Q1. What is conductive compound?
Dispersing conductive fillers into a polymer so the electron or heat and transfer faster in the material. The electrically conductive compound is mainly for the application of ESD (Electrostatic Discharge), anti-static or EMI (Electromagnetic Interference) protection. The thermally conductive compound is mainly for heat dissipation.
Q2. What kind of fillers do we use in the electrically conductive compound?
Depending on what level of resistance we expect to achieve, conductive carbon is the most popular in ESD application, but it will cause the color into black and not stable with low dosage. Ionic type agent is a good option for anti-static application. For EMI protect, metal fibers can work much better than others.
Q3. How do we define the conductive range related to the applications?
Surface or volume resistivity of the material decides where it can be used. Typically, 103-108 is for ESD, 109-1011 is for anti-static, 10-2-102 is for EMI protection, but each user has its own standard and resistance is not the first issue for EMI.
Q4. I see many technical data of electrically conductive compounds show resistance with a range, does that mean their quality is not stable?
The structure of conductive compound is complicated, not like metal. It’s reasonable that resistance has 100 times as tolerance. In ESD application, 103-105, 104-106, 106-108 are quite popular.
Q5. Why can’t I get as low resistance as TDS shows on my injected item?
There are many reasons will cause such situation. But they all follow one principle. Only a conductive structure built in the polymer can reduce the resistance of material. If the conductive structure loses continuity, it won’t reduce the resistance to the target. In this case, the melt flow rate of compound may be too low, the polymer running in the mold couldn’t synchronize with conductive fillers. Finally, the conductive structure in the item is incomplete. Raise the temperature of mold, expand the diameter of runner, improving the MFR of material, avoiding tortuous design will help.
Q6. Can you make every thermoplastic polymer conductive?
Technically, we can disperse conductive fillers into each polymer. However, most conductive fillers are inorganic which do not have good compatibility with polymers. That’s why the mechanical properties of conductive compounds are worse than virgin resins.
Q7. There are so many grades of conductive compounds, which grade should I use?
First, you should decide the base polymer following your application. Then you need to confirm what level of either surface or volume resistivity needed. Melt flow rate and impact property are two data should be paid attention.
Q8. I am making my product with unmodified polymer resins. Can I use conductive compound based on the same polymer on current equipment?
If your equipment is an injection machine, it will be able to handle the conductive compound. The problem may occur on your mold as we mentioned in Q5. If your equipment is an extruder for sheet or film, its torque might be too low to push the compounds forward.
Q9. Can I sacrifice a little conductivity by reducing the conductive filler to get better mechanical properties or higher MFR?
The relationship between dosage of conductive filler and conductivity is not a straight line. Polymer won’t have conductivity until the conductive structure built with enough filler. For example, if you add 15% filler to get SR 103-105, reducing 0.5-1% filler may give you SR 104-106. Unfortunately, the mechanical properties or MFR won’t have much difference between 14% and 15% of filler.
Q10. Can I sacrifice a little conductivity by reducing the conductive filler to lower the material cost?
Same as Q9, minor change of filler content will affect the conductivity pretty much. When the dosage of filler is less than certain amount, compound will lose all the conductivity. The risk is much higher than cost here.