Over 30 years of PVC granulation factory reveals: how to choose cable materials?

A cable factory once used insulation material at 70 ℃ in an order for 90 ℃ working conditions. After the entire batch of cables was delivered, the insulation performance was not qualified and they were returned, resulting in losses far exceeding the saved material costs.

　　cableThe easiest pitfall for customers is never the price, but the wrong brand selection.

　　The letters and numbers of the brand are in the user manual

　　wire and cableUsing SoftPVCMaterial executionGB/T 8815 standardThe brand name is very straightforward:

J=insulation grade, H=sheath grade, R=flexible type, GD=high electrical performance

The number represents the long-term allowable working temperature: 70 is 70 ℃, and 90 is 90 ℃

So J-70 is a 70 ℃ insulation material, H-90 is a 90 ℃ sheath material, and JR-105 is a 105 ℃ soft insulation material. It should be noted that the 2008 version of the national standard grade list mainly includes two levels, 70 and 90. Level 105 is widely used in industry and enterprise standards, and can be confirmed according to actual working conditions before placing an order.

　　70, 90, the difference is not just in temperature

Different temperature levels result in completely different formula systems:

　　70 ℃ material:Used for ordinary building wiring and insulation layers, universal plasticizers can meet the requirements, with the highest cost-effectiveness;

　　90 ℃ material:For sheath and heat-resistant applications, both plasticizer and stabilizer systems need to be upgraded;

That's also why, also known as "cable material", the price can differ significantly - the cost of raw materials varies depending on the temperature resistance level, so it's important to confirm the required level before comparing prices.

　　5 indicators are the bottom line for factory acceptance

Regardless of which brand to purchase, these 5 items must be closely monitored:

　　Volume resistivity:The lifeline of insulation materials, J-70 requires a minimum of 1.0 × 10 ¹Ω· m at 20 ℃

　　Dielectric strength:The insulation level shall not be less than 20 MV/m, and the sheath level shall not be less than 18 MV/m

　　Mechanical properties:According to different grades, the tensile strength is usually not less than 15.0 MPa or 16.0 MPa, and the specific standard value of the corresponding grade shall prevail; The elongation at break shall not be less than 150%, and the softness level shall be above 180%

　　Thermal stability:The 200 ℃ Congo Red test requires a minimum of 50 minutes for 70 ℃ grade products and 80 minutes for 90 ℃ grade products;

　　Thermal aging:After 168 hours at 100 ℃, the change rate of tensile strength and elongation does not exceed ± 20%

In addition, the brittleness temperature should also be considered for outdoor and cold resistant occasions in the north.

These indicators are alsoTongxiang Xiaobaozi Special Plastic Products Co., LtdofFactory inspection items——Each batch of materials is fully inspected and traceable, and any non-conforming materials will never leave the factory.

　　Low smoke and halogen-free, not PVC at all

This is the most common misconception in procurement.

　　PVCContaining about 57% chlorine, it has good flame retardant properties, but combustion inevitably releases hydrogen chloride;

　　Low smoke halogen-free materialLSZH is usually based on halogen-free polymers such as polyolefins (PE/EVA/XLPE), filled with 50% to 65% of the total formula of aluminum hydroxide or magnesium hydroxide. It burns with low smoke, non-toxic, and non corrosive gases.

　　Smoke density dataThe gap is significant: the smoke transmittance of low smoke halogen-free materials is not less than 60%, while the smoke transmittance of ordinary PVC cable materials is much lower, usually below 60%.

When the project model specifies WDZ (halogen-free low smoke flame retardant), the polyolefin system should be selected and not found in the PVC formula.

　　Three step selection method

Step 1: Positioning: Insulation layer or outer sheath?

Step 2 Temperature Determination: What is the long-term operating temperature of the cable?

Step 3: Special requirements: Should it be soft, cold resistant, high electrical performance, or export certified?

The small boss's technical team often reminds customers that clarifying equipment parameters and operating conditions is much more important than comparing prices everywhere. Accumulated granulation factories will recommend brands according to customers' actual needs, rather than pushing the most expensive ones.

Behind the brand is the formula, and behind the formula is accumulation. By understanding the brand, focusing on the indicators, and distinguishing the system, there will be no major mistakes in material selection.

　　Author/Zhang Ziyi