Purpose: An article is supposed to show an influence of processing industry and gas assisted injection moulding into plastic parts on its durability conditions. The main goal of the article is to calculate the characteristics of geometrical sections described as the durability of bending index. Design/methodology/approach: in the article presents an influence of the most valuable parameters of the process like the temperature of injected material, an over time of injection material faze on gas injection and time of gas injection on plastic moulding durability on bending process. The research was made till the deflection was equal 5 mm. The results of the durability index of bending process were compared with the results of bending force measurement. Findings: The result of all researches was comparison of an influence of material and gas injection conditions on plastic moulding durability in bending process and value of bending force used to gain the deflection equal 5 mm. Research limitations/implications: All the researches were just limited to the one type of material - it was a copolymer polipropylene – ethylene. The plastic moulding in shape of proms equipment were made using technology of gas injection moulding. The researches were made according to the research plan, included extreme value of manufacturing parameters. Practical implications: Conducted researches give an information about temperatures of injected material and an over times and gas injection on plastic moulding durability in bending process. An exact selection of those parameters allow to gain plastic mouldings with satisfied quality and durability properties. Originality/value: The process of gas assisted injection moulding is a modern technology that gives possibility of getting an empty plastic mouldings. This process, as it is incredibly dynamic, has not been well known or written about yet.