Preparation and Performances of UV-Cured Methacrylated Polyacrylic Acid-Based Core-Shell Hybrid Phase Change Materials.
Phase change materials (PCMs) are materials that undergo the solid-liquid and solid-solid phase transformation, more commonly known as the melting-solidification cycle, at a temperature within the operating range of a selected thermal application [1-3]. PCMs are designed to store latent heat and also regulate temperature as they can absorb and dispense thermal energy during phase transition process. Solar energy storage and transfer, electronics, biosensors for detecting biological species, thermal comfort in vehicles, temperature controlled distributions, industrial waste heat recovery systems, and thermal regulating fabrics can be given as some examples of emerging applications for PCMs .
There are many different types of PCMs available, but the vast majority fall into three main classifications: organics, inorganic, and liquid metals . PCMs are classified into the three categories: organic materials, inorganic salt hydrates, and eutectics of inorganic and organic materials. These organic materials include fatty acids, fatty alcohols, organic eutectics, and paraffin waxes. The literature shows that organic PCMs have a leakage problem. However, this leakage problem can be eliminated by modifying the PCMs. For this purpose, microencapsulation is used for the best solution . The various advantages of microencapsulated PCMs are avoiding leakage of organic materials during a melting process, reduction of volume changes during phase transition, growing heat-transfer area, and decreasing reactivity with the outside environment. The size of micro-PCMs typically varies from <1 to >1000 [micro]m . Organic PCMs such as paraffin , fatty acids , and fatty alcohol have been successfully microencapsulated with polymethyl methacrylate (PMMA) , acrylic polymer , polyurethane , polystyrene , polysiloxane , melamine and urea-formaldehyde resin [14, 15], low-density and high-density polyethylene (HDPE)  shell.
In recent years, the use of organic-inorganic hybrid micro-PCMs materials continues to grow as these materials increasingly replace pure organic PCMs in various applications , Most of the research in this area has concentrated on inorganic materials such as carbon materials  and silica , as they have high porosity, high surface area, and high thermal conductivity . The sol-gel process has been widely used as a method for preparation of the organic-inorganic hybrid materials in nano-, micro-, or macro-scale. Organic-inorganic hybrid materials have the potential advantage to display combination of both organic and inorganic features in one single material, such as ductility and ease of processing of organic polymers and thermal stability, corrosion resistance, and abrasion resistance of inorganic components [20, 21]. It was revealed that the phase change properties of PCMs were influenced by the pore size, surface functional groups, and pore geometry. Porous silica with a high porosity and a large internal surface area is generally obtained by an extensively studied sol-gel process, which involves the hydrolysis of silica precursors and the condensation of the resulting hydroxyl groups to form a network structure suitable for confining the PCMs .
Ultraviolet (UV)-curing technology offers a number of advantages compared to other traditional methods of curing; these advantages include high speed, high chemical stability, decreased energy consumption, and low processing costs. The main resin types used for the formulation of UV-curing technologies are radically polymerizable unsaturated polyesters, acrylate terminated molecules, such as epoxy, aliphatic and aromatic urethane, silicone, polyether, melamine, and oil as well as thiolene system. UV-cured resins have been widely used as PCM shell materials [22, 23]. The photocrosslinkable resin shell materials have received extensive attention in the last several years. The micro-PCMs have exhibited properties such as good thermal stability, water resistance and fire resistance. In terms of applications, micro-PCMs are used in industries such as automotive, food product cooling, smart textiles, solar power plants, electronics, and biomedical applications [24, 25].
In this study, a novel UV-curable microencapsulated organicinorganic hybrid phase change materials (micro-PCMs) were prepared by using n-octadecanol and n-eicosanol as core material and methacrylated polyacrylic acid and methacrylated Si[O.sub.2] precursor as shell material. First, the core material of methacrylated polyacrylic acid (m-PAA) was synthesized from of polyacrylic acid with glycidyl methacrylate. Methacrylated Si[O.sub.2] precursor was used as shell material and was prepared using sol-gel method. And then, the fatty alcohols were microencapsulated via emulsion technique. The chemical structure of the methacrylated polyacrylic acid and all UV-cured hybrid micro-PCMs were investigated by ATR-FTIR technique. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for the the phase change behaviors and thermal stability characterization of UV-cured microencapsulated organic-inorganic hybrid PCMs. The morphology of the UV-cured organic-inorganic hybrid micro-PCMs were investigated by scanning electron microscope (SEM).
