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What combination of polymer and cross-linking agent will optimise the…

- - - - Anti-bacterial Properties, Antioxidizing Properties
        
        These factors are important to test but effective testing would require trials spanning weeks or longer to test how fresh produce may last within the packaging. Another deterrent is the fact that a way to create a film coating would have to be engineered, requiring a greater number of resources and a more intricate method that would likely have more potential areas for error or uncertainty. While it may be possible, for an accurate and reliable experiment within the time constraints provided, these DVs would likely not be the best option.
      - Clarity
        
        Clarity may be a factor that companies look for when producing food packaging, ensuring that the customer can see what is in the packaging and that it looks more appealing. However, this is mostly an aesthetic property and not entirely fundamental to the use of the polymer. Therefore, it would not be as important to test for this property.
      - Strength
        
        Tensile strength
        
        Tensile strength is quite important in a film as they are relied on not to break even through packaging, handling and transport. And, as the films are pulled over produce it must be able to withstand 'pulling strength' or tensile strength particularly well.
        
        measuring time
        
        By measuring the time it takes for the film to rip while supporting the maximum weight that can fit, the experiment is no longer limited by the physical surface area of the film. Measuring time as opposed to the weight also eliminates the variable of different waiting times in between adding new weights reducing the risk of possible random errors.
        
        measuring weight
        
        As each film's surface area is relatively small in comparison to its weight baring capacity there is a limit to the amount of weight that can be safely placed on the film. As the films are likely to reach this limit quite quickly, limiting the results of the experiment, it may not be the best way to measure tensile strength.
        
        Compressive strength
        
        In the context of food packaging compressive strength or the ability to apply inwards pressure on both sides of the film, is not particularly important to consider as even a fairly low amount of compressive strength is adequate to prevent breaking of the film in transport or handling.
        
        While measurements are limited in that they would be arbitrary individually, in comparison to the trials completed the trend is something that can be used and can provide helpful insight. Biodegradable, food safe plastics would commonly be used as an alternate to paper packaging but in order for it to have other uses has to have some strength.
- - - - Citric acid has several carboxyl functional groups and so has the potential to form crosslinks between two starch polymer chains, leading to changes in the physical properties of the resulting crosslinked polymer.
    - - Acetic acid contains only one carboxyl functional group and no other functional groups that might be able to form crosslinks between the polymer chains. While acetic acid may influence the number of crosslinks formed, it does not have the potential to change the types of crosslinking that is formed.
- - - - Certain factors like the other objects in the oven and how often the oven is opened will influence the humidity of the oven, however, in a shared lab this cannot be fully controlled. As this variable will also likely have little to no effect on the results it will be mostly disregarded.
  - - - This variable can be somewhat controlled however there may be some discrepancies
- - - - If citric acid gets into eyes, wash out eyes for 10 minutes with running water
- - - - Not only is 1,2,3,4-Butanetetracarboxylic acid hard to access but the crosslinking reaction is quite sensitive requiring temperatures above 150 and long mixing times that may make successfully forming crosslinks difficult to achieve within the time constraints.
  - - - Starch and glycerol are easily accessible and cheap but their crosslinking can be altered through various factors that could be tested. The physical properties that form once this crosslink has occurred like flexibility, strength or tackiness also have several potential ways they can be tested.
        
        Potato Starch
        
        Both potato starch and corn starch are common and cheap starches which are made up of proportions of amylose and amylopectin. Amylose is a straight chain glucose polymer whereas amylopectin is a glucose polymer with a lot of branching. While both can form crosslinks with glycerol it would be easier to create crosslinks with amylose as all the hydroxyl groups are more accessible. The difference between the two starches is in the percentages of each polymer with potato starch containing approximately 20% amylose, 80% amylopectin and corn starch at 25% amylose, 75% amylopectin. While these percentages may not be significantly different with a greater proportion amylose corn starch would in theory be more prone to creating crosslinks with glycerol and so will be used.
        
        Corn Starch
        
        *see potato starch
  - - - To form crosslinks with primary interactions requires more intricate processes like completing reactions in sealed pressurized crucibles with N2 flow which is too dangerous to attempt within the limitations of this experiment: skill level, time constraints, lab equipment, etc.
  - - - A popular reason for adding sugar crosslinking agents to gelatin is to create a digestible gel coating to slow drug release in the body. While the reaction to make this gel may be possible in the lab the methods generally used to test relevant physical properties of the gel are not as available and would greatly limit the findings if this reaction was chosen.
    - - Finding a practical use for slime is slightly harder than other crosslinked polymers meaning investigating the optimal combination of polymer and crosslinking agent may not be as useful for further research. It is also a well researched combination and it may be more worthwhile to investigate a less researched combination in order to create new findings/strengthen less established findings.
    - - Glutaraldehyde while technically accessible is still a very dangerous chemical with potential for serious harmful impacts to lungs, skin, eyes, etc. For this reason it is decided that using this crosslinking agent is beyond the scope of this practical.
  - - - The physical properties that result from these crosslinks may be hard to test accurately particular when considering the context that the product is used for applications like wound dressing and enzyme entrapment.
  - - - Formaldehyde is a human carcinogen and can cause severe irritation after exposure. As such using it in such proximity to complete the experiment and without proper safety equipment would be very dangerous and therefore shouldn't be considered.