Reactive additives allow to adapt the properties of thermoplastic polymers during processing and for their later use. The chemical modification using multifunctional epoxide styrene-acrylic chain extenders (CE) in reactive processes is by now an established method to prevent degradation and to improve the process ability as well as the final properties of thermoplastics. One of the most common representatives of these CE is better known under its trade name Joncryl®. Since several years ago, Joncryl® ADR owes an ever-growing importance in industry and academia. It can be applied as reactive melt modifier for numerous polymers, mainly polyesters, where it largely affects the rheological properties and the thermal behavior. This review focuses on the reactive behavior of Joncryl® ADR as well as the induced changes in the rheological behavior of the polymers caused by this modification. The Joncryl® ADR incorporation leads to an increased shear viscosity, a higher melt strength and induces strain hardening due to the formation of branched chains and/or even crosslinking. The crystallization is also directly influenced by the changed chain topology. Eventually, this review article extensively addresses the benefits of using Joncryl® for processing such as stabilization, recycling, foaming, and polymer blending. Graphical Abstract

Due to their light‐weight and cost‐effectiveness, cellular thermoplastic foams are considered as important engineering materials. On the other hand, additive manufacturing or 3D printing is one of the emerging and fastest growing manufacturing technologies due to its advantages such as design freedom and tool‐less production. Nowadays, 3D printing of polymer compounds is mostly limited to manufacturing of solid parts. In this context, a merged foaming and printing technology can introduce a great alternative for the currently used foam manufacturing technologies such as foam injection molding. This perspective review article tackles the attempts taken toward initiating this novel technology to simultaneously foam and print thermoplastics. After explaining the basics of polymer foaming and additive manufacturing, this article classifies different attempts that have been made toward generating foamed printed structures while highlighting their challenges. These attempts are clustered into 1) architected porous structures, 2) syntactic foaming, 3) post‐foaming of printed parts, and eventually 4) printing of blowing agents saturated filaments. Among these, the latest approach is the most practical route although it has not been thoroughly studied yet. A filament free approach that can be introduced as a potential strategy to unlock the difficulties to produce printed foam structures is also proposed.

For a long time, the number of available bead foam variants limited to standard polymers which restricted their functionality mainly to packaging, thermal insulation (e.g. in construction) and shock absorption (e.g. in transportation). In particular, standard polymers such as expanded polystyrene, expanded polyethylene and expanded polypropylene were used for components requiring good insulating properties and high energy absorption at low cost. Mainly since the last two decades, new polymer variants have found their way into the world of bead foams and are currently adding further functionalities, such as sustainability, flame retardancy, increased thermal stability and enhanced mechanical performance (e.g. improvements in energy absorption and impact resistance). Versatile fields of application open up, revolutionizing both industry and design sectors. This review article emphasizes the special development progress of new bead foam variants and their processing technologies. Upcoming opportunities of digital methods for modelling and simulation are highlighted.