Base resin for compounders and masterbatch makers

How we help compounders and masterbatch makers

Your base resin is most of the pound you sell. A shift in melt flow, viscosity, moisture or yellowness in the base shows up in your compound, then on your customer’s press, and your customer holds you to the property sheet, not your supplier. Many of your grades are approved by a customer, sometimes through an automotive or appliance spec, so changing the base can mean retesting. Bulk deliveries need to land before your silo runs out, and a tight market for one polymer, PA66 being the usual example, can stall a whole product line.

We quote the exact base grade you run now when it is available. When it is not, a polymer chemist compares candidates on the numbers that matter to a compounder: MFR or viscosity, stabilizer and nucleation package, powder or pellet form, moisture, color and ash. We tell you plainly when a substitute needs a lab compound and customer approval before it can go into production. Every prime lot from our suppliers ships with a COA. We quote single gaylords and bulk bags for trials, and bulk truck, railcar and contract volumes for production, shipped to your plant or your toll compounder.

Materials we commonly source for this industry

• Polypropylene: homopolymer and impact copolymer base, reactor powder or pellets, high-MFR and controlled-rheology grades
• Nylon: natural PA6 and PA66 base by relative viscosity, with or without heat stabilizer
• PBT: natural base by intrinsic viscosity, low-IV grades for high glass loading
• Polycarbonate: natural base by MFR for FR, colored and PC/ABS compounds
• ABS and SAN: base for alloys and carriers for styrenic masterbatch
• Polyethylene: high-MI LLDPE and LDPE carriers, HDPE base, PE wax as a dispersing aid
• EVA: carriers by vinyl acetate content and melt index for high-load and universal masterbatch
• Polystyrene: GPPS and HIPS carriers
• POE and POP: ethylene-octene and ethylene-butene impact modifiers for TPO and toughened PP; SEBS for TPE compounds
• Recycled PCR and PIR feedstocks, plus wide-spec and near-prime lots for non-critical compounds

Typical products and the resins behind them

Typical choices only. Formulations and base grades vary by compounder and end use, so confirm properties on the data sheet and COA for the exact grade.

What to specify

Compounders usually buy base resin against a short internal spec: grade name, MFR or viscosity range, form (powder or pellet), stabilizer package, moisture limit and packaging. Many also hold a customer approval that names the base grade or the base family. Send us the grade you run and the values you check on the COA, and we match against those, not just the resin name.

