Recrystallization and secondary crystallization in polymers

Yagfarov, M.Sh.; Mitrofanova, E.P.

doi:10.1016/0032-3950(86)90246-7

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…Moreover, it was realized that “recrystallization is observed over the whole interval between T c and T m ” . Apart from the works on PET, , the complex DSC traces with multiple exothermic and endothermic peaks have been recorded on many other polymers such as poly(ether ether ketone) (PEEK), − poly(trimethylene terephthalate) (PTT), , etc. Since it was not always known if the structural reorganization takes place during the reported experiments, the results of these studies remain ambiguous.…”

mentioning

confidence: 99%

What Thermal Analysis Can Tell Us About Melting of Semicrystalline Polymers: Exploring the General Validity of the Technique

2018

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Thermal characterization of semicrystalline polymers can constitute a difficult task due to the metastable nature of polymer crystals. It is well documented that polymer structure can reorganize during the thermoanalytical experiment. It has become also clear that thermal analysis alone cannot discriminate the reorganization processes from multiple melting events. Therefore, instead of studying the initial sample state the measurements may simply reflect the structural evolution uncontrollably occurring during the experiment. Here an original setup combining in situ ultrafast chip calorimetry with millisecond time-resolved X-ray scattering is used to find the structural signature of the reorganization processes. The information is further used to construct the heating-rate versus crystallization-temperature reorganization (HR-CT-R) diagram. The diagram allows rationally designing thermoanalytical experiments in which one can completely exclude uncontrolled evolution of the semicrystalline structure. For a typical aromatic polyester, poly(trimethylene terephthalate), the critical heating rate above which all reorganization processes cease to exist can reach 1000 K/s and more.

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confidence: 99%

What Thermal Analysis Can Tell Us About Melting of Semicrystalline Polymers: Exploring the General Validity of the Technique

2018

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“…Heating duration: If a semi crystalline polymer is heated above its glass transition temperature, the amorphous region will become mobile and this mobility will impact its mechanical properties [37]. It was anticipated that the heating duration will promote the mobility of the amorphous region, and thus it can be considered as a process variable.…”

Section: Outcome Of Phase I and Design Of Phase Iimentioning

confidence: 99%

Investigation and development of friction stir welding process for unreinforced polyphenylene sulfide and reinforced polyetheretherketone

Ahmed

Tooren

Justice

et al. 2018

Journal of Thermoplastic Composite Materials

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The joining of thermoplastics through welding offers numerous advantages over mechanical joining. Most importantly, it eliminates the use of costly fasteners and has only a limited effect on the strength of the parts being joined. Since it does not require the introduction of holes, loading pins, and the associated stress concentrations, a specific form of welding, friction stir welding (FSW), was investigated for the creation of butt joints of unreinforced polyphenylene sulfide (PPS) and short carbon fiber (CF)-reinforced polyetheretherketone (PEEK) plates. Unlike metals, analytical models and experimental results show that the heat generated by the FSW tool is insufficient to produce the heat required to weld thermoplastic materials. Therefore, a second heat source is required for preheating these thermoplastics. In this research, a resistance type surface heater was placed at the bottom of two identical weld pieces to produce good quality welds. Two types of shoulder design such as rotating shoulder and stationary shoulder were developed in this study. Taguchi’s design of experiment method was utilized to develop the welding process, where heating duration, material temperature, tool rotational speed, and tool traverse speed were used as the welding parameters. One of the process parameters, tool traverse speed, had significant influence on the tensile strength of PPS samples. While PPS sample showed relatively lower tensile strength with higher traverse speed, short CF-reinforced PEEK samples had higher tensile strength with a higher traverse speed. In addition to tensile tests, fracture toughness tests were performed for both PPS and PEEK samples to observe the influence of unwelded segments in the welded parts. In this study, joint efficiency of PEEK samples was found to be higher than that of PPS samples. Micrographs of PEEK samples showed uniform homogenous mixture of part materials.

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“…This makes P3EHT similar to the classical representatives of the semirigid chain family such as poly(ethylene terephthalate) (PET), poly(ether ether ketone) (PEEK) and others. These polymers display the socalled double-melting behavior, which has been a highly debated topic in polymer physics since several decades [5][6][7][8]. Several models have been put in the past to account for the presence of several endothermic peaks on the DSC heating traces of these polymers.…”

Section: Introductionmentioning

confidence: 99%

Thermal Properties of Poly(3-(2′-Ethyl)Hexylthiophene): Study with a Real-Time Combination of Synchrotron X-Ray Scattering and Ultrafast Chip Calorimetry

Мельников

Rosenthal

Erdmann

et al. 2020

KEM

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Here we report on reorganization on heating of a perspective organic semiconductor poly(3-(2′-ethyl)hexylthiophene) (P3EHT). P3EHT is an analogue of a well-known poly(3-hexylthiophene) (P3HT), which has comparable optoelectronic properties and the advantage of a lower processing temperature. The processes of structural reorganization during heating of P3EHT have been explored with a combination of synchrotron X-ray scattering and ultrafast chip calorimetry. The signature of reorganization has been identified from an increase of d-spacing of 100 peak of the P3EHT unit cell. It was observed that reorganization operates during heating of P3EHT at conventional rates of a DSC experiment (i.e., at 10 deg/min), whereas it is largely suppressed at a heating rate of 100 deg/s. Despite the absence of reorganization at high heating rates the calorimetric curves exhibit pronounced double melting, which corroborates the model of the negative pressure building up during crystallization of semi-rigid chain polymers.

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Recrystallization and secondary crystallization in polymers

Cited by 5 publications

References 2 publications

What Thermal Analysis Can Tell Us About Melting of Semicrystalline Polymers: Exploring the General Validity of the Technique

What Thermal Analysis Can Tell Us About Melting of Semicrystalline Polymers: Exploring the General Validity of the Technique

Investigation and development of friction stir welding process for unreinforced polyphenylene sulfide and reinforced polyetheretherketone

Thermal Properties of Poly(3-(2′-Ethyl)Hexylthiophene): Study with a Real-Time Combination of Synchrotron X-Ray Scattering and Ultrafast Chip Calorimetry

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