How to solve these five problems in PVC cable material?

2022-03-13
PVC cable material is a particle prepared by mixing, kneading and extrusion based on PVC resin, adding stabilizer, lubricant and inorganic filler. Although its intermediate point performance is general and not environmentally friendly, it has low price and simple process; PVC cable material is still one of the most used cable materials at present.
When using PVC cable,  there may be pores, rough surface, embrittlement and other phenomena. Let's discuss in detail how these phenomena are caused:
1、 Cable material porosity

There are two main reasons for this problem, one is the problem of water and the other is the problem of degradation.

A. The moisture in raw materials is too high. The raw materials that may exceed the water standard include PVC resin, plasticizer, filler and stabilizer. Due to the large amount of addition, PVC resin and filler should be the focus of inspection. This situation is generally manifested in the kneading process and the vacuum pumping of the extruder.

B. The formula system is unstable or the high temperature residence time of the material is too long, and the material decomposes, resulting in pores. When this problem is serious, it is usually accompanied by color changes.

2、 Rough surface of cable material
PVC cable material

 


There are two kinds of rough surface, one is pimple and the other is pitting.

A. Pimple phenomenon

Mainly: it is formed in the cable material by some powder aggregates that are unevenly dispersed during mixing and cannot be plasticized during extrusion. The plasticized PVC material is wrapped and extruded by the die.

Fish eyes of PVC resin and PVC resin particles that do not fully absorb plasticizer will also cause pimples, but they are generally small.

Today's formula pursues finer and more fillers. If the filler surface is not treated well, the effect of mixing is poor, and the probability of agglomeration will be relatively large. But is the degree of agglomeration and whether it is serious in the cable material? Is it a problem?

B. Pitting problem

Pitting is relatively complex, which is generally considered to be related to small molecular substances running out of materials. These small molecular substances come from the resin itself, plasticizers and lubricants.

Since vacuum pumping is required in the production of cable material by extrusion granulation, it is reasonable that these small molecular substances should be extracted, but why do they still appear? Through analysis, it is found that in fact, these small molecular substances are mostly produced in the materials after vacuum pumping. Many of them come from lubricants in small quantities, and of course, plasticizers.

3、 Poor insulation of PVC cable material

Because of the limitation of PVC material and the influence of plasticizer and other additives, the insulation of PVC cable material has a certain limit. For ordinary cable materials, if the insulation is obviously deviated, there are mainly the following reasons:

a. Too many impurities

The mixing of impurities will have an adverse impact on the cable material, and excessive impurities will cause insulation problems. These impurities may come from PVC resin and various additives, or from mixing and feeding links.

b. The powder particles are too coarse

The powder additives in the cable material are generally used after grinding. If it is easy to use or some mechanical faults cause the added powder particles to be too coarse, it will have an adverse impact on the insulation of the cable material.

c. Heavy metals in colorants

Many pigments are heavy metal salts. These heavy metal ions will improve the conductivity of cable materials and reduce their insulation. Therefore, the choice of cable pigment is very important.

4、 Cable material moisture problem

Because there is a certain proportion of filler in the cable material, and some will also have a certain proportion of low-grade plasticizer (or plasticizer substitutes). Cable materials that are not easy to suffer from moisture will also have such problems in a certain season.

The damp of cable material is closely related to the packaging process and packaging materials. Drying should be strengthened to cool it to a certain temperature before sealing. In addition, the packaging materials should be improved and moisture-proof measures should be taken.

At the same time, attention should also be paid to the phenomenon of false moisture caused by potential degradation and surface adhesion.

5、 Brittleness of cable material

The brittleness of cable material is generally related to the formula components such as PVC resin model, plasticizer, lubricant and filler.

a. The higher model is selected

If the model of PVC resin is on the high side, the performance of the cable material will be brittle due to the short molecular chain of PVC. The amount of plasticizer added is small, the cable material is hard, and sometimes it will feel brittle.

b. Too much filler is added

It is more because the addition of filler is too large, resulting in the decline of cable material performance and poor strength.

c. Lubricant

Lubricant is another key point. If the external lubrication is excessive, it will often lead to poor plasticization (low plasticization temperature is another main reason for poor plasticization). At this time, the cable material will obviously have poor strength and brittle.