The chemical structure of a polymer plays a significant role in determining its mechanical properties when used in 3D printing. Several factors related to the polymer's chemical structure influence its behavior during the printing process and the final properties of the printed object. These factors include:1. Molecular weight: Polymers with higher molecular weights generally exhibit better mechanical properties, such as tensile strength and impact resistance. However, they may also require higher processing temperatures and longer cooling times during 3D printing.2. Degree of polymerization: The degree of polymerization refers to the number of monomer units in a polymer chain. Polymers with a higher degree of polymerization typically have better mechanical properties but may be more challenging to process during 3D printing.3. Chain branching: The presence of side chains or branches in a polymer can affect its mechanical properties. Highly branched polymers may have lower tensile strength and stiffness but better impact resistance compared to linear polymers.4. Crystallinity: Polymers can be either amorphous non-crystalline or semi-crystalline. Semi-crystalline polymers generally have better mechanical properties due to their ordered molecular structure. However, they may also require higher processing temperatures and longer cooling times during 3D printing.5. Glass transition temperature Tg and melting temperature Tm : The Tg and Tm of a polymer influence its processing conditions and the temperature range in which it can be 3D printed. Polymers with a low Tg may be more prone to deformation during printing, while those with a high Tm may require higher printing temperatures.Some of the most suitable polymers for producing robust and functional 3D printed objects include:1. Polylactic acid PLA : PLA is a biodegradable and environmentally friendly polymer derived from renewable resources. It has good mechanical properties, is easy to print, and has a low Tg, making it suitable for a wide range of applications.2. Acrylonitrile butadiene styrene ABS : ABS is a strong and durable polymer with good impact resistance and high-temperature resistance. It is widely used in 3D printing for functional parts and prototypes.3. Polyethylene terephthalate glycol PETG : PETG is a strong, flexible, and chemically resistant polymer with excellent layer adhesion. It is suitable for 3D printing functional parts and objects that require high strength and durability.4. Thermoplastic polyurethane TPU : TPU is a flexible and elastic polymer with excellent abrasion and impact resistance. It is suitable for 3D printing flexible parts and objects that require high resilience.5. Polycarbonate PC : PC is a strong, durable, and heat-resistant polymer with excellent mechanical properties. It is suitable for 3D printing parts and objects that require high strength, stiffness, and temperature resistance.The choice of polymer for 3D printing depends on the specific application, desired mechanical properties, and processing requirements.