Annex 1. Investigation of Phase-Change Materials for Vaccine Cold Chain Equipment

Transcription

1 Annex 1. Investigation of Phase-Change Materials for Vaccine Cold Chain Equipment July 2016 MAILING ADDRESS PO Box Seattle, WA USA ADDRESS 2201 Westlake Avenue Suite 200 Seattle, WA, USA TEL: FAX:

2 This work was written by PATH and supported in whole or part by a grant from the Bill & Melinda Gates Foundation. The views expressed herein are solely those of the authors and do not necessarily reflect the views of the Foundation. PATH thanks the Solar Electric Light Fund, United Nations Children s Fund, and the World Health Organization for providing guidance for this research. Suggested citation PATH. Annex 1. Investigation of Phase-Change Materials for Vaccine Cold Chain Equipment. Seattle: PATH; Contact information Pat Lennon Portfolio Leader, Supply Systems and Equipment, Vaccine and Pharmaceutical Technologies PATH plennon@path.org For more information on PATH s work in vaccine and pharmaceutical technologies, visit: Copyright 2016, PATH. The material in this document may be freely used for educational or noncommercial purposes, provided that the material is accompanied by an acknowledgment. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. To view a copy of this license, visit All other rights reserved. Photos: All photos in this report are credited to PATH. ii

3 Annex 1. Investigation of Phase-Change Materials for Vaccine Cold Chain Equipment iii

4 Contents Acronyms... v 1. Introduction Dimensional, mass, and mechanical property test Changes in dimension and mass Instron testing data and observations Plastics Metals Foams Visual inspection of painted steel and hookup wire Painted steel Hookup wire Discussion and conclusions Instron testing iv

5 Acronyms CCE HDPE PCM PEG PP PVC cold chain equipment high-density polyethylene phase-change material polyethylene glycol polypropylene polyvinyl chloride v

6 vi

7 1. Introduction This annex to the report Investigations of Phase-Change Materials for Vaccine Cold Chain Equipment (report) presents results from a long-term test of the compatibility of phase-change materials (PCMs) with materials commonly used in vaccine cold chain equipment (CCE). The report included background on PCMs, a landscape of PCMs with melting points in the 0 C to 10 C range, results from a short-term PCM-CCE material compatibility test, and testing of the thermodynamic properties of the PCMs investigated in the compatibility test. The annex includes data from the long-term tests and compares them to data from the short-term test from the report. All baseline data were collected at the start of the short-term test, and short-term and long-term test samples were generally started at the same time. This annex is divided into the following sections: Section 2. Dimensional, mass, and mechanical material property test results. Section 3. Visual inspection of painted steel and electrical hookup wire. Section 4. Discussion and conclusions. 2. Dimensional, mass, and mechanical property test For the compatibility test, samples of materials commonly used in CCE (see Table 1) were immersed in PCM and then tested for changes in mechanical properties. Table 2 gives the PCMs selected for compatibility testing. For the short-term test, samples were immersed for 14 to 23 days. For the long-term test, plastic and metal samples were immersed between 91 and 105 days. The long-term foam samples were immersed between 101 and 140 days. Table 3 gives the sample immersion times. After soaking, changes in dimension, volume, and mass of the material samples were measured. The mechanical properties were then measured using an Instron 5565 materials testing machine. Readers are referred to the report for details on PCM and materials selection as well as testing procedures and equipment. Table 1. Materials selected for phase-change material compatibility test. Material Aluminum (6061) Copper Steel (mild, structural) Polyvinyl chloride Polypropylene High-density polyethylene Polyisocyanurate foam Polyurethane foam Abbreviation: CCE, cold chain equipment. Application in CCE Refrigerator structural Refrigerator wiring, heat exchange coils Refrigerator structural Refrigerator wire coating Vaccine carrier structural Vaccine carrier structural Refrigerator insulation Vaccine carrier insulation