Poly(acrylic acid) (PAA; average Mv ~ 450,000), glycidyl methacrylate (97%), methacryloxypropyltrimethoxysilane (MEMO) and sodium dodecylsulphate (SDS) were provided by Sigma-Aldrich. 1-Octadecanol (97%) and 1-Eicosanol were purchased from Alfa Aesar. Darocure 1173 was used as photoinitiator and supplied from Ciba Speciality. p-Toluenesulfonic acid (PTSA) and hydrochloric acid (HCI) were supplied from Merck Ac (Germany) and were used as received. Ethanol and all other chemicals were used as received. All the reagents were used without further purification.
Synthesis of Methacrylated Polyacrylic Acid (m-PAA)
Methacrylated polyacrylic acid (m-PAA) was synthesized as described in the literature . Reaction system was set up with a three-neck round-bottom flask, a condenser, a dropping funnel, a mechanical stirrer and a nitrogen gas inlet. First step was to load 10 g PAA and 90 g distilled water into the system. The mixture was stirred at 80[degrees]C for 2 h. For over a period of 2 h, 5 g of excess glycidyl methacrylate was added dropwise. After the addition, stirring continued gently under at room temperature for 24 h. The final obtained product was clear and viscous. The acrylation reaction is given in Scheme 1.
Preparation of Sol-Gel Precursor
0.012 mol (2.98 g) methacryloxypropyltrimethoxysilane (MEMO), 0.024 mol (0.43 g) deionized water, 0.002 g PTSA, and 0.012 mol (0.55 g) ethanol were charged into a dark glass bottle, and were stirred for 24 h. With these amounts given above MEMO was allowed to hydrolyze partially in the water. The hydrolysis reaction is shown in Scheme 2.
Preparation of Octadecanol and Eicosanol Emulsion
30 g of fatty alcohol, 4 g of SDS, and 300 mL of distilled water were emulsified and mechanically stirred at 80CC for 2 h.
The emulsion system was controlled with hydrochloric acid solution so that pH is 4.5-5.5.The mixture was sonicated for 30 min to form a stable emulsion.
Preparation of UV-Curable Organic-Inorganic Hybrid Phase Change Materials (Micro-PCMs)
Organic-inorganic hybrid micro-PCMs formulations were prepared by mixing m-PAA (methacrylated polyacrylic acid), 1octadecanol, and eicosanol emulsion and sol-gel precursor and photoinitiator (Darocure 1173) were mixed in glass vials at ambient temperature. The micro-PCMs formulations are presented in Table 1.
The micro-PCMs hybrid formulations were also casted on Teflon[TM] wells. Teflon[TM] templates (50 mm x 50 mm x 1 mm) were used for UV-cured hybrid PCMs applications. The wet formulations were initially cured using a UV-lamp (300 W). After 160 s, UV-cured organic-inorganic hybrid micro-PCMs were obtained. Preparation of the microencapsulated UV-curable organic-inorganic hybrid PCMs are shown in Scheme 3.
Measurements and Characterization
Chemical structure of synthesized polymer and micro-PCMs were examined by Perkin Elmer ATR FT-IR spectrometer. The parameters of the device for the analysis had a resolution of 8 [cm.sup.-1] and a frequency range of 400-4000 [cm.sup.-1].
DSC was used to determine the phase change temperatures and the enthalpies of the UV-cured micro-PCMs. A Pyris Diamond DSC instrument was programmed to heat from 0[degrees]C to 100[degrees]C the samples under nitrogen at a heating and cooling rate of 5[degrees]C min The phase change temperature and enthalpies were determined from the endotherm and exotherm cooling peak.
Thermal gravimetric analysis was performed in nitrogen to assess the thermal stability of UV-cured micro-PCMs. The samples were heated at a rate of 10[degrees]C/min from 30[degrees]C to 750[degrees]C in a
Perkin Elmer (Pyris 1 TGA) instrument and thermal behavior of all the micro-PCMs was determined.
The UV-cured hybrid micro-PCMs morphology were examined by a Phillips XL 30 ESEM-FEG scanning electron microscopy.
