Mechanical properties of orthopedic materials

Uvod: Na področju ortotike, bolj natančno na področju ortopedskih vložkov, uporabljamo različne naravne kot tudi umetne materiale. Izbira materiala temelji na različnih mehanskih in površinskih lastnostih materiala, kot so: mejni kot, barva, hrapavost, trdota, natezna trdnost, zeta potencial in gostota. Izbira materiala je odvisna od potrebe pacienta. Namen: Določiti površinske in mehanske lastnosti penjenih in nepenjenih polimerov, ki se veliko uporabljajo v ortotiki in protetiki. Metode dela: Uporabili smo šest različnih materialov, natančno štiri penjene polimere: penjen polietilen, Poliform, Nora (EVA), prešano pluto in dva nepenjena polimera: polietilen in polipropilen. Vsem materialom smo določili mejni kot, barvne vrednosti, natezno trdnost, trdoto, zeta potencial in hrapavost. Z merjenjem mejnega kota na površini smo določili hidrofobnost oziroma hidrofilnost materialov. Pri barvnih vrednosti smo določili parametre CIE L*, a* in b*. Izmerili smo Youngov modul, natezno trdnost, raztezek in plastičnost materialov. Trdoto smo določili po metodi Shore A. Izmerili smo tudi topografije površin in določili Ra (aritmetično srednjo hrapavost) in Rq (kvadratična srednja hrapavost). Velikost zeta potenciala pa smo dobili z meritvijo pretočnega potenciala. Vsak material smo pomerili večkrat, nato pa smo izračunali povprečno vrednost ter standardni odklon. Rezultati: Najbolj hidrofoben material je zaprto celični PE. Poliform in penjen PE sta najbolj barvita materiala. Nora in pluta se po barvi približata barvi porjavele in rjave kože, medtem ko barva PE in PP ustreza barvi običajnega tipa kože. Poliform in penjen PE se ujemata s svetlejšo barvo kože. Natezna trdnost in trdota sta bile najvišje pri PE in PP. Največji negativni naboj je imel PE. Hrapavost pa je bila najbolj izrazita pri penjenem PE. Najmanjša hrapavost pa je bila pri PP. Razprava in zaključek: Ugotovili smo, da se penjeni in trdni materiali glede na mehanske lastnosti med seboj razlikujejo. Na splošno bi lahko rekli, da je izbrani PE v primerjavi z izbranim PP vzorcem trši, bolj hidrofoben, z višjo natezno trdnostjo, bolj negativno nabit in ima manjšo hrapavost. Med skupino penjenih polimerov pa je v veliki meri odstopal penjeni polietilen.Introduction: In the field of orthotics, more precisely in the field of orthopaedic insoles, we use various natural as well as artificial materials. The choice of material is based on different properties of the material, such as: the angle, colour, roughness, hardness, tensile strength, zeta potential and density. The choice of material depends on the needs of the patient. Purpose: Determine the superficial and mechanical properties of foamed and un-foamed polymers, which are widely used in the orthotics and prosthetics. Methods: We used six different materials, exactly four foamed polymers: foamed polyethylene, Poliform, Nora (EVA), a pressed cork and two unpadded polymers: polyethylene and polypropylene. All materials were defined as limit angle, colour values, tensile strength, hardness, zeta potential and roughness. By measuring the boundary angle on the surface, we determined the hydrophobicity or hydrophilicity of the materials. For colour values the CIE parameters L*, a* and b* were determined. Measured Young\u27s modulus, tensile strength, elongation and plasticity of materials. Hardness was determined by methods Shore A. Surface topographies were also measured and Ra (arithmetic mean roughness) and Rq (square mean roughness) were determined. The magnitude of the zeta potential was measured by measuring the flow potential. Each material was calibrated several times, and then the mean value and standard deviation were calculated. Results: The most hydrophobic material is closed cell PE. Polyform and foam PE are the most colourful materials. Nora and cork approach the colour of tanned and brown skin, while the colour PE and PP correspond to the colour of the normal skin type. Polyform and PEfoam match the brighter colour of the skin. Tensile strength and hardness were highest in PE and PP. The biggest negative charge was PE. Roughness was most pronounced in PEfoam. However, the lowest roughness was in PP. Discussion and conclusion: We found that foam materials and solid materials differ from each other in terms of mechanical properties. In general, it could be said that the chosen PE is harder compared to the selected PP sample, more hydrophobic, with higher tensile strength, more negatively charged and has lowest roughness. Among the group of foamed polymers, however, PEfoam differed greatly