8 Table 2. Phase-change materials selected for testing. PCM Manufacturer/supplier Type Class Subclass Description Distilled water Mountain Mist Chemical Inorganic PlusICE A6 PCM Products Engineered Organic Paraffin Long chain hydrocarbon RT3HC Rubitherm Engineered Organic Paraffin Long chain hydrocarbon OM06P RGEES Engineered Organic Paraffin Long chain hydrocarbon PureTemp 8 PureTemp Engineered Organic Non-paraffin Fatty acid PlusICE S8 PCM Products Engineered Inorganic Salt hydrate Hydrated sodium sulfate, ammonium chloride PlusICE E0 PCM Products Engineered Eutectic Inorganic- Organic Water with biocide PEG 400 ChemWorld Chemical Organic Non-paraffin Polyethylene glycol Triacetin Sigma-Aldrich Chemical Organic Non-paraffin Fatty acid ester Abbreviation: CCE, cold chain equipment; PCM, phase-change material; PEG, polyethylene glycol. Table 3. Sample immersion times. Test type Short term Long term PCM Sample immersion time (days) Foam Plastic Metal Polyisocyanurate Polyurethane PVC PP HDPE Aluminum Copper Mild steel Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Abbreviations: HDPE, high-density polyethylene; PCM, phase-change material; PEG, polyethylene glycol; PP, polypropylene; PVC, polyvinyl chloride. 2

9 2.1 Changes in dimension and mass After soaking in PCM, samples were measured for changes in dimension and mass. The results are given in Tables 4, 5, and 6 for plastic, metal, and foam samples, respectively. The largest of the change values are highlighted in the tables in yellow. Generally, most samples did not show large, consistent changes in dimension or mass for either the short- or long-term tests. For the plastics, only the paraffins caused a consistent, relatively large increase in mass compared to all of the other samples for high-density polyethylene (HDPE) and the polypropylene (PP) for the short- and long-term soak tests. In absolute terms, the increases were still small; less than 4%. For the metals, E0 caused a consistent increase in thickness and mass of the aluminum samples. The increases in thickness and mass were the result of deposits formed on the samples by the E0. S8 caused a consistent, progressive decrease in the width and mass of copper that was the result of corrosion of the copper. Extensive rusting was observed for the steel immersed in distilled water, leading to a measureable decrease of mass of the steel samples in the long-term test sample. For the foams, polyurethane immersed in polyethylene glycol (PEG) 400 was the only PCM-foam combination that resulted in a large increase in mass as the PEG 400 was strongly absorbed into the polyurethane. The PEG 400 also broke down the outer layers of foam resulting in a decrease in volume of the polyurethane foam sample. 3

10 Table 4. Changes in sample dimension and mass for plastics soaked in PCMs. PVC PP HDPE Test type PCM average width average thickness mass average width average thickness mass average width average thickness mass Long term Short term Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Distilled water A OM06P RT3HC PureTemp S E PEG Triacetin Abbreviations: HDPE, high-density polyethylene; PCM, phase-change material; PEG, polyethylene glycol; PP, polypropylene; PVC, polyvinyl chloride. 4

11 Table 5. Changes in sample dimension and mass for metals soaked in PCMs. Copper Aluminum Steel Test type PCM average width average thickness mass average width average thickness mass average width average thickness mass Long term Short term Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 5

12 Table 6. Changes in sample dimension and mass for foams soaked in PCMs. Polyisocyanurate Polyurethane Test type PCM volume mass volume mass Long term Short term Distilled water A RT3HC OM06P Puretemp S E PEG Triacetin Distilled water A RT3HC OM06P Puretemp S E PEG Triacetin Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 2.2 Instron testing data and observations Material samples were tested for tensile (plastics and metals) or compressive (foams) properties after soaking. Tables 7 to 14 and Figures 1 to 22 give the results of the mechanical properties testing Plastics Polypropylene After the long-term exposure to OM06P, the Young s was further decreased for OM06P compared to the baseline and the short-term test results. The increase in Young s that was seen for S8 in the short-term results disappeared in the long-term results. The other PCMs that showed little effect on the Young s in the short-term test also showed little or no effect in the long-term test results. 6