RESULTS AND DISCUSSION
Synthesis of Methacrylated Polyacrylic Acid (m-PAA)
The main goal of this work was to obtain methacrylated polyacrylic acid (m-PAA) as polymeric shell material. For this purpose, methacrylated polyacrylic acid was synthesized as shown in Scheme 1. The ATR-FTIR spectra of pure polyacrylic acid and methacrylated polyacrylic acid are given in Fig. 1. The peaks at 3315 [cm.sup.-1] and 1701 [cm.sup.-1] correspond to O-H and C=O, respectively. The appearance of characteristic methacrylate groups vibration peaks at 1630 [cm.sup.-1] (C=C) and 1715 [cm.sup.-1] (C=0)  confirmed the reaction occurred.
The FTIR spectra for UV-cured microencapsulated organic-inorganic hybrid PCMs are given in Fig. 2. The FT-IR spectra of these micro-PCMs exhibited peaks at 3327 [cm.sup.-1] (OH stretching). The peaks at 2955, 1472, and 1374 [cm.sup.-1] indicated the characteristic fatty alcohol [22, 23]. The vibration peak at 2848 [cm.sup.-1] is attributed to C-C vibrations of the alkyl groups and vibrations of the 830-1080 [cm.sup.-1] region represents the characteristic peak of Si-O-Si . After the UV-curing crosslinking process, there was no (C=C) peak at 1630 [cm.sup.-1] for these micro-PCMs. These results indicate that fatty alcohols have been microencapsulated as core material successfully with methacrylated polyacrylic acid resin as the shell material.
Phase Transition Properties of the UV-Curable Organic-Inorganic Hybrid Phase Change Materials (Micro-PCMs)
The thermal performance of UV-cured hybrid micro-PCMs depend on the phase change temperature, the amount of PCM that is microencapsulated, and the amount of energy it absorbs or releases during a phase change [28, 29]. DSC measurements were used to identify the melting and freezing temperature of the fatty alcohols and UV-cured hybrid micro-PCMs and evaluate the phase change enthalpy. The DSC endothermic and exothermic curves (the temperature of the melting ([T.sub.m]) and freezing ([T.sub.f])), melting ([DELTA][H.sub.m]) and freezing ([DELTA][H.sub.f]) phase change enthalpy) of UV-cured hybrid micro-PCM are shown in Figs. 3 and 4. These DSC results of the fatty alcohols and hybrid micro-PCMs are given in Table 2.
1-Octadecanol melting and freezing phase change temperature are 63.66[degrees]C and 53.51[degrees]C, but1-Eicosanol melting, and freezing phase change temperature are 71.63[degrees]C and 60.06[degrees]C, respectively. When we examine Table 2, we see that, an increase in the chain length of the fatty alcohol resulted with an increase in the melting and freezing peak temperatures of PCMs for both the fatty alcohols and the hybrid micro-PCMs.
The melting and freezing phase change temperatures are found to be 62.27[degrees]C, 40.13[degrees]C; 63.77[degrees]C, 42.33[degrees]C; 69.68[degrees]C, 52.54[degrees]C; 69.99[degrees]C, 53.38[degrees]C; 62.60[degrees]C, 37.13[degrees]C; and 63.77[degrees]C, 40.07[degrees]C for Micro-PAA-OD1, Micro-PAA-OD2, Micro-PAA-EI1, Micro-PAA-EI2, Micro-PAA-OD-EI1, and Micro-PAAOD-EI2, respectively. The melting temperature of UV-cured hybrid micro-PCMs has only one endothermic peak, whereas the freezing temperature of micro-PCM has two exothermic peaks. It is observed that the melting and freezing temperatures of micro-PCMs increased with an increase in fatty alcohol molecular length and core material content.
The heating and freezing phase change enthalpy is considered another critical factor to evaluate the performance applications of micro-PCMs . The heating and freezing curves obtained from DSC measurements of Micro-PAA-ODl, MicroPAA-OD2, Micro-PAA-EI1, Micro-PAA-EI2, Micro-PAA-ODEI1, and Micro-PAA-OD-EI2 are presented in Figs. 2 and 3. DSC curve of m-PAA shows no peaks demonstrating that no endothermic and exothermic behaviors have occurred. It can also be observed that the UV-cured hybrid micro-PCM samples showed endothermic and exothermic behaviors. Melting latent heat enthalpy of the micro-PCMs was increased from 0 to 140 J/g with respect to m-PAA shell material. Enthalpy for these materials was also increased with the increased length of fatty alcohols and core material content, from 105 to 140 J/g for octadecanol core material and from 120 to 127 J/g for eicosanol core material containing micro-PCMs, respectively. Freezing latent heat enthalpy of UV-cured hybrid micro-PCM was increased from 0 to 130 J/g with respect to m-PAA shell material. Enthalpy for these materials was also increased with the increased length of fatty alcohols and core material content, from 94 to 130 J/g for octadecanol core material and from 117 to 122 J/g for eicosanol core material containing organic-inorganic hybrid micro-PCMs, respectively. The thermal energy storage properties of different microencapsulated PCMs that are reported in the literature are presented in Table 3 [9, 25, 31].
