A Review on Polymeric-Based Phase Change Material for Thermo-Regulating Fabric Application

Mitigating heat effects in the workplace with a ventilation jacket: Simulations of the whole-body and local human thermophysiological response with a sweating thermal manikin in a warm-dry environment

Climate change is increasingly affecting human well-being and will inevitably impact on occupational sectors in terms of costs, productivity, workers' health and injuries. Among the cooling garment developed to reduce heat strain, the ventilation jacket could be considered for possible use in workplaces, as it is wearable without limiting the user's mobility and autonomy. In this study, simulations with a sweating manikin are carried out to investigate the effects of a short-sleeved ventilation jacket on human thermophysiological responses in a warm-dry scenario. Simulations were performed in a climatic chamber (air temperature = 30.1 °C; air velocity = 0.29 m/s; relative humidity = 30.0 %), considering two constant levels of metabolic rate M (M1 = 2.4 MET; M2 = 3.2 MET), a sequence of these two (Work), and three levels of fan velocities (lf = 0; lf=2; lf=4). The results revealed a more evident impact on the mean skin temperature (Tsk) compared to the rectal temperature (Tre), with significant decreases (compared to fan-off) at all M levels, for Tsk from the beginning and for Tre from the 61st minute. Skin temperatures of the torso zones decreased significantly (compared to fan-off) at all M levels, and a greater drop was registered for the Back. The fans at the highest level (lf=4) were significantly effective in improving whole-body and local thermal sensations when compared to fan-off, at all M levels. At the intermediate level (lf=2), the statistical significance varied with thermal zone, M and time interval considered. The results of the simulations also showed that the Lower Torso needs to be monitored at M2 level, as the drop in skin temperature could lead to local overcooling and thermal discomfort. Simulations showed the potential effectiveness of the ventilation jacket, but human trials are needed to verify its cooling power in real working conditions.

Polyethylene Glycol Confined in SiO2-Modified Expanded Graphite as Novel Form-Stable Phase Change Materials for Thermal Energy Storage

Form-stable phase change materials (FSPCMs) composed of poly(ethylene glycol) (PEG) encapsulated in SiO2-modified expanded graphite (EG@SiO2) were prepared and investigated for thermal energy storage behaviors. The modification of SiO2 on EG was done using a simple sol-gel method, and then the resulting EG@SiO2 was introduced to confine PEG at varying content (60-90 wt %). Surface properties (including microstructure, morphology, and functional groups), PEG adsorptivity, leakage-proof ability, and thermal energy storage of the prepared materials were thoroughly characterized and discussed. The EG@SiO2 with 15 wt % SiO2 outstandingly adsorbed PEG as compared to the pristine EG, showing up >80 wt % of PEG. As a result, PEG was well stabilized in EG@SiO2 porous network without leakage, owing to capillary force, surface tension, and hydrogen bonding interactions. The optimal 80 wt % PEG/EG@SiO2 composite possessed high crystallinity (93.5%), high thermal energy storage capacity (132.5 J/g), and excellent thermal conductivity (4.086 W/m·K). In addition, it exhibited good cycling durability after 500 repeated melting/crystallization cycles. The high thermal efficacy and inexpensiveness would make the PEG/EG@SiO2 FSPCMs suitable for scale-up applications in thermal energy storage.

Impact of implant-based breast reconstruction on bra fit

Comfortable and well-fitting bras are necessary for good quality of life but hard to find for women who undergo reconstruction after breast cancer treatment. This study aimed to provide data to inform bra designs for breast cancer survivors. We measured anatomical distances used in bra design on 3D clinical photographs of patients who underwent unilateral and bilateral implant-based reconstruction to quantify changes after reconstruction relative to the measured values before the person underwent surgery. We performed additional assessments of symmetry before surgery and after reconstruction, and we used regression analyses to identify associations between the measurements and patient characteristics, such as BMI. Overall, almost all measurements changed significantly in implant-based reconstructed breasts relative to native breasts. We highlight several aspects of ergonomic bra design that will be impacted by the changes in anatomical distances. Practitioner summary: Implant-based breast reconstruction surgery changes the breast so that off-the-rack bras are inadequate. This study provides designers with measurement data from women who underwent implant-based reconstruction to inform bra designs for this population. The key factor designers need to account for is the semi-spherical shape of the reconstructed breast.

