Mechanical behavior and failure analysis of recycled polymers by use of miniature punch specimens

Abstract

In today's society, recycling is a priority, and using recycled materials to obtain new 100% reusable materials is an important aspect of some manufacturing sectors. Clearly, the mechanical properties of these new materials can vary considerably from the original material, so it is necessary to carry out a complete mechanical characterization to know its behavior for both standard specimens and final components. One of the common drawbacks is the inability to extract standard size specimens from a final component with a reduced size. In this paper, the use of the small punch test is proposed as a means of solving this problem. At present, this test is used for estimating mechanical properties in those cases when there is not a sufficient amount of material to perform standard tests. The main purpose of this paper is to analyse the feasibility of using miniature punch specimens for the mechanical characterization of recycled polymers. The results are compared with those obtained from standard uniaxial tensile specimens, and a corresponding correlation between the two tests is established.

Using the small punch test to analyse the influence of ultraviolet radiation on the mechanical behaviour of recycled polyethylene terephthalate

“…These results demonstrate again the direct relationship between the SPT and the tensile test parameters (expressions 1 to 3) as already indicated by other authors 10,11,13,14 and consolidate the SPT as a valuable mechanical characterization method for polymeric materials, especially in cases where the amount of available material is small, as it was the case of this industrially UV-irradiated material.…”

“…7 The SPT has also been used in the mechanical characterization of different types of materials other than steel 8,9 and its applicability in the estimation of the tensile properties of different types of polymers has been proved. [10][11][12][13][14] During the test, the specimens are firmly clamped between two circular dies and are punched into a circular hole by a hemispherical punch until failure. Figure 1(a) shows a sketch of the SPT and the location of the specimen in the device.…”

Application of the miniature small punch test for the mechanical characterization of polymer materials

“…in the case of PLA and EVOH it is well known that the barrier properties improve upon MMT incorporation which is beneficial for food packaging. Injected PP, which had been used in [19] to study the effect on mechanical strength of adding different percentages of recycled material, corresponded to grade BASELL X9077. PET and PETg were supplied by NUDEC in form of extrusion-calendered laminates.…”

“…While some experiments were conducted in different laboratories, special care is taken to ensure that the same conditions apply in all case studies. In the case of polypropylene, analyzed at the University of Burgos, 5A type standard tensile specimens and rectangular samples (60 x 10 x 4 mm), both obtained by an injection process, were supplied by the manufacturer [19]. The rest of the polymers were manufactured in the Centre Catalá del Plastic.…”

“…To a much lesser extent, the SPT has also been employed in the characterization of polymeric materials [13][14][15][16][17][18][19]. Most of the studies on these materials have been purely devoted to analyze the form of the SPT curves [13,15], and correlations between the tensile properties of polymers and their corresponding SPT parameters are yet to be identified.…”