Dynamic and Relaxation of PEG polymer Chain Segment for Phase Change Materials (PCMs)

This work’s most notable memory concept for next-generation novels was a reversible phase shift in a substance called phase change materials (PCMs). Here, a polyethylene glycol (PEG) polymer relaxation study employing DMA will be conducted to investigate the qualities of PCMs as superior materials. Through the method of wet mixing, PEG polymer with reinforcement made of silica was synthesized. The variation of silica xerogel was a composition of up to 20% silica xerogel. Adding silica is quite good in reducing the loss factor up to 50 MPa at the addition of 20% silica xerogel. This condition was due to the bonds formed in the polymer chain causing shrinkage and flexibility of composites. Due to the addition of silica xerogel as filler, we can study the relaxation behavior and loss factor of a material using DMA and learn more about its viscoelastic characteristics, including its capacity to absorb vibrations, resistance to impacts, and overall mechanical performance at various temperatures. Relaxation was frequently used to describe phase change materials (PCMs), especially when discussing their capacity to store thermal energy. The release or absorption of thermal energy by a PCM during its phase transition was referred to as the relaxation process.


Introduction
Phase change materials (PCMs) are substances with the remarkable ability to store and release large amounts of thermal energy during phase transitions [1].They undergo a physical change in their molecular structure, transitioning between solid, liquid, and sometimes gaseous states, absorbing or releasing heat [2].This unique characteristic makes them valuable for various applications in various industries, including energy storage, construction, electronics, and more.
Using phase change materials has existed for centuries, but recent advancements in materials science and engineering have significantly expanded their potential applications [3].PCMs are carefully designed to have specific phase transition temperatures, typically within a desired range for a particular application [4][5][6].This characteristic allows them to absorb heat when transitioning from solid to liquid (melting) and release heat from liquid to solid (solidification).In conclusion, phase change materials offer a versatile and efficient thermal energy storage and management solution.Their ability to store and release heat during phase transitions makes them valuable in numerous applications across different industries, contributing to energy conservation, improved comfort, and sustainability.
Relaxation is a concept commonly associated with phase change materials (PCMs), particularly in the context of their thermal energy storage capabilities [7].The relaxation process refers to the release or absorption of thermal energy by a PCM during its phase transition.Understanding the correlation between relaxation and PCMs is crucial for evaluating their performance and efficiency in various applications.Dynamic Mechanical Analysis (DMA) is a commonly used technique to investigate the viscoelastic properties of materials, including their relaxation behavior and damping characteristics [8].DMA measures the response of a material to an applied oscillatory stress or strain [9], allowing researchers to analyze its mechanical properties as a function of temperature, frequency, and time.
Previous studies have examined materials' relaxation behavior and damping factors using DMA.Li et al. have investigated the relaxation behavior of polymer thin film materials using DMA [10].This study analyzed the materials' storage modulus, loss modulus, and damping factor over a range of frequencies and temperatures.They observed variations in relaxation behavior for different polymer types and discussed the influence of molecular structure and thermal transitions on damping properties.In the other study, the viscoelastic relaxation and damping behavior of epoxy composites was done by Prasob et al. [11].This research focused on the viscoelastic relaxation and damping behavior of epoxy composites.DMA was employed to investigate the composites' storage modulus, loss modulus, and damping factor as a function of temperature and frequency.Katsiropoulus et al. have studied the damping behavior of fiber-reinforced polymer composites using DMA [12].They analyzed the effect of fiber type, fiber orientation, and matrix properties on the storage modulus, loss modulus, and damping factor.The results showed that the fiber content and alignment significantly affected the damping properties, with higher fiber volume fractions leading to increased damping.However, based on previous studies, the relationship between loss factor ("E") and relaxation has not been studied in PEGbased composites on temperature function with DMA.
This study highlighted the use of DMA to investigate the relaxation behavior and dynamic loss factor ("E") of composite materials.Therefore, it is crucial to understand and continue researching the loss factor ("E") and relaxation method of PCMs materials, particularly in isotropic composite materials.This study will concentrate on PEG-based composite materials with various loss factors of silica xerogel fillers.Therefore, it is crucial to research DMA to ascertain its physical characteristics.

Method
The synthesis of silica xerogel was the first step in preparing PEG composites.Tanah Laut sand was used to make silica xerogel, extracted using the same alkaline fusion method as in the previous study [13,14].The composite samples contained 0, 5, 10, and 20% silica xerogel.Synthesized silica xerogel has been reported as in the previous results using XRD analysis to determine the crystal structure formed [15].To establish a correlation between the relaxation and loss factor ("E") that takes place in the composite, the generated composite samples were next examined using DMA in tension mode with temperature function, which is concerned with the loss factor ("E").It took 30 minutes to measure DMA from 25qC to 70qC.

