Research On Properties Of Cushioning Packaging Materials

Packaging mainly serves to protect products from damage caused by handling or exposure to environmental conditions involving temperature, moisture, electronic interference and radiation during storage and transportation. These factors affect the properties of cushioning material inside the package as well, thus making it necessary to obtain the performance of the cushioning material based on statistics and analysis from experimental tests designed considering the environment. Moreover, to improve test and evalutation to the cushioning materials efficiently in order to meet the increasing expanding application to a variety of product protection is also a problem to be solved.Expanded Polyethylene (EPE with apparent desity of 20kg/m3) was chosen in this research due to its recyclability, excellent static electricity resistance and cushioning properties. Because of its anisotropy caused by EPE processing technique, forces vertical to the layers and parallel to the layers forming the EPE block were divided as to loading forms. The static cushioning properties, creep properties and dynamic cushioning properties to the cushioning samples were investigated by static compression test, creep test and dynamic compression test respectively.Static compression test results indicate the loading force and thickness differences of the samples had minor effect on the trend of EPE static cushioning coefficient-strain curves and maximum static stress-strain curves. When EPE had a range of strain from 65%-70%, optimal cushioning factor was got and correspondent maximum stress varied from 0.15MPa to 0.18MPa.Creep test results showed that loading force of the samples had an effect on EPE creep-strain curves and its residual strain. Environment temperature and test time were also important factors that lead to the change of EPE creep properties. In a range of test environment temperature from 13 degrees to 32 degrees,50mm thick EPE with loading force vertical to the layers had 14% ceep at largest, wherease that with loading force parallel to the layers got only 2% creep at most.Laser distance sensor was used to obtain dynamic deformation of EPE during impact tests to the samples synchronized with acceleration recording. The dynamic deformation can provide evidence for energy absoption and strain during the dynamic compression, and properties involving the relationship among drop weight, drop height, and impact acceleration of EPE with varied cushion thicknesses. The results showed that when dynamic strain of EPE samples with different thicknesses ranged from 65% to 70% under 76cm drop height, which was agreed with static compression properties, they all got the best energy absorption efficiency and thicker EPE samples had better dynamic cushion properties under larger dynamic loads. Those relationships between peak acceleration and static stress under the same dorp height, and relationships between peak acceleration and drop heights under the same drop mass made it possible to estimate related peak acceleration and static stress data for EPE samples with thicknesses ranging from 30mm to 60mm under 46cm to 97cm drop height. The connection between static cushioning properties and dynamic cushioning properties was also investigated in the study. This layed a foundation for estimating dynamic cushioning properties and related strains of EPE in any drop height, thus vastly raised the test efficiency.