Chlorinated Water Induced Aging of Pipe Grade Polypropylene Random Copolymers

Microplastics and chemical leachates from plastic pipes are associated with increased virulence and antimicrobial resistance potential of drinking water microbial communities

There is increasing recognition of the potential impacts of microplastics (MPs) on human health. As drinking water is the most direct route of human exposure to MPs, there is an urgent need to elucidate MPs source and fate in drinking water distribution system (DWDS). Here, we showed polypropylene random plastic pipes exposed to different water quality (chlorination and heating) and environmental (freeze-thaw) conditions accelerated MPs generation and chemical leaching. MPs showed various morphology and aggregation states, and chemical leaches exhibited distinct profiles due to different physicochemical treatments. Based on the physiological toxicity of leachates, oxidative stress level was negatively correlated with disinfection by-products in the leachates. Microbial network analysis demonstrated exposure to leachates (under three treatments) undermined microbial community stability and increased the relative abundance and dominance of pathogenic bacteria. Leachate physical and chemical properties (i.e., MPs abundance, hydrodynamic diameter, zeta potential, total organic carbon, dissolved ECs) exerted significant (p < 0.05) effects on the functional genes related to virulence, antibiotic resistance and metabolic pathways. Notably, chlorination significantly increased correlations among pathogenic bacteria, virulence genes, and antibiotic resistance genes. Overall, this study advances the understanding of direct and indirect risks of these MPs released from plastic pipes in the DWDS.

β-Nucleated Polypropylene: Preparation, Nucleating Efficiency, Composite, and Future Prospects

The β-crystals of polypropylene have a metastable crystal form. The formation of β-crystals can improve the toughness and heat resistance of a material. The introduction of a β-nucleating agent, over many other methods, is undoubtedly the most reliable method through which to obtain β-PP. Furthermore, in this study, certain newly developed β-nucleating agents and their compounds in recent years are listed in detail, including the less-mentioned polymer β-nucleating agents and their nucleation characteristics. In addition, the various influencing factors of β-nucleation efficiency, including the polymer matrix and processing conditions, are analyzed in detail and the corresponding improvement measures are summarized. Finally, the composites and synergistic toughening effects are discussed, and three potential future research directions are speculated upon based on previous research.

Polypropylene Pipe Compounds with Varying Post-Consumer Packaging Recyclate Content

The high recycling targets set by the European Commission will create an increased availability of polypropylene (PP) post-consumer recyclates (PCRs). However, no regulations mandate the use of recycled PP (rPP), so the industry is challenged to explore possibilities to utilize such materials. One option, as suggested by the European Commission, is the introduction of rPP in pipe applications. According to existing standards, the use of recyclate is not allowed in pressurized gas and drinking water systems. However, many other pipe and underground applications, such as stormwater systems, open the increased use of PCRs. Additionally, even for less-demanding applications, such as non-pressure sewage systems, highly durable solutions are needed to cover the requested lifetime and request an ambitious property profile to fulfill the application needs that cannot be met by PP packaging materials and even less by PCRs thereof. Hence, this work explores the possible use of commercially available PCRs out of polypropylene from packaging applications in compounds together with virgin PP pipe grades to meet the demands for less-demanding applications. Two different commercially available rPPs and one commercially available recycled polyolefin (rPO) from mixed polyethylene and PP waste were acquired and, together with two predefined virgin PP pipe grades, were blended to compounds in the range of 10 m%, 20 m%, and 30 m% recyclate content. The compounds and three virgin PP pipe grades, acting as benchmarks, were tested in terms of short- and long-term mechanical performance as well as for many other physical properties. All of the compounds showed good results regarding fatigue crack (FCG) resistance with virgin polymer as the reference. The factors influencing FCG resistance, such as melt flow rate and polyolefin cross-contamination, were thoroughly investigated as the used virgin grades and recyclates cover a broad range of these properties.

Short- and Long-Term Performance of Pipe Compounds Containing Polyethylene Post-Consumer Recyclates from Packaging Waste

The polymer industry is pushed to present solutions that lead to a circular plastics economy. High plastic packaging waste recycling targets will eventually lead to a high availability of packaging material recyclates. Although the use of polyethylene terephthalate (PET) recyclates is prescribed by regulations to be used in new PET bottles, no such regulation prescribes the use of polyethylene recyclate (rPE) in new products. One possibility of using rPE, which is considered by the European Union, is the use within pipe materials. Pipe applications demand a certain property profile, most prominently a high slow crack growth (SCG) resistance, which is not met by most packaging materials or recyclates made from it. Hence, this work investigates the use of commercially available post-consumer recyclates out of high-density polyethylene from packaging applications in compounds together with high SCG-resistant virgin PE pipe material with a PE100-RC specification. Two rPEs were acquired from German producers and blended to compounds consisting of 25 m%, 50 m% and 75 m% recyclate. These compounds, together with the pure recyclates and several virgin pipe materials acting as benchmarks were tested in terms of short- and long-term mechanical performance and with other basic characterization methods. Several compounds exceeded the performance of one tested virgin PE pipe material, an injection molding PE80 grade, in several categories. The content of recyclate needed to outperform this benchmark grade was mostly dependent on the resulting melt flow rate (MFR) of the compound and thus also of the MFR of the pure recyclate. Furthermore, different levels of polypropylene contaminations within the recyclates resulted in differently contaminated compounds. This is proved to influence the SCG resistance too, as compounds of similar MFRs but with different SCG resistances were found.

