The knot strength of the polypropylene high-strength filament: The drawing process has met the standards. But after knotting, how much can be left? 

When purchasing polypropylene high-strength filament, many customers tend to consider the direct drawing strength as the core indicator. A high direct drawing strength is of course desirable, but in actual usage - especially in applications such as ropes, nets, and webbing - the yarn often needs to be knotted or bent to bear force. At this point, the actual strength that determines the product's firmness may not be the direct drawing strength, but the knot strength. Below, from two perspectives, we will help you understand why knot strength is more worthy of attention. 

1. Tensile strength vs. Nodule strength: What's the difference? 

The tensile strength is the breaking force tested under standard conditions, representing the ultimate load-bearing capacity of the thread when in a straight tensile state. The knot strength, on the other hand, is the actual load-bearing capacity of the thread after it has been knotted. 

Strength loss rate: When polypropylene high-strength yarns get knotted, due to the stress concentrating at the bent part of the knot, the strength usually suffers significant loss. The lower the loss rate, the better the flexibility and anti-bending fatigue performance of the yarn. This is particularly important for products such as ropes and safety nets that require knotting - because in actual use, the weak point of the rope often lies at the knot. 

Application scenario differences: For the threads used in industrial ropes or trailer ropes, if the knot strength is insufficient, at the time of mooring or binding, the knot area may become the starting point of the rope breakage. When purchasing, one should not only consider the direct pulling strength but also request the knot strength or strength loss rate data. Shanghai JinCai Industrial has complete testing equipment, including strength testers and fineness testers, and is responsible for the entire process from sample confirmation to production delivery by dedicated personnel. 

II. How to assess and select sutures with high strength of knots? 

Since the strength of the nodules is so crucial, how should we ensure quality during the procurement process? 

The supplier is requested to provide data on the strength of the knots: During the procurement process, it is advisable to proactively inquire whether the supplier has tested the knot strength and require them to provide comparative data on the direct drawing strength and knot strength of the same specification of thread. By calculating the strength loss rate (the lower the loss rate, the better), the flexibility and bending resistance of the thread can be preliminarily judged. 

Pay attention to the flexibility and surface smoothness of the thread: The knot strength is related to the flexibility of the thread, the surface friction coefficient, and the number of single strands. Threads with good flexibility are easier to uniformly tighten when making knots, reducing local stress concentration. When purchasing, you can inform the supplier of your specific application (such as industrial ropes, safety nets, luggage accessories, etc.) so that the supplier can recommend a more suitable specification. 

Actual knotting test: After sampling, conduct a manual tension test in your actual knotting method to feel the force exerted on the knot. This is the most intuitive way to determine whether the knot strength meets the requirements. 

Summary and Selection Suggestions 

When purchasing polypropylene high-strength filament, it is recommended to follow the steps below for confirmation: 

Provide the data on the strength of the knots: Do not merely focus on the direct pulling strength; you must request the data on the knot strength or the rate of strength loss. This is an important indicator for evaluating the actual reliability of the use of the thread. 

Pay attention to the flexibility of the thread: When using ropes or nets that require frequent knotting, choose products with a low rate of knot strength loss and good flexibility. 

Choose the specification based on the application: Inform the supplier of your specific usage (such as industrial ropes, fire hoses, luggage accessories), so as to match the appropriate fineness, twist, and strength grade. 

Shanghai JinCui Industrial Co., Ltd. was established in 2006. It has extensive experience in producing polypropylene fibers and offers a range of products including high-strength polypropylene fibers, polypropylene FDY fibers, hollow polypropylene fibers, and lightweight polypropylene fibers. It possesses the ability to customize colors independently and has multiple imported production lines. We can tailor specifications and colors according to customer requirements. Please feel free to request samples for testing. 

Official website: http://www.jcfibre.com/