Nylon PBT bristle filament: How to achieve both wear resistance and elasticity? What are the misunderstandings in model selection?

Nylon PBT bristle filament: Why is it difficult to balance wear resistance and elasticity?​

In industrial production and daily life, nylon PBT bristle filament is everywhere, from various brushes used for household cleaning to key cleaning components in industrial equipment, it plays an important role. However, a problem that has long plagued the industry is that it seems difficult to achieve a perfect balance between the abrasion resistance and elasticity of nylon PBT bristle filaments.​

When we expect the bristles to have good wear resistance and be able to maintain their shape and cleaning effect over a long period of use, the elasticity is often affected and becomes stiff, unable to flexibly fit the surface of the object being cleaned, and the cleaning efficiency is greatly reduced. On the contrary, if high elasticity is pursued so that the bristles can easily adapt to various complex surfaces, the wear resistance will be insufficient, and the bristles will wear and break in a short period of time, shortening the service life of the product. This contradiction has caused headaches for many manufacturers and users. So, what exactly causes this difficult-to-balance situation?​

What are the factors that affect the abrasion resistance and elasticity of nylon PBT bristle filament?​

How do raw material characteristics affect performance?​

Nylon, as a common synthetic fiber, contains amide groups in its molecular structure. These groups can form hydrogen bonds, giving nylon high strength and wear resistance. The regularity and crystallinity of nylon molecular chains also have an important impact on its performance. Higher crystallinity causes the molecular chains to be arranged more closely, thereby increasing the material's hardness and wear resistance, but it also reduces its elasticity. For example, nylon 610 has relatively good wear resistance and is often used as brush parts in household dust removal and cleaning because its molecular structure allows it to maintain good shape stability during friction.​

And PBT, or polybutylene terephthalate, has a unique chemical composition and molecular structure. The ester bond in the PBT molecule gives it a certain degree of flexibility, making it have excellent elasticity. The regularity of the PBT molecular chain is relatively low, and the crystallinity is not as good as that of some nylon materials. This makes it easier for the molecular chain to shift and deform when subjected to external forces, thus showing good elasticity. However, this structural feature also makes it slightly inferior in wear resistance. In some application scenarios that require long-term friction, the bristles are prone to wear.​

What role does the production process play?​

In the production process of nylon PBT bristle filament, the drawing process is one of the key links that affects its performance. The stretching process can align the molecular chains along the stretching direction, thereby improving the strength and wear resistance of the material. An appropriate stretching ratio can arrange the molecular chains more closely, enhance the interaction between molecules, and thereby improve the wear resistance of the bristles. If it is stretched too much, the flexibility of the molecular chain will be reduced, causing the bristles to become stiff and easy to break.​

The forming process also has an important influence on the performance of the bristle filaments. Different molding methods, such as injection molding, extrusion molding, etc., will cause differences in the internal structure and surface morphology of the bristles. Injection molding can make the bristles have high precision and surface quality, but it may create stress concentration points inside, affecting the durability of the bristles. Extrusion molding can better orient the molecular chains in the extrusion direction, which is beneficial to improving the longitudinal strength and wear resistance of the bristles. However, some defects may be introduced during the molding process, such as bubbles, impurities, etc. These defects will become sources of stress concentration and reduce the elasticity and overall performance of the bristles.​

How to scientifically balance the abrasion resistance and elasticity of nylon PBT bristle filament?​

How to optimize from the perspective of material formulation?​

From a material formulation perspective, adjusting the ratio of nylon and PBT is a straightforward and effective method. Through extensive experimental research, it was found that when the ratio of nylon to PBT changes within a certain range, the performance of the bristle filament will change significantly. When the nylon content is higher, the wear resistance of the bristles will be significantly improved. The high strength and high crystallinity of nylon enable the bristles to better maintain their shape and structural integrity during friction. If the nylon content is too high, PBT's elasticity benefits won't be fully utilized and the bristles will become too stiff. Therefore, it is necessary to find a suitable proportional balance point to meet the requirements for wear resistance and elasticity in different application scenarios.​

In addition to adjusting the ratio of nylon and PBT, adding other additives is also an important means to optimize the performance of bristle filaments. For example, adding plasticizers can increase the flexibility of molecular chains, thereby improving the elasticity of bristles. Plasticizers can be inserted between molecular chains, weakening the interaction between molecules, making the molecular chains more susceptible to displacement and deformation. When selecting a plasticizer, consider its compatibility with nylon and PBT, as well as its impact on other bristles' properties. Some plasticizers may reduce the bristles' resistance to heat or chemicals, so a comprehensive evaluation is required before making a choice.​

What are the adjustment strategies for the production process?​

In terms of production technology, temperature and pressure are two key parameters that have an important impact on the performance of nylon PBT bristle filament. In the melt spinning process, temperature control is crucial. Appropriately increasing the spinning temperature can reduce the viscosity of the melt and make it more fluid, which is beneficial to the orientation and arrangement of molecular chains, thus improving the strength and wear resistance of the bristles. If the temperature is too high, it will lead to the degradation and thermal oxidation of the molecular chain, which will reduce the performance of the bristles. Therefore, it is necessary to accurately control the spinning temperature according to the characteristics of nylon and PBT to obtain the best performance.​

Pressure also plays a key role in the molding process. During injection molding or extrusion molding, appropriately increasing the pressure can make the internal structure of the bristles denser and reduce internal defects and pores, thereby improving the strength and wear resistance of the bristles. Excessive pressure may cause stress concentration inside the bristles, reducing the elasticity and toughness of the bristles. Therefore, it is necessary to reasonably adjust the pressure parameters according to different molding processes and product requirements to achieve a balance between wear resistance and elasticity.​

What are the common misunderstandings when choosing nylon PBT bristle filament?​

What will happen if we only look at wear resistance and ignore elasticity?​

When selecting nylon PBT bristle filament, focusing only on abrasion resistance and ignoring elasticity may cause many problems. In household cleaning, if the bristle filament used is too focused on wear resistance and lacks elasticity, the bristles cannot flexibly bend and fit when cleaning some appliances with uneven surfaces, resulting in an increase in cleaning dead spots and greatly reducing the cleaning effect. For example, when cleaning curved glassware, stiff bristles cannot penetrate deep into the corners, making it difficult to completely remove stains.​

In industrial applications, this problem may be even more severe. In precision cleaning of electronic equipment, inelastic bristles may cause scratches and damage to the equipment because they cannot adapt to the complex shape of the parts. After long-term use, some bristles are prone to stress concentration at the roots due to lack of elasticity, causing the bristles to fall off the brush handle, affecting the normal use of the product.​

Is it feasible to pursue elasticity too much at the expense of wear resistance?​

It is also not advisable to sacrifice wear resistance by pursuing elasticity too much. Take a toothbrush as an example. If the elasticity of the bristle filaments is too good but the wear resistance is insufficient, the bristles will soon wear out during daily brushing and will not be able to effectively clean plaque and food residue on the tooth surface, affecting the oral cleaning effect. Moreover, frequent replacement of toothbrushes not only increases the cost of use, but also causes a waste of resources.​

In industrial production lines, some brushes used for product surface polishing or grinding, if the bristles are too elastic and have poor wear resistance, they cannot withstand long-term friction and need to be replaced frequently. This will not only affect production efficiency, but also increase production costs. For some products that require high-precision processing, rapid wear of the bristles may also lead to unstable processing quality and affect the product's qualification rate.