The encapsulation ratio and encapsulation efficiency of micro-PCMs have a profound effect on phase-change properties. The encapsulation ratio (R) and the encapsulation efficiency (E) of micro-PCMs were calculated from the results from the DSC measurements (Eqs. 1 and 2) . These calculated results are given in Table 2.
R = [DELTA][H.sub.m], Micro-PCMs/[DELTA][H.sub.m], PCM x 100% (1)
E = [DELTA][H.sub.m], Micro - PCMs + [DELTA][H.sub.f], Micro - PCMs / [DELTA][H.sub.m], PCM + [DELTA][H.sub.f], PCM x 100% (2)
where [DELTA][H.sub.m,PCM] and [DELTA][H.sub.f,PCM] are the melting and freezing latent heat enthalpy of the bulk fatty alcohols, respectively. [DELTA][H.sub.m,Micro.PCMs] and [DELTA][H.sub.f,Micro.PCMs] are the fusion heat and freezing latent heat enthalpy of the hybrid micro-PCMs, respectively. These results suggest that the encapsulation ratio and encapsulation efficiency are improved by increasing the core material content in the formulation.
Thermal Stability of the UV-Curable Organic-Inorganic Hybrid Phase Change Materials (Micro-PCMs)
One of the most important applications of TGA is the assessment of the thermal stability of UV-cured hybrid microPCMs in various technological thermal energy storage applications. Micro-PCMs should be stable at ambient temperatures . The thermal stabilities of the UV-cured hybrid micro-PCMs were characterized in terms of the temperatures at 5%, 10%, and 50% weight loss. The TGA thermograms are presented in Fig. 5a-c and the TGA data are shown in Table 4.
The octadecanol and eicosanol decompose completely in a single step, whereas the UV-cured hybrid micro-PCMs exhibit a two-step degradation. Micro-PAA-OD1, Micro-PAA-OD2, Micro-PAA-EI1, Micro-PAA-EI2, Micro-PAA-OD-EI1, and Micro-PAA-OD-EI2 displayed similar thermal behavior, with a %50 weight loss at 281[degrees]C, 292[degrees]C, 355[degrees]C, 325[degrees]C, 296[degrees]C, and 302[degrees]C, respectively. The thermal weight loss temperature increased with the increased chain length of fatty alcohol within the micro-PCMs. In other words, thermogravimetric analysis showed that 50% weight loss temperatures changed to higher values with the increase in the fatty alcohol microcapsules content. Fig. 5a-c shows the fatty alcohol microcapsules are completely decomposed at nearly 250[degrees]C, whereas Fig. 4a-c illustrates that with the addition of UV-cured hybrid micro-PCMs in the structure; thermal resistance of the fatty alcohols have increased . The char yields of Micro-PAA-OD1, Micro-PAA-OD2, Micro-PAA-EI1, Micro-PAA-EI2, Micro-PAA-OD-EI1, Micro-PAA-OD-EI2 were found as 5.50, 5.36, 9.31, 7.12, 6.23, and 6.04, respectively. As it can be seen in Table 4, the higher sol-gel content in the hybrid micro-PCMs, the more char yield were monitored. Thus, the UV-cured hybrid micro-PCMs could be referred as formstable PCMs and that they possess good thermal stability and which make them suitable for their applications in wide temperature range.
Morphology of the UV-Curable Organic-Inorganic Hybrid Phase Change Materials (Micro-PCMs)
The morphologies of the UV-cured hybrid micro-PCMs were characterized by scanning electron microscopy (SEM). Figure 6a and b shows SEM images of Micro-PAA-OD2 and MicroPAA-EI2 prepared by using octadecanol and eicosanol, respectively. The particles have irregular spherical shapes and their sizes are in the range of 100-150 [micro]m. The fatty alcohol microcapsules are dispersed in the polymeric matrix, and they are mostly intact.
