Team:PuiChing Macau/Engineering
Investigate the potential of synthesized amino acids-based flame retardants for fabrics
With the overall project goal of creating a flame retardant product that is sustainable, environmentally friendly, and efficient, we have reviewed all our possible approaches within our resource limitation. Considering polymeric fabrics material products being ubiquitous in different fields of day-to-day life, yet a majority of them carry a limitation of being flammable. In the prevention of these potential threats to user safety, essential modulation is approached, aiming to reduce polymeric material's flammability through a new manufacturing process and new multi-functional materials. However, this requires innovative molecular design, sophisticated synthesis, and therefore long hour input and expensive resources. Therefore, we carried out the investigation to:
• Validate the feasibility of amino acid based flame retardant.
• Generate basic data for future protein flame retardancy ranking system.
• Establish prototype and procedure for flame retardancy testing in our school lab.
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Potential Factors
Taking into account the potential factors causing the fire, it can be divided into “Geographical factors”, “Natural factors” and “Materials”. According to our opinions, fire retardancy will be influenced by several factors, such as the structure of the surroundings, humidity, temperature, weather, and material, etc.
1. Geographical factors:
Unlike humans, fires usually travel uphill much faster than downhill. The steeper the slope is, the faster the fire travels. The speed of the fire travels would double when a hill is going upwards at a 10% gradient. In the same way, if a slope is going upwards at a 20% gradient, it would quadruple the speed of the fire. It is because smoke and heat that are caused by the fire are rising uphill. As a result, the fuel further up the hill had been pre-heated before the fire approached. In addition, it is obvious that the occurrence of fire depends on the layout of the surrounding environment. For example, the closer the trees in the forest are arranged, the trees nearby are more likely to be burned when wildfires happen.
2. Natural factors
The higher percentage of the humidity in the air, they are higher moisture in the fuels and the less likely they are to catch fire. As a result, when it’s autumn and winter, wildfires are more likely to occur. On the other hand, the influence of season and temperature are mutually influencing. In some areas, extremely high temperatures may be reached in summer. The heat will evaporate the water in the trees, which will dry out the trees and leaves causing a fire. For example, in many parts of West Africa, the dry drought of the Sahara Desert during the dry season has begun to make fire burning easier.
3. Materials
One of the important factors here is the flammability of materials. The flammable items at home were mainly curtains, bed sheets, furniture, etc. With ranking of the fabrics (from easiest to hardest flammability) demonstrated: Linen →Cotton → Wool → Silk → Polyester Fabrics
Current researches established by other people all over the world have already conducted sufficient research on the natural factors affecting fire. Considering our constraints, we are prohibited from building a model to test the influence of slope or surrounding layout. Therefore, we decided to conduct burning experiments on different materials, mainly wood and polyester fabrics, which are the main material at home.
Fire Standard & Testing Method
For testing, we employ ASTM-D6413 which is called the Standard Test Method for Flame Resistance of Bedsheets (Vertical Burning Test). After we considered our limited equipment and time and the real situation in target applicative places, we anticipate that ASTM-D6413 is the most suitable testing method for us to test our proteins/ amino acids.
The ASTM-D6413 standard is an American standard for testing the Flame Resistance of Bedsheets. In our city, we don’t have our own standard and our adjacent cities like Hong Kong, Taiwan, and so on both create their own standards that refer to the US one. The further industry application realization also provided us with the details of fire retardants’ criteria, of which at the moment they are meeting the FSD requirements from Hong Kong as Macau does not consist of a consummate institution.
As a result, we both agreed that this test is the most accessible and accurate one, which is American Standards ASTM-D6413.
According to the ASTM-D6413 authoritative documents, it is mentioned that:
1 This test method determines the response of bedsheets to a standard ignition source, deriving measurement values for after flame time, afterglow time, and char length.
2 The vertical flame resistance, as determined by this test method, only relates to a specified flame exposure and application time.
3 This test method maintains the specimen in a static, draft-free, vertical position and does not involve movement except that resulting from the exposure.
4 Test Method D6413 has been adopted from the Federal Test Standard No. 191A method 5903.1, which has been used for many years in acceptance testing.
