annex 1. investigation of phase-change materials for vaccine … · 2018-06-28 · 1. introduction...

Annex 1. Investigation

of Phase-Change

Materials for Vaccine

Cold Chain Equipment

July 2016

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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; 2016.

Contact information

Pat Lennon Portfolio Leader, Supply Systems and Equipment, Vaccine and Pharmaceutical Technologies PATH Email: [email protected] For more information on PATH’s work in vaccine and pharmaceutical technologies, visit: http://sites.path.org/vpt/.

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 http://creativecommons.org/licenses/by-nc-nd/4.0/. All other rights reserved.

Photos: All photos in this report are credited to PATH.

mailto:[email protected]

http://sites.path.org/vpt/

http://creativecommons.org/licenses/by-nc-nd/4.0/

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Annex 1. Investigation

of Phase-Change

Materials for Vaccine

Cold Chain Equipment

iv

Contents

Acronyms ......................................................................................................................................... v

1. Introduction ............................................................................................................................. 1

2. Dimensional, mass, and mechanical property test .................................................................. 1

2.1 Changes in dimension and mass ................................................................................. 3

2.2 Instron testing data and observations .......................................................................... 6

2.2.1 Plastics .......................................................................................................... 6

2.2.2 Metals .......................................................................................................... 14

2.2.3 Foams .......................................................................................................... 22

3. Visual inspection of painted steel and hookup wire .............................................................. 26

3.1 Painted steel .............................................................................................................. 26

3.2 Hookup wire ............................................................................................................. 29

4. Discussion and conclusions ................................................................................................... 31

4.1 Instron testing ........................................................................................................... 31

v

Acronyms

CCE cold chain equipment

HDPE high-density polyethylene

PCM phase-change material

PEG polyethylene glycol

PP polypropylene

PVC polyvinyl chloride

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 Application in CCE

Aluminum (6061) Refrigerator—structural

Copper Refrigerator—wiring, heat exchange coils

Steel (mild, structural) Refrigerator—structural

Polyvinyl chloride Refrigerator—wire coating

Polypropylene Vaccine carrier—structural

High-density polyethylene Vaccine carrier—structural

Polyisocyanurate foam Refrigerator—insulation

Polyurethane foam Vaccine carrier—insulation

Abbreviation: CCE, cold chain equipment.

2

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

PCM

Sample immersion time (days)

Foam Plastic Metal

Polyisocyanurate Polyurethane PVC PP HDPE Aluminum Copper Mild steel

Sho

rt t

erm

Distilled water 21 23 14 14 14 14 14 14

A6 17 14 19 14 14 14 14 14

RT3HC 21 23 14 14 14 14 14 14

OM06P 21 23 14 14 14 14 14 14

PureTemp 8 21 23 14 14 14 14 14 14

S8 17 14 19 14 14 14 14 14

E0 17 14 19 14 14 14 14 14

PEG 400 21 23 14 14 14 14 14 14

Triacetin 21 23 14 14 14 14 14 14

Lon

g te

rm

Distilled water 139 140 92 92 92 91 91 91

A6 132 130 105 105 105 105 105 105

RT3HC 139 140 92 92 92 91 91 91

OM06P 139 140 92 92 92 91 91 91

PureTemp 8 139 140 95 92 95 91 91 91

S8 132 130 105 105 105 105 105 105

E0 132 130 105 105 105 105 105 105

PEG 400 139 140 92 92 92 91 91 91

Triacetin 101 140 92 92 92 91 91 91

Abbreviations: HDPE, high-density polyethylene; PCM, phase-change material; PEG, polyethylene glycol; PP, polypropylene; PVC, polyvinyl chloride.

3

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.

4

Table 4. Changes in sample dimension and mass for plastics soaked in PCMs.

