THE EFFECT OF STRAIN RATE ON TENSILE PROPERTIES OF POLYPROPYLENE

Polimeri se ubrajaju u najvažnije tehničke materijale današnjice. U mnogim primjenama polimeri ne samo da su zamijenili materijale kao što su drvo, staklo, papir i metali nego su omogućili i razvoj nekih proizvoda i područja koja su obilježila suvremenu civilizaciju. U prvom dijelu rada dat je osvrt na povijesni razvoj polimera, te je prikazana globalna proizvodnja plastike od početka uporabe u industriji do danas. Ukupna godišnja svjetska proizvodnja polimera već je prije dva desetljeća volumenom nadmašila proizvodnju željeza i čelika. Dalje u radu je opisana struktura polimera, te je izvršena sistematizacija polimera u kojoj su s posebnim osvrtom obrađeni polimeri obzirom na ponašanje pri povišenoj temperaturi. Zatim se značajnije govori o polipropilenu, te o ispitivanju rasteznih svojstava prema normi ISO 527. U eksperimentalnom dijelu rada ispitivan je utjecaj brzine opterećenja na rasteznu čvrstoću uzoraka izrađenih od polipropilena (PP BC 250 MO). Uzorci su pripravljeni na hidrauličkoj preši, a testovi su provedeni na univerzalnoj mehaničkoj kidalici pri čemu je brzina opterećenja varirana na tri razine.Polymers are among the most important technical materials of today. In many applications polymers not only replaced materials such as wood, glass, paper and metals but also enabled the development of some products and areas that marked modern civilization. The first part of the paper gives an overview of the historical development of polymers and is graphically depicted global plastic production since the beginning of use in the industry to date. The annual total production of polymers exceeded production of iron and steel by two decades ago. Further on, the structure of the polymer is described and a polymerization systematization was carried out, in which special polymers were treated with regard to behavior at elevated temperature. Then, more importantly, the polypropylene, and the extensional properties test according to ISO 527. In the experimental part, the impact of the load speed on the tensile strength of the sample made of polypropylene (PP BC 250 MO) was examined. Samples were prepared on a hydraulic press, and tests were demonstrated on a universal mechanical ladder where the load speed varied to three levels