Conferring the descriptions of this test in the ASTM INTERNATIONAL website which is https://www.astm.org/Standards/D6413.htm. This information validates our use of this vertical flame resistance of the bedsheets. Our experiment’s safety and accuracy can be conferred based on the reference to this standard. Although this test does have drawbacks listed in 5.4, it is however the most feasible method that enables us to conduct it in our school laboratory.
Imagine: Develop Possible Solutions & Design: Select a Promising Solution
Biomaterial such as protein have been reported as an alternative option for fire retardant because of the high amount of phosphorus and nitrogen, which would generate thermally stable char during combustion as a protective layer and inhibits oxygen supply.
According to Xu et al (2019), several novel Nitrogen-containing amino acids (glycine, aspartic acid, and lysine) with specifically designed group molecules have been demonstrated their potential as a flame retardant for cotton fabrics via char formation. This result showed that an amino acid-based flame retardant is feasible. Amino acids are the building block of protein, each consists of an alpha carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable component called side chain. In proteins, multiple amino acids are linked together by biochemically induced peptide bonds to form a long chain. The linear sequence of amino acids in a protein is considered as the primary structure of the protein (Nature Education, 2014). In a review of other literature, there were suggestions that milk protein would also be an option of flame retardant. Since amino acid is the basic building block of protein, we hypothesis that amino acid-based flame retardants would be feasible material choices.
Due to the COVID-19 pandemic, we decided to use the syntheized amino acid to conduct our experiments on fabrics instead of the conventional e.coli produced material to prove our hypothesis.
Information about the Prototype
1. 0.25m, 0.5m and 1m Concentration of Amino Acids will be tested
Before the experiments, we tried different concentration of amino acid and found some amino acids have lower solubility. In order to completely dissolve the amino acids and make the experiment fairer and more consistent, we decided to use concentrations of 0.25m, 0.5m and 1m.
2. Only 5 amino acids will be tested
For the purpose of making sure that our experiments are accurate, we burn each amino acid three times at each concentration. However, that would be a huge amount. Because of the limited amino acids, we chose five amino acids with the consideration of nitrogen percentage.
3. Materials-Used to make the Equipment
As mentioned, the vertical testing with ASTM-D6413 will be employed. Therefore, we referred to the required equipment and built a similar device ourselves. In order to minimize the influence of external factors on the experiment such as oxygen level, we process the experiment inside the tin box made by ourselves with only one side for ventilation. It is also convenient for us to do experiments and take photos.
Materials to make the equipment: Tin Foil, Lab Racks, Alcohol Lamp, Fire Mat
4. Experimental Steps (including Adjustment of the Fire Testing)
We tried to ignite the bedsheets for 12 seconds according to ASTM D6413. However, we found that the whole bedsheets were burned. It is quite difficult for us to analyze. Finally, we changed it to 5 seconds.
The above adjustment can also be regarded as a cycle. In order to make our description clear, We summarized the above content rather than showing all the experimental results which are less valuable
Experimental steps
1. The solution was made in a beaker and the bedsheets were soaked in the beaker for a day to ensure complete absorption.
2. The bedsheets were taken out and put on the lab racks
3. The equipment made by ourselves was set up
4. The bedsheets were hold using four clips and hole by the lab racks
5. The bedsheets were ignited for 5 seconds and put out
6. Step 4 and 5 were repeated for every soaked bedsheet
In total, there are two people to conduct the experiment. One person is responsible for lighting the alcohol lamp and removing the alcohol lamp after burning for 5 seconds. The other one is responsible for video recording and timing.
Learn & Analysis
Placed the bedsheets in trays and soaked the bedsheets with different amino acids overnight to let them coated with the amino acid. According to the IR results of different 1M amino acid, the nitrogen percentage of Arginine is the highest, thus the bedsheets coated with it took the longest time to be fully burnt out.