Test type PCM

PVC PP HDPE

Average change in average width

(%)

Average change in average

thickness (%)

Average change in

mass (%)


(%)


thickness (%)

Average change in

mass (%)


(%)


thickness (%)

Average change in

mass (%)

Sho

rt t

erm

Distilled water 0.24 0.11 0.11 -0.52 -1.70 0.00 0.34 -0.33 -0.16

A6 -0.13 1.41 -0.10 0.27 0.70 0.69 0.79 1.98 4.19

RT3HC 0.02 -0.33 -0.10 0.44 0.35 1.04 1.78 1.91 4.92

OM06P 0.42 0.11 0.11 0.31 -0.24 1.91 1.99 0.99 5.19

PureTemp 8 0.31 0.11 0.10 0.35 -0.23 0.00 0.80 1.66 1.39

S8 0.29 0.54 -0.63 0.38 0.53 -1.38 1.06 0.78 -0.62

E0 0.02 0.86 -0.94 0.09 0.47 -1.72 0.35 0.89 -1.71

PEG 400 0.49 0.33 0.11 0.57 0.12 0.00 0.29 0.11 0.31

Triacetin 0.27 0.11 0.10 0.07 -0.12 0.17 0.33 0.22 0.47

Lon

g te

rm

Distilled water -0.58 0.00 0.00 -1.60 -1.63 0.00 -0.58 0.34 -0.16

A6 -1.60 -0.11 0.00 -0.24 -0.12 3.96 -0.88 -0.33 3.53

OM06P -0.85 -0.22 -0.11 -0.04 0.83 2.59 -0.47 0.67 1.72

RT3HC -0.60 -0.11 -0.11 -0.64 0.65 3.13 -0.24 0.44 2.02

PureTemp 8 -0.66 -0.43 0.00 -0.52 0.24 0.87 -0.43 0.67 3.69

S8 -1.51 -0.11 0.42 -1.35 -1.29 0.17 -1.98 -0.67 0.31

E0 -1.16 -0.11 0.00 -1.35 -1.29 -0.17 -1.27 -0.45 0.16

PEG 400 -0.94 -0.11 0.00 -0.92 0.24 0.00 -0.71 0.22 -0.16

Triacetin -0.76 -0.43 -0.10 -1.05 -0.23 0.00 -0.88 -0.11 0.00

Abbreviations: HDPE, high-density polyethylene; PCM, phase-change material; PEG, polyethylene glycol; PP, polypropylene; PVC, polyvinyl chloride.

5

Table 5. Changes in sample dimension and mass for metals soaked in PCMs.

Test type PCM

Copper Aluminum Steel


(%)


thickness (%)

Average change in

mass (%)


(%)


thickness (%)

Average change in

mass (%)


(%)


thickness (%)

Average change in

mass (%)

