*3.1.1 Tensile strength*

Tensile strength is the ability of a material to resist a force that tends to pull it apart. It is a basic provision for classifying the properties of given polymer materials at a specified loading rate and temperature. The ultimate tensile strength of PE at 0-70°C is 11 MPa–25 MPa, while its yield strength at the same temperature range is 6 MPa-30 MPa. This polymer property depends on percentage crystallinity, the thermodynamic stability of the primary PE chain, chain orientation, and packing density of the crystalline chain [17]. Polyethylene's strength, rigidity, friction, and hardness are low but have high impact strength and ductility. Three main tensile strengths are essential in the study of the properties of a polymer. The yield strength is the stress the PE can withstand without permanent deformation. The ultimate tensile strength is the maximum stress the PE can withstand, while the breaking strength is the stress coordinate on the strain–stress curve at the point of rupture.

Polyethylene shows excellent creep under an applied force. Elastic strain is the strain in the region of stress/strain curve of material under deformation, which recovers its shape on the release of applied stress. Elastic strain is reversible. Young's modulus is the slope of the graph ab covering from a being the origin of the stress–strain graph to point b, representing the reversible region of the stress–strain in **Figure 1**. After point b, strain is no longer proportional to stress, and the slope of the stress–strain graph changes at an increasing rate, and the strain is irreversible. The materials continue to deform after point c until it breaks at point d [18]. The percentage elongation we get during a tensile experiment is significant because it provides information on the ductility of the polyethylene under investigation. Materials with a high degree of elongation will exhibit high ductility. This is because the force necessary to sustain sample elongation and finally break the specimen changes very little at the yield point, and this makes the value of the yield strength and the breaking strength quite close [14].
