When I took over purchasing for a 145-person food manufacturer in 2020, I thought cutting resin costs meant finding a supplier who could sell plastic parts for less. It took one failed supplier switch in 2023 to teach me otherwise. I still kick myself for comparing only the per-pound resin price. The new molder's part was cheaper, but it needed more material to reach the same stacking strength, so the finished price per part was not lower.
In early 2025, two resin price notices arrived in the same month. The first was for the PET clamshells we use on a fresh berry line. The second was for flexible film. I had 48 hours to accept one of the increases before production locked, so I approved it and started looking for savings in packaging specs.
The problem is that there is no single answer. The right decision depends on whether you are buying rigid PET packaging, using plastic foam for protection, or comparing one film type with another. The question I now ask is not which material is cheapest? but where is the waste in my current package?
Scenario 1: High-volume rigid PET packaging
If you buy clear PET clamshells, bottles, trays, or jars by the truckload, start with grams per unit. Our fresh berry clamshell used to weigh about 24 g. At roughly 80,000 units per week, every 1 g of PET repeated across that volume equals 80 kg of resin per week. That is more than 4 tonnes per year. A price reduction of a few cents per lb cannot compete with design work that removes 2 or 3 g without hurting package strength.
That is why I started the last RFQ with Amcor PET packaging as the baseline. The initial quote was not the lowest. The bigger reason was that Amcor's spec review focused on wall thickness, distribution, and top-load performance before price. In the end, the package design came down from 24 g to 21 g. The resin cost per container fell by roughly 8%, and the packaging performed the same in our line trials.
To be fair, the first trial was not perfect. The lighter base flexed more under wet conditions. I had not put the new clamshell through a cold condensation test. A quick fix took two extra weeks. I should have scheduled that test before committing to the new part.
If you are moving to flexible packaging
Several of our SKUs moved from rigid PET containers to pouches. Resin costs hide in places other than the film itself. Ask the converter whether the laminating adhesive is based on aliphatic resin. Aliphatic resin systems tend to stay clear and have lower odor than some aromatic alternatives, which matters when the film will sit under bright store lighting next to food. In 2024, we rejected a pouch sample because the film yellowed after a month on the shelf; the yellowing came from the adhesive. The aliphatic-resin version cost a little more, but it was cheaper than losing retail display space.
Scenario 2: Plastic foam for protection, not packaging politics
Plastic foam is easy to criticize. I get that. Packaging buyers have to answer for what ends up in recycling bins. But if your product is fragile and gets damaged in transit, a plastic foam insert can reduce total cost.
In a 2024 transit test, a plastic foam insert cost $0.12 per unit and reduced breakage from 4.2% to 0.7%. The insert added roughly $7,200 a year to our packaging budget. The breakage reduction saved more than double that. So glad I did not remove the foam simply because someone on the team wanted to use less plastic. Foam is not the answer unless it earns its place through lower damage claims.
We also started measuring damage as replacement product plus the labor to repack, not only the cost of the broken item. That changes the math. A $12 food product can become a $20 problem after rework and shipping.
The same logic failed on a different line. That product was light, non-fragile, and moved by air. The foam only added dimensional weight. Switching to corrugated separators reduced freight cost without increasing damage. The conclusion is the same either way: foam should be selected for measured loss prevention, not because a protective material makes people feel safer.
Scenario 3: Polyethylene sheeting vs plastic sheeting
Polyethylene sheeting vs plastic sheeting looks like a small wording difference. It is not. Polyethylene sheeting is one type of plastic sheeting. If you order plastic sheeting without naming the polymer, the supplier can choose something that looks similar but behaves differently.
A few years ago, I ordered plastic sheeting as a food-contact liner. The roll cost 11% less than PE, but it did not heat-seal at the same temperature. Our line speed dropped while the operator adjusted settings. I should have written polyethylene sheeting on the purchase order. Which, honestly, is a rookie mistake after three years of buying film.
Use polyethylene sheeting when you need a heat-sealable film, a moisture barrier, or a material that will sit against food. Use general plastic sheeting only for temporary covers, dust barriers, and non-food surface protection. If the supplier accepts plastic sheeting without asking what it touches or how it will be sealed, that is a warning. A good supplier asks. The cheap quote usually does not. Surprise, surprise.
How to tell which situation you are in
Still not sure? I use three filters.
- Is the package rigid, clear, and purchased in high volume? Start with the weight of the current part. If you do not know part weight, a scale is more useful than a price quote. Lightweighting is often the first place to save resin, not changing suppliers.
- Is damage your real problem? Measure the current damage rate first. If shipping damage is low, do not add plastic foam. If damage claims are costing real money, compare the insert against the claim cost.
- Are you buying film or sheet? Name the polymer and the sealing method before requesting quotes. If the film touches food or needs to be sealed on existing equipment, a vague material code is a spec failure.
Amcor publishes public sustainability documents on amcor.com that describe its approach to packaging design. As of early 2025, those documents were current. I find them useful for questions about material reduction, but your own warehouse trial is the decisive test.
Resin costs keep moving. I don't know where PET, aliphatic resin, or PE film prices will be next quarter. I do know the most expensive mistake is switching materials without knowing which packaging scenario you are in.