Sho

rt t

erm

Distilled water -0.34 1.60 -0.20 -0.81 1.62 -0.23 -0.64 2.41 0.21

A6 -0.69 1.57 0.00 -0.84 1.06 0.23 -0.71 1.70 0.11

RT3HC -0.45 1.78 -0.07 -0.75 1.34 -0.23 -0.66 1.02 0.11

OM06P -0.48 1.06 0.20 -0.77 1.08 0.46 -0.95 1.02 -0.11

PureTemp 8 -0.57 1.07 0.34 -0.62 1.60 0.68 -0.80 1.37 -0.11

S8 -0.77 1.60 -1.42 -0.02 2.68 0.00 -0.19 6.12 -0.32

E0 -0.28 2.93 -0.07 0.64 24.86 2.49 -0.14 4.42 -1.27

PEG 400 -0.19 1.59 0.00 -0.64 1.61 -0.23 -0.78 1.71 0.43

Triacetin -0.60 1.06 0.14 -0.74 1.89 -0.45 -0.76 2.07 -0.11

Lon

g te

rm

Distilled water -1.10 0.27 0.00 -0.95 0.27 0.00 -1.18 -0.34 -1.47

A6 -0.99 -1.82 0.07 -1.08 -0.80 0.23 -0.61 -1.03 -0.11

RT3HC -0.90 0.27 0.07 -0.91 -0.27 0.23 -0.71 -1.69 -0.32

OM06P -0.86 0.00 0.00 -0.77 0.00 -0.23 -0.90 -1.02 0.11

PureTemp 8 -0.91 1.34 0.14 -0.91 1.34 0.00 -0.91 -1.03 0.11

S8 -2.05 4.27 -4.82 -0.63 2.96 0.00 -0.76 -1.69 -0.32

E0 -0.67 1.60 -0.07 0.24 27.81 3.15 -0.31 0.34 -1.06

PEG 400 -0.96 0.53 0.07 -1.23 0.00 -0.22 -1.04 -1.03 0.11

Triacetin -1.14 0.00 -0.07 -1.03 0.00 0.68 -0.90 0.00 -0.21

Abbreviations: PCM, phase-change material; PEG, polyethylene glycol.

6

Table 6. Changes in sample dimension and mass for foams soaked in PCMs.

Test type PCM

Polyisocyanurate Polyurethane

Average change in volume

(%)

Average change in

mass (%)

Average change in volume

(%)

Average change in

mass (%)

Sho

rt t

erm

Distilled water 1.23 73.0 -0.37 132

A6 0.41 62.8 -0.31 56.7

RT3HC 0.15 82.5 -0.74 61.4

OM06P -0.24 74.4 -0.60 55.6

Puretemp 8 -0.14 86.1 -1.05 59.9

S8 1.27 77.8 -0.82 133

E0 1.42 42.2 -0.55 63.8

PEG 400 -0.46 125 -9.61 341

Triacetin -0.23 131 -2.83 122

Lon

g te

rm

Distilled water 1.89 75.6 -1.48 102

A6 0.63 61.1 0.09 51.3

RT3HC 0.34 63.8 0.33 67.8

OM06P 0.70 72.3 0.79 79.8

Puretemp 8 0.55 79.3 0.00 109

S8 1.10 127 -2.29 156

E0 1.86 62.0 -0.48 68.4

PEG 400 -0.31 111 -4.81 414

Triacetin -0.13 84.6 -0.25 180


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.

2.2.1 Plastics

Polypropylene

After the long-term exposure to OM06P, the Young’s modulus was further decreased for OM06P compared to the baseline and the short-term test results. The increase in Young’s modulus 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 modulus in the short-term test also showed little or no effect in the long-term test results.

7

The offset yield stress 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 stress 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

PCM

Average Young’s modulus (MPa)

Standard deviation Young’s modulus (MPa)

Average offset yield stress (MPa)

Standard deviation offset yield stress (MPa)

Average ultimate tensile strength (MPa)

Standard deviation ultimate tensile strength (MPa)

Number of samples

Sho

rt t

erm

Baseline 1,400 100 29.0 0.3 34.88 0.04 3

Distilled water 1,400 100 28.9 0.5 34.84 0.09 3

A6 1,500 200 24.1 0.7 32.5 0.1 3

RT3HC 1,250 20 24.1 0.2 32.26 0.04 3

OM06P 1,110 30 24.4 0.1 32.4 0.2 3

PureTemp 8 1,300 100 27.4 0.4 34.0 0.2 3

S8 2,500 400 27.8 0.2 34.90 0.04 3

E0 1,700 100 29.1 0.6 35.1 0.3 3

PEG 400 1,500 100 28.5 0.1 34.58 0.09 3

Triacetin 1,540 70 28.7 0.3 34.8 0.1 3

Lon

g te

rm

Distilled water 1,580 90 28.1 0.5 34.6 0.1 3

A6 1,200 100 18.8 0.4 29.85 0.06 3

RT3HC 1,500 300 21.4 0.9 31.21 0.01 3

OM06P 800 200 25 1 31.53 0.08 3

PureTemp 8 1,200 100 25.5 0.4 32.9 0.1 3

S8 1,600 200 28.7 0.6 34.9 0.3 3

E0 1,600 60 29.4 0.1 35.5 0.3 3

PEG 400 1,900 300 28.2 0.5 34.7 0.2 3

Triacetin 1,180 70 29.8 0.4 34.71 0.03 2


8

Figure 1. Average Young’s modulus for polypropylene soaked in phase-change material.

