Is CaCO3 the answer to your applications' requirements?

If that question comes up in your shop, then the K show this week is a great place to find your answer. Holly Hansen, VP Technical Services at Heritage Plastics Inc., is at her company's stand, Stand 8aK19, welcoming attendees and helping them with their questions on the use of calcium carbonate in their plastics processing lines.

According to Hansen, identifying the right products for calcium carbonate (CaCO₃)is not that difficult: Just identify a product on which you would like to reduce costs, to more quickly process and to claim it is more environmentally friendly, and you have your target. That probably accounts for every part you make but before you say you want the filler for all of them, there are a few basic attributes of calcium carbonate concentrate/resin blends that you should consider before you select your target products and applications.

Calcium carbonate is a natural mineral with a stable price point, making CaCO₃ concentrates a viable means to combat the fluctuating—but upward—trend in plastics' pricing.  CaCO₃ concentrates are used in blown film, cast film, blowmolding and thermoforming applications. In injection molding, these concentrates also see use, says Hansen, and have generated dramatic cost savings for molders by switching from a fully formulated or press-ready calcium-filled compound to a concentrate, where they combine concentrates with virgin material at the machine to achieve the targeted percentages.

One nice benefit is you might even see energy savings. The enhanced thermal conductivity of the CaCO₃ concentrate/resin blend allows reduced cycle times. Recently a closure molder and customer of Heritage Plastics found that adding the concentrate to one of his products reduced his energy consumption by 10%. Displace a percentage of the virgin plastics component in products plus the decrease in energy use further augments the carbon footprint gains.

Calcium carbonate is basically a fine white powder; once the calcium is dispersed into a plastic system, it will add haze (which explains why it is commonly used as a TiO₂ extender). While displacement of TiO₂ masterbatch with CaCO₃ concentrate offers another cost saving opportunity, CaCO₃ alone is not going to drastically increase the opacity of the product like a TiO₂ colorant. This means that in typically hazy resins such as HDPE, the added haze is not going to be such a dramatic or visual difference at CaCO₃  concentrate.  More importantly, the contact clarity will be maintained, making a blowmolded bottle that will still easily show the level of liquid contained within. 

Calcium carbonate concentrates have a specific gravity of about 1.9 g/cc. To maximize the profitability generated by using the concentrates, the part weight must remain the same.  This means that volume will have to be reduced somewhat with the addition of a CaCO₃ concentrate.  This is easily accomplished in films, thermoformed sheet, and blowmolded parts. The reinforcing benefits of the calcium carbonate allow the gauge or wall thickness to be reduced and physical properties to be maintained.  However, in some cases the cost of the resin being used is high enough that the cost of the added CaCO₃ concentrate will provide a raw material saving even though the product weight increases slightly. And in other cases, the gains in productivity offered by the mineral will offset the need for additional machines for a different cost savings. In other words, it pays to evaluate every potential product on a case-by-case basis to see if the use of a CaCO₃ concentrate can offer advantages.