Results and Discussion
Figure 1 shows the diffraction profile from silica xerogel and PEG, which was prepared using the previous method [15].The diffraction properties of the silica xerogel made from beach sand extraction and its composites demonstrate an amorphous structure with an increase in the background diffraction at 2-theta between 20 and 29q.These findings have been verified based on the findings of earlier investigations on silica xerogel [16][17][18][19], these findings have been verified.The highest peaks of PEG's semicrystalline structure, which arise at two theta and correspond to 19.09 and 23.19q, respectively, are numerous.In previous studies [20][21][22], the PEG crystallized peaks exhibit both elastic and non-elastic dispersion.Elastic and non-elastic scattering will happen when X-rays strike an atom because of the vibrations that will take place.Research from the past has also shown that this phenomenon exists.The width of te peak occurring, which was connected to an increase in crystallinity and crystal size, was demonstrated by Londoño-Restrepo et al. to suggest the presence of nanocrystalline apatite in raw beef bone [14,23].The existence of elastic and inelastic scattering, which controls it, causes this occurrence.As a result, the first step in determining the sample crystallinity percentage is this diffraction characterization.In the meantime, an amorphous region and tool backdrop are indicated by the "hump" generated below the diffraction pattern.The effectively synthesized silica from Figure 1 is next wet mixed with PEG to create a composite.Additionally, DMA is utilized to assess the thermomechanical characteristics of the composite; nevertheless, in this study, the loss modulus will be the main focus.
Figure 2 shows the loss factor profile of the PEG/silica xerogel composite by DMA analysis.Based on the appearance in Figure 2, a consistent pattern of loss factor/loss energy ("E") released by the polymer chain appears.The more silica xerogel added, the greater the on-set temperature of the composite (Table 1).This pattern is also clearly shown in the inset of Figure 2. The role of silica xerogel in inhibiting energy loss due to the free movement of polymer chains significantly impacts relaxation conditions.

Intensity (a.u)
Figure 2. The loss factor of composites with additional silica xerogel.The inset image shows the shift of a set temperature to a higher temperature.
The formation energy of the compounds has been calculated, and the results are shown in Table 1.
Table 1.On-set, off-set temperature, and peak width of the loss factor profile from PEG/silica xerogel.

Samples (% silica xerogel)
On set (q qC) Offset (q qC) The peak width of the loss factor profile DMA measures relaxation by subjecting the material to a sinusoidal deformation (stress or strain) at a constant frequency.The response of the material is recorded as a function of time.The relaxation behavior is typically represented by a relaxation modulus curve, which shows how the modulus (a measure of material stiffness) changes over time during the relaxation process.The curve may exhibit multiple relaxation processes associated with different relaxation timescales.While the loss factor, or loss energy, quantifies the ability of a material to dissipate energy when subjected to cyclic loading.It is defined as the ratio of the energy dissipated per cycle to the energy stored in the material during that cycle.The dimensionless damping factor is usually expressed as a fraction or a percentage.In DMA, the loss factor is calculated by comparing the amplitude of the deformation (e.g., strain or stress) with the amplitude of the corresponding response (e.g., strain or stress) [1].It represents the extent to which the material absorbs and dissipates energy as heat rather than storing it elastically.A higher damping factor indicates a greater energy dissipation capacity and a more viscoelastic behavior.Based on this explanation, Figure 2 shows that the composite with the most PEG has the highest peak loss factor height.This result indicates that the role of silica as heat storage is not visible because no silica is added to pure PEG (0%).This result is supported by the wider peak loss factor in the pure PEG sample (Table 1).
By studying a material's relaxation behavior and loss factor using DMA, we can gain insights into its viscoelastic properties, such as its ability to absorb vibrations, impact resistance, and overall mechanical performance across different temperatures because of additional silica xerogel as filler.These characteristics are crucial in various applications, including designing and optimizing materials for engineering, automotive, aerospace, and biomedical fields.

Conclusion
The correlation between dynamic phenomena and composite relaxation has been analyzed in this article through DMA characterization.Based on the prior investigation, it was determined that the alkaline fusion process had been successful in achieving the desired xerogel properties.The loss factor, which shows energy dissipation due to the free movement of the polymer, can be reduced by adding silica xerogel as a filler.Adding silica is quite good in reducing the loss factor up to 50 MPa at the addition of 20% silica xerogel.This additional was due to the bonds formed in the polymer chain causing shrinkage and flexibility of composites.