So what are the characteristics of bio-based chemical fibers?
First of all, the raw materials are the by-products of plants and animals, which are renewable and can achieve sustainable development.
Secondly, bio-based chemical fibers have a lower carbon footprint: compared with traditional petroleum-based fibers, the carbon atoms contained in bio-based chemical fibers are all or part of biomass. In the case of biomass, plants absorb CO₂ from the earth's atmosphere and synthesize new natural molecules containing carbon through photosynthesis. It does not generate additional carbon emissions in the whole life cycle, whether through biodegradation in the environment or combustion into CO₂. Therefore, bio-based chemical fibers have the characteristics of overall carbon emission reduction or no carbon emission increase.
Thirdly, most of the bio-based chemical fibers can present excellent biodegradability and biocompatibility: according to the specific chemical structure, some bio-based chemical fibers can be degraded in compost, natural environment and organisms, and have good biocompatibility, which can be used in biomedical fields.
What is the relationship between biosynthetic fibers and biodegradable fibers?
In recent years, the development of biodegradable plastics and fiber products has become particularly important as the global environmental pollution caused by the difficult degradation of traditional plastics and fiber products in the natural environment and the increasingly serious pollution problem of microplastics. In particular, the gradual implementation of the "ban on plastic" in various countries will prohibit the use of some products that have the potential to cause microplastic pollution. However, biodegradable chemical fiber mainly refers to its raw material containing renewable plant biomass or animal biomass components, while biodegradable fiber can be derived from biological base or petroleum base.
Therefore, biosynthetic fiber ≠ biodegradable fiber
● Petroleum based, non-biodegradable fibers (Quadrant II):
Traditional petroleum-based chemical fibers such as polyester, polyamide, polypropylene and spandex are all in this quadrant. These fibers have high melting point, high crystallinity, regular molecular structure, excellent mechanical properties, and have good hydrolysis resistance and chemical corrosion resistance, so degradation in the natural environment is very slow. For example, in the natural environment, polyolefin can be degraded by thermal oxygen when exposed to sunlight, but the degradation rate is very low. Low density polyzene (LDPE) is considered non-biodegradable because it degrades to CO₂ at a rate of only 0.35 percent in 2.5 years.
● Bio-based, biodegradable fibers (quadrant I):
All bio-based primary 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 that of natural biomass. However, bio-based synthetic fibers, such as polylactic acid (PLA) and polycaprolactone (PCL), have good biodegradability due to mass loss, mechanical degradation, and mineralization into small molecules such as carbon dioxide and water in compost and neutral enzyme degradation solutions. From the perspective of life cycle analysis, this kind of fiber is the most environmentally and ecologically friendly fiber material.
● Bio-based but non-biodegradable fibers (Quadrant IV):
The biodegradation of polymer materials is a complex process, which is closely related to the chemical structure and properties of the materials themselves. Although some chemical fiber materials have biological properties, they are difficult to degrade because of their high crystallinity and excellent thermal properties. For example:
(1) Biological PTT(poly (propylene glycol terephthalate) fiber:
The dialcohol monomer used in biological PTT polyesters is biological 1, 3-propanediol (PDO). PDO can be produced from grain using biological methods. Further use of direct esterification method (with p-benzenecarboxylic acid and PDO direct reaction) or transesterification method (terephthalic acid = methyl ester and PDO transesterification reaction) prepared. PTT fiber has better resilience, lower tensile modulus and higher elongation at break than other polyester fibers. It has good dyeing property. Shoulder folds and soft touch. It is a new type of bio-based fiber with international leading position in China in recent years. However, bio-based PTT polyester is similar to polyester and does not have biodegradability. Its ecological advantage is that it can effectively reduce the carbon footprint of the product, but it is difficult to degrade the product through the natural environment after waste.
(2)PEF(polyethylene furan diarboxylate) fiber:
Similar to bio-based PTT polyester, PEF polyester is prepared from bio-based dicarboxylic monomer, i.e., bio-based furan-2, 5-dicarboxylic acid and ethylene glycol. Furan diformic acid can be prepared from natural biomass such as starch or cellulose by biological fermentation or chemical methods. PEF fiber is similar to PET fiber in melting point and glass transition temperature. Although it has been reported that PEF has certain biodegradability, its biodegradation rate is relatively slow. According to current biodegradable composting standards, PEF fiber is not biodegradable. 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 of polymer materials is a relatively complex process, which is closely related to the chemical structure and properties of the materials themselves. Although some chemical fiber materials are mainly derived from petroleum, they show good biodegradation performance due to their flexible molecular chain structure, hydrolysis of ester bonds, and microbial or enzymatic degradation. For example:
Preparation of PGA(polyacetate alcohol) important compound - dimethyl oxalate (DMO), it is prepared from coal as raw material, through hydrogenation, hydrolysis, polymerization. Although PGA is made from coal, it has good biodegradability and can be completely degraded within 1-3 months. The degradation products are water and carbon dioxide, which are completely non-toxic and harmless. PGA is often used for absorbable surgical sutures with high biodegradability and biocompatibility. PGLA(poly (ethylene lactide)) is prepared by copolymerization of 9 ethyl lactide (PGA) and 1 lactide (PLA) in a certain proportion. If lactide is prepared by biological method, PGLA can be called bio-based and biodegradable fiber. PGLA has high tensile strength, good biocompatibility and biodegradability, and is also commonly used in absorbable surgical sutures.
Source:https://mp.weixin.qq.com/s/hY3G8X05Daktu6K5j8sJ6w
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