Differential scanning calorimetry studies on poly(ethylene glycol) with different molecular weights for thermal energy storage materials

Abstract

Melting and crystallization behaviour of poly(ethylene glycol) (PEG) with different molecular weights (from 1000 to 35 000) and chosen blends of PEG is investigated by means of differential scanning calorimetry (DSC) operating in dynamic mode at different heating rates. The influence of the molecular weight of PEG on its melting point and enthalpy of fusion is evaluated; from the DSC data the degree of crystallinity is calculated–it is found that there is an increased tendency of higher‐molecular‐weight PEGs towards the formation of crystalline phase owing to their lower segmental mobility and more convenient geometrical alignment. During the freezing cycle, an increase in the molecular weight of PEG causes an increase in the solidification temperature and heat of crystallization. Thermal transition data are supplemented by optical microscopy–numerous small sphere‐shaped crystalline structures are observed to join together and impinge on their neighbours, forming eventually a multilayered lamellar texture. By implementing second polymeric component the polydispersity of the system increases, thus lowering the crystallization degree during preparation phase. It influences also the course of solidification by lowering the crystallization temperature, Tc. An additional effect observed in the case of the blend's freezing is associated with larger supercooling, probably due to morphological constraints and entanglements in interlamellar regions. The possible advantage of using PEG blends to replace pure components is connected with the possibility of changing the temperature range and heat associated with melting/freezing. Copyright © 2003 John Wiley & Sons, Ltd.

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

“…Experiments were conducted with aerosol systems containing PEG with average molecular masses of 200 ("PEG200"), 1000 ("PEG1000"), and 10 000 ("PEG10000") g mol −1 . This corresponds to a range in T g from 208.15 to 313.65 K (Pielichowski and Flejtuch, 2002;Dow, 2011). Under dry conditions and at room temperature, PEG200 is a liquid, PEG1000 is a waxy semisolid, and PEG10000 exists as solid flakes.…”

Investigation of the effects of thermal, oxidative and irradiation treatments on the behaviour of poly-ethylene glycol as a phase change material in thermal energy storage systems

“…Its advantages include a relatively large heat of fusion [1,6,7], non-corrosiveness [8], non-toxicity [9] and a wide range of phase change temperatures, which can be manipulated by modifying its molecular weight [7,8]. The flexibility of PEG is the main reason why it has been proposed for both heating and cooling systems, based on the appropriate selection of its molecular weight [10]. It has also been found that PEG is more reliable in melting-freezing cycles than any other inorganic salt hydrate PCM, as there is no super-cooling phenomenon occurring during its freezing cycles [8].…”

Triblock copolymers of PLLA-PEG-PLLA for nerve guidance channel scaffolds via 3D printing

“…A summary for all DSC results for the synthesized copolymers is shown in Table 3 where all copolymers were tested 3 times to assess reproducibility and the ramping temperature was kept at 5°C /min from 0°C to 100°C . with DSC, the melting peak stays relatively the same when the heating rate is 5°C/min or lower [15]. All samples were ramped to 200°C only once, however none of them showed an endothermic peak above 100°C indicating no PLLA homopolymer or water was mixed with the synthesized copolymers.…”

“…As shown in Figure 15, a clear trend of melting peak shifting to lower temperatures can be captured as more PLLA was added onto the PEG block. Generally, the PEG degree of crystallinity increases with the increment of its molecular weights [15], however, the presence of PLLA decreases the crystallinity of the copolymer and it requires less energy for the material to melt. This can also be proved in Figure 14 where the melting enthalpy also decreased with the presence of PLLA.…”