What is the relationship between bio-based synthetic fibers and biodegradable fibers?
In recent years, with the global attention to the serious environmental pollution caused by traditional plastics that are difficult to degrade in the natural environment, as well as the increasingly serious microplastic pollution problem, the development of biodegradable plastics and fiber products has become particularly important. In particular, with the gradual implementation of the "plastic ban" in various countries, some products that have the potential to cause microplastic pollution will be banned.
However, bio-based chemical fibers mainly refer to the raw materials containing renewable plant biomass or animal biomass, while biodegradable fibers can be derived from either bio-based or petroleum-based, so bio-based synthetic fibers ≠ bio-based Degradable fiber. Which bio-based synthetic fibers are also biodegradable fibers?
Which biodegradable fibers are not bio-based synthetic fibers? Are petroleum-based polymer materials or fibers non-biodegradable?
In order to answer these questions, we can divide polymer materials or fibers into 4 quadrants according to the source of raw materials and whether they can be biodegraded. The main categories are as follows:
▲Petroleum-based, non-biodegradable fibers (Quadrant III): Traditional petroleum-based chemical fibers such as polyester, nylon, polypropylene and spandex are in this quadrant. These fibers have high melting point, high crystallinity, regular molecular structure, excellent mechanical properties, and good resistance to hydrolysis and chemical corrosion, so they degrade very slowly in the natural environment. For example, in the natural environment, polyolefin can undergo thermo-oxidative degradation when exposed to sunlight, but the degradation rate is extremely low. The proportion of low density polyethylene (LDPE) degraded into CO2 within 2.5 years is only 0.35%, so we usually consider this kind of fiber material as non-biodegradable fiber.
▲Bio-based, biodegradable fibers (Quadrant I):
All bio-based virgin fibers (natural fibers) and bio-based regenerated chemical fibers retain the polysaccharide or protein structure of natural biomass, so their fiber products have complete biodegradability similar to natural biomass. Bio-based synthetic fibers such as polylactic acid (PLA) and polycaprolactone (PCL) can experience mass loss, mechanical properties degradation, and mineralization to carbon dioxide and water in composting and neutral enzymatic degradation solutions. molecules, so it has better biodegradable properties. From the full life cycle analysis, such fibers are eco-friendly fiber materials. picture
▲Bio-based but difficult to biodegradable fibers (Quadrant IV): The biodegradation performance of polymer materials is a relatively complex process, which is closely related to the chemical structure and properties of the material itself. Although some chemical fiber materials have bio-based properties, they are difficult to degrade fiber materials due to their high crystallinity and excellent thermal properties, which restrict their biodegradability.
(1) Bio-based PTT (polytrimethylene terephthalate) fiber:
The diol monomer used in the bio-PTT polyester is bio-based 1,3-propanediol (PDO). PDO can be produced by biological methods from grains. It is further prepared by direct esterification (direct reaction of terephthalic acid and PDO) or transesterification (transesterification of dimethyl terephthalate and PDO). PTT fiber has better resilience than other polyester fibers, lower tensile modulus, higher elongation at break; better dyeing performance; wrinkle resistance and soft hand. It is a new type of bio-based fiber that has an international leading position in my country in recent years. However, bio-based PTT polyester fibers are close to polyester and do not have biodegradable properties. Its ecological advantage is that it can effectively reduce the carbon footprint of products, but it is difficult for products to be degraded by the natural environment after being discarded.
(2) PEF (polyethylene furandicarboxylate) fiber Similar to bio-based PTT polyester fibers, PEF polyester fibers are prepared from bio-based dibasic carboxyl monomers, namely bio-based furan-2,5-dicarboxylic acid and ethylene glycol. Furandicarboxylic acid can be prepared from natural biomass such as starch or cellulose by biological fermentation or chemical methods. PEF fiber is similar to polyester PET fiber and has a relatively close melting point and glass transition temperature. Although it is reported that PEF has a certain degree of biodegradability, its biodegradation rate is relatively slow. According to the current biodegradable compost standard, it is not a biodegradable compost Degradable fiber.
Other bio-based fiber materials such as nylon 56 and bio-based PDT fibers also fall into this category.
▲Petroleum-based biodegradable polymer materials and fibers (Quadrant II):
As mentioned above, the biodegradation performance of polymer materials is a relatively complex process, which is closely related to the chemical structure and properties of the material itself. Although some chemical fiber materials are mainly derived from petroleum-based, due to their flexible molecular chain structure, ester bonds are prone to hydrolysis, and microorganisms or biological enzymes are degraded, so they have good biodegradation properties, such as:
Dimethyl oxalate (DMO), an important compound for the preparation of PGA (polyacetic acid alcohol), is prepared from coal as raw material, and is obtained by hydrogenation, hydrolysis and polymerization. Although PGA is made from coal, its biodegradability is very good, and it can be completely degraded within 1-3 months. The degradation products are water and carbon dioxide, which are completely non-toxic and harmless. It is often used in absorbable surgical sutures. Highly biodegradable and biocompatible.
PGLA (polyglycolide) is obtained by copolymerizing 9 parts of glycolide (PGA) and 1 part of lactide (PLA) according to a certain proportion. (Refer to seawater degradable plastics) If lactide is prepared by biological methods, PGLA can be called bio-based and biodegradable fibers. PGLA has high tensile strength, good biocompatibility and biodegradability, and is also commonly used in absorbable surgical sutures.
Others such as PBAT and PBST are also mainly derived from petroleum-based. PBAT and PBST are prepared by copolymerization of butylene adipate (PBA), butylene succinate (PBA) and butylene terephthalate (PBT), respectively, and their material properties have both the properties of PBA and PBT , has good elongation at break, ductility, heat resistance and impact properties, as well as excellent biodegradability. To be applied as agricultural mulch and other film materials, the application of fiber is still in the development stage.