Figure 2. Average offset yield stress for polypropylene soaked in phase-change material.

9

Figure 3. Average ultimate tensile strength for polypropylene soaked in phase-change material.

Polyvinyl chloride

The increase in Young’s modulus 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 modulus compared to baseline grew even larger in the long-term test results. The PCMs had little or no effect on offset yield stress or ultimate tensile strength during either the short-term or long-term tests.

Table 8. Polyvinyl chloride test results.

Test type

PCM Average Young’s modulus (MPa)






Number of samples

Sho

rt t

erm

Baseline 2,310 65 51 1 59 0.8 3

Distilled water 2,500 100 52 1 59 0.5 3

A6 3,100 300 47 5 60 0.4 3

RT3HC 2,600 100 52 1 61 0.3 3

OM06P 2,700 200 49 4 59 0.5 3

PureTemp 8 2,430 60 52 2 59 0.2 3

S8 2,730 70 53 2 60 0.6 2

E0 3,000 100 48 1 59 0.4 3

PEG 400 2,690 30 49 1 60 0.7 3

Triacetin 2,500 200 51 2 60 0.6 3

10

Test type







Number of samples

Lon

g te

rm

Distilled water 3,000 100 48 0.9 60 0.6 3

A6 3,100 100 50 1 59 0.6 3

RT3HC 3,200 200 48 2 59 0.8 3

OM06P 3,000 300 50 4 58 2 3

PureTemp 8 3,100 200 51 2 60 0.4 3

S8 3,100 200 48 3 60 0.5 3

E0 3,040 40 50 0.8 60 0.0 2

PEG 400 3,100 100 51 0.4 60 0.4 3

Triacetin 3,300 100 48 1 61 0.1 3


Figure 4. Average Young’s modulus for polyvinyl chloride soaked in phase-change material.

11

Figure 5. Average offset yield stress for polyvinyl chloride soaked in phase-change material.

Figure 6. Average 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 modulus compared to baseline after the short-term test also decreased Young’s modulus in the long-term test. Distilled water, S8, E0, and PEG 400, which showed little or no effect on Young’s modulus during the short-term test, showed significant decreases in the long-term test.

Similarly, the engineered organic PCMs that had decreased the offset yield stress 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,

12

RT3HC, and OM06P) and slightly larger for PureTemp 8. Other PCMs had little or no effect on offset yield stress or ultimate tensile strength.

Table 9. High-density polyethylene test results.

Test type



Average offset yield stress




Number of samples

Sho

rt t

erm

Baseline 800 20 19.1 0.3 25.1 0.3 3

Distilled water 720 20 18.4 0.8 24.7 0.2 3

A6 450 20 14.5 0.3 21.4 0.2 3

RT3HC 400 30 14.5 0.5 21.32 0.06 3

OM06P 405 6 13.74 0.07 20.62 0.09 3

PureTemp 8 590 20 16.05 0.08 23.1 0.3 3

S8 870 60 19.2 0.2 25.0 0.1 3

E0 750 70 19.9 0.3 25.14 0.08 3

PEG 400 810 30 19.26 0.09 25.2 0.1 3

Triacetin 822 8 18.9 0.2 25.0 0.1 3

Lon

g te

rm

Distilled water 695 7 18.7 0.2 24.4 0.1 3

A6 460 30 17.5 0.2 23.2 0.1 2

RT3HC 550 60 17.3 0.4 23.2 0.1 3

OM06P 520 30 18.1 0.5 23.8 0.2 3

PureTemp 8 460 10 15.3 0.1 21.9 0.2 3

S8 730 30 19.0 0.1 24.7 0.2 3

E0 680 20 20.3 0.2 25.5 0.0 3

PEG 400 620 80 19.2 0.5 24.2 0.2 3

Triacetin 760 20 19.0 0.6 24.6 0.4 3


13

Figure 7. Average Young’s modulus for high-density polyethylene soaked in phase-change material.

