Study of the Ultraviolet Effect and Thermal Analysis on Polypropylene Nonwoven Geotextile

Research and application of polypropylene: a review

Polypropylene (PP) is a versatile polymer with numerous applications that has undergone substantial changes in recent years, focusing on the demand for next-generation polymers. This article provides a comprehensive review of recent research in PP and its advanced functional applications. The chronological development and fundamentals of PP are mentioned. Notably, the incorporation of nanomaterial like graphene, MXene, nano-clay, borophane, silver nanoparticles, etc., with PP for advanced applications has been tabulated with their key features and challenges. The article also conducts a detailed analysis of advancements and research gaps within three key forms of PP: fiber, membrane, and matrix. The versatile applications of PP across sectors like biomedical, automotive, aerospace, and air/water filtration are highlighted. However, challenges such as limited UV resistance, bonding issues, and flammability are noted. The study emphasizes the promising potential of PP while addressing unresolved concerns, with the goal of guiding future research and promoting innovation in polymer applications.

Mechanical and Thermoanalytical Study of Polypropylene Geomats Exposed in the Field and the Laboratory

A Hydroelectric Power Plant (HPP) presents erosion problems on reservoir slopes and margins. Geomats are a biotechnical composite technology increasingly used to protect soils against erosion. Survivability or durability of geomats is essential for successful application. This work analyses the degradation of geomats exposed in the field for more than six years. These geomats were used as erosion-control treatment in a slope at HPP Simplício in Brazil. The degradation of the geomats in the laboratory was also analysed through exposure in a UV ageing chamber for 500 h and 1000 h. Degradation was quantitatively evaluated by testing the tensile strength of the geomat wires and thermal tests such as thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed that the geomat wires exposed in the field had a greater decrease in resistance compared to the samples exposed in the laboratory. In the samples collected in the field, it could be observed that the degradation of the virgin sample occurred earlier than in the exposed samples, contrary to what was observed in the TG tests carried out with the samples exposed in the laboratory. The DSC analysis showed that the samples had similar behaviours for the melting peaks. This evaluation of the wires of the geomats was presented as an alternative to analysing the tensile strengths of discontinuous geosynthetic materials such as the geomats.

Weathering of a Nonwoven Polypropylene Geotextile: Field vs. Laboratory Exposure

Like other plastic materials, geosynthetics can undergo changes in their properties due to weathering. These changes must be known and, if necessary, duly accounted for in the design phase. This work evaluates the resistance of a nonwoven polypropylene geotextile to weathering, both in the field (under natural degradation conditions) and in the laboratory (under accelerated degradation conditions). The damage experienced by the geotextile in the field weathering tests was evaluated by monitoring changes in its physical (mass per unit area and thickness), mechanical (tensile, tearing and puncture behaviour) and hydraulic (water permeability normal to the plane) properties. Microscopic damage was assessed by scanning electron microscopy. In the laboratory weathering tests, only the tensile behaviour of the geotextile was monitored. The results showed that all geotextile properties were affected by weathering. The mechanical strength of the geotextile decreased in the field weathering tests. Microscopic transverse cracks were found in the weathered polypropylene fibres, which may explain the reduction in mechanical strength. The accumulation of dirt on the nonwoven structure altered the physical and hydraulic properties of the geotextile. Comparing the field and laboratory weathering tests, the reduction in tensile strength found after 24 months outdoors (roughly 30%) was very similar to that observed after 4000 h in the laboratory. This relationship may not be valid for other geotextiles or other exposure locations.

Environmental Decay of Single Use Surgical Face Masks as an Agent of Plastic Micro-Fiber Pollution

Large numbers of Single Use Surgical-type Face Masks, used by the public as personal protective equipment during the 2020–2022 COVID-19 pandemic, have been lost or intentionally discarded and have entered the environment rather than the waste management stream. These masks, made from non-woven polypropylene fibers, will undergo environmental decay which will release fiber fragments as microplastics into the environment. While the photochemical process of the decay of polypropylene polymers (photo-oxidation) is well understood, and while there are numerous studies that investigate mask decay and micro-fiber shedding in laboratory settings, there are no observational data that describe the progress and speed of decay on polypropylene face masks in real-life environmental settings. This paper examines the breakdown of single use surgical-type face masks under natural conditions. Masks from three manufacturers were exposed to natural sunlight over a ten-week period and their state of decay was photographically recorded in situ at weekly intervals. Visible decay accelerated after three weeks, with masks made from thinner spunbond fabric decaying more rapidly. Among same-weight fabric, photo-oxidation affected fabric dyed light blue more than undyed fabric, leading to a total breakdown after six weeks. The results are novel as they demonstrate a differential decay between the spunbonded and the melt-blown fabric, which cracks and breaks down much faster due to thinner fibers of shorter length and the lack of thermal bonding points. The resultant extensive micro-fiber generation was accelerated by external physical forces such as wind. This experiment highlights the fact that municipal agencies have only a narrow window of time to remove stray face masks from the urban environment if micro-fiber pollution is to be prevented.

