing polymers, and crystalline domains were observed near the burn surface in transmission electron micrographs.

Structure-Properties Relationships in Processed Poly(ethylene terephthalate)

2013 ◽  
Vol 554-557 ◽  
pp. 1757-1762
Author(s):  
Júlio C. Viana ◽  
Lyudmil Todorov
Keyword(s):  
Molecular Orientation ◽  
Ethylene Terephthalate ◽  
Degree Of Crystallinity ◽  
Thickness Variation ◽  
Pet Bottles ◽  
Poly Ethylene Terephthalate ◽  
Initial Modulus ◽  
Poly Ethylene ◽  
The Degree Of Crystallinity ◽  
Structure Properties

Abstract. Upon processing, polymeric products feature a complex microstructure. Besides evolving over the molded component, a through-the-thickness variation is also developed. This is the result of the thermo-mechanical environment (combined thermal and mechanical fields) applied during processing, which varies with the molding technique, the selected molding conditions and polymer properties (rheological, thermal, constitution). This complex microstructure makes rather intricate the establishment of structure-properties relationships in processed polymers. In fact, the basic identification of most relevant morphological parameters determining the behavior of the moldings is been revealed a difficult endeavor, further complicated by the multi-scale morphology presented by polymeric materials. This work follows an inductive approach for establishing the relationships between the structure and the properties (mechanical and barrier) of molded poly(ethylene terephthalate), PET. These relationships are investigated for specimens prepared by different methods, from “simple” to more “complex” stretching modes. Initially, PET specimens were prepared by stretching thin films at different high temperatures and strain rates, followed by quick cooling in a universal testing machine equipped with a thermal camera (uniaxial stretched specimens). More closely to processing, PET injection molded preforms were free blown without a mold with distinct conditions (free blown specimens). Finally, PET bottles were produced from the preforms also under different blown conditions. The morphology of all specimens was assessed by bi- and tri-refringence and DSC. The mechanical properties were evaluated by tensile tests at room temperature. Also, the oxygen transmission rate, OTR, was assessed for the PET bottles. For this low crystallinity and slowly crystallizable polymer, the initial modulus is mainly related to the amorphous phase (i.e., molecular mobility and orientation level). The yield stress appears to be determined by the degree of crystallinity and level of molecular orientation. In the case of free blown specimens (bi-axially stretched) the anisotropy of the initial modulus depends upon the induced anisotropy of the molecular orientation. OTR is influenced by the molecular orientation and the degree of crystallinity of the polymer. An attempt to interpret these types of relationships by molecular dynamics simulations is made.

scholarly journals Addition of Graphite Filler to Enhance Electrical, Morphological, Thermal, and Mechanical Properties in Poly (Ethylene Terephthalate): Experimental Characterization and Material Modeling

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1411 ◽  
Author(s):  
Basheer A. Alshammari ◽  
Fahad S. Al-Mubaddel ◽  
Mohammad Rezaul Karim ◽  
Mokarram Hossain ◽  
Abdullah S. Al-Mutairi ◽  
...  
Keyword(s):  
Percolation Threshold ◽  
Ethylene Terephthalate ◽  
Material Behavior ◽  
Degree Of Crystallinity ◽  
Experimental Characterization ◽  
Threshold Values ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Carbon Fillers ◽  
The Degree Of Crystallinity

Poly(ethylene terephthalate)/graphite (PET/G) micro-composites were fabricated by the melt compounding method using a minilab extruder. The carbon fillers were found to act as nucleating agents for the PET matrix and hence accelerated crystallization and increased the degree of crystallinity. TGA showed that carbon fillers improved the resistance to thermal and thermo-oxidative degradation under both air and nitrogen atmospheres. However, a poor agreement was observed at higher loadings of the filler where the composites displayed reduced reinforcement efficiency. The results demonstrate that the addition of graphite at loading >14.5 wt.% made electrically conductive composites. It was calculated that the electric conductivities of PET/graphite micro-composites were enhanced, above the percolation threshold values by two orders of magnitudes compared to the PET matrix. The minimum value of conductivity required to avoid electrostatic charge application of an insulating polymer was achieved, just above the threshold values. The addition of graphite also improved thermal stability of PET, accelerated its crystallization process and increased the degree of crystallinity. Microscopic results exhibit no indication of aggregations at 2 wt.% graphite, whereas more agglomeration and rolling up could be seen as the graphite content was increased in the PET matrix (in particular, above the percolation threshold value). Furthermore, based on the mechanical experimental characterization of the PET/graphite micro-composites, a large deformation-based mathematical model is proposed for material behavior predictions. The model fits well the experimental data and predicts other mechanical data that are not included in the parameter identification.

scholarly journals Role of Surfactants in the Properties of Poly(Ethylene Terephthalate)/Purified Clay Nanocomposites

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1397 ◽  
Author(s):  
Elaine dos Santos ◽  
Marcus Fook ◽  
Oscar Malta ◽  
Suédina de Lima Silva ◽  
Itamara Leite
Keyword(s):  
Clay Nanocomposites ◽  
Phosphonium Salts ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Alkyl Ammonium ◽  
Pet Crystallization

Purified clay was modified with different amounts of alkyl ammonium and phosphonium salts and used as filler in the preparation of PET nanocomposites via melt intercalation. The effect of this type of filler on morphology and thermal and mechanical properties of PET nanocomposites was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile properties, and transmission electron microscopy (TEM). The results showed that the mixture of alkyl ammonium and phosphonium salts favored the production of PET nanocomposites with intercalated and partially exfoliated morphologies with slight improvement in thermal stability. In addition, the incorporation of these organoclays tended to inhibit PET crystallization behavior, which is profitable in the production of transparent bottles.

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