• MFR and viscosity, by the right test. Olefins and PC are bought by MFR: PP at 230°C / 2.16 kg, PE at 190°C / 2.16 kg and PC at 300°C / 1.2 kg (ASTM D1238 or ISO 1133). Nylon is bought by solution viscosity: in North America PA66 is usually sold by relative viscosity in formic acid (ASTM D789), PA6 is often given as relative viscosity in sulfuric acid, and many producers report viscosity number per ISO 307. PBT is bought by intrinsic viscosity, usually about 0.7–1.3 dL/g. Make sure a substitute is reported by the same method and conditions, because the numbers do not convert cleanly. See what melt flow index means.
• Additive package in the base. Ask whether the base is unstabilized, lightly stabilized or fully stabilized, and which antioxidant system it carries. Also ask about nucleating or clarifying agents, antistat (often GMS in PP and PE), slip, calcium stearate or other acid scavengers, and heat stabilizer in nylon. Two bases with the same MFR can behave differently in your compound if the package differs, and an additive you did not expect can interfere with pigment, coupling agent or FR chemistry.
• Powder vs. pellet. Reactor powder (flake) mixes well with fillers and pigments, can cost less, and is often sold with little or no stabilizer, so you add your own. It also has lower bulk density, flows differently in feeders and needs dust control. Pellets feed more predictably. Confirm form, bulk density and particle size before switching, because feeder calibration and side-feed rates change. See bulk density by resin.
• Moisture. Nylon, PBT and PC pick up water and degrade if compounded wet. Nylon base usually ships in moisture-barrier packaging at about 0.2% or less, and PBT and PC are typically dried to a few hundredths of a percent before extrusion. Check the moisture value on the COA, check packaging integrity on arrival, and test by Karl Fischer when it matters. See the resin drying guide.
• Color, yellowness and ash. For natural and light-color compounds, ask for pellet color or yellowness index (ASTM E313 or the producer’s method) and a limit. Ash (ASTM D5630 or ISO 3451) on a natural base should be low and consistent; an unexpected ash value can signal filler, catalyst residue or a mixed lot.
• Carrier match for masterbatch. The carrier should be compatible with the customer’s let-down resin, and its melt index is usually at or above the let-down resin’s so the concentrate melts and spreads first. Too high a melt index, or too much carrier at high let-down ratios, can cut properties or cause die build-up in film. PE carriers suit PE and often PP; EVA carriers give broad compatibility but limit process temperature; engineering resins usually need a carrier of the same polymer.
• Food contact and regulatory statements. For food-contact masterbatch, get the producer’s FDA letter for the exact carrier grade; PE and PP carriers typically reference 21 CFR 177.1520 and EVA carriers 21 CFR 177.1350. Pigments and additives need their own status at your loading and let-down. Customers also ask for REACH SVHC, RoHS and California Prop 65 statements, and sometimes TSCA and heavy-metal statements. See compliance documents to request.
• COA values to check per lot. At minimum: lot number, MFR or viscosity, moisture for hygroscopic resins, and density for PE and EVA. Add pellet color or YI, ash, VA content for EVA, and IV or RV for polyesters and nylons. Compare each lot to your spec, not only to the producer’s range, and keep retains. See what a COA shows and the incoming inspection checklist.

Qualifying a second base resin, and buying it in bulk

A second base resin is cheap insurance, especially for PA66, which has tightened in the past when one of the few plants making its intermediates (adiponitrile and HMDA) went down (see PA66 shortage alternatives). Qualify it before you need it. Run a lab compound with your exact formulation on the candidate, then compare it with your current production on the properties your customer sees: MFR or viscosity of the compound, tensile and flexural properties, notched Izod, HDT, color and, for masterbatch, dispersion. If the properties sit inside your sheet, run a production lot and send samples to the customers whose approval names the base. Automotive and UL-listed compounds usually need a formal change notice or new testing, so start those early. We can quote trial quantities in gaylords or bulk bags so the lab work does not tie up a bulk delivery. See qualifying a second source and our backup source program.

For production, most base polyolefins move in bulk hopper railcars and bulk trucks, and engineering resins more often in bulk bags or gaylords with liners. Tell us your silo capacity, whether you have a rail siding, and your usage per month, and we plan releases around that. Large buyers often price on contract, sometimes tied to a published index; terms depend on the resin and the supplier, so we confirm them on each quote. See how resin is priced. Wide-spec and near-prime lots can lower cost for black, filled or non-critical compounds, but the off-spec property can be the one that matters, the next lot may differ, and they do not belong in food-contact, UL or automotive-spec compounds. We send whatever lot data the seller provides, tell you whether it was measured on that lot, and pass on what the seller reports about why the lot is off-spec, before you buy. If you also need custom color or compounding capacity yourself, see our compounding page.

Guides for this industry

• How to qualify a second resin source: the testing and approval steps, from lab trial to customer sign-off.
• PA66 shortage alternatives: why nylon 66 tightens and what replaces it in which parts.
• Prime vs. wide-spec vs. off-grade: what each quality tier means and when it is safe to use.
• How resin is priced: feedstocks, contract and index pricing, spot lots and freight.
• What a COA shows: the lot values to check and what a COA does not prove.
• Masterbatch vs. precolored resin: how your customers weigh concentrate against precolored compound.
• Force majeure or allocation: a 48-hour plan when a base resin supplier declares.
• Working with PCR resin: variation, odor, gels and color when recycled content goes in.

Common questions

If your grade is not listed, tell us what you run. We source commodity, engineering and specialty resins.