Figure 8. Average offset yield stress for high-density polyethylene soaked in phase-change material.

14

Figure 9. Average ultimate tensile strength for high-density polyethylene soaked in phase-change material.

2.2.2 Metals

Copper

With the exception of distilled water, all of the PCMs decreased Young’s modulus 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 stress 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.

15

Table 10. Copper test results.

Test length







Number of samples

Sho

rt t

erm

Baseline 113,000 4,000 264 1 283 4 2

Distilled water 100,000 3,000 266 4 284 3 3

A6 80,000 10,000 265 4 281 4 3

RT3HC 97,000 2,000 265.1 0.9 280.9 0.8 3

OM06P 91,000 7,000 263 3 280 1 3

PureTemp 8 93,000 7,000 265 2 283 2 3

S8 90,000 10,000 255 3 271.5 0.6 3

E0 70,000 10,000 267 9 277 4 3

PEG 400 124,000 7,000 263 2 281.0 0.4 2

Triacetin 100,000 20,000 262.2 0.1 280 2 3

Lon

g te

rm

Distilled water 120,000 30,000 263 7 285 2 2

A6 96,000 6,000 268.3 0.6 284.8 0.6 3

RT3HC 93,000 2,000 279 13 286.3 0.3 3

OM06P 93,000 — 265 — 285 — 1

PureTemp 8 91,000 7,000 271 4 285 2 3

S8 77,000 7,000 210 31 235 8 3

E0 90,000 8,000 266 5 281 3 3

PEG 400 90,000 10,000 266 4 284 1 3

Triacetin 98,000 4,000 266.0 0.9 285.2 0.5 3


16

Figure 10. Average Young’s modulus for copper soaked in phase-change material.

Figure 11. Average offset yield stress for copper soaked in phase-change material.

17

Figure 12. Average 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 modulus in the long-term test. The decreases in Young’s modulus 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







Number of samples

Sho

rt t

erm

Baseline 75,000 2,000 293 3 334 5 3

Distilled water 72,000 3,000 285 4 328 1 3

A6 66,000 5,000 288 2 329 3 2

RT3HC 69,000 5,000 277 11 317 16 3

OM06P 70,000 8,000 283.6 0.2 325 1 3

PureTemp 8 74,000 5,000 283.4 0.4 324 2 3

S8 72,000 3,000 285 4 328 1 3

E0 52,000 6,000 230 4 257 4 3

PEG 400 63,000 5,000 284 4 320 9 3

Triacetin 80,000 2,000 291 5 330 1 3

18

Test type







Number of samples

Lon

g te

rm

Distilled water 68,000 4,000 287 5 329 1 3

A6 75,000 2,000 291 2 332 3 3

RT3HC 71,000 2,000 293 2 332 2 3

OM06P 72,000 2,000 291 6 331 5 3

PureTemp 8 64,000 5,000 290 4 329 2 3

S8 74,000 7,000 282 2 320 1 3

E0 65,000 5,000 271 3 307 5 2

PEG 400 74,000 2,000 294 5 333 2 3

Triacetin 72,000 6,000 289 2 332 2 3


Figure 13. Average Young’s modulus for aluminum soaked in phase-change material.

19

Figure 14. Average offset yield stress for aluminum soaked in phase-change material.