13 The offset yield decrease seen in the short-term test results for the engineered organic PCMs (A6, OM06P, RT3HC, and PureTemp 8) was either maintained or deepened in the long-term test results. Offset yield continued to be unaffected by the other PCMs. Similarly, the decrease in ultimate tensile strength seen in the short-term test results for the engineered organic PCMs was also maintained or deepened. The ultimate tensile strength was unaffected by other PCMs. Table 7. Polypropylene test results. Test type Short term Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Baseline 1, Distilled water 1, A6 1, RT3HC 1, OM06P 1, PureTemp 8 1, S8 2, E0 1, PEG 400 1, Triacetin 1, Distilled water 1, A6 1, RT3HC 1, OM06P PureTemp 8 1, S8 1, E0 1, PEG 400 1, Triacetin 1, Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 7

14 Figure 1. Young s for polypropylene soaked in phase-change material. Figure 2. offset yield for polypropylene soaked in phase-change material. 8

15 Figure 3. ultimate tensile strength for polypropylene soaked in phase-change material. Polyvinyl chloride The increase in Young s that was seen for most PCMs during the short-term test was extended to all PCMs in the long-term test results. For several PCMs, the increase in Young s compared to baseline grew even larger in the long-term test results. The PCMs had little or no effect on offset yield or ultimate tensile strength during either the short-term or long-term tests. Table 8. Polyvinyl chloride test results. Test type Short term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Baseline 2, Distilled water 2, A6 3, RT3HC 2, OM06P 2, PureTemp 8 2, S8 2, E0 3, PEG 400 2, Triacetin 2,

16 Test type Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Distilled water 3, A6 3, RT3HC 3, OM06P 3, PureTemp 8 3, S8 3, E0 3, PEG 400 3, Triacetin 3, Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. Figure 4. Young s for polyvinyl chloride soaked in phase-change material. 10

17 Figure 5. offset yield for polyvinyl chloride soaked in phase-change material. Figure 6. ultimate tensile strength for polyvinyl chloride soaked in phase-change material. High-density polyethylene The engineered organic PCMs that had markedly decreased the Young s compared to baseline after the short-term test also decreased Young s in the long-term test. Distilled water, S8, E0, and PEG 400, which showed little or no effect on Young s during the short-term test, showed significant decreases in the long-term test. Similarly, the engineered organic PCMs that had decreased the offset yield and ultimate tensile strength after the short-term test also decreased those tensile properties after the long-term test when compared to the baseline. The magnitude of the decrease grew smaller for the paraffin PCMs (A6, 11

18 RT3HC, and OM06P) and slightly larger for PureTemp 8. Other PCMs had little or no effect on offset yield or ultimate tensile strength. Table 9. High-density polyethylene test results. Test type Short term Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Baseline Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 12

19 Figure 7. Young s for high-density polyethylene soaked in phase-change material. Figure 8. offset yield for high-density polyethylene soaked in phase-change material. 13

20 Figure 9. ultimate tensile strength for high-density polyethylene soaked in phase-change material Metals Copper With the exception of distilled water, all of the PCMs decreased Young s in the long-term soak test. Distilled water had shown a decrease in the short-term test, but data from the long-term test had too much variability to determine whether that decrease was maintained during the long-term test. Offset yield and ultimate tensile strength were unaffected by all of the PCMs except for S8, which further decreased those tensile property values from the short-term test results. 14

21 Table 10. Copper test results. Test length Short term Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Baseline 113,000 4, Distilled water 100,000 3, A6 80,000 10, RT3HC 97,000 2, OM06P 91,000 7, PureTemp 8 93,000 7, S8 90,000 10, E0 70,000 10, PEG ,000 7, Triacetin 100,000 20, Distilled water 120,000 30, A6 96,000 6, RT3HC 93,000 2, OM06P 93, PureTemp 8 91,000 7, S8 77,000 7, E0 90,000 8, PEG ,000 10, Triacetin 98,000 4, Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 15

22 Figure 10. Young s for copper soaked in phase-change material. Figure 11. offset yield for copper soaked in phase-change material. 16

