Thread Content
Polylactic acid synthesis process: One-step method https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG646.png?x-oss-process=image%2Fformat,webp Overview: The one-step method, also known as the direct polycondensation method, refers to a synthesis process in which lactic acid molecules undergo direct polycondensation and dehydration reactions between their hydroxyl and carboxyl groups in the presence of a dehydrating agent, thereby producing polylactic acid. Advantages: The monomer conversion rate is high, the processing procedure is simple, and there is no need for the purification of intermediates, resulting in lower production costs. Disadvantage: There is a balance among free lactic acid, water, oligomers, and lactide. By-products such as water generated by the reaction are difficult to remove from the viscous melt, making it hard for the reaction to proceed in the desired direction. It is difficult to obtain polymers with high molecular weights using the one-step method; the molecular weight of the polymers obtained is generally low, only in the tens of thousands, and they usually have color. Polylactic acid synthesis process: two-step method https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG647.png?x-oss-process=image%2Fformat,webp Overview: In the two-step method, lactic acid monomers are first polycondensed and dehydrated to yield lactide, which is then ring-opened and polymerized to produce polylactic acid. Since no by-product water is generated during the open-chain polymerization reaction, it is possible to precisely control the molecular weight of the polymer to over 100,000. Moreover, impurities present in the lactic acid starting material, as well as small amounts of racemic lactic acid, can be removed during the preparation and purification of lactide, thereby further improving both the chemical purity and optical purity. Advantages: Polylactic acid produced via the two-step method has high mechanical strength, with a molecular weight that can reach several million; it is thus suitable for large-scale industrial production. Disadvantages: Compared to the one-step method, the two-step production process has a longer workflow and higher production costs.