How can non-woven fabrics achieve high quality
Quality control is crucial in the nonwoven lamination process. Without it, you could end up with inferior products and wasting valuable materials and resources, and in an era of extreme competition in this industry (in 2019, global nonwoven consumption exceeded 11 million tons, valued at $46.8 billion), facing Risk of losing market share.
In order to achieve and maintain the required quality control when producing nonwoven composites, it is critical to have a deep understanding of the control process and turn it into an advantage. Let's take a look.
How to ensure the highest quality control of the compounding process?
There are only a few processes that really determine the quality of the final non-woven composite material, which must be strictly controlled, mainly the application of tension, temperature, line pressure and adhesive.
Tension Control
The web tension is the force (MD) in the machine direction applied to the web. Tension is extremely important throughout the lamination process. When properly handling the web, the web must always be pulled by the rollers, and it must not be under too much or too little tension.
Tension control is critical at all stages of web processing. In general, post-processing is divided into three distinct tension zones:
●Unwinding
●Processing
●Rewinding
Each tension zone must be controlled independently, but must work in concert with other zones. The tension applied in each zone is different, depending on the torque of the rollers. The torque must be changed as the roll is unwound or unwound to maintain proper tension.
Temperature Control
Temperature settings for nonwoven laminations are critical to obtaining top quality products.
During hot melt adhesive compounding, the temperature of the adhesive layer needs to be precisely controlled, and the composite material needs to be cooled to avoid changing the properties of the composite material.
The thermal composite process requires high temperatures to take advantage of the thermoplasticity of one or more composite layers in the composite. The high temperature and pressure will melt the synthetic fiber layer enough to bond with the nonwoven fiber layer. However, the temperature setting must be precise. If the temperature is too low, it will not glue and it will not last. Conversely, if the temperature is too high, it can lead to the degradation of the material in the cloth layer, thereby affecting the structural integrity of the composite material.
Line pressure control
The line pressure is the gap between the two rolls along the compound line. When the cloth surface passes through the pressing line, apply pressure to make the cloth flat and ensure the uniform distribution of the adhesive. The amount of pressure applied in the lamination process can be a game-changer as the web passes through the crimping line.
The key to controlling line pressure is to keep it as small as possible: too much pressure can press the web too tightly and even tear it. In addition, line pressure helps control web tension. It is also important to understand how the relationship between the two rolls is affected as the web passes through the nip. Defects such as cut-off wrinkles can occur if the positioning or torque of the composite roll is not correct.
Quality of adhesives
Controlling the use of adhesives is the key to quality control. If there is too little adhesive, the bond will not be strong enough, and there may be parts that are not bonded at all. If there is too much glue, thick, hard areas will appear inside the composite. Regardless of the gluing method used, the control of gluing is relevant. Glue methods include:
Coater head - for contact coating of the entire substrate surface
Spray - non-contact, available in a variety of modes , such as beaded, meltblown or sinusoidal
Controlling the adhesive application to keep it consistent with the speed of web movement is critical. The faster the web moves, the faster the gluing needs to be applied, and these settings must be precise to obtain the best coat weight for the final product.
The role of Industry 4.0 in quality control
The measurement of various parameters of non-woven composite equipment is cumbersome, and it is inevitable that human errors will occur when manually adjusting parameters. However, Industry 4.0 has changed the game for quality control.
Industry 4.0 is considered the next stage of the technological revolution, transforming the computerization of tasks into full automation with the help of technologies such as cloud computing and the Internet of Things (IoT).
The non-woven composite equipment based on Industry 4.0 design includes:
●Sensors, distributed throughout the production line
●The interface between the equipment and the main software platform Cloud connectivity
An easy-to-operate control panel provides full visibility and real-time control of the production process
Sensors located on the device measure settings such as temperature, pressure and torque, and can Detect defects in products. Since this data is sent in real time, adjustments can be made during production. Thanks to artificial intelligence (AI), these adjustments can be made through software, maintaining optimal production speeds and optimal settings at all times.
