Green development brings green business opportunities, and the times need to give birth to new industries. The future of new biodegradable materials must be full of vitality, and calcium carbonate will occupy a place in degradable materials.
Calcium carbonate is an important functional inorganic filler, which has the advantages of low price, non-toxic, odorless, good color and high whiteness and is widely used in plastics. Adding calcium carbonate to the resin can not only reduce the cost of the product, but also effectively improve the rigidity, dimensional stability, hardness and mechanical properties of the polymer.
However, because there are many hydroxyl groups on the surface of calcium carbonate, it is not very compatible with organic polymer materials, and it is easy to agglomerate and cause poor dispersion, which brings a series of problems to the production, processing and performance of plastic products.
Powder surface modification is one of the most effective methods to solve the problems of agglomeration and incompatibility, while titanate and silane are the most widely used coupling agents. According to the reaction mechanism, titanate is a proton reaction that does not require water condensation. Silane is a hydroxyl reactant that requires water condensation. When the surface of calcium carbonate is combined with a degradable polyester such as polybutylene terephthalate/adipate PBAT, it is more suitable to be modified with a silane coupling agent. This is because siloxane can react with CaCO3 and residual water molecules on the surface of PBAT, slowing down the degradation rate of molecular chains.
Using silane coupling agents with different chemical structures to modify micron calcium carbonate, and compounding it with PBAT, a PBAT/CaCO3 film with performance similar to PE film was prepared, which overcomes high filling content of micron calcium carbonate and biodegradable plastics. The problem of poor dispersion and easy agglomeration during blending.
Through artificial aging experiments on pure PBAT membrane and PBAT/CaCO3 membrane in two different environments, dry and wet, the results show that:
(1) Under two different aging conditions, the degradation rate of pure PBAT membrane was the fastest. After adding calcium carbonate, the degradation rate was delayed due to the shading effect of calcium carbonate.
(2) For the film containing silane-modified calcium carbonate, the dispersibility and the binding property of calcium carbonate to the matrix are improved after surface modification. Compared with the unmodified calcium carbonate film, its shading effect is improved and the anti-aging function is enhanced.
(3) Under the two different aging conditions, the degradation rate of PBAT under water mist condition is higher than that under dry condition, which is due to the accelerated degradation rate of PBAT by hydrolysis. However, the mechanical properties of the silane-coated calcium carbonate films decreased more slowly under water spray conditions than under dry conditions. Although the hydrolysis reaction accelerated the molecular weight reduction rate of PBAT, at the same time, the silane molecules self-crosslinked in the presence of water to form a three-dimensional network, which compensated for the loss of the mechanical properties of the PBAT matrix due to the molecular weight reduction.
(4) Due to the existence of water molecules in the actual environment, it is crucial to prolong the service life of the PBAT/CaCO3 membrane in the actual environment. Therefore, the PBAT/CaCO3 composite film is expected to serve as a viable alternative to traditional mulching film applications.