Dow Brands & Materials: 5 Questions I Wish Someone Had Asked Me About PP, PU, and Foam Board Adhesives - Forward polymer systems for demanding manufacturers

Five Questions About Dow Materials I Learned the Hard Way

If you're sourcing materials for a project—maybe polypropylene (PP) for packaging, polyurethane (PU) for a midsole, or you're staring at a piece of foam board wondering what glue actually works—I've been there. And I've made the mistakes so you don't have to.

Here are five questions that come up constantly, answered with the benefit of a few expensive screw-ups.

1. What actually is 'Dow' in the context of materials? Is it one brand or many?

This was my first surprise when I started handling orders for industrial materials. Most people think of 'Dow' as one big brand, but when you're ordering Dow-branded materials, you're usually looking at a few distinct product families under the Dow umbrella. The key ones for us have been:

Dow Packaging & Specialty Plastics – This is where the PP (polypropylene) and PE (polyethylene) resins live. These are the raw materials for films, containers, and molded parts.
Dow Performance Silicones – The old Dow Corning line. This is where the sealants, greases, and rubber compounds come from.
Dow Polyurethanes – Raw materials for foams, coatings, and adhesives.

I don't have hard data on how many internal divisions Dow has, but from my experience placing orders, you can be talking to completely different customer service teams depending on whether you need a PP resin pellet or a Dow 795 silicone sealant.

2. What do I need to know about PP plastic material before I start ordering?

Oh boy. If I remember correctly, my first order of PP for a packaging client went wrong for one simple reason: I didn't check the melt flow index (MFI).

In my first year (2017), I made the classic specification error: assumed 'polypropylene' meant one thing to every vendor. It doesn't. A PP with a high MFI flows like water when molten—great for thin-wall injection molding. A low MFI is stiffer, better for thicker parts or thermoforming. I ordered the wrong grade. Cost me about $600 in wasted material and a 1-week delay.

Here's what you need to know: Dow produces a range of PP resins (like the Inspire™ line for packaging, or the Developmental grades for specialty uses), but the grade number is everything. If you see a spec sheet, look for:

Melt Flow Index (MFI) – Lower number = thicker viscosity.
Impact resistance – For packaging that falls off a shelf.
Clarity – For see-through containers vs. opaque.

Take this with a grain of salt, but I've found that for general packaging, an MFI of 10-20 g/10 min is a safe starting point for injection molding. For film, you'll want a lower MFI (2-5). I'm not 100% sure on every application, but that's what our vendor specs have consistently shown.

3. I'm working with polyurethane midsole foam. What's the best way to bond it?

I still kick myself for the first PU midsole project I took on. The client wanted a two-part assembly: a PU foam midsole bonded to a rubber outsole. I thought, “Surely any strong adhesive works.” Nope.

The surprise wasn't the bonding strength. It was the chemical reaction. Some standard contact adhesives contain solvents that literally melt the PU foam. The foam crumpled like a sponge in a puddle. 47 pairs, straight to the trash. Total waste: about $450 plus the embarrassment of telling the client.

Put another way: you need an adhesive formulated for low surface energy and foam compatibility. Here's what I've learned works:

Two-part polyurethane adhesives – They bond chemically with the PU foam itself. Almost invisible line.
Water-based contact cements (like Dow's offerings, e.g., the ones in the silicone adhesive range, but specifically the polyurethane-compatible grades) – Lower odor, but slower setting time.

If you've ever had a sneaker delaminate after a week, 9 times out of 10 it was the wrong adhesive. Don't quote me on the exact statistic, but that's been my experience.

4. Can you glue foam board together? And if so, what with?

This one comes up a lot in our shop, especially for signage and display work. The answer is yes, but the devil is in the details.

Foam board (also known as foam core or Gatorboard) is basically a polystyrene or polyurethane foam core with a paper or plastic veneer. The problem? The core is soluble in many common solvents.

In my second year of handling orders, I approved a delivery of 100 foam board signs for an event. The assembly crew used a standard spray adhesive. By the time the glue dried, the foam core had dissolved in spots, leaving ripples visible from 3 feet away. The client asked for a redo. $890, plus a rushed turnaround.

Here's what you need to know: Use a water-based or low-VOC adhesive. Something like a pH-neutral PVA (like Elmer's, but in a spray format) or a specific foam board adhesive from a trusted brand like Dow's silicone range won't work here—silicone isn't the right chemistry for foam board. Instead, look for:

Spray mount (repositionable) – For temporary or light-duty bonding.
Two-part epoxy (low exotherm) – For permanent, structural bonds.
Hot glue (low temperature) – Works in a pinch, but can melt thin foam if too hot.

One tip I learned: test on a scrap piece first. Spray a small area, wait 5 minutes. If the foam surface gets tacky or starts to pucker, that's the wrong glue.

5. How do I choose between different Dow brands for my specific project?

This is the million-dollar question. If you've ever spent an hour on the Dow website feeling lost, you're not alone.

The way I see it, the decision usually comes down to three things:

What property is most critical? – For a PP plastic material used in packaging, clarity and impact resistance are often #1. For a PU midsole, it's flexibility and compression set. For an adhesive for foam board, it's the solvent profile.
What's the processing method? – Injection molding vs. extrusion vs. casting all require different grades.
What's your budget for failure? – If the part can't fail (medical or safety), you pay for the premium Dow grade with full certification. If it's a cosmetic part that can be swapped out later, maybe a developmental grade saves you 20%.

To be fair, Dow's technical documentation is actually very good once you learn to read it. The data sheets usually have a section called 'Suggested Applications' that is gold. I wish I had read those more carefully in 2018.