Incorporation of MPCM on cotton fabric for potential application in hospital bed sheet

Over the last few decades, phase change materials (PCM) have attracted a great deal of interest in medical textiles due to its superior thermoregulation system, simple application, and so on. Patients, however, confined to bed in a medical facility face the serious risk of developing bed sores, which is not mitigated by the use of a standard bed sheet. Numerous articles and patents have been studied related to development of thermal bed sheets using PCM applied by various techniques; however, no such initiates was found to prepare and characterize of hospital bed sheets using microencapsulated phase change material (MPCM) through screen printing method. Thus, this study aims to develop a hospital bed sheet constructed from cotton fabric incorporated with MPCM. To accomplish this, MPCM was mixed into the printing paste that had been applied on the fabric by screen printing method, and then dried at room temperature. Thermal behavior, thermal transition, and thermal conductivity of the developed samples had been investigated. Moisture management properties, mechanical properties, and bonding behavior of the samples were also examined. Scanning electron microscope (SEM) was used to analyze the sample's morphology, and a differential scanning calorimeter (DSC) was used to determine how polymeric materials behaved when heated. Thermogravimetric analysis (TGA) demonstrated that the MPCM incorporated sample lost weight slowly, while the DSC test confirmed that melting began at 20 °C and ended at 30 °C. Furthermore, fabricated sample had higher heat conductivity (0.1760822 w.m^-1 k^-1). Overall, the results revealed a great potential for using the developed samples as hospital bed sheets to prevent patients from developing bed sores.

Cotton functionalized with polyethylene glycol and graphene oxide for dual thermoregulating and UV-protection applications

A thermoregulating smart textile based on phase change material (PCM) polyethylene glycol (PEG) was prepared by chemically grafting carboxyl-terminated PEG onto cotton. Further deposits of graphene oxide (GO) nanosheets were made on the PEG grafted cotton (PEG-g-Cotton) to improve the thermal conductivity of the fabric and to block harmful UV radiation. The GO-PEG-g-Cotton was characterized by Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and field emission-scanning electron microscopy (FE-SEM). With an enthalpy of 37 and 36 J/g, respectively, the DSC data revealed that the functionalized cotton's melting and crystallization maxima occurred at 58 °C and 40 °C, respectively. The thermogravimetric analysis (TGA) presented that GO-PEG-g-Cotton was thermally more stable in comparison to pure cotton. The thermal conductivity of PEG-g-Cotton increased to 0.52 W/m K after GO deposition, while pure cotton conductivity was measured as 0.045 W/m K. The improvement in the UV protection factor (UPF) of GO-PEG-g-Cotton was observed indicating excellent UV blocking. This temperature-regulating smart cotton offers a high thermal energy storage capability, better thermal conductivity, thermal stability, and excellent UV protection.

A review of the thermal storage of phase change material, morphology, synthesis methods, characterization, and applications of microencapsulated phase change material

In the thermal energy storage area, microencapsulated phase change material (MPCM) is getting more popular among researchers. When phase change materials (PCMs) shift from one phase to another at a specific temperature, a significant quantity of thermal energy is stored. The PCM application focuses on upgrading worldwide energy conservation efforts in light of the rapidly dwindling fossil fuels. The thermal energy supplied by PCM is significantly influenced by the choice of supporting materials and encapsulation methods. A solution to the volume change issues of PCM, phase separation, and leakage is the PCM microencapsulation technique. One of the most common methods to increase the effectiveness of thermal storage material is attained by using PCM with microencapsulation. The preparation processes and thermal characteristics of the MPCM are summarized in this paper. This paper gives information about MPCM with its types, properties, testing, and characterizations. Tables describe specific examples of PCM with thermal properties. Applications in various fields are defined. This review gives as much information to help and be useful for new researchers in the field of thermal management systems to guide their future research.

