Search

Reactive polymer processing is an effective and environmentally-friendly means of preparing new materials based on combining components with various properties. Numerous investigations have been carried out to explore the reaction processes that occur during the melt blending of polymers. However, reactive processing is far from fully understood because it involves a complicated combination of shear and extensional flows as well as high temperatures and pressures. In this work, a two-step compatibilizing strategy (called reactive splicing compatibilization) has been used to compatibilize immiscible Poly(lactic acid) (PLLA)/Poly(butylene adipate- co -terephthalate) (PBAT) blends with two different PBAT molecular weights (termed H-PBAT and L-PBAT, respectively), using styrene- co -glycidyl methacrylate (SG) as the grafting counterpart. Reactive compatibilizers with various architectures were prepared by pre-grafting either PLLA or PBAT (or both) onto the SG main chains. The remaining unreacted epoxide groups of the pregrafted SG underwent in situ reactions to form double grafted copolymers as compatibilizers for the final blends. The reactivity of SG with these polymers was found to decrease in the order of L-PBAT > PLLA > H-PBAT. Reactive compatibilizers having various architectures were applied to PLLA/PBAT blends with compositions ranging from 90/10 to 10/90 (w/w). The most efficient pre-grafted reactive compatibilizer was determined for the blends with certain composition. A higher proportion of H-PBAT had to be pre-grafted onto the SG to achieve the best compatibilization efficiency when increasing the PLLA content in PLLA/H-PBAT blends. In the case of PLLA/L-PBAT blends, PLLA chains had to be pre-grafted onto the SG for the best compatibilization when L-PBAT was the primary component of the blend. These results provide a better understanding of the reactive processing mechanism. Evidently, the dynamic shear applied during melt processing continuously renews the interface between the different phases to provide sites for reactions between the blend components. These reactions are affected by both the reactivity of the components and the contact time, which in turn is determined by the blend composition. The compatibilizers located at the blend interface were found to have very similar symmetrical binary grafted structures for blends with different compositions. Image 1 • A two-step compatibilizing strategy (called reactive splicing compatibilization) has been used to compatibilize the immiscible Poly(lactic acid) (PLLA)/Poly(butylene adipate- co -terephthalate) (PBAT) blends with two different PBAT molecular weights, using styrene-co-glycidyl methacrylate (SG) as the grafting counterpart. • More than 100 compatibilized blends have been prepared and compared the compatibilization effects of the different compatibilizers. • This work demonstrates the locations of the various reactions and the factors affecting the reactive processing. • The work is very important for better understanding the reactive processing, especially the functions of the dynamic shearing, the reactivity and the composition effects. [ABSTRACT FROM AUTHOR]

Reactive compatibilization is an effective method to improve the compatibility of immiscible polymer blends. The in-situ-formed graft/block copolymers should be thermodynamically located at the interface to bridge the neighboring phases. Unfortunately, they are often pulled out of the interface because of the asymmetric molecular structures. Here, we propose a new strategy to compatibilize immiscible polymer blends called reactive splicing compatibilization. Poly (styrene- co -glycidyl methacrylate) (SG) with high glycidyl methacrylate (GMA) content is used as the reactive backbone chain. Both poly (l -lactic acid) (PLLA) and poly (butylene adipate-co-terephthalate) (PBAT) molecular chains can be easily grafted onto the SG main backbone by the reaction of the terminal carboxylic acid groups with the epoxide groups in the melt. Direct melt blending SG with PLLA and/or PBAT leads to reactive compatibilizers with various molecular architectures, which are used for subsequent compatibilization of PLLA/PBAT blends. It was found that the compatibilizer architecture significantly affects the compatibilization efficiency. The best compatibilization occurs with a reactive compatibilizer of SG-g-PBAT with the SG to PBAT weight ratio of 1:2. The compatibilized PLLA/PBAT (50/50 w/w) blend has precise co-continuous phase morphology with very few micelles. The blend exhibits extremely high Charpy notched impact strength of 90.2 kJ/m2 and tensile strength of 33.3 MPa. The principle of the facile splicing compatibilization strategy is highly applicable to many other immiscible blends with both components containing reactive groups. We report the splicing compatibilization strategy for immiscible polymer blends. The compatibilizer architecture effects on the compatiblization efficiency were investigated. Image 1 • New compatibilization strategy called reactive splicing compatibilization was proposed. • Reactive comb compatibilizers with various architectures were synthesized by melt blending. • Molecular architecture effects on compatibilization of PBAT/PLLA blends were investigated. • PLLA/PBAT blends with superior toughness and high tensile strength were prepared. [ABSTRACT FROM AUTHOR]