23 Figure 12. ultimate tensile strength for copper soaked in phase-change material. Aluminum None of the tensile properties were greatly affected by any of the PCMs during the long-term test except for E0 which decreased the values of all of the properties and PureTemp 8 which decreased Young s in the long-term test. The decreases in Young s caused by A6 and PEG 400 in the short-term test were not present in the long-term test results. Table 11. Aluminum test results. Test type Short term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Baseline 75,000 2, Distilled water 72,000 3, A6 66,000 5, RT3HC 69,000 5, OM06P 70,000 8, PureTemp 8 74,000 5, S8 72,000 3, E0 52,000 6, PEG ,000 5, Triacetin 80,000 2,

24 Test type Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Number of samples Distilled water 68,000 4, A6 75,000 2, RT3HC 71,000 2, OM06P 72,000 2, PureTemp 8 64,000 5, S8 74,000 7, E0 65,000 5, PEG ,000 2, Triacetin 72,000 6, Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. Figure 13. Young s for aluminum soaked in phase-change material. 18

25 Figure 14. offset yield for aluminum soaked in phase-change material. Figure 15. ultimate tensile strength for aluminum soaked in phase-change material. Steel During the short-term test, the strain data collected for the steel samples contained too much noise to reliably determine the Young s and offset yield, so only ultimate tensile strength data were collected. Improved strain measurement equipment allowed determination of Young s and offset yield after the long-term test. Young s and offset yield values from the long-term test were compared to published values from the steel supplier and the engineering literature. Compared to the published values, all of the PCMs except for the paraffins decreased Young s. None of the PCMs affected the offset yield during the long-term test compared to the published 19

26 values. Consistent with the short-term test, ultimate tensile strength was not affected by any of the PCMs during the long-term test compared to the baseline value. Table 12. Steel test results. Test length Short term Long term PCM Young s Young s offset yield offset yield ultimate tensile strength ultimate tensile strength Published 1 200,000 10, N/A Number of samples Baseline Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Distilled water 130,000 20, A6 180,000 20, RT3HC 190,000 30, OM06P 210,000 60, PureTemp 8 130,000 20, S8 90,000 30, E0 91,000 6, PEG ,000 10, Triacetin 140,000 20, and standard s were calculated from the range of manufacturer published values. Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 20

27 Figure 16. Young s for steel soaked in phase-change material. Figure 17. offset yield for steel soaked in phase-change material. 21

28 Figure 18. ultimate tensile strength for steel soaked in phase-change material Foams Polyisocyanurate All of the PCMs had little to no effect on the compressive in the long-term test. The increase in compressive caused by A6 and the decrease caused by triacetin that were present in the shortterm test results disappeared in the long-term test results. All of the organic PCMs, including PEG 400 and triacetin, increased the yield at 5% strain in the long-term test. Only A6 had affected yield at 5% strain in the short-term test. Table 13. Polyisocyanurate test results. Test type Short term PCM compressive compressive 5% yield 5% yield Number of samples Baseline Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin

29 Test type Long term PCM compressive compressive 5% yield 5% yield Number of samples Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. Figure 19. compressive for polyisocyanurate soaked in phase-change material. 23

30 Figure 20. yield at 5% strain for polyisocyanurate soaked in phase-change material. Polyurethane All of the organic PCMs except PEG 400 increased the compressive in the long-term test, though the experimental error in the RT3HC result is large, so the increase above baseline may not be significant for RT3HC. This increase is consistent with the increase seen for A6 in the short-term test for which only one sample yielded usable data, thus strengthening our confidence in the short-term test result for A6. S8 also increased the compressive, an effect that was also seen in the short-term test results. An increase in compressive seen for distilled water in the short-term test results disappeared in the long-term test results. Consistent with the short-term test results, the paraffins (A6, RT3HC, and OM06P), S8, and E0 all increased the yield in the long-term test. Triacetin increased the yield only in the long-term test. The other PCMs had no significant effect. As was noted in the physical properties section above, the polyurethane had absorbed a large quantity of PEG 400 that appeared to degrade the outer layers of the foam. The degradation and release of PEG 400 during compression testing made and strain measurements challenging and may have caused conflicting results between the long-term and short-term test measurements of compressive. 24

