The molecular weight of a polymer has a significant impact on the mechanical properties of 3D printed objects. In general, as the molecular weight of the polymer increases, the mechanical properties of the 3D printed object improve. This is due to the following reasons:1. Chain entanglement: Higher molecular weight polymers have longer chains, which leads to increased chain entanglement. This entanglement results in a stronger network within the material, improving properties such as tensile strength, elongation at break, and toughness.2. Interlayer adhesion: In 3D printing, objects are built layer by layer. Higher molecular weight polymers exhibit better interlayer adhesion due to the increased chain entanglement and stronger van der Waals forces between the layers. This results in improved mechanical properties, particularly in the z-direction the direction perpendicular to the layers .3. Viscosity: Polymers with higher molecular weight generally have higher viscosity, which can lead to better layer-to-layer adhesion during the printing process. This is because the higher viscosity helps to prevent the layers from separating or delaminating during the printing process.4. Thermal stability: Higher molecular weight polymers typically have better thermal stability, which can improve the overall performance of the 3D printed object. This is particularly important for applications where the printed object will be exposed to high temperatures or harsh environments.However, it is important to note that using polymers with very high molecular weight can also have some drawbacks in 3D printing. For example, higher molecular weight polymers may require higher processing temperatures and longer processing times, which can increase the risk of thermal degradation or other processing issues.In summary, the molecular weight of a polymer plays a crucial role in determining the mechanical properties of 3D printed objects. Higher molecular weight polymers generally result in improved mechanical properties, but there may be trade-offs in terms of processing conditions and printability.