Accelerated Aging Ultraviolet of a PET Nonwoven Geotextile and Thermoanalytical Evaluation

Nonwoven geotextiles are geosynthetic products that are highly susceptible to ultraviolet degradation because light can reach a large area of the material due to its fiber arrangement. Even with additives, which delay the degradation process, material decomposition still occurs, and therefore the product's long-term durability can be affected. In this paper, the mechanical and thermal behavior of a commercial nonwoven polyester geotextile subjected to accelerated ultraviolet aging tests were evaluated. The deterioration was evaluated by comparing the physical properties (mass per unit area, thickness, and tensile strength) and thermal behavior (thermogravimetry-TG, thermomechanical analysis-TMA, and differential scanning calorimetry-DSC) before and after exposure times of 500 h and 1000 h. The results showed that the ultraviolet aging tests induced some damage in the polyester fibers, leading to the deterioration of their tensile strength. For 1000 h of exposure, in which the reduction was larger, scanning electron microscopy (SEM) found some superficial disruption of the fibers, indicative of damage. TG and DSC could not capture the effects of UV radiation on polymer degradation, unlike TMA. This latter technique was effective in showing the differences between specimens before and after UV exposure.

Weathering of geotextiles under ultraviolet exposure: A neglected source of microfibers from coastal reclamation

Geotextiles are a group of polymeric materials widely used in coastal reclamation projects. However, long-term exposure to solar illumination deteriorates the performance of geotextiles, resulting in physicochemical changes and high risks of releasing microfibers. This study investigated the photoaging behavior of geotextiles and evaluated the capacity of geotextiles to release microfibers in coastal reclamation areas through a combination of field research and laboratory experiments. A field survey in the coastal reclamation area of Yancheng (China) confirmed that many geotextiles made from polyethylene terephthalate (PET) existed on the beach, which was accompanied by a high value of carbonyl index of 0.70-0.93. The results from laboratory experiments revealed that ultraviolet exposure activated the photooxidative process and promoted the breakdown of PET geotextiles. Data of scanning electron microscope and laser particle analyzer showed that, initially, particles with the size of less than 1 μm were generated on the surface of geotextiles, followed by fragments with sizes of 1-100 μm falling off with the passage of time. The number of particles on the surface was calculated using Image-Pro Plus software and the maximum particle density was found to be around 2.52 million particles·mm^-2. In addition, based upon the conversion of irradiance between the simulated solar and natural solar, it was roughly estimated that the annual emissions of PET geotextile fibers in coastal reclamation areas were 0.24-0.79 million tons all over the world. It is inferred that polymer-made geotextile is a significant source of microplastic pollution in reclamation zones of coastal areas.

Geomats Used to Control Erosion on Reservoir Margins in Brazilian Hydroelectric Power Plants

Erosion on reservoir margins causes losses in the production of energy in Hydroelectric Power Plants (HPPs), making it necessary to implement control techniques that ensure the reduction in sediment deposits inside reservoirs. Among these techniques, geomats (geosynthetic erosion mats) are widely used to control erosion processes in slopes and watercourses. This material protects the margins both in the short and long term, contributing to strengthening the vegetation’s roots developed in the erosion areas. This paper studies the performance of geomats (with and without sack gabion) installed in six margin sections distributed in three experimental units of the Brazilian HPPs called Porto Colômbia and Volta Grande. The geomat performance was evaluated over four years of monitoring through a qualitative evaluation matrix and differential bathymetry. The influence of ultraviolet (UV) radiation on the degradation of geomats installed in each section (natural conditions), as well as on geomat ultraviolet-aging samples in the laboratory (accelerated conditions), was also evaluated using differential scanning calorimetry (DSC). The results showed no significant difference in performance between using the erosion control technique consisting only of geomats and the technique consisting of geomats and sack gabion. The highest bathymetric difference value obtained in the present study was 1.62 m in the experimental unit VG1, controlled with geomat without the application of sack gabion on the margin.