31 Table 14. Polyurethane test results. Test length Short term Long term PCM compressive compressive yield yield Number of samples Baseline Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Baseline Distilled water A RT3HC OM06P PureTemp S E PEG Triacetin Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 25

32 Figure 21. compressive for polyurethane soaked in phase-change material. Figure 22. yield for polyurethane soaked in phase-change material. 3. Visual inspection of painted steel and hookup wire 3.1 Painted steel Results for the painted steel after the long-term test were very similar to the results after the short-term test. The enamel on the painted steel samples was generally softer after being immersed in PCMs, as 26

33 tested by scratching the painted surface with a steel nail. The two exceptions were for RT3HC, which seemed to make the paint harder, and A6, which did not cause any change. The PCM with the greatest effect was distilled water. Distilled water caused rusting during the short-term test that became much more extensive during the long-term test. Distilled water and S8 caused a rusty color change to the white paint. E0 and distilled water caused bubbling in the paint surface. Some peeling was observed on the PEG 400 sample near the air-peg 400 interface. Table 15 summarizes observations for the painted steel. Figure 23 presents photographs of the baseline and soaked painted steel. Table 15. Visual inspection results of painted mild steel samples. Sample number PCM Immersion duration in days Post-immersion inspection notes 1 PureTemp Paint peels slightly upon etch, slight discoloring of paint, Softer 2 PureTemp 8 no visible change to steel Softer 3 Triacetin 168 Paint peels slightly upon etch, no visible change to steel Softer 4 Triacetin Softer 5 OM06P 168 Paint peels slightly upon etch, no visible change to steel Softer 6 OM06P Softer Scratch test with steel nail 7 PEG Paint peels easily upon etch, paint has wrinkled at PCM-air Much softer 8 PEG 400 interface, no visible change to steel Much softer 9 RT3HC 168 Paint was maybe harder than baseline, if any change; no No change 10 RT3HC visible change to steel No change 11 Distilled water 168 Extensive peeling upon etch, extensive rust and Much softer 12 Distilled water discoloration, bubbling of paint Much softer 13 S8 165 Paint peels slightly upon etch, some rusting of steel visible, Softer 14 S8 slight discoloration of paint Softer 15 E0 165 Paint peels easily upon etch, bubbling and slight Much softer 16 E0 discoloration of paint, no visible change to steel Much softer 17 A6 165 Paint was maybe harder than baseline, if any change; no No change 18 A6 visible change to steel No change Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 27

34 Figure 23. Visual inspection of the painted steel samples. The baseline (upper right) was not soaked in any chemical. Significant peeling, usually correlated with paint softness, can be seen in some samples. Two samples were treated for each phase-change material. 28

35 3.2 Hookup wire Results for the hookup wire after the long-term test were very similar to the results after the short-term test. The hookup wires (copper covered in PVC insulation) gave the same visual results as seen for the separate PVC and copper samples used in the tensile testing. The PVC had no visible change for all samples. The copper color was darker for samples immersed in PureTemp 8, S8, and E0. The exposed copper on one of the samples soaked in S8 had largely corroded away. Observations for the hookup wires are summarized in Table 16. Figure 24 presents photographs of the baseline and soaked hookup wires. Table 16. Visual inspection results for PVC-insulated copper hookup wire. Sample number PCM Immersion duration in days Post-immersion inspection notes 1 PureTemp Copper appears darker 2 PureTemp 8 3 Triacetin 168 No visible change 4 Triacetin 5 OM06P 168 No visible change 6 OM06P 7 PEG No visible change 8 PEG RT3HC 168 No visible change 10 RT3HC 11 Distilled water 168 No visible change 12 Distilled water 13 S8 165 Copper appears darker, some of the copper was 14 S8 corroded away 15 E0 165 Copper appears darker 16 E0 17 A6 165 No visible change 18 A6 Abbreviations: PCM, phase-change material; PEG, polyethylene glycol. 29

36 Figure 24. Visual inspection of the PVC-insulated copper hookup wires. The baseline (upper right) was not soaked in any chemical. Darkening of the copper was consistent with the darkening seen in the copper tensile test samples. 30

