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All biodegradable polymers should be stable and durable enough for use in their particular application, but upon disposal they should easily break down. [citation needed] Polymers, specifically biodegradable polymers, have extremely strong carbon backbones that are difficult to break, such that degradation often starts from the end-groups.
Photodegradation of plastics and other materials can be inhibited with polymer stabilizers, which are widely used. These additives include antioxidants, which interrupt degradation processes. Typical antioxidants are derivatives of aniline. Another type of additive are UV-absorbers.
Many biodegradable polymers that come from renewable resources (i.e. starch-based, PHA, PLA) also compete with food production, as the primary feedstock is currently corn. For the US to meet its current output of plastics production with BPs, it would require 1.62 square meters per kilogram produced. [70]
Susceptibility to biodegradation is highly dependent on the chemical backbone structure of the polymer, and different bioplastics have different structures, thus it cannot be assumed that bioplastic in the environment will readily disintegrate. Conversely, biodegradable plastics can also be synthesized from fossil fuels. [4] [12]
Starch: Starch is an inexpensive biodegradable biopolymer and copious in supply. Nanofibers and microfibers can be added to the polymer matrix to increase the mechanical properties of starch improving elasticity and strength. Without the fibers, starch has poor mechanical properties due to its sensitivity to moisture.
Once implanted, a biodegradable device should maintain its mechanical properties until it is no longer needed and then be absorbed by the body leaving no trace. The backbone of the polymer is hydrolytically unstable. That is, the polymer is unstable in a water based environment. This is the prevailing mechanism for the polymers degradation.
Biodegradable additives can convert the plastic degradation process to one of biodegradation. Instead of being degraded simply by environmental factors, such as sunlight (photo-oxidation) or heat (thermal degradation), biodegradable additives allow polymers to be degraded by microorganisms and bacteria through direct or indirect attack.
Polymers that form networks during photopolymerization are referred to as negative resist. Conversely, polymers that decompose during photopolymerization are referred to as positive resists . Both positive and negative resists have found many applications including the design and production of micro-fabricated chips.
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