FlowMarket
Where to source plastic raw materials: FlowMarket is a B2B sourcing network powered by an AI agent. You describe the requirement — polymer type and grade, melt flow index, fillers and additives, the processing method it must run on, colour, required approvals such as food contact or flammability, delivery form and annual volume — and the AI agent matches you with verified resin producers, compounders and distributors, then requests prices and lead times from every match at once. Getting matched is free for buyers.
Sourcing plastic raw materials
A polymer name is a family, not a product. "PP" spans hundreds of commercial grades that differ in melt flow, impact strength, filler content and additive package, and two of them can behave so differently that one will not run on your machine at all.
The detail that ties the material to the machine is the melt flow index, and it follows directly from the process. Injection moulding wants a flowable grade; extrusion and blow moulding want a stiff melt that holds its shape. Specify the process and the rest of the conversation gets much shorter.
Polymer families
Commodity polymers
Polyethylene in high, low and linear low density, polypropylene as homopolymer or impact copolymer, polystyrene, PVC and PET. These carry the bulk of the volume, are priced against monomer contracts and move with feedstock costs. Grade selection here is mostly about melt flow and the additive package rather than about the base polymer.
Engineering polymers
ABS, polyamide 6 and 66, POM, polycarbonate, PBT and blends, chosen where mechanical properties, dimensional stability or temperature resistance matter. Frequently supplied glass-filled — PA6 GF30 being the common example — which raises stiffness and strength substantially and changes shrinkage, tool wear and drying requirements with it.
Specialty, additives and recyclate
- High-performance — PEEK, PPS, PEI and PSU for continuous high temperature and chemical exposure.
- Elastomers — TPE and TPU where flexibility or soft-touch is needed.
- Masterbatch & additives — colour, UV stabilisation, flame retardancy, anti-static, nucleation.
- Recyclates — post-consumer and post-industrial material, increasingly required by regulation.
What to specify when sourcing
These details decide both the grade and the price:
- Polymer & grade — the type plus the specific grade or an existing trade name you are matching.
- Processing method — injection, extrusion, blow moulding, film or thermoforming; it sets the melt flow.
- Melt flow index — with the test conditions, since values are only comparable at the same load and temperature.
- Fillers & reinforcement — glass or mineral content, stated as a percentage.
- Additives — UV, flame retardant with the rating required, anti-static, impact modifier.
- Colour — natural, black, or a colour reference, and whether you compound with masterbatch yourself.
- Approvals — food contact, potable water, medical, UL listing with the yellow card.
- Mechanical & thermal targets — what the part must achieve, if you are open on the exact grade.
- Delivery form & volume — bags, octabins or silo, per call-off and per year.
- Recycled content — required percentage and whether certified recyclate is needed.
Melt flow, drying and the drop-in that is not a drop-in
The most common sourcing failure with polymers is a grade that meets the datasheet and fails on the machine. Melt flow index is usually why. A high-MFI grade flows easily and fills thin injection sections beautifully, and the same material extruded will sag out of the die because the melt has no strength; a low-MFI extrusion grade put into an injection tool will short-shoot. Always name the process alongside the polymer, and quote the melt flow with its test conditions, because a figure measured at a different load and temperature is not comparable. If you are replacing a grade that is being discontinued or resourced for price, give the incumbent trade name — suppliers cross-reference against it far more reliably than against a property list. The second thing worth stating is what happens before the material reaches the screw. Polyamide, polycarbonate, PET and PBT are hygroscopic: they absorb moisture from the air, and moulding them without drying to the specified residual level causes hydrolysis that degrades the polymer, producing splay, voids and parts that fail well below their rated strength. That is a process failure often blamed on the supplier. Ask what drying regime a grade needs and confirm you can meet it. Finally, if recycled content is a target, say so early — recyclate quality varies far more batch to batch than virgin material, and matching a colour or an impact requirement with post-consumer material is a different conversation with a different set of suppliers.