Applications of phase change materials in smart drug delivery for cancer treatment

Phase change materials (PCMs) are materials that are stimulated by the external enthalpy change (temperature) to realize solid-liquid and liquid-solid phase transformation. Due to temperature sensitivity, friendly modification, and low toxicity, PCMs have been widely used in smart drug delivery. More often than not, the drug was encapsulated in a solid PCMs matrix, a thermally responsive material. After the trigger implementation, PCMs change into a solid-liquid phase, and the loading drug is released accordingly. Therefore, PCMs can achieve precise release control with different temperature adjustments, which is especially important for small molecular drugs with severe side effects. The combination of drug therapy and hyperthermia through PCMs can achieve more accurate and effective treatment of tumor target areas. This study briefly summarizes the latest developments on PCMs as smart gate-keepers for anti-tumor applications in light of PCMs becoming a research hot spot in the nanomedicine sector in recent years.

A Rapid Thermal Absorption Rate and High Latent Heat Enthalpy Phase Change Fiber Derived from Bio-Based Low Melting Point Copolyesters

A series of poly(butylene adipate-co-hexamethylene adipate) (PBHA) copolymers with different content of 1,4-cyclohexanedimethanol (CHDM) was synthesized via one-step melt polymerization. The PBHA copolymer with 5 mol% CHDM (PBHA-C5) exhibited a low melting point (T_m) and high enthalpy of fusion (∆H_m) of 35.7 °C and 43.9 J g⁻¹, respectively, making it a potential candidate for an ambient temperature adjustment textile phase change material (PCM). Polybutylene terephthalate (PBT) was selected as the matrix and blended at different weight ratios of PBHA-C5, and the blended samples showed comparable T_m and ∆H_m after three cycles of cooling and reheating, indicating good maintenance of their phase changing ability. Samples were then processed via melt spinning with a take-up speed of 200 m min⁻¹ at draw ratios (DR) of 1.0 to 3.0 at 50 °C. The fiber’s mechanical strength could be enhanced to 2.35 g den⁻¹ by increasing the DR and lowering the PBHA-C5 content. Infrared thermography showed that a significant difference of more than 5 °C between PBT and other samples was achieved within 1 min of heating, indicating the ability of PBHA-C5 to adjust the temperature. After heating for 30 min, the temperatures of neat PBT, blended samples with 27, 30, and 33 wt% PBHA-C5, and neat PBHA-C5 were 53.8, 50.2, 48.3, 47.2, and 46.5 °C, respectively, and reached an equilibrium state, confirming the temperature adjustment ability of PBHA-C5 and suggesting that it can be utilized in thermoregulating applications.

Emulsion-based, flexible and recyclable aerogel composites for latent heat storage

Although emulsion-based, phase change material-encapsulated monolithic composites are promising for latent heat storage, their rigidity and non-recyclability imposed by the relatively dense covalent crosslinking hinder the composites from real applications. Herein, we report the fabrication of aerogel composites with flexibility and recyclability from cellulose nanocrystal-stabilized, octadecane-encapsulated Pickering emulsions solidified using physical gelation. The resulting monolithic composites exhibited controllable external shapes, and the introduction of poly(vinyl alcohol) significantly reduced the leakage of the encapsulated octadecane. The aerogel composites showed flexibility at temperature over 30 °C, and robust compressive behavior, without fracture at 70% compressive strain. The composites possessed similar heat storage (melting) temperature and heat release (crystallization) temperature to that of bulk octadecane, high heat capacity (up to 253 J^.g^-1) and high reusability, without obvious deterioration in heat capacity after 100 heating-cooling cycles. Moreover, the aerogel composites exhibited recyclability, simply by dissolving the composites in hot water to form emulsions and then by freeze drying to form aerogel composites. The flexibility and recyclability, together with robust compression, controllable external shapes, high heat capacity and good reusability, make the aerogel composites to be excellent candidates for latent heat storage.

