How To Avoid Plastic Hose (TPU Tube) Yellowing?

- Nov 16, 2018-

How can we prevent PU from turning yellow?

PU pipe can be divided into polyester type PU pipe and polyether type PU pipe according to material, PU air pressure hose, PU yarn jacket reinforcing pipe, PU industrial hose, PU steel wire stretching pipe, PU spiral pipe, PU stretching pipe, PU spring pipe, PU yarn jacket pipe, PU braided pipe, PU net pipe, PU single pipe and PU straight pipe. PU tube is the preferred pneumatic pressure hose in the pneumatic industry. The highly transparent TPU is transparent after extrusion. Even the TPU tube can be seen shining and shining. However, after a period of time (the period of time is related to the environment, the shorter the period of humidity and easy contact with the light source), it becomes opaque, which is somewhat similar to the white of rice.

The main reason for this phenomenon is that TPU absorbs moisture in the air, leading to color gradient, or the main ingredient added in the extrusion process is that the smoothing agent migrates out when the TPU hose contacts the air. Look at the characteristics of PU and TPU: "opaque, yellowing". Why? Because PU is a yellowing resin, MDI in ISO will yellowing under ultraviolet irradiation, so PU yellowing is an attribute, so we need to delay the time of PU yellowing. So how can we prevent PU from yellowing?

(1) sunlight should be avoided.

PU hose or high pressure hose (TPU), PU clip tube is no exception. All PU pipes are required to be stored in a cool and ventilated place. Plastic bags can be used to pack PU plastic hoses or transparent hoses in places without sunlight.

(2) spraying yellow paint:

Paint spraying usually has two forms, one is in-mold spraying, the other is out-of-mold spraying, butter-resistant paint spraying will form a protective layer on the surface of PU pipes, to avoid TPU fibers increase hoses or other TPU pipes contact with the atmosphere and pollution yellowing;

(3) add anti yellowing agent:

In order to enhance the anti-yellowing ability of PU tubes, a special anti-yellowing agent is often added to the raw materials, but the price of anti-yellowing agent is expensive. We should also measure its economic benefits when using anti-yellowing agent. For example, our black type is insensitive to yellowing, so we can use cheaper non-anti-yellowing material without anti-yellowing agent. Because anti-yellowing agent is a kind of raw material additive, it is added to ingredient A. When we mix, we need to mix in order to distribute evenly and achieve anti-yellowing effect. Otherwise, local yellowing will occur.

(4) use a good mixture ratio:

A good proportion can make I and P liquids reach the fullest mixing reaction without incomplete reflection. When these phenomena occur, the hydrolysis resistance and yellowing resistance of finished products will be greatly reduced, especially when ISO in the proportion is too high, the yellowing of finished products will be accelerated.

(5) avoid contamination during manual operation.

There are more PU tubes and high-pressure hoses contaminated in the finishing process, resulting in yellowing, such as human sweat and organic solvents, so PU products should pay special attention to the cleanliness of contacts, while minimizing the finishing procedures. After the extrusion of PU yarn-jacket tube (fiber-reinforced hose), clean, reorganize and roll up. The next step is to wrap each roll with plastic film, which directly protects the surface of PU tube and avoids contact with other substances, thus delaying the period of discoloration and yellowing of PU plastic hose to a large extent, and helping users prolong the service life.


怎样避免塑料软管(TPU管)黄变?

如何防止PU变黄呢?

    PU管按材料分为聚酯型PU管,聚醚型PU管;按使用要求和称呼不同分为PU空压软管,PU夹纱增强管,PU工业软管,PU钢丝伸缩管,PU螺旋管,PU伸缩管,PU弹簧管,PU夹纱管,PU编织管,PU网纹管,PU单管,PU直管。PU管是气动行业首选的气动压力软管,高度透明的TPU,挤压成型后PU软管是透明的,甚至看到TPU管发亮发光,但是放置一段时间(时间周期与放置环境有关系,潮湿容易接触光源的周期越短)开始不透明,有点近似大米的白色.

 

    这种现象主要是TPU会在空气中吸收空气的水份,从而发生颜色的渐变,抑或是挤出加工过程中添加的主要成分为滑爽剂在TPU软管接触空气时迁移出来。再来看看PU,TPU的特点:“不透明,黄变”,为什么呢?因为PU是一种黄变性树脂,ISO中MDI在紫外线照射下会变黄,因而PU变黄是一种属性,所以我们要延缓PU黄变的时间。那么如何防止PU黄变呢?

 

(1)应避免日光照射:

    PU软管或者高压软管(TPU),PU夹纱管也不例外。所有PU管都要求存放在阴凉通风处,可用塑胶袋将PU塑料软管或者PU透明软管封包放置在无阳光照射的地方;

 

(2)喷施耐黄油漆:

    油漆的喷施通常有两种形式,一种是模内喷施,一种是模外喷施,耐黄油漆的喷施会在PU管的表面形成一种保护层,避免TPU纤维增加软管或者其他TPU管材与大气接触而污染黄变;

 

(3)添加抗黄剂:

    为了加强PU管的抗黄能力,往往要在原料中添加一种专用抗黄的抗黄剂,但是抗黄剂价格昂贵,我们在使用抗黄剂时也应衡量其经济效益,如我们的黑色型体对黄变就不敏感,所以我们可使用较便宜的未添加抗黄剂的非抗黄原料,由于抗黄剂是一种原料添加剂,它添加于A成份中,我们配料时要求搅拌就是为了分布均匀,达到抗黄效果,否则会出现局部黄变现象。

 

(4)使用良好的混合比:

    良好的比例可以使I液和P液达到最充分的混合反应而不会有未完全反映的部分,而有这些现象出现时会使成品抗水解,抗黄能力大大降低,特别是比例中ISO偏多时会加速成品的黄变。

 

(5)避免人工操作过程中污染:

    有较多的PU管及高压软管在整理过程中被污染而产生黄变如人体汗液和有机溶剂等,因此PU制品要特别注意接触体的干净,同时尽可能减少整理程序。在对PU夹纱管(纤维增强软管)挤出成型后,进行清洁再整理打成卷,下一步工序就是给每卷缠上塑料薄膜,此层薄膜直接保护PU管的表面,避免与其他物质接触,从而从很大程度上对PU塑料软管延缓变色变黄的周期,帮助用户延长使用周期。