Paint Additive Evaluation and Characterization

=Problem Definition= Our goal is to evaluate the thermal resistance, solar heat reflectance, and microstructure durability of two novel paint additive technologies.

Background
Many paint additives have started being tested in many various applications. There have been multiple tests that show that these additives can have some benefits to thermal resistivity, temperature reduction, and some degree of EMF protection. There are two main types of different paint additives that have been tested the first being a nano-ceramic additive and the second being a phase change additive. Both of these additives modify the thermal conductivity (k) and the emissivity (Ɛ) of the base paint. These help to reduce the heat absorption rate from radiated and latent heat. In addition to the beneficial properties, these additives are relatively cheap when compared to the price of a coating system. if a temperature drop could be observed under strenuous testing in a variety of environments and meet paint coating test specifications it could be a great cost per benefit solution to reflect heat and reduce internal temperatures.

Deliverables
The addition of these paint additives must show the following:
 * Show a temperature reduction of 5 degrees Fahrenheit in warm weather
 * Increase thermal resistivity to provide insulation and an increase from the ambient temperature of 5 degrees
 * Meet Salt fog testing (ASTM B117) Requirements for 1500 hours of testing ​
 * Meet Mean Creepback Rating (ASTM D1654, Procedure A) for 1500 hours of testing

Value Proposistion Statement
The lifetime of electronic devices, found inside enclosures, is significantly shortened when exposed to environmental extremes. Because there are thousands of enclosures in rural locations, hot and cold climates, it is essential to develop an affordable, maintenance-free method to extend the life of the enclosure’s internal electronic devices. By using affordable paint additive technologies any improvement in performance and extension of application life will be financially beneficial for the client. The Nano-Vandalizers are offering an affordable, simple solution to reduce the thermal degradation of electrical enclosures in order to extend the battery life and reduce the possibilities of a short circuit due to a buildup of condensation. We will coat SEL’s enclosures with the paint additive technologies to evaluate the thermal resistance, solar heat reflectance, and microstructure durability of the enclosure surface.

=Design Considerations=

Testing Stand Design
A test stand had to be designed to create a uniform and consistent testing environment to achieve the best results from temperature and resistivity testing. In addition to these requirements. The test stands also had to be designed to assemble quickly and take up a minimum amount of room. The test stand was designed to be mounted on a 4' by 4' piece of plywood with a 4" by 4" stand to mount the cabinets with a large lag screw. The 4" by 4" is supported by three 2"x4" struts cut at a 45-degree angle and fastened to the plywood.

Revisions to the test stand
After consulting with the party that was going to house our enclosures and monitor our testing, It was then made clear that our stand had to revise for space and assembly considerations. The design was kept very similar but the sizes of the 2x4 struts and plywood were revised. It was decided to cut the 2x4 struts to an equal length due to the relatively light load of the cabinet being supported. The plywood was decided to be cut to a 28 by 28 square footprint rather than the previously 4' by 4' footprint. The two by fours were then decided to be cut to even lengths of 30" rather than having two sizes of 2x4 cuts. The revised views can be seen below

Final Test Stand Images
Our test stands were assembled on November 11th of 2020 in the design suite.

=Thermal Testing procedures=

Thermal resistivity Testing
In order to create thermal resistivity models, the thermal conductivity constant (k) of each coating had to be found. These values are found by using Fourier's law in one dimension : $$\phi_\text{q} = -k \frac{dT(x)}{dx}$$ With (k) being the thermal conductivity factor, $$\phi_\text{q}$$ representing the heat flux across the surface and $$\frac{dT(x)}{dx}$$ representing the temperature gradient across the surface. To measure the heat flux across the entire surface of the cabinets we will be calculated by first finding the thermal conductivity of the control cabinet. after this is completed, then the heat flux across the surface can be found by the use of a temperature sensor positioned on the inner and outer surface of the cabinet. With these values calculated the heat flux across the surface from convective and conductive heat transfer can be calculated. With this information, the thermal conductivity of each paint coating with its respective additive can be quantified

Temperature Sensor Placement and outdoor data collection
In the electronics that are placed inside of these containers, There is a battery that powers the previously mentioned electronics. This component is one of the most susceptible to damage from extreme temperatures and extreme temperature fluctuations. In the cabinets, the battery is placed in the bottom right of the enclosure. Because of this, the sensors were placed on the front door of the cabinet, the bottom of the cabinet, and on the inside of the cabinet near the bottom of the enclosure. these locations allowed us to have temperature information where it is most important to the supplier. The types of Sensors that will be used to collect data are called HOBO sensors and can be seen below.

