## 1 Introduction
### Market Identification  
The current chain market offers a wide variety of products made from steel, composites, and thermoplastics (Table 1). Depending on their intended application, chains serve as transport, load-bearing, or protective elements. Steel chains dominate technical applications due to their high tensile strength (>800 Mpa) and yield strength (~600 Mpa), with elongation at break exceeding 15% for selected grades [28; 29]. In contrast, chains made from thermoplastics such as PA6, HDPE, or PC are primarily used for protective or structural enclosures (Table 2). These materials show lower tensile strength (typically 40-90 Mpa) but high elongation (up to 300%) and low density (~1.1-1.5 g/cm\({}^{3}\)) [30]. Despite favorable environmental resistance and electrical insulation properties (resistivity > 10\({}^{9}\)\(\Omega\cdot\)m), polymer chains face mechanical limitations, mainly due to manufacturing constraints. Injection molding requires splitting (Figure 1a) or welding the link (Figure 1b), which introduces stress concentration zones and reduces mechanical strength by up to 50% [31]. Currently, design standards such as EN 818 or ISO 1834 focus solely on metal chains. There are no specific guidelines for evaluating the mechanical performance of composite chains, which limits their wider adoption. This regulatory gap hinders the development of advanced solutions based on fiber-reinforced polymers (e.g., GFRP, CFRP). Nonetheless, polymer chains remain advantageous in applications where non-conductivity, corrosion resistance, and high deformability are critical, such as in mining or electrostatically sensitive environments [32]. Another factor limiting the popularity of polymer components stems from logistical and manufacturing challenges. The lack of detailed design guidelines discourages manufacturers from adopting such solutions. Implementing a new material requires both time and financial investment, which often deters innovation. Moreover, the limited number of facilities equipped with the necessary laboratory and production infrastructure for polymer components further reduces their availability. As a result, manufacturers tend to favor established and widely accessible steel-based solutions. Importantly, chains made from materials other than steel typically do not have specified load capacities or breaking forces. Despite the existence of advanced composite materials with excellent mechanical performance [44; 45; 46; 47; 48] -- including high tensile strength, fatigue resistance, and low weight -- their use in commercial chain production remains marginal. Several key factors limit their widespread adoption. Major barriers include high manufacturing costs, complex production processes, and lower resistance to point loads and abrasion when compared to steel. The absence of dedicated standards and design guidelines further hampers the market introduction of composite chains, leading manufacturers to favor proven steel-based solutions, which are more cost-effective and reliable. While composites may find niche applications, commercial chain production is still domi \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Chain Type** & **Material** & **Diameter** & **Breaking Force** \\  & **Material** & **[mm]** & **[kN]** \\ \hline Link chain DIN 766 [33] & Stainless steel & 2–16 & 1.2–127.5 \\ Link chain DIN 763 [34] & Carbon steel & 2–32 & 1.25–400 \\ Lifting chain, grade 80 [35] & Alloy steel, quenched and tempered & 6–42 & 45.2–2200 \\ Roller drive chain “B” ISO [36] & High-grade steel & 3.28–8.28 & 24.9–160 \\ Plastic link chain [37] & Polyethylene & 6 & 0.4 \\ Plastic roller chain [38] & Polyethylene & 3 & 0.44 \\ Link chain AL-31 [39] & PVC & 6.5 & - \\ Single Pitch P Chain [40] & Polyacetal chain/steel pins & 4–6 & - \\ XK Plastic Chain Conveyors [41] & PVC chain/steel pins & 5 & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Load capacities of selected chain types depending on material and geometry.