Figure 15. Average 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 modulus and offset yield stress, so only ultimate tensile strength data were collected. Improved strain measurement equipment allowed determination of Young’s modulus and offset yield stress after the long-term test. Young’s modulus and offset yield stress 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 modulus. None of the PCMs affected the offset yield stress during the long-term test compared to the published

20

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







Number of samples

Published1 200,000 10,000 210 30 330 28 N/A

Sho

rt t

erm

Baseline — — — — 351 5 2

Distilled water — — — — 347 3 3

A6 — — — — 341 5 3

RT3HC — — — — 349 4 3

OM06P — — — — 352 3 3

PureTemp 8 — — — — 352 1 3

S8 — — — — 348 3 3

E0 — — — — 341 9 3

PEG 400 — — — — 348 4 3

Triacetin — — — — 350 1 3

Lon

g te

rm

Distilled water 130,000 20,000 206 2 350 3 3

A6 180,000 20,000 205 4 355 3 3

RT3HC 190,000 30,000 208.0 0.2 354.7 0.1 2

OM06P 210,000 60,000 208 4 355 4 3

PureTemp 8 130,000 20,000 209 1 356 1 3

S8 90,000 30,000 208 4 356 9 2

E0 91,000 6,000 198 7 341 13 2

PEG 400 150,000 10,000 208 3 354 4 3

Triacetin 140,000 20,000 206 6 353 3 3

1—Average and standard deviations were calculated from the range of manufacturer published values.


21

Figure 16. Average Young’s modulus for steel soaked in phase-change material.

Figure 17. Average offset yield stress for steel soaked in phase-change material.

22

Figure 18. Average ultimate tensile strength for steel soaked in phase-change material.

2.2.3 Foams

Polyisocyanurate

All of the PCMs had little to no effect on the compressive modulus in the long-term test. The increase in compressive modulus caused by A6 and the decrease caused by triacetin that were present in the short-term test results disappeared in the long-term test results.

All of the organic PCMs, including PEG 400 and triacetin, increased the yield stress at 5% strain in the long-term test. Only A6 had affected yield stress at 5% strain in the short-term test.

Table 13. Polyisocyanurate test results.

Test type

PCM Average compressive modulus (MPa)

Standard deviation compressive modulus (MPa)

Average 5% yield stress (MPa)

Standard deviation 5% yield stress (MPa)

Number of samples

Sho

rt t

erm

Baseline 4.1 0.5 0.131 0.004 3

Distilled water 3.6 0.7 0.12 0.02 3

A6 5.3 0.3 0.162 0.004 3

RT3HC 4.4 0.5 0.138 0.007 3

OM06P 4.0 0.1 0.124 0.004 3

PureTemp 8 4.2 0.2 0.140 0.009 3

S8 3.7 0.2 0.133 0.007 3

E0 3.6 0.1 0.126 0.001 3

PEG 400 4.4 0.4 0.13 0.01 3

Triacetin 3.1 0.1 0.11 0.01 3

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Test type



Average 5% yield stress (MPa)

Standard deviation 5% yield stress (MPa)

Number of samples

Lon

g te

rm

Distilled water 4 1 0.13 0.02 2

A6 4.9 0.7 0.16 0.01 3

RT3HC 5.0 0.3 0.18 0.01 3

OM06P 4.7 0.3 0.163 0.004 3

PureTemp 8 4.5 0.6 0.162 0.006 3

S8 4.1 0.8 0.14 0.01 3

E0 3.8 0.1 0.134 0.005 3

PEG 400 4.8 0.2 0.151 0.003 3

Triacetin 4.4 0.1 0.157 0.008 3


Figure 19. Average compressive modulus for polyisocyanurate soaked in phase-change material.

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Figure 20. Average yield stress at 5% strain for polyisocyanurate soaked in phase-change material.

Polyurethane

All of the organic PCMs except PEG 400 increased the compressive modulus 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 modulus, an effect that was also seen in the short-term test results. An increase in compressive modulus 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 stress in the long-term test. Triacetin increased the yield stress 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 stress and strain measurements challenging and may have caused conflicting results between the long-term and short-term test measurements of compressive modulus.

