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In this study, the maleic anhydride (MAH) and styrene (St) dual monomers grafted polypropylene (PP) and poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), i.e. PP-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are prepared as multi-phase compatibilizers and used to compatibilize the PA6/PS/PP/SEBS (70/10/10/10) model quaternary blends. Both PS and SEBS are encapsulated by the hard shell of PP-g-(MAH-co-St) in the dispersed domains (about 2 μm) of the PA6/PS/PP-g-(MAH-co-St)/SEBS (70/10/10/10) quaternary blend. In contrast, inside the dispersed domains (about 1 μm) of the PA6/PS/PP/SEBS-g-(MAH-co-St) (70/10/10/10) quaternary blend, the soft SEBS-g-(MAH-co-St) encapsulates both the hard PS and PP phases and separates them. With increasing the content of the compatibilizers equally, the morphology of the PA6/PS/(PP+PP-g-(MAH-co-St))/(SEBS+SEBS-g-(MAH-co-St)) (70/10/10/10) quaternary blends evolves from the soft (SEBS+SEBS-g-(MAH-co-St)) encapsulating PS and partially encapsulating PP (about 1 μm), then to PS exclusively encapsulated by the soft SEBS-g-(MAH-co-St) and then separated by PP-g-(MAH-co-St) inside the smaller domains (about 0.6 μm). This morphology evolution has been well predicted by spreading coefficients and explained by the reaction between the matrix PA6 and the compatibilizers. The quaternary blends compatibilized by more compatibilizers exhibit stronger hierarchical interfacial adhesions and smaller dispersed domain, which results in the further improved mechanical properties. Compared to the uncompatibilized blend, the blend with both 10 wt% PP-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) has the best mechanical properties with the stress at break, strain at break and impact failure energy improved significantly by 97%, 71% and 261%, respectively. There is a strong correlation between the structure and property in the blends.

To prepare GO/Polyolefin nanocomposites with enhanced mechanical, electrical, or thermal properties is still a challenge due to the poor interfacial adhesion between GO and non-polar polyolefins. In this study, we report an effective strategy for the polyolefin-functionalized graphene oxide (fGO) using two-step methods GO was firstly modified by using glycidyl methacrylate (GMA) and styrene (St) dual monomers grafting method, thus GO- g -(GMA- co -St) with numerous epoxide groups is obtained. Then through the reaction between the epoxide group of GMA and anhydride group of maleic anhydrides (MAH) of the prepared HDPE- g -(MAH- co -St), GO- g -HDPE- g -(MAH- co -St) could be obtained. The successful preparation of the GO- g -HDPE- g -(MAH- co -St) was confirmed by AFM, TEM, FTIR, XRD, DSC, and TGA characterization. The results show the grafting ratios of the poly(GMA- co -St) and HDPE- g -(MAH- co -St) being up to 50.4 wt% and 70.4 wt%, respectively. The functionalized GO shows homogeneous dispersion in the nanocomposites with HDPE, and the stress at break and strain at break of the nanocomposite is increased by 28.7% and 130% respectively with only 0.2 wt% fGO loading. The approach of the polyolefin-functionalized GO paves a new way to develop not only polyolefin/graphene nanocomposites but also excellent nanocomposites of polyolefin/engineering plastic blends with graphene.

It is well known that polyolefins, styrene polymers and engineering plastics occupy the largest share of the plastic market and constitute nearly 80% of the world's plastic. However, these plastics are usually used or recycled in mixed state and immiscible with each other. It is hard to define or separate these plastics, respectively, from recycled materials. In this letter, a maleic anhydride (MAH) and styrene (St) dual monomers grafted poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), SEBS-g-(MAH-co-St) was developed as a multi-functionalized compatibilizer for combining engineering plastics, styrene polymers and polyolefins. With the help of the compatibilizer, the model quaternary blend PA6/PS/PP/SEBS (70/10/10/10) transforms from brittle into tough blends, and shows controllable morphologies and significantly improved mechanical properties. This highly efficient compatibilization strategy casts new light on both the development of high-performance multi-phase polymer blends and the recycling of waste plastics.

Multi-phase compatibilizers are potentially attractive, not only for the preparation of ternary or multi-phase immiscible polymer blends with high performance, but also for recycling and reuse of waste plastics mixture. In this study, the maleic anhydride (MAH) and styrene (St) dual monomers grafted PP, PP-g-(MAH-co-St) is prepared as a multi-phase compatibilizer, which exhibits highly effective compatibility on the PP/PA6/SEBS (70/15/15) ternary blends. Scanning electron microscopy (SEM) reveals that, with increasing the compatibilizer, the morphology evolves from the individual PA6 particle encapsulated by SEBS to several smaller-size PA6 particles partially encapsulated by SEBS phase, then to the tiny PA6 particles and some larger-size SEBS agglomerates predominantly dispersed separately in PP matrix. The morphology development predicted by spreading coefficients shows a consummate consistency with that observed by SEM. Moreover, the good compatibilization and corresponding morphologies result in superior enhancement of mechanical properties. Compared to the uncompatibilized blend, adding 15 wt% multi-phase compatibilizer to the blend leads to the best mechanical properties with the yield stress, stress at break, strain at break and impact failure energy improved significantly by 23%, 132%, 647% and 220%, respectively. The results verify that the domains with small-size PA6 particles (0.3–0.4 μm) partially encapsulated by SEBS (0.5–0.7 μm) in PP matrix are very effective to enhance the mechanical properties of the blends. The morphologies of large-size PA6 particles encapsulated by SEBS or tiny PA6 particles and some larger-size SEBS agglomerates dispersed separately in PP matrix for the enhancement in mechanical properties of the blends are very limited. Consequently, the enhanced interfacial interactions and the morphology with the rigid particles partially encapsulated by a rubber-like phase in matrix are crucial for the ternary polymer blends.