Effects of Screw Conﬁgurations on the Grafting of Maleic Anhydride
The chemical modification of thermoplastics in twin- screw extruders is a widely used approach to tailor the properties of polymers according to their applications. Carrying out the reaction via extrusion has economic advantages, such as a short reaction time and a solvent-free process. Twin screw extruders as continuous flow reactors for polymers have been playing an important role in producing high-performance materials.
Free-radical grafting of maleic anhydride (MA) onto polyethylene (PE) via reactive extrusion has gained widespread industrial applications and has been studied by numerous authors. Several studies have shown that the reaction pathways depend on the PE molecular structure. When peroxide is used as an initiator, crosslinking may occur simultaneously with the grafting reaction. Furthermore, the analysis of the reactive extrusion process is very complicated because of the multiple operating variables involved. A number of interdependent factors need to be determined and optimized to maximize the efficiency of the process.
Most grafting studiesof PE in reactive extrusion focus on the effects of grafting recipes (type and amount of peroxide and MA content) and processing conditions (throughput and temperature) on the reaction progression in the extruder.The aforementioned factors are important inreactive extrusion. However, it has been well known for years that the mixing method strongly influences the grafting process of PE in the extruder. The mixing of the monomer (MA), initiator(peroxide), and polymer melt is verycritical in the manufacturing of high-grafting products, and the screw configuration, a core component of an extruder, has a significant impact on the reactive extrusion process.
In this work, the influence of various screw configurationson grafting reactive extrusion was investigated with a corotating twin-screw extruder.To further explore the effects of the degree of fill,residence time distribution(RTD),and mixing performance of screws on grafting reactive extrusion, another three extrusion experiments were performed to evaluate these properties.