Advanced materials for personal thermal and moisture management of health care workers wearing PPE

In recent years, the development of personal protective equipment (PPE) for health care workers (HCWs) attracted enormous attention, especially during the pandemic of COVID-19. The semi-permeable protective clothing and the prolonged working hours make the thermal comfort a critical issue for HCWs. Although there are many commercially available personal cooling products for PPE systems, they are either heavy in weight or have limited durability. Besides, most of the existing solutions cannot relieve the perspiration efficiently within the insolation gowns. To avoid heat strain and ensure a longtime thermal comfort, new strategies that provide efficient personal thermal and moisture management without compromising health protection are required. This paper reviews the emerging materials for protective gown layers and advanced technologies for personal thermal and moisture management of PPE systems. These materials and strategies are examined in detail with respect to their fundamental working principles, thermal and mechanical properties, fabrication methods as well as advantages and limitations in their prospective applications, aiming at stimulating creative thinking and multidisciplinary collaboration to improve the thermal comfort of PPEs.

Recent Advances in Polymer-Containing Multifunctional Phase-Change Materials

Phase-change materials (PCMs) play a key role in thermal energy storage owing to their high-energy storage density and small temperature fluctuation during the phase-transition stage. Polymers, either as a supporting material to prevent liquid leakage during the phase-change process or used with specific target, have been widely recognized in the fabrication of PCM composites. In the meantime, due to the continued demand for variety of PCMs, a single thermal energy storage function seems to be insufficient to meet these needs. Thanks to the good compatibility with PCMs and the structural adjustable properties of polymers, they have been broadly used as the second component in the multifunctional PCMs composite. In this Review, strategies for multifunctional PCMs supported by polymers and their potential energy applications, such as thermal energy harvesting and storage, shape memory, wearable devices, self-cleaning, and other forms of applications, are summarized comprehensively. The future research directions and challenges of multifunctional PCMs with polymers are also discussed.

Electrospun Shape-Stabilized Phase Change Materials Based on Photo-Crosslinked Polyethylene Oxide

Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal energy storage ability and tunable working temperature are of high interest to produce smart thermoregulating textiles, useful for increasing human thermal comfort while avoiding energy waste. Common organic PCMs suffer from instability in their molten state, which limits their applicability as highly performing fibrous systems. In this work, electrospun fibrous mats made of polyethylene oxide (PEO), a PCM with excellent thermal properties and biocompatibility, were fabricated and their shape instability in the molten state was improved through UV photo-crosslinking. The characterization aimed to assess the performance of these shape-stable electrospun mats as nanofibrous PCMs for thermal management applications. In addition to an enhanced resistance to water-based solvents, UV-cured electrospun PEO mats demonstrated a remarkable latent heat (≈112 J/g), maintained over 80 heating/cooling cycles across the phase change temperature. Moreover, their morphological stability above their melting point was demonstrated both macroscopically and microscopically, with the retention of the initial nanofibrous morphology. Tensile mechanical tests demonstrated that the UV crosslinking considerably enhanced the ultimate properties of the fibrous mat, with a five-fold increase in both the tensile strength (from 0.15 MPa to 0.74 MPa) and the strain at break (from 2.5% to 12.2%) compared to the uncrosslinked mat. In conclusion, the photo-crosslinked electrospun PEO material exhibited high thermal properties and good shape stability without displaying leakage; accordingly, in the proposed PCM system, the necessity for encapsulation or use of a supporting layer has been eliminated. Photo-crosslinking thus proved itself as an effective, fast, and environmentally friendly method to dramatically improve the shape-stability of nanofibrous PEO electrospun mats for smart thermoregulating textiles.