In this study, microencapsulated organic-inorganic hybrid phase-change materials (micro-PCM), which are based on an octadecanol and eicosanol core and a methacrylated polyacrylic acid (m-PAA) shell, were successfully synthesized using sol-gel and UV-curing technique. Phase change properties of UV-cured hybrid micro-PCMs were investigated by differential scanning calorimeter (DSC). An increase in microcapsule content resulted in an increase in the melting and freezing enthalpy of microPCMs for both the octedanol and the eicosanol core components. The latent heat enthalpies of UV-cured hybrid microPCMs heating and freezing cycles varied from 100 to 140 and 90 to 130 J/g, respectively. The thermogravimetric analysis results showed that the thermal stability of the micro-PCMs increased with an increase in microcapsules and sol-gel precursor content as a consequence of higher thermal stability of both octadecanol and eicosanol. The SEM images of the micro-PCMs showed that the microcapsules were grouped in irregular spherical shapes of sizes of 100-150 [micro]m. Microcapsules were dispersed into photocrosslinked m-PAA matrix. The SEM results also indicated fairly good interaction between the microcapsules and the polymer matrix. Considering our findings, these UV-cured hybrid micro-PCMs can be promising and useful in thermal energy storage applications.
The authors would also like to thank Tubitak Bideb.
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Emre Basturk, Memet Vezir Kahraman (iD)
Department of Chemistry, Marmara University, Istanbul 34722, Turkey
Correspondence to: M.V. Kahraman; e-mail: firstname.lastname@example.org
Published online in Wiley Online Library (wileyonlinelibrary.com).
Caption: SCHEME 1. Synthesis of methacrylated polyacrylic acid (m-PAA). [Color figure can be viewed at wileyonlinelibrary.com]
Caption: SCHEME 2. Hydrolysis reaction mechanism of the MEMO. [Color figure can be viewed at wileyonlinelibrary.com]
Caption: SCHEME 3. Schematic formation of the UV-cured microencapsulated organic-inorganic hybrid PCMs. [Color figure can be viewed at wileyonlinelibrary.com]
Caption: FIG. 1. ATR-FTIR spectra of (a) polyacrylic acid (b) methacrylated polyacrylic acid (m-PAA). [Color figure can be viewed at wileyonlinelibrary.com]
Caption: FIG. 2. ATR-FTIR spectra of Micro-PAA-OD2, Micro-PAA-EI2, and Micro-PAA-OD-EI2. [Color figure can be viewed at wileyonlinelibrary.com]
Caption: FIG. 3. DSC curves of the UV-cured hybrid micro-PCMs in the heating process. [Color figure can be viewed at wileyonlinelibrary .com]
Caption: FIG. 4. DSC curves of the UV-cured hybrid micro-PCMs in the freezing process. [Color figure can be viewed at wileyonlinelibrary.com]
Caption: FIG. 5. Thermogravimetric analysis of UV-cured hybrid micro-PCMs: (a) Micro-PAA-OD1, Micro-PAA-OD2, and Octadecanol; (b) Micro-PAA-EI1, Micro-PAA-EI2, and Eicosanol; (c) Micro-PAA-OD-EI1, Micro-PAA-OD-EI2, Octadecanol, and Eicosanol. [Color figure can be viewed at wileyonlinelibrary.com]
Caption: FIG. 6. SEM micrographs of the UV-cured hybrid micro-PCMs: (a) Micro-PAA-OD2 and (b) Micro-PAA-EI2.
