Chemical degradation and failure analyses by acoustic emission of <scp>PP</scp>/<scp>EOC</scp> blends exposed to ultraviolet radiation

Silva, Jéssica Raquel M. B. da; Cavalcanti, Rebecca Stéfani F. B.; Rabello, Marcelo S.

doi:10.1002/pen.25542

Cited by 3 publications

(4 citation statements)

References 30 publications

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“…16 A few dealt with PBT, such as on the evaluation of the effect of glass fiber 20,21 and the friction effect of PBT reinforced with glass microspheres on steel surfaces. 22 One of the current authors made some recent contribution on this theme, studying the failure of polypropylene by photodegradation, 17,18 and polyethylene terephthalate by stress cracking 19 with the use of AE as a tool.…”

Section: Introductionmentioning

confidence: 99%

The investigation of the stress cracking behavior of PBT by acoustic emission

Braz

Silva

Wellen

et al. 2021

Polymers for Advanced Techs

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Despite being a major cause of failure of polymer products under service, environmental stress cracking (ESC) is still a phenomenon poorly investigated and, as consequence, not fully understood. This article aims to contribute to this field in a study of the stress cracking behavior of polybutylene terephthalate (PBT) exposed to ethanol (a common fluid, used in several daily situations), by means of two types of mechanical tests (tensile and stress relaxation). During mechanical testing the technique of acoustic emission (AE) was applied to identify certain mechanisms of internal failure.As a non-destructive technique, AE is widely used with metals to monitor the integrity of components but it is very scarcely applied to polymers. The article, therefore, innovates by using AE as a tool to better understand the ESC behavior of an engineering polymer produced under different conditions. The PBT samples were prepared by injection molding, using different mold temperatures (20 C, 40 C, and 80 C), resulting in different crystallinities. The results showed that the tensile properties were highly dependent on the crosshead speed and that ethanol affected the mechanical performance of the materials, anticipating the necking, but its evaporation during the experiment reduced the actual temperature on the sample bar. This latter effect caused an unexpected behavior, with an increase in tensile strength and reduction of stress relaxation rate, the opposite trends that would be expected from a stress cracking agent. The crystallinity of PBT had some influence on the results, with the more crystalline samples being more resistant to ESC, as observed by both stress relaxation and AE analyses. The technique of AE showed to be a very useful tool to understand the mechanical behavior and to differentiate the various testing conditions, with the detection and quantification of hits and released energy, related to the several stages of deformation and failure, including the formation of shear bands, nucleation and growth of crazes and cracks, and so forth. The fracture surface analyses by scanning electron microscopy were very consistent with the AE experiments, in which rough topography were related to high acoustic activities.

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Section: Introductionmentioning

confidence: 99%

The investigation of the stress cracking behavior of PBT by acoustic emission

Braz

Silva

Wellen

et al. 2021

Polymers for Advanced Techs

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“…Compared with conventional elastomers, EOC has exhibited better compatibility with PP because of its long chain branches and the resultant low interfacial tension. [10][11][12][13][14][15] In the last decade, the PP/EOC blends have been studied in many different aspects, including as morphology development, rheological behavior, [16][17][18] mechanical properties, 19,20 and crystallization behavior. [21][22][23] Among others, the present research is focused on crystallization behavior because of its critical importance in polymer processing and mechanical behavior.…”

Section: Introductionmentioning

confidence: 99%

“…Ethylene octene copolymer (EOC) has been highly regarded among ethylene α‐olefin copolymers derivatives. Compared with conventional elastomers, EOC has exhibited better compatibility with PP because of its long chain branches and the resultant low interfacial tension 10–15 . In the last decade, the PP/EOC blends have been studied in many different aspects, including as morphology development, rheological behavior, 16–18 mechanical properties, 19,20 and crystallization behavior 21–23 .…”

Section: Introductionmentioning

confidence: 99%

Toward understanding the crystallization behavior of polypropylene‐based nanocomposites: Effect of ethylene–octene copolymer and nanoclay localization

et al. 2023

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The crystallization properties of polypropylene (PP), a widely used polymer in industry, can be modified to overcome its mechanical limitations. In the current work, we investigated the effect of ethylene octene copolymer (EOC), blend morphology, nanoclay loading, nano‐localization, and component ratios on PP/EOC crystallization behavior in various aspects, including crystallization rate, degree of crystallinity, nucleation state, and crystalline phases. The results revealed that adding EOC with varying ratios can decrease PP crystallinity both in degree and rate due to the partial miscibility of components through grafting. Furthermore, it was found that the effect of the nanoclay on the crystallization behavior of PP is dependent on the nanoclay loading and its localization in the blend. The nanoclay, therefore, served as a nucleation agent at low nanoparticle contents, accelerating the crystallization rate regardless of the blend's microstructure. However, the crystallization rate of the blend samples at high nanoclay contents (above the rheological percolation threshold) was strongly influenced by the type of morphology. Accordingly, high nanoclay concentrations in blends with matrix‐dispersed morphologies reduced crystallization rates (increasing half‐time from 164 to 216 and 186 s), primarily because PP chains slowed down due to their interactions with nanoparticles and nanoclay hindrance. In contrast, in a blend with a co‐continues‐type morphology, the crystallization rates increased (decreasing half‐time from 624 to 270 and 236 s) due to nano‐localization at the interface and morphology transformation to the matrix‐dispersed one. The blends and nanocomposites based on PP/EOC were also investigated to determine the relationship between the crystallization behavior and mechanical properties.

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“…[ 18 ] Although the AE technique is widely used to monitor crack propagation in metallic components, there are just a few studies in the literature that address polymer failure analysis using AE, and most of them are related to composite materials. [ 19 ] Some studies on the use of AE to investigate polymers were conducted by one the current authors on the effects of photodegradation [ 20,21 ] and stress cracking. [ 6 ] These studies were shown to be very helpful to a better understanding of product failure.…”

Section: Introductionmentioning

confidence: 99%

Monitoring by acoustic emission the mechanical behavior of polystyrene submitted to stress cracking at different temperatures

Trindade

Rabello

2021

Polymer Engineering & Sci

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Environmental stress cracking (ESC) is one of the main phenomena that limit the use of polymers, being responsible for an expressive number of premature failures in service. This occurs when mechanical loading is combined with a certain kind of chemical agent, causing surface cracks and, eventually, catastrophic failure. This issue is not widely reported in the literature, and the usual procedures for investigation involve conventional mechanical testing. Alternative tools, such as, the technique of acoustic emission (AE) to monitor the stages of fracture, are rarely used. In this work, injection molded polystyrene were submitted to stress cracking conditions, using two types of active fluids and different exposure temperatures (25, 40, and 55°C). The AE technique was applied simultaneously with the mechanical testing to monitor parameters like intensity of the hits and energy released during the deformation and fracture. The results showed that the failure by ESC was related to the fluid interaction with the polymer and was very dependent on the exposure temperature. The use of acoustic emission technique was very useful to differentiate the effects of the various exposure conditions and to explain certain fracture characteristics observed by visual inspection and by scanning electron microscopy.

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Chemical degradation and failure analyses by acoustic emission of PP/EOC blends exposed to ultraviolet radiation

Cited by 3 publications

References 30 publications

The investigation of the stress cracking behavior of PBT by acoustic emission

The investigation of the stress cracking behavior of PBT by acoustic emission

Toward understanding the crystallization behavior of polypropylene‐based nanocomposites: Effect of ethylene–octene copolymer and nanoclay localization

Monitoring by acoustic emission the mechanical behavior of polystyrene submitted to stress cracking at different temperatures

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