Currently, accelerated aging tests are widely used to study the aging process of polyethylene pipelines. However, this approach can only simulate one or several main influencing factors in the natural environment, which are often quite different from the actual environment of the buried pipelines. In this study, five types of PE80 buried pipelines in service for 9–18 years were taken as the research object, while new PE80 pipelines were taken as the reference group. The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis. The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0–18 years. The aging degree and law of the inner and outer surface of the pipeline were compared, and the observed mechanism of both surfaces was explained. After 18 years in service, the elongation at the break of the pipe decreased by 16.2%, and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties. Finally, after 18 years in service, the oxidation induction time of the pipeline was 25.7 min, which was 28.5% higher than the national standard value. There were no potential safety hazards during continuous long-term service. The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.

After around 50 years of development, the key substance known as polyethylene has been extremely influential in a variety of industries. This paper investigates how polyethylene materials have been used in the domains of water, packaging, and medicine to advance contemporary society in order to comprehend the physical and chemical alterations that polyethylene undergoes after being subjected to long-term environmental variables (e.g., temperature, light, pressure, microbiological factors, etc.). For the safe operation of polyethylene materials, it has always been of the utmost importance to evaluate polyethylene’s service life effectively. This paper reviews some of the most common literature journals on the influence of environmental factors on the degradation process of polyethylene materials and describes methods for predicting the lifetime of degradable polyethylene materials using accelerated aging tests. The Arrhenius equation, the Ozawa–Flynn–Wall (OFW) method, the Friedman method, the Coats–Redfern method, the Kissinger method and Kissinger–Akahira–Sunose (KAS) method, Augis and Bennett’s method, and Advanced Isoconversional methods are all discussed, as well as the future development of polyethylene.

Thermal fusion welding is a common method for high-density polyethylene (HDPE) pipelines. However, defects are easy to occur at the joints in the welding process, causing hidden danger. In this study, HDPE pipes with thermal fusion welding defects were made and the X-ray technology was used for detection. The results show that the testing effects of different defects are quite different. The X-ray cannot detect cold-welding defects. The weld seam of the over-welding in the negative is narrowed. Besides, the unfilled holes collapse during welding, resulting in poor detection results. The filled holes can be detected.

Electro-fusion welding is a common method for high-density polyethylene (HDPE) pipes. It has a high degree of automation and mature technology. However, during the welding process, various buried defects are easily generated. In this paper, HDPE pipes with welding defects were processed, and X-ray technology was used to detect the defects. The results show that: The X-ray detection technology is sensitive to the defects of sockets and ultralight clay-filled holes. But it is difficult to distinguish the size of the holes. Unfilled holes are partially fused during the welding process, which makes them difficult to detect. In addition, the defects of cold-welding and unscratched oxide skin cannot be detected.

As a common welding method for polyethylene natural gas pipelines, electro-fusion welding has been widely used. However, defects are easy to occur in the fusion area during the welding. In this paper, high-density polyethylene (HDPE) pipes with different types of electric welding joint defects are processed, and the detection effect of the ultrasonic phased array on joint defects is explored. The results show that: Ultrasonic phased array detection technology is easy to operate and reliable. It can detect three common defects: inadequate socket, cold welding, and scratch of oxide scale. In addition, according to the inspection result chart, the defect type can be accurately judged.

The welding joint is the weak link of the high-density polyethylene pipeline. The continuous development of ultrasonic phased array technology is expected to replace traditional non-destructive testing methods. In this paper, ultrasonic phased array technology is used to detect the defects of butt fusion welding. The results show that the ultrasonic phased array can distinguish between metallic and non-metallic inclusions, and the inclusion size can be displayed. Besides, insufficient fusion defects have no obvious defect features in the sector scan results. The types of insufficient fusion defects can be judged from the end-face line scan results.

To avoid the issues of seeds lying atop straw, where the seeds cannot germinate, during no-till maize seeding, a seed furrow cleaning device is proposed. The device uses rotating spring teeth and a curved sliding shovel to clear the straw from the seed furrow to the outside. The critical components of the side throwing mechanism, rotary disc and spring teeth design are analyzed, and the value range of the installation inclination angle, rotating speed and bending angle of spring teeth are determined. The force on the straw at the moment of starting to touch and throw it is analyzed theoretically in the three installation directions of forward inclination, radial and backward inclination on the rotary disc, and the backward inclination of the spring teeth is determined. A simulation model of the seed furrow cleaning device is established by using the discrete element method simulation software; the forwarding speed, rotating speed, installation inclination angle, and bending angle of spring teeth are used as influencing factors to carry out single-factor experiments. The influence characteristics of different parameters on seed ditch cleaning effect are analyzed from the aspects of straw cleaning quantity and soil disturbance. A field validation experiment is carried out, and the results show that when rotating speed is 180 r/min, installation inclination angle of spring teeth is 40°, and bending angle is 30°, the straw cleaning rate is 82.26%. The research could provide references to develop the no-till seeder for maize seeding.

According to the applications of materials in food and biology etc. fields, the open-cell macroporous polymer composite must contain a non-toxic component, and be bio-compatible, and the preparation processes should be green and facile. Herein, bio-compatible macro-porous nano-hydroxyapatite particles (n-HAPs)/polymer monolithic composites were templated from green and facile CO2-in-Water high internal phase emulsion (C/W HIPE). The bio-active n-HAPs that acted as emulsifiers were incorporated, which enable the well-dispersion of functional fillers in these monolithic composites. Green and facile C/W HIPE templating combined with radical polymerization of bio-compatible monomers involves nontoxic chemicals, and produced polymer monolith with macro-porous open-cell structure (80–120 μm in pore size, 20–40 μm in pore-throat size), and enable the n-HAPs/polymer improved flexibility and mechanical performance (above 80% compression strain, > 400 kPa of compression strength). Results of bio-compatibility tests show that these n-HAPs/polymer monoliths have non-cytotoxicity on HepG2 cells; Furthermore, the immobilization of pectinase by the composite indicates that composites have physical adsorption of pectinase, and the introduction of n-HAPs is more conducive to the immobilization of pectinase and the improvement and maintenance of enzyme activity; after reusing the immobilized pectinase 10 times, the relative catalytic activity can still be above 85%. Therefore, this kind of porous composite has promising potential in applications of bio-tissue engineering, food, and pharmaceutical.