Fusabond® Resins as Coupling Agents in Halogen-Free Wire & Cable Applications
DuPont™ Fusabond® maleic anhydride grafted resins can be used as coupling agents between polymers --mainly polyolefins such as polyethylene and polypropylene --and fillers, in order to increase the filler acceptability of polymers. Typical levels of Fusabond® are in the range of 2-5 weight % based on the entire compound. Fillers that show an affinity to Fusabond® maleic anhydride grafted resins include flame-retardant fillers, such as alumina trihydrate (ATH) and magnesium hydroxide (Mg[OH]2). Improvement in properties also can be seen when Fusabond® is used in combination with common fillers such as calcium carbonate.
Extensive trials have been undertaken using Fusabond® E as a coupling agent in halogen-free, flame retardant wire and cable formulations containing approximately 65% ATH in a LLDPE/EVA matrix.
Figure 1 compares typical property data for extruded sheet made from compounds containing varying levels of Fusabond®, versus a control compound containing a silane-based coupling agent. Result show that Fusabond® has a significant influence on elongation at break and, therefore, the flexibility of a compound. Compared with liquid silanes, Fusabond® resins are solid particles, which generally can be handled more easily and dosed more accurately.
Figure 2 shows how heat-aging of the described PE/ATH formulations affects tensile strength, elongation at break, and viscosity (melt flow index).
In a related application, compounds containing polypropylene with approximately 65% calcium carbonate were examined. Figure 3 is a photomicrograph comparing the microstructures of compounds made with and without Fusabond® coupling agent. With coupling agent added at 4% weight, based on the entire compound weight, properties mainly impacted are stiffness, tensile strength and impact strength as shown in Figure 4. Note that impact strength is significantly improved (by almost a factor of 3) at temperatures of -20°C (-4°F) and 4°C (39°F), in the compounds containing Fusabond®.
FIGURE 3. Effect of PP-g MAH (Fusabond® M613-05 on Fracture Toughness of PP/CaCO3)
The above examples show that Fusabond® can be used as a coupling agent for flame retardant fillers in custom wire and cable formulations.
The technical data contained herein are guides to the use of Dow and DuPont resins. The advice contained herein is based upon tests and information believed to be reliable, but users should not rely upon it absolutely for specific applications because performance properties will vary with processing conditions. It is given and accepted at user's risk and confirmation of its validity and suitability in particular cases should be obtained independently. The Dow Company makes no guarantees of results and assumes no obligations or liability in connection with its advice. This publication is not to be taken as a license to operate under, or recommendation to infringe, any patents.
CAUTION: Do not use in medical applications involving permanent implantation in the human body. For other medical applications, request Dow Medical Caution Statement, Document #H-50102.