=Paint durability tests=

Salt Fog Testing
One test that SEL conducts to characterize the durability of their paint coating is a salt fog test. In addition to characterizing the durability of the paint coatings, it can also help characterize the corrosion resistance of a paint coating. In order for these paint additives to be implemented into SEL's existing paint process, each respective coating must be able to protect the base metal underneath the cabinets to a certain standard that meets or exceeds the current paint coating. These Standards are as follows: MEK Test (ASTM D4752-03), Cross-Hatch Adhesion Test (ASTM D3539), Salt Fog Testing Period (ASTM B117), Mean Creepback Rating (ASTM D1654), Maximum Creepback Rating (ASTM D1654), Corrosion and Blisters (ASTM D1654). Multiple Paint samples are used in the evaluation of these tests and must meet the standards for a 1500 hour exposure to be considered a viable addition to the painting process. To evaluate the creep back and Corrosion tests a scribe must be inscribed into the coating and will be evaluated during its time while in the salt fog machine. The inspection intervals are conducted at 500 hours and 1000 hours up to the end of the test at 1500 hours.

images before scribing procedure

MEK Standard
This test technique is utilized to decide the level of fix of a heated film by the paint film protection from a predefined dissolvable. The Solvent Rub Test is generally performed utilizing methyl ethyl ketone (MEK) as the dissolvable. The MEK opposition or level of fix applies to paint topcoats and preliminaries. The paint coatings must meet the MEK Test (ASTM D4752-03) standard for 1500 hours. Methyl Ethyl Ketone (MEK) was rubbed on our samples, both the regular painted sample and the sample treated with a paint additive, to test to determine the level of resistance the paint surface film has against a specific solvent. The label for the sample with the paint additive applied is labeled as ThermaCell in order to match up with how the samples were labeled upon delivery.

Procedure
1. Wipe clean the rub area on the sample to remove any residue with a dry cloth or cheesecloth and measure the sample thickness of the rub area with calipers.

2. Mark with a sharpie a straight line to distinguish the two sides of which you will perform your MEK rub test. On one side of the line will be the before, and on the other side of the line will be the rub after the testing.

3. Once your line is marked, take your dry cheesecloth and press down on the sample using. Apply pressure with one finger at a 45-degree angle and rub 50 times. One rub is considered a single there and back motion.

4. After the 50 rubs, measure the thickness of the rub area on the sample. There should be no difference in thickness for the dry rub test. Rate the results of the rub based on a 1-5 scale provided by SEL. The characteristics of the ratings are 1 being the worst outcome and 5 having no effect on the surface and no paint on the cloth.

5. Repeat this process with MEK dampened cheesecloth. Press down on the sample with the dampened section of cheesecloth. Apply pressure with one finger at a 45-degree angle and rub 50 times. One rub is considered a single there and back motion.

6. Measure the thickness and rate your sample based on the 1-5 scale.

Creepback Testing
A typical test includes the intentional harm of the covering layer to decide a property alluded to as rust creep, a quantitative proportion of how far the consumption goes along the substrate/covering interface to one or the other side of a precisely actuated scratch during the introduction to a destructive climate—ordinarily an unbiased salt splash or cycle erosion test