37 4. Discussion and conclusions 4.1 Instron testing Overall, results from the long-term tests were very similar to those for the short-term immersion tests with some effects increasing in magnitude. HDPE and PP were most affected by the engineered organic PCMs. All tensile properties decreased for HDPE while offset yield and ultimate tensile strength decreased for PP. OM06P also decreased Young s in PP. All PCMs increased the Young s for PVC, while no PCMs affected PVC s offset yield or ultimate tensile strength. There was also an increase in Young s for PVC in the short-term test, though to a lesser degree. We speculate that the PCMs are leaching the plasticizer out of the PVC, thus stiffening the PVC progressively over time. All PCMs except for distilled water decreased Young s in copper during the long-term test. This effect had been seen for all PCMs except PEG 400 and triacetin during the short-term test. Only S8 affected the offset yield and ultimate tensile strength in the long-term test. The decrease in those properties was a continuation of decrease that occurred in the short-term test for S8, suggesting that progressive corrosion of the copper by S8 was responsible. As was observed during the short-term test, aluminum was only affected by E0 during the long-term test. The reaction between E0 and the aluminum continued to form deposits on the aluminum, and some of the decrease in properties is likely due to the increase in cross-sectional area caused by the deposits. Examination of the aluminum sample surface under a binocular microscope showed extensive, obvious pitting, suggesting that the aluminum was being corroded by E0 and that the properties was more than just an effect of the cross-sectional area caused by the reaction products depositing on the surface of the aluminum. All of the PCMs except for the paraffins decreased the Young s of mild steel in the long-term study when compared to published data. None of the PCMs significantly affected the offset yield or ultimate tensile strength compared to the published data or baseline samples, respectively. There was a slight decrease for offset yield and ultimate tensile strength for E0, but it may not be significant. Heavy corrosion of steel was observed for distilled water. PureTemp 8 and S8 discolored the surface, suggesting that there was some reaction between the steel and those PCMs. The compressive for polyisocyanurate was not significantly affected by any of the PCMs during the long-term test, except for a slight increase for RT3HC. There was an increase in the offset yield at 5% strain for all of the organic PCMs. A6, OM06P, PureTemp 8, S8, and triacetin all increased the compressive for polyurethane, while other PCMs had no significant effect during the long-term test. The yield of polyurethane was increased by all PCMs except distilled water, PureTemp 8, and PEG 400 during the long-term test. It was surprising that the compressive properties of polyurethane foam were not more affected by PEG 400 since the outer layers of the polyurethane appeared to be completely broken down and the mass increase of the sample indicated that the polyurethane had absorbed large quantities of PEG 400. One possible 31

38 explanation is that the outer layers of foam were so degraded that they offered virtually no resistance to compression and so produced little impact on the compression data. The effects of the PCMs on the painted steel samples during the long-term test were very similar to the effects of the short-term test. With the exception of RT3HC and A6, the PCMs caused softening of the enamel paint. The RT3HC-soaked enamel seemed slightly harder than the baseline, and perhaps RT3HC created an environment to promote curing of the enamel. However, the hardness of the enamel was difficult to differentiate with a qualitative test when there was only a slight change. The A6 also had little effect on the enamel. The rusting caused by distilled water and S8 continued into the long-term test, with extensive bubbling and peeling of the enamel paint worsening for the distilled water-soaked sample. E0 also caused bubbling of the paint. PEG 400 caused cracking and peeling of the paint near the air-peg 400 interface. PureTemp 8 caused slight discoloration of the paint. Since the enamel paint is not designed to be in continuous contact with liquids, contact with liquids should be avoided. As for the short-term test, the hookup wire was generally unaffected in the long-term test by the PCMs. Consistent with visual observations of the PVC samples used in the tensile testing, the PVC insulation did not show visible impacts from the PCMs. Exposed copper wire was darkened by the PureTemp 8, S8, and E0. The S8 had corroded away much of the exposed copper in one sample. Corrosion by S8 could negatively affect electrical connections made with copper hookup wire. 32