IR of Bedsheets soaked with different Amino Acids
Generally, the average burning time increases as the nitrogen percentage increases. The most significant increase trend in which the concentration is 1m, followed by 0.5m and 0.25m. In terms of R-value, 1m concentration has the highest value which is 0.788, which means that the relationship between burning time and nitrogen percentage is mostly related during the burning testing for 1m concentration. Although the r value for the other two is low, this does not indicate that the relationship is less. Theoretically, they must be related. It can only be commented that the influenced caused by human error and unprofessional equipment have a more significant impact on the burning test for lower concentration. This can also be reflected in the scattered data, especially the 0.5m and 0.25m concentration. In terms of the trend line of 1m, the burning time suddenly increases when the nitrogen level is 21.2%. For 0.5m, the burning time is keep decreasing with the increase in the nitrogen level. Until 21.2% nitrogen level, burning time starts to increase. In the aspect of 0.25m, the data points are fluctuation. In overall, it can be said that the data points are slightly in line with the theory although the data points are scattered. It is worth to mention that the burning time of the bedsheet soaked with water is only around 17second only. Therefore, all the bedsheets soaked with different amino acids have a better fire retardancy compared to the bedsheets soaked with water.
Correlation of Nitrogen Level and Burning Time
Burning Test Data with the Order of Nitrogen Level
Based on the concept, it is assumed that the burning time increases when the concentration of amino acid increases. As shown in the graph and table, the average burning time for 3 different concentrations with respect to 5 different amino acids is presented. Based on these data points, their R-value is also estimated. According to the data, the R-values of L-Asparagine, L-Arginine and L-Alanine are about 0.9936, 0.9878 and 0.9449 respectively, which indicate strong positive linear relationships. In contrast, L-Serine and Glycine present relatively lower R-value, which is 0.7289 and 0.5. However, they still remain strong positive linear relationships overall. In terms of L-Arginine and L-Asparagine, their burning time increases with the increase in concentration. For the other three, their burning times are not totally meet the theory because some burning times are lower/higher with the increase/decrease of concentration. As mentioned above, the burning time of the bedsheet soaked with water is around 17 second. This means the fire retardancy of all bedsheets soaked with different amino acid is better compared to the bedsheets soaked with water.
Correlation of Concentration and Burning Time
Burning Test Data with the Order of Concentration
Improve & Suggestion
Based on the data in the first cycle, the result basically fit the theory. The higher the solution concentration or the nitrogen percentage of the amino acid, the longer the burning time. After our first cycle, the epidemic in Macau is basically under control. Therefore, we can also make the protein in the laboratory at the University of Macau. As protein consists of several amino acids, we decided to verify whether the effect of burning bedsheets soaked with protein is better. This can also make up for the lack of burning the bedsheets soaked with protein.
Information about the Prototype
Two Types of Protein: SR & Alpha-Caesin
Two Types of Adhesion Domain: Mfp5 & CBD
Control: Deionised Water and pET-11a
Experimental steps
Since only the soaking solution is different, the experiment procedure is the same as the first cycle1. The solution was made in a beaker and the bedsheets were soaked in the beaker for a day to ensure complete absorption.
2. The bedsheets were taken out and put on the lab racks
3. The equipment made by ourselves was set up
4. The bedsheets were hold using four clips and hole by the lab racks
5. The bedsheets were ignited for 5 seconds and put out
6. Step 4 and 5 were repeated for every soaked bedsheet
In total, there are two people to conduct the experiment. One person is responsible for lighting the alcohol lamp and removing the alcohol lamp after burning for 5 seconds. The other one is responsible for video recording and timing.
Left:CBD-SR; Middle:pET11a; Right:Deionised Water
Learn & Analysis
According to the data, we confirmed the fire retardancy can be improved with our fire retardance protein, the material with fire retardance protein have a great improvement on fire-resisting. Furthermore, we found out that with protein with adhesion domain can last longer time, especially in CBD- SR,CBD Alpha casein have a great deal of fire defending, following with mfp5-SR, which can prove that adhesion domain can help with the fire retardant. . The detailed analysis can be referred to the Result Part.
Improve & Suggestion
Based on the analysis of the first and second cycle mentioned, our data are slightly in line with the theory. In order to increase the accuracy of the burning test, professional equipment is required. For this time, it is impossible for us to control the oxygen level, temperature and humidity during the experiment. In addition, the moisture content of the texture is also expected to be the same. In the aspect of data recording, the burning times is recorded artificially. If it is feasible, a flame sensor, such as One Way DC 12V Flame Sensor Relay Module or 5 Way Flame Sensor Module as shown below, can also be applied for the purpose of recording the burning time accurately