Cross-hatch adhesion test
Each sample was scratched with the Elcometer 107 Crosshatch Cutter in order to create several parallel scratch marks ensuring the paint coating has bonded to the substrate. This test is performed by securing the sample in a vice and scratching it with the Crosshatch tool in a single, smooth motion. Two scratches will be made, one perpendicular to the other, creating a lattice cut where the scratches are intersecting. Three separate sites are created for each sample. Once the sites have been created, lightly brush off any loose debris and place a strip of Crosshatch Coating Adhesion Tape is laid on the intersection sites at a 45-degree angle to the intersection. Firmly press the tape on the site to ensure it has the most surface area contact with the scratch marks. Once firmly pressed on the surface, pull the tape off quickly revealing the lattice cut and making them available for analysis. This process was performed on our paint additive ThermaCell sample and the Regular painted sample and sent away to SEL for analysis.

crosshatch test imaging
Standard Paint coating

UV Testing
Ultraviolet Exposure testing (UV testing) is going to be conducted on our coated coupons to understand how each respective coating will perform under the effects of ultraviolet exposure. With UV testing, we can simulate years of ultraviolet exposure in the time frame of a few days. With this test, we can evaluate the paint coatings for cracking, discoloration, and overall coating durability to UV rays.

Nanoindentation
Nanoindentation is a series of micro indentations on a substrate to characterize its material properties. We used this style of the test to characterize each respective paint coating and compare their values to the baseline coating. to begin the nanoindentation, the mounting plates that the samples were to be mounted to were cleaned in an ultrasonic cleaner. To mount each respective sample, We used double-sided tape to adhere to the mounts. The machine used tests the properties of the materials with the use of constant strain loading. In order to ensure the previous test didn't interfere with the next respective test space of 300 nanometers was given between each respective test and to account for the plastic deformation of the previous test. In order to ensure accuracy in our tests, we performed 25 tests on each respective coating. We decided to use a Poisson's ratio of .48 when conducting these tests which were similar to similar coatings of this style. We performed two separate rounds of testing with 1x1 coupons.

Nanoindentation images
=Project Learning=

Expected results

 * A vast array of temperature data in various climates
 * Material properties of each respective coating
 * data about the durability of each coating in various environments
 * Thermal conductivity and resistivity information and models
 * EMF protection information for each respective coating if time permits

Phase Change Material (PCM) complications
When this project was started the initial plan was going to be to test two paint additives with uniform testing and measurements. Once the PCM was shipped to our team we found that it was incompatible with the oil-based paint that was used for SEL's enclosures. (See Image Below)

In order to quantify the thermal properties of the PCM material we changed our focus and created separate enclosures. We then painted these enclosures with a water-based Sherman Williams paint and added the phase change material to one coating. In addition to static thermal testing, we also made an auxiliary heater circuit to further quantify the insulation properties of the PCM as well as the Nanoceramic coating.

=Results=

MEK
Regular Paint Sample:

Thickness before MEK rub: 0.145 inch

Thickness after MEK rub: 0.143 inch

Resistance Rating: 3, minimal marring, some paint on cloth

Paint Added Sample:

Thickness before MEK rub: 0.145 inch

Thickness after MEK rub: 0.145 inch

Resistance Rating: 5, no effect on the surface, some paint on cloth but primarily from the sharpie mark

500 hour interval results
the quantification began by vigorously using a spatula scraper tool and scraping the scribe mark indicated with the 500 hour mark at a 45 degree angle to determine paint wear on both the ThermaCell and Regular “ear” paint samples. Next, the samples were cleaned with water to rid of any debris caused by scraping. With the now cleaned samples, calipers were used to measure the width of the 500 hr scribe marks for both paint additives. scribe marks in six different locations along the line (ensuring at least an eighth of an inch from the endpoints).

initial observations
Both samples had minimal paint loss, but the ThermaCell had slightly more than that of the regular sample when conducting the scraping using the spatula. an important note: The rust-colored substance is not actually rusted on these samples but rather a salt build-up

rust evaluation
This is a visual test, and to determine rust evaluation both samples were flipped over (bottom side up without scribe marks) and evaluated within the central parts of the ear (away from edges or holes) to get the most accurate result.

ThermaCell – score: 10 (0 rust)

Regular – score: 10 (0 rust)

blistering
This is a visual test to determine if there is any blistering in the paint. The test requires the same part of the sample as the rust evaluation.