An Effective Package of Antioxidants for Avoiding Premature Failure in Polypropylene Random Copolymer Plastic Pipes under Hydrostatic Pressure and High Temperature

Pipes of polypropylene random (PP-R) copolymers are the best choice for hot- and cold-water networks. Validation of a severe test, accomplishing the ISO 1167 standard, is mandatory to assess their service lifetime expectancy. This work evaluates the behavior shown by three commercial pipes, either the original ones (new pipes) or after being subjected to a hydrostatic pressure test at elevated temperature (aged pipes). Several features with relevance for the final performance have been examined: crystalline characteristics, phase transitions in crystalline regions, effect of high temperature and pressure on these transitions, and oxidation induction time. Moreover, the presence of inorganic fillers, and the content of different antioxidants together with their depletion, have also been analyzed. Films from the new pipes were also prepared for replication of the different environments in order to achieve a better and complete understanding of the phase transitions in the crystalline regions and of the consumption of antioxidants. Distinct environments surrounded the inner and outer parts of the pipes exposed to the failure aging test at 110 °C: hot water and warm dry air, respectively. These features play a key role in the loss of additives and in the subsequent initiation of degradation. Even if the crystalline characteristics are appropriate in the polymeric matrix, the success of a pipe lies in the homogeneous dispersion of components for avoiding damage at interfacial properties, and in a correct package of antioxidants used in its formulation.

Industrial Internet of Things and Fog Computing to Reduce Energy Consumption in Drinking Water Facilities

The industry is generally preoccupied with the evolution towards Industry 4.0 principles and the associated advantages as cost reduction, respectively safety, availability, and productivity increase. So far, it is not completely clear how to reach these advantages and what their exact representation or impact is. It is necessary for industrial systems, even legacy ones, to assure interoperability in the context of chronologically dispersed and currently functional solutions, respectively; the Open Platform Communications Unified Architecture (OPC UA) protocol is an essential requirement. Then, following data accumulation, the resulting process-aware strategies have to present learning capabilities, pattern identification, and conclusions to increase efficiency or safety. Finally, model-based analysis and decision and control procedures applied in a non-invasive manner over functioning systems close the optimizing loop. Drinking water facilities, as generally the entire water sector, are confronted with several issues in their functioning, with a high variety of implemented technologies. The solution to these problems is expected to create a more extensive connection between the physical and the digital worlds. Following previous research focused on data accumulation and data dependency analysis, the current paper aims to provide the next step in obtaining a proactive historian application and proposes a non-invasive decision and control solution in the context of the Industrial Internet of Things, meant to reduce energy consumption in a water treatment and distribution process. The solution is conceived for the fog computing concept to be close to local automation, and it is automatically adaptable to changes in the process’s main characteristics caused by various factors. The developments were applied to a water facility model realized for this purpose and on a real system. The results prove the efficiency of the concept.

Global and Local Aging in Differently Stabilized Polypropylenes Exposed to Hot Chlorinated Water with and without Superimposed Mechanical-Environmental Loads

The influence of chlorinated water on the global and local aging behavior of polypropylene (PP) was investigated for three differently stabilized PP grades consisting of the same PP base polymer. While one of the PP grades contained only a processing stabilizer (PP-S0), the other two were modified with a primary phenolic antioxidant (PP-S1) and a combination of a primary phenolic antioxidant and a hindered amine stabilizer (PP-S3). To study global aging effects, micro-sized specimens were pre-exposed to chlorinated water (5 mg/L free chlorine) at 60 °C for up to 750 h. Over the entire exposure period, significant material aging was detected by monitoring a continuous decrease in stabilizer content, oxidation induction temperature, mean molar mass, and mechanical strain at break. In terms of aging resistance and ultimate mechanical performance, PP-S1 was found to outperform the other two material formulations under these test conditions. Moreover, superimposed mechanical-environmental fatigue tests with cracked round bar specimens were carried out with the three PP grades in non-chlorinated (0 mg/L free chlorine) and chlorinated (5 mg/L free chlorine) water at 80 °C and 95 °C to study local crack tip aging effects. While the fatigue crack growth resistance substantially deteriorated for all three materials in chlorinated water, a significantly stronger effect was found for the higher temperature, with crack growth rates at a given stress intensity factor range in chlorinated water being ca. 30 to 50 times faster than in non-chlorinated water, depending on the material. Molar mass measurements of material samples taken from various positions of the tested CRB specimens provided clear evidence of enhanced local crack tip aging due to the chlorinated water environment.