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Table 14. Polyurethane test results.

Test length



Average yield stress (MPa)

Standard deviation yield stress (MPa)

Number of samples

Sho

rt t

erm

Baseline 3.8 0.3 0.13 0.01 4

Distilled water 4.7 0.3 0.125 0.002 3

A6 6 — 0.174 — 1

RT3HC 4 — 0.153 — 1

OM06P 4.3 0.4 0.150 0.005 3

PureTemp 8 4.3 0.2 0.137 0.005 3

S8 4.8 0.5 0.16 0.01 3

E0 5 1 0.154 0.005 2

PEG 400 2.7 0.1 0.118 0.003 3

Triacetin 4.2 0.2 0.138 0.003 3

Lon

g te

rm

Baseline 3.8 0.3 0.13 0.01 4

Distilled water 3.2 0.6 0.1238 0.0004 3

A6 6.6 0.6 0.19 0.01 3

RT3HC 5 1 0.151 0.004 3

OM06P 4.6 0.2 0.15 0.01 3

PureTemp 8 5.1 0.3 0.14 0.01 3

S8 5.6 0.9 0.17 0.02 3

E0 4.3 0.5 0.163 0.001 3

PEG 400 3.9 0.8 0.118 0.002 2

Triacetin 5.3 0.5 0.16 0.01 3


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Figure 21. Average compressive modulus for polyurethane soaked in phase-change material.

Figure 22. Average yield stress 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

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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 Scratch test with steel nail

1 PureTemp 8 168 Paint peels slightly upon etch, slight discoloring of paint, no visible change to steel

Softer

2 PureTemp 8 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

7 PEG 400 168 Paint peels easily upon etch, paint has wrinkled at PCM-air interface, no visible change to steel

Much softer

8 PEG 400 Much softer

9 RT3HC 168 Paint was maybe harder than baseline, if any change; no visible change to steel

No change

10 RT3HC No change

11 Distilled water 168 Extensive peeling upon etch, extensive rust and discoloration, bubbling of paint

Much softer

12 Distilled water Much softer

13 S8 165 Paint peels slightly upon etch, some rusting of steel visible, slight discoloration of paint

Softer

14 S8 Softer

15 E0 165 Paint peels easily upon etch, bubbling and slight discoloration of paint, no visible change to steel

Much softer

16 E0 Much softer

17 A6 165 Paint was maybe harder than baseline, if any change; no visible change to steel

No change

18 A6 No change


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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.

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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 8 168 Copper appears darker

2 PureTemp 8

3 Triacetin 168 No visible change

4 Triacetin

5 OM06P 168 No visible change

6 OM06P

7 PEG 400 168 No visible change

8 PEG 400

9 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 corroded away 14 S8

15 E0 165 Copper appears darker

16 E0

17 A6 165 No visible change

18 A6


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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.

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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 stress and ultimate tensile strength decreased for PP. OM06P also decreased Young’s modulus in PP. All PCMs increased the Young’s modulus for PVC, while no PCMs affected PVC’s offset yield stress or ultimate tensile strength. There was also an increase in Young’s modulus 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 modulus 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 stress 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 change in properties was more than just an effect of the change in 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 modulus of mild steel in the long-term study when compared to published data. None of the PCMs significantly affected the offset yield stress or ultimate tensile strength compared to the published data or baseline samples, respectively. There was a slight decrease for offset yield stress 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 modulus 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 stress at 5% strain for all of the organic PCMs.

A6, OM06P, PureTemp 8, S8, and triacetin all increased the compressive modulus for polyurethane, while other PCMs had no significant effect during the long-term test. The yield stress 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

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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.

annex 1. investigation of phase-change materials for vaccine … · 2018-06-28 · 1. introduction...

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