Under The Trend of Plastic Replacing Steel——Industrialization Breakthrough of High-performance Strapping Band Extrusion Equipment

I、Material Revolution: The Turning Point of the Industry from Metal Monopoly to High-Molecular-Weight Substitution

The global packaging industry is undergoing a silent material revolution. Although traditional steel bands have high strength, they suffer from problems such as easy rusting, heavy weight, and significant cost fluctuations, which have long plagued logistics and manufacturing. According to industry data, the global market size of plastic steel bands reached 748 million US dollars in 2024, and is expected to rise to 1.046 billion US dollars by 2031, with a compound annual growth rate of 5.10%. This growth is attributed to the performance leap achieved by PET (polyethylene terephthalate) and PP (polypropylene) polymer materials through modification technologies - their tensile strength can reach over 80% of that of steel bands, while their weight is only 1/6 of that of steel bands, and they possess properties such as resistance to acids and alkalis, non-absorbency, and no loosening after bundling.

In this wave of substitution, the process accuracy of the extrusion equipment has become the key bottleneck for the release of material properties. Qingdao Zhongrui Plastic Machinery Co., Ltd., as a leading enterprise in domestic fiber packaging tape extrusion equipment, has successfully enhanced the tensile strength of its PP/PET fiber packaging tape production line to the industry-leading level through breakthroughs in melt homogenization and molecular orientation control technology. This marks the industrial breakthrough of domestic high-end extrusion equipment in the specialized field.

II. Precise Extrusion: An In-depth Analysis of the Technical Capabilities of Zhongrui Plastic Machinery Equipment

1. Thermodynamic optimization of the melt plasticization system

The core performance of plastic strapping tapes depends on the plasticization quality of the melt during the extrusion process and the integrity of the molecular chains. The production line of Qingdao Zhongrui uses a new parallel twin-screw extruder as the main plasticization unit. Compared with traditional single-screw equipment, its shear heat distribution is more uniform, and it is particularly suitable for engineering plastics such as PET that are sensitive to hydrolysis. The equipment is equipped with a two-stage vacuum exhaust system. In the melting section and the homogenization section, high negative pressure evaporation ports are set respectively, effectively removing residual moisture and oligomers in PET chips, and avoiding thermal degradation of the melt under high pressure.

The temperature control module combines the PID closed-loop algorithm with ceramic heating elements to keep the temperature fluctuations in each section of the barrel within ±1.5℃. This level of precision is crucial for PET processing - excessively high temperatures can cause molecular chains to break and reduce strength, while insufficient temperatures result in uneven plasticization and the formation of "crystalline points", which affects the surface smoothness of the finished product.

2. Melt metering and rheological design of the die head flow channel

The packaging tape, as a typical extruded profile product, has its thickness uniformity directly determining the orientation consistency during the downstream hot stretching process. Qingdao Zhongrui has equipped a melt metering pump (Gear Pump) as the pressure stabilization unit to eliminate the flow fluctuations caused by the screw pulsation and ensure a constant melt pressure entering the garment hanger-style die head. The die head flow channel is optimized through computational fluid dynamics (CFD) design, with internal hard chrome plating and a flow-blocking zone, enabling the melt to achieve laminar distribution in the width direction and avoiding the "thin edge and thick middle" expansion effect of the die head.

Based on the characteristics of PP and PET materials, the equipment supports the rapid replacement of mold lips and flow channel plates. Due to the low melt viscosity of PP, a slit mold head combined with an air knife for cooling is adopted; for PET, with its fast crystallization rate, a dedicated constant-temperature mold head and rapid cooling roller combination is configured. By controlling the cooling rate, the size of spherical crystals can be regulated, providing molecular orientation space for the subsequent biaxial stretching process.

3. Equipment integration innovation of the online stretching system

The high strength of the fiber packaging tape stems from the orientation crystallization of the polymer chains during the stretching process. The production line of Qingdao Zhongrui integrates multiple levels of thermal stretching units and adopts a combination of infrared radiation heating and a heat transfer oil roller group to preheat the blank tape to 10-15°C above the glass transition temperature (Tg). Subsequently, through differential speed stretching rollers, a 4-6 times longitudinal stretching ratio is achieved. The key innovation lies in the tension closed-loop control system - by installing piezoelectric tension sensors on the stretching roller group, real-time tension signals of the tape are collected and fed back to the servo motor to adjust the roller speed, ensuring that the stretching ratio fluctuation is less than ±2%, thereby guaranteeing the batch stability of the mechanical properties of the finished tape.

For high-end customers, the bidirectional stretching (BOPET) module can be optionally equipped. Through the transverse stretching machine, the longitudinal and transverse strength can be balanced, meeting the strict requirements of heavy machinery bundling for the isotropy of the packaging tape.

III.Energy efficiency breakthrough: From single-machine automation to intelligentization of the entire production line

Under the "dual carbon" strategy, the energy efficiency indicators of the equipment have become the core consideration for downstream customers when making purchasing decisions. Qingdao Zhongrui achieves energy reduction through two paths: driving system innovation and thermal management optimization.：

Servo direct drive technology: The main extruder adopts permanent magnet synchronous servo motors instead of traditional asynchronous motors, combined with vector frequency converters. Even under low-speed and high-torque conditions, it still maintains over 90% motor efficiency, and the overall energy-saving rate is approximately 15-20%.

Utilization of residual heat in a cascade manner: The hot water from the cooling section of the extruder barrel and the die zone is introduced into the raw material pre-crystallization drying system. The waste heat is utilized to dehumidify the PET pellets, reducing the drying power consumption by more than 30%.

Digital monitoring platform: The entire production line is equipped with a SCADA system, which can collect 128 process parameters such as melt pressure, melt temperature, line speed, and energy consumption in real time. Through cloud-based algorithms, it optimizes the operating parameters of the equipment to achieve automatic optimization of the "optimal energy efficiency range".

IV. Market Outlook: Opportunities for Equipment Upgrades in Specific Market Segments

Currently, the extrusion equipment market for packaging tapes in China is characterized by both "high-end import substitution" and "low-end capacity liquidation". The technical route of Qingdao Zhongrui represents a typical path for domestic equipment to transition to the high-end market - through the integration of precise mechanical design, high-molecular processing mechanism research, and intelligent control systems, it has broken the monopoly of European brands in the PET high-strength packaging tape equipment sector.

The future trend points towards multi-functional integration and compatibility with the circular economy. On one hand, the equipment needs to be capable of processing recycled PET (rPET) and biobased PP. Through optimizing the evaporation and filtration systems, impurities and volatile substances in the recycled materials can be handled. On the other hand, the modular design concept enables a single production line to quickly switch between the PP light-load belt and the PET heavy-load belt, thereby improving the utilization rate of equipment assets.

Under the irreversible trend of replacing steel with plastic, high-performance extrusion equipment for packaging tapes is no longer merely a production tool; it has become an innovative carrier that integrates material science, mechanical engineering, and intelligent manufacturing. Domestic equipment manufacturers, through continuous in-depth technological investment, are establishing unique industrial competitive advantages in this specialized field.