Enhancement of the Thermal Performance of the Paraffin-Based Microcapsules Intended for Textile Applications

Phase changing materials (PCMs) microcapsules MPCM32D, consisting of a polymeric melamine-formaldehyde (MF) resin shell surrounding a paraffin core (melting point: 30–32 °C), have been modified by introducing thermally conductive additives on their outer shell surface. As additives, multiwall carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxyoxythiophene) poly (styrene sulphonate) (PEDOT: PSS) were used in different parts by weight (1 wt.%, 5 wt.%, and 10 wt.%). The main aim of this modification—to enhance the thermal performance of the microencapsulated PCMs intended for textile applications. The morphologic analysis of the newly formed coating of MWCNTs or PEDOT: PSS microcapsules shell was observed by SEM. The heat storage and release capacity were evaluated by changing microcapsules MPCM32D shell modification. In order to evaluate the influence of the modified MF outer shell on the thermal properties of paraffin PCM, a thermal conductivity coefficient (λ) of these unmodified and shell-modified microcapsules was also measured by the comparative method. Based on the identified optimal parameters of the thermal performance of the tested PCM microcapsules, a 3D warp-knitted spacer fabric from PET was treated with a composition containing 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS shell-modified microcapsules MPCM32D and acrylic resin binder. To assess the dynamic thermal behaviour of the treated fabric samples, an IR heating source and IR camera were used. The fabric with 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS in shell-modified paraffin microcapsules MPCM32D revealed much faster heating and significantly slower cooling compared to the fabric treated with the unmodified ones. The thermal conductivity of the investigated fabric samples with modified microcapsules MPCM32D has been improved in comparison to the fabric samples with unmodified ones. That confirms the positive influence of using thermally conductive enhancing additives for the heat transfer rate within the textile sample containing these modified paraffin PCM microcapsules.

Examination of the Coating Method in Transferring Phase-Changing Materials

In this study, it is intended to identify the characteristics of heat regulation in heat storage microencapsulated fabrics and it is aimed to examine the effect of application method for microcapsules. For this purpose, phase-changing materials (PCM) microcapsules were applied according to the method of impregnation and coating on cotton fabrics. The presence and distribution of microcapsules on the fabric surface were investigated by scanning electron microscopy (SEM). The temperature regulation of the fabrics was examined utilizing the temperature measurement sensor and the data recorder system (Thermal camera). According to the DSC analysis, the melting process in fabrics coated with Mikrathermic P microcapsules occurred between 25.83oC - 31.04oC and the amount of heat energy stored by the cotton fabric during the melting period was measured as 2.70 J/g. Changes in fabric surface temperature due to the presence of microcapsules in the fabric structure were determined in the measurements. When comparing the transfer methods of PCM capsules, the contact angle of impregnated and coated fabric was obtained as 42o and 73o, respectively. As a result of the study, when the analysis results of the microcapsules transferred to the fabric by the impregnation and coating method are evaluated, it is seen that the PCM transferred fabric with the impregnation method performs more efficient temperature regulation. However, the analysis results show that fabrics transferred with PCM by coating also perform heat absorption, although not as much as the impregnation method. Performance evaluation according to the target properties of textile material will give the most accurate result for the fabrics which are treated by coating and impregnation method.

Consistent DSC and TGA Methodology as Basis for the Measurement and Comparison of Thermo-Physical Properties of Phase Change Materials

Measuring thermo-physical properties of phase change materials (PCM) in a consistent and reliable manner is essential for system layout of thermal energy storages and correspondingly material selection. Only if basic properties are assessed in a comparable way a selection process leads to the top candidate for any given application and thus enhances market penetration of renewable energy sources coupled with thermal energy storage. In this study, we focus on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) as basic assessment techniques and develop consistent measurement procedures to create a database with comparable results. We show consistency of the measured results through analysis of coefficient of variation (CV), being in the mean 1.69%, 0.05%, 0.06% and 4.00% for enthalpy, melting onset, melting peak and maximum operating temperature, respectively. Overall, 23 PCM have been measured with the presented methodology, which was mainly possible due to the reduced measurement and preparation time per PCM compared to standard techniques, while achieving similar accuracy and precision.