PSI - Issue 47

Mario A. Sánchez Miranda et al. / Procedia Structural Integrity 47 (2023) 310–324 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

312

3

2. Materials and experimental procedures.

UHMWPE is characterized by white color and non-transparency; it is manufactured by molding, compression and extrusion and presents a high abrasion-wear-shock resistance, low stickiness, low friction coefficient, it is non-toxic and its capacity of water absorption is very low. The resistance of abrasion, together with its low friction coefficient and hardness, generates a self-lubricating and non-stick surface thermoplastic. In addition, it presents sound damping and energy absorption properties, as well as dielectric and insulating properties; such properties allowing to manufacture parts working in severe abrasion conditions and under relatively low mechanical loads. Furthermore, it presents low density, high chemical resistance, and it is easy to machining. Concerning its industrial applications, this thermoplastic has been approved to work in contact with food by the FDA (Food and Drug Administration), and the USDA (U.S. Department of Agriculture); agencies that endorse this material to be in contact with food. Additional industrial uses are: bearings, electrical insulators, electrical components, structural supports, scrapers, gears, wheels, rollers, valve seals, among others. Concerning PP, this thermoplastic offers variety of physic mechanical properties, such as: excellent resistance to chemicals (alkaline acids and solvents) and corrosive environments; thermoformability capacity and a good electrical insulator, showing high mechanical strength, high tensile strength, and medium impact resistance. In addition, its operating temperature ranges from 5° C to 99° C, and it is highly machinable and weldable. The main industrial applications of this polymer are : structural tanks and covers, anodized tanks, orthopaedic prostheses, pumps, valves, seals, toys, bushings, and others. Besides these properties, it is a material approved by the FDA (Food and drugs administration). Table 1 presents the main physic mechanical properties of these two thermoplastics.

Table 1. Main physic-mechanical properties of PP and UHMWPE.

Property

PP

UHMWPE 144-152

Melting temperature (°C) Glass transition temperature (°C) Viscosity (Pa-s) (200°C – s. rate 10/s) Tensile modulus of elasticity (GPa) Ultimate tensile strength (MPa) Density (Kg/ m 3 )

130 - 171 -34, -10 855 - 946 1.3 - 1.8 34 - 40 2800 -7100 2000

-80, -50 932-945 0.8- 1.6 39-48 4500

Molecular weight (g/mol)

2,000,000 – 6,000,000

Figure 1. Pins profiles tested for FSW of the joint UHMWPE – PP: a) Hexagonal, b) cylindrical and c) conical.