Three Modification of PBAT Biodegradable Materials

PBAT modification

PBAT has excellent ductility and fast forming speed, which can give it better processing performance; PBAT has similar properties to polyethylene (PE), so it is more used in film bag products. However, the properties of PBAT itself, such as drafting strength and film opening, are weaker than those of PE, and the cost is higher than that of PE. Therefore, after blending and modification, it can effectively reduce costs and improve product performance.

PBAT/starch modification

Advantages: Starch has high degradation efficiency in a composting environment, can be completely biodegraded, and does not have any microplastic residues. It is the best material to deal with white pollution.

Disadvantages: starch itself has poor plasticity, and there are intermolecular and intramolecular hydrogen bonds, so it has certain crystallization properties.

Solution: When using starch filling, the starch needs to be processed in advance. By adding cross-linking agents, plasticizers, etc., the starch powder is made into easy-to-add granules, which facilitates the modification of PBAT, so as to obtain a PBAT/starch blend with good comprehensive properties.

* Some companies use corn starch and PBAT as the main raw materials, glycerol as the main plasticizer, sorbitol, PEG200, etc. as the auxiliary plasticizers, and make starch-filled PBAT film by extruder granulation and then blow molding. The research shows that the better the plasticizing effect of starch, the more uniform the particle size distribution, the smaller the surface roughness of the film, and the higher the tensile strength, pendulum impact strength and elongation at break of the film.

PBAT/PLA modification

Advantages: Polylactic acid (PLA) has good transparency, biocompatibility and biodegradability. Its degradation occurs under the conditions of industrial composting, and the final products of complete degradation are carbon dioxide and water, which will not pollute the environment. And PLA has high tensile strength and tensile modulus.

Disadvantages: High hardness, poor heat resistance, poor toughness and other shortcomings limit its industrial application.

Solution: Using PLA as the filler of PBAT can effectively improve the tensile properties of PBAT, reduce the hardness of PLA alone, improve its toughness, increase the glass transition temperature of the composite material, and improve the thermal stability of the blend. Finally, a product with good comprehensive performance is obtained.

* Some scholars have found that the aggregated structure of PBAT and PLA confirms that the biodegradation and hydrolysis rate of the amorphous region is higher than that of the crystalline region, which is because the structure of the amorphous region is looser and more susceptible to microorganisms and enzymes. This phenomenon also causes the crystallinity of the composite to increase over time. In addition, the degradation of composites was reflected by the change of carbon-to-oxygen ratio, and the increase of carbon-to-oxygen ratio after degradation was related to the content of PLA in the composites.

PBAT/Inorganic filling modification

Activated calcium carbonate has a high reinforcing effect in PBAT modification due to its extremely small particle size and high activity. When using activated calcium carbonate to blend and modify PBAT, a certain amount of compatibilizer needs to be added to improve the physical and mechanical properties of the product. The material modified by calcium carbonate can be quickly and completely biodegraded, and the product cost is greatly reduced, and it has better practical operability for the manufacture of film bags and other products.

*Some scholars have found that: when filling and modifying PBAT with ultrafine calcium carbonate, if the mass fraction of ultrafine calcium carbonate is 10% and the mass fraction of compatibilizer is 3 parts, the tensile properties of PBAT/ultrafine calcium carbonate blends are greatly improved; if the mass fraction of ultrafine calcium carbonate reaches 20%, the film bag still has good mechanical properties. In addition to calcium carbonate, talc and montmorillonite can also be used as inorganic fillers to modify PBAT, which can effectively reduce the cost of PBAT blends and enhance some properties.

To sum up, when modifying materials, it is necessary to take advantage of its advantages to make up for its disadvantages, and finally a product with good comprehensive performance can be obtained.

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