True, but in the spiderman universe, a teenager gets powers by being bitten by an arachnid. To say that everything in that universe or even the attempts at justifiable realism in that book (I loved their explanation of spider sense) are accurate is off hand. I think we need a heirarchy (sic) of properties that the fluid must meet. The top will be the most important, while the bottom will contain the fantastic. For example:
1.) shear thinning. Without this, the web won't actually harden. a chemical or thermal attempt will either leave it un-hardened or give the recipient burns.
Exception: silly string style formulations that consist of resins, propellants, and surfactants.
Very close 2.) adhesive and non-toxic. The web has to be as sticky as it is safe. Once the web has taken shapes, it must adhere, and not injure anyone (for example, the before mentioned burning)
exceptions: None. Despite the fact that Shear thinning gives webbing it's physical composition, these two properties will set apart the nylon 6,10's of the formula chain from webbing.
3.) Strength/fire resistant. Now that we've made a fiber that can hold it's shape and stick, it's time to make it indestructable.
exceptions: If you are using this to decorate your house for halloween. Or, you know, using it for self defense. Making it too strong may kill or blind someone (adhesive plus face equals bad idea). In which case, just buy that cheap cotton webbing at Walmart.
4.) Biodegradability- So low on the list because it is possibly the most difficult property to obtain. This will make the webbing very hard to engineer.
Exceptions: If you are making the webbing to support collapsing structures. Firemen need their buildings to stay intact right?
Repeat this for all properties. Include properties like translucent, conductive, elastic, expansive, etc.