ThermaCell – score: 10 or “none” (no blistering)

Regular – score: 10 or “none” (no blistering)

Creepback Results
Creep back is determined by the equation below C = (wc - w)/2 C = creepage W_c = mean overall width of corrosion zone W = width of the original scribe mark Creepback testing results
 * the variations in measurements are caused by user error due to the very small crack widths (hundredths of an inch) and the lack of a very precise measurement device for the required usage. Results can be found in the document below.

1000 hour test results
Upon cleaning of both coupons, the regular sample had a little amount of flaking of paint. The ThermaCell, unfortunately, had a substantial chunk fail. The ThermaCell paint looks like it struggled to stay adhered to the metal surface. There was no blistering or rust on the backside of either paint sample except near the edges which we do not count.

1500 hour test results
On the final interval of testing, we found that both the standard coating and the nano-ceramic coating had large chips in the paint. We think that the large chips were caused by the large circle on the mounting ear. In future testing, we will be using a uniform 4x6 coupon with a scribe stencil for more consistent testing.

Round 1 testing
The raw data can be found tabulated in the excel sheet below. The Minimum hardness factor found from the nanoindentation was a hardness of .122 GPA. The depth on the nanoindentation was limited to quantify solely the paint coating and not the substrate.

Nano Indentation Bulk Data

Nano Indentation Summary

Round 2 testing
For this test, we compared two 1x1 coupons of each paint additive. Our tests indicated that the hardness of the Nanoceramic coating was lower at every average depth. in addition, there was a larger error indicated by the standard deviation of the mean. In the graph below, The bars represent the Standard deviation of the mean from the value

The bulk data can be found in the excel spreadsheets below

NanoIndentation bulk data second round (nanoceramic)

Nanoindentation Bulk Data Second round (standard coating)

Hypothesis
Our current working hypothesis on the smaller hardness levels has to do with the paint curing process. Due to the extra space that the nanobeads take up in the paint, we think they don't allow the paint to adhere to the base surface and cure effectively because of the space they take up in the paint.

Thermal Resistivity Results
To analyze the thermal properties of each of the respective paint coating we started by taking temperature measurements on the outer surface of the cabinet along with the inside surface of the cabinet. With these temperature data points and their respective ΔT we were able to estimate the heat flux across the surfaces of the cabinet by estimating the thermal conductivity factor for the control cabinet with the standard coating. With this heat flux value, the respective thermal conductivity for the cabinets with the modified coating were collected and used to show heat transfer.

Conduction equation: Q(w) = kA(Th - T∞)

We found that the average thermal conductivity for a .2mm paint coating was about .2 w*m^-1*k^-1. With the primer and topcoat configuration of our coating system we estimated that our paint thickness was about .4mm which equates to a .4 w*m^-1K^-1 thermal conductivity of the paint for each side of the base material. With this, the total thermal conductivity addition to the base metal was estimated to be .8 w*m^-1K^-1. With these estimates in mind, we calculated the total thermal conductivity of the material to be 54.8 w*m^-1K^-1 for the base material. With this value, temperature data from 12/6/20 at 13:45 to find a base heat flux (q”) of 294.799 w*m^-1K^-1. By using this data in addition to the temperature delta information from the same date and found that the thermal conductivity value was found to be 52.2076 w*m^-1K^-1. With both thermal conductivity values found, the thermal resistivity values were found to be 0.000124136 K⋅m/W and.0001303 K⋅m/W for the control coating and ThermaCell coating respectively. This represents an increase of a little under 5% thermal resistivity between the two coatings.

Temperature Testing Results
=External References= Jung Yen Chou - Phase Change Materials.NW.2008

=Team Members=

=Additional Documentation= Meeting Minutes Budget Schedule Snapshot Presentations Concept Design Presentation
 * NanoTech Vandalizers Meeting minutes
 * NanoTech Vandalizers Budget
 * NanoTech Vandalizers Gannt Chart
 * NanoTech Vandalizers Snapshot 1
 * NanoTech Vandalizers Concept Design Review