Jianlong shares: The R&D story behind improving the impact resistance of PVC pipes

Insight into needs, lock in problems

Mr. Li, a senior engineer in the R&D department, recalled: "About 5 years ago, we received feedback from customers that PVC pipes were broken during construction in the northern winter, affecting the progress and cost of the project. In addition, in some areas with complex construction environments, pipes were damaged by slight bumps during transportation and installation. This made us realize that it is urgent to improve the impact resistance of PVC pipes." Therefore, Mr. Li's R&D team, in conjunction with material science experts, embarked on a long and arduous R&D journey.

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Starting from the formula, looking for a breakthrough

In the early stages of R&D, the team focused on formula optimization. "We know that the rigidity of PVC molecular chains is one of the reasons for its brittleness, so we have to find a way to make the molecular chains 'softer' without destroying their inherent advantages." Engineer Li introduced that they tried to add various additives, such as plasticizers, impact modifiers, etc. After numerous tests, it was found that powdered nitrile rubber (PNBR) had a significant effect. It turns out that the polar groups of acrylonitrile in PNBR interact with the PVC molecular chains to form a three-dimensional network structure in the PVC matrix, which can induce silver streaks and absorb impact energy when cracks expand. But new problems followed. Adding too much PNBR would affect the processing fluidity of the pipe, resulting in reduced production efficiency. To this end, the team successfully solved this problem by optimizing the segmented mixing process of the twin-screw extruder, adjusting the barrel temperature curve, setting the feeding section temperature to 150°C, and raising the homogenization section to 175°C, and using a specially designed barrier screw. ​

Innovative process, comprehensive performance improvement​

In addition to the formula, the processing technology is also crucial. Engineers used a biaxial stretching process to orient the molecules of PVC pipes, which not only improved the strength but also enhanced the toughness. At the same time, they developed a slow cooling process, which slowly cooled the pipes in an 80°C water bath after forming to avoid internal stress caused by rapid cooling and further improve the impact resistance. Supported by a series of research and development results, the new PVC pipes launched by the company performed well in the -10℃ low-temperature drop hammer impact test, and the sealing pressure at the pipe joints was greatly improved, far exceeding the national standard. ​

Today, these PVC pipes with greatly improved impact resistance have been used in many major projects, such as Jinan Century China City and Jining Municipal Engineering Company, providing a solid guarantee for project safety and quality. It is precisely because of such a group of persistent pipe engineers that PVC pipes have been continuously innovated and continue to shine in various fields. ​