TABLE 1. Compositions of the UV-cured microencapsulated organic-inorganic hybrid PCMs. PAA-g- OD EI Sol-gel Daracure Samples GMA (g) (g) (g) precursor (g) 1173 (g) Micro-PAA-OD1 2 1 -- 0.3 0.06 Micro-PAA-OD2 2 2 -- 0.4 0.06 Micro-PAA-EI1 2 -- 1 0.3 0.06 Micro-PAA-EI2 2 -- 2 0.4 0.06 Micro-PAA-OD-EI1 2 0.5 0.5 0.3 0.06 Micro-PAA-OD-EI2 2 1 1 0.4 0.06 Definitions: PAA-g-GMA, methacrylated polyacrylic acid; micro-PCM, microencapsulated phase-change materials; OD, octadecanol; EI, eicosanol. TABLE 2. Phase change behavior of the fatty alcohols and UV-cured microencapsulated organic-inorganic hybrid PCMs. Melting Freezing Samples [T.sub.m] [DELTA][H.sub.m] [T.sub.f] ([degrees]C) (J/g) ([degrees]C) 1-Octadecanol 63.66 253.92 50.81 56.2 1-Eicosanol 71.63 259.97 57.52 62.59 m-PAA -- -- -- -- Micro-PAA-OD1 62.27 104.97 33.94 46.31 Micro-PAA-OD2 63.77 140.49 33.96 50.7 Micro-PAA-EI1 69.68 120.32 47.16 57.92 Micro-PAA-EI2 69.99 126.99 48.33 58.43 Micro-PAA-OD-EI1 62.6 106.92 23.08 51.18 Micro-PAA-OD-EI2 63.77 118.95 26.78 52.36 Freezing Samples [DELTA][H.sub.f] Encapsulation Encapsulation (J/g) ratio (%) efficiency (%) 1-Octadecanol -244.79 -- -- 1-Eicosanol -249.31 -- -- m-PAA -- -- -- Micro-PAA-OD1 -94.65 41.3 40.0 Micro-PAA-OD2 -129.82 55.3 54.2 Micro-PAA-EI1 -117.79 46.3 46.7 Micro-PAA-EI2 -122.16 48.8 48.9 Micro-PAA-OD-EI1 -96.76 41.6 40.4 Micro-PAA-OD-EI2 -104.03 46.3 44.2 Definition: [T.sub.m], temperature of the endothermic peak; [T.sub.f], temperature of the exothermic peak; [DELTA][H.sub.m], phase transition enthalpy of melting; [DELTA][H.sub.f], phase transition enthalpy of freezing. TABLE 3. Comparisons on thermal energy storage properties of some microencapsulated PCMs. Microencapsulated PCMs Melting Temperature Latent ([degrees]C) heat (J/g) Methylmethacrylate/n-octadecane 24.2 83.7 (7:10) Methylmethacrylate/1,4-butylene 23.9 126.2 glycol diacrylate/n-octadecane (7:3:10) Epoxy acrylate/Micro PCM (8:2) 40.73 33.5 Epoxy acrylate/Micro PCM 40.73 23.9 (6.5:2.5) n-Octadecane/TEOS (7:3) 26.6 130.7 n-Octadecane/TEOS (1:1) 26.9 123.0 Microencapsulated PCMs Freezing Refs. Temperature Latent ([degrees]C) heat (J/g) Methylmethacrylate/n-octadecane 19.9 -83.6 9 (7:10) Methylmethacrylate/1,4-butylene 25.9 -126.1 9 glycol diacrylate/n-octadecane (7:3:10) Epoxy acrylate/Micro PCM (8:2) 37.90 -31.0 25 Epoxy acrylate/Micro PCM 38.06 -22.3 25 (6.5:2.5) n-Octadecane/TEOS (7:3) 20.7 -131.5 31 n-Octadecane/TEOS (1:1) 20.9 -125.4 31 TABLE 4. Thermal properties of the fatty alcohols and UV-cured microencapsulated organic-inorganic hybrid PCMs. Samples [T.sub.5%] [T.sub.10%] ([degrees]C) ([degrees]C) 1-Octadecanol 206 219 1-Eicosanol 220 235 Micro-PAA-OD1 165 194 Micro-PAA-OD2 176 202 Micro-PAA-EI1 173 208 Micro-PAA-EI2 187 212 Micro-PAA-OD-EI1 160 186 Micro-PAA-OD-EI2 176 205 Samples [T.sub.50%] Char ([degrees]C) yield (%) 1-Octadecanol 256 0 1-Eicosanol 275 0 Micro-PAA-OD1 281 5.5 Micro-PAA-OD2 292 5.36 Micro-PAA-EI1 355 9.31 Micro-PAA-EI2 325 7.12 Micro-PAA-OD-EI1 296 6.23 Micro-PAA-OD-EI2 302 6.04 Definition: [T.sub.5%, 10 and 50], 5, 10, and 50 wt% weight loss temperature.
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|Author:||Basturk, Emre; Kahraman, Memet Vezir|
|Publication:||Polymer Engineering and Science|
|Date:||Dec 1, 2018|
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