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Cost Saving using CaCO3 in blow molding

Cost Saving using CaCO3 in blow molding

Can someone advise with what the Industry norm is for CaCO3 in blow molded items? Say for personal care items or milk jugs or motor oil cans or seats? Do companies add CaCO3 in these items to get a cost saving? How do you achieve this? What I've seen with injection molding is that the overral weight increases and if we are selling by the volume it is a loss compared to selling 100% plastic. Would you reduce thickness while keeping the weight of the item constant? Allow the weight to increase a bit while reducing thickness? How much on average could you load an item before it fails? (I know this depends on the product but what a general rule of thumb?) How about the color? Would you need to add more or less color? Or would this depend on the color and it can go either way?

Thank you for the advise.

RE: Cost Saving using CaCO3 in blow molding

I have a lot of experience in exactly this topic, in particular from my time at Electrolux/Frigidaire who use an enormous amount of calcium carbonate filled polypropylene (tens of thousands of tons). You are right that the filler is more dense so you have to calculate based on cost per unit volume of material not cost per unit weight. The short answer is that adding calcium carbonate does reduce cost in PE and PP and that's why it's used. The calcium carbonate grade would be D50 (average particle size) of 2 microns and D98 (largest particles smaller than) 10 microns. From memory, these should cost around $100/metric ton delivered. Try to find a supplier with a mine near you as transportation costs can dominate.

Typical loading would be 40 weight% and you'll get a big increase in modulus, slightly lower yield strength. If impact resistance decreases too much then add some stearic acid during compounding. You can probably find articles with examples of exact properties you can expect for your PE type or ask the supplier. If you're really interested in filled plastics I have been giving training on the performance and cost for over a decade.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

Webinars on plastics, fillers & impact modification:

RE: Cost Saving using CaCO3 in blow molding

Thank you again for your reply.

I was hoping to test at 5% loading to see what effect it would have. I'm trying to obtain a sample with 1micron particle size (according to the supplier)

If people are loading at 40%, I hopefully can convince my boss to let me load at 5% to see the results.

Thank you again.

RE: Cost Saving using CaCO3 in blow molding

In my experience 1 micron D50 is too fine as it may agglomerate and give terrible properties (impact resistance). I have results to that effect so it's not mere speculation. Go for a 2 micron D50 and 10 micron topcut and consider a surface treated grade (stearic acid) to improve dispersion. At low loadings like you mentioned there will probably be no cost benefit. It cost e.g. $0.20/lb to compound in the filler so you need to add quite a bit to recover that cost and get into savings territory. If you really do want to add 5% then perhaps add it as a concentrate. I believe Heritage Plastics are one of the dominant players in supplying those.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

Webinars on plastics, fillers & impact modification:

RE: Cost Saving using CaCO3 in blow molding

Thank you again for the helpful reply.

We do not have a compounding capability at the moment. We dry blend all material. Thats the main reason I have to go with a concentrate.

I set my target at 5% because it will be easier for me to convince both my boss and production to allow me to do a trial. There is a beleif at my company that Personal Care items must be produced with 100% food grade virgin material + food grade color MB. No filler can be added. I need to disprove this before proceeding.

Also other blow molded items such as stadium seats, motor oil cans, detergent bottles the belief is filler will adversly affect the stregnth/properties. I thought at 5% the effect on properties will be less and then I can evaluate how much I can increase the loading.

I was able to source a 2 micron filler. Once I am able to do the trial I will write back with the results so that this maybe helpful to others.

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