A professional injection molding supplier can process commodity plastics, engineering resins, elastomers, reinforced compounds, and high-temperature polymers. Common choices include PP, PE, ABS, PC, PC/ABS, PA6, PA66, POM, PBT, PET, PMMA, TPE, TPU, PPS, PEI, and PEEK. Processing temperatures can range from about 180°C for PE to nearly 400°C for PEEK, while mold temperatures may range from 20°C to 200°C. Material preparation also changes by resin: PEEK may require moisture below 0.02%, while PA66 and PBT need controlled drying. Glass-filled grades commonly contain 20–50% reinforcement and require wear-resistant tooling and tighter process control.
Material range alone does not show whether a supplier can manufacture a stable part. PP may run with relatively moderate barrel temperatures and forgiving flow behavior, while PC usually needs roughly 260–320°C melt temperatures and careful moisture control. A plant handling both materials needs dryers, temperature-controlled molds, suitable screw designs, accurate dosing, and process records rather than one machine setting reused across resin families.
Commodity thermoplastics usually cover the highest-volume work. PP has a density near 0.90 g/cm³ and is widely used for housings, closures, living hinges, automotive trim, appliance parts, and packaging. Depending on grade, wall thickness, orientation, and molding conditions, its mold shrinkage can commonly fall around 1.0–2.5%, so cavity dimensions cannot simply copy the finished-part CAD size.
PE offers another low-density option, with HDPE typically around 0.94–0.97 g/cm³. Its chemical resistance suits caps, containers, industrial covers, fluid-contact components, and electrical parts. PS provides easier dimensional control for rigid housings and consumer products, while HIPS uses rubber modification to increase impact resistance compared with general-purpose PS.
Moving from commodity resin to engineering plastic raises both performance and processing requirements. ABS typically runs around 200–260°C and gives a useful balance of impact strength, surface quality, dimensional stability, coloring, painting, and plating. It remains common in appliance housings, automotive interiors, electronics, controls, and visible consumer parts.
PC operates at a higher processing temperature and absorbs moisture before molding. Poor drying can cause hydrolytic degradation at processing temperature even when the molded surface appears acceptable. For transparent PC, gate stress, weld lines, trapped gas, scratches, black specks, and flow marks also become inspection points, so optical work requires cleaner material handling than an internal structural component.
Two parts made from the same polymer name can require different settings. A flame-retardant PC, high-flow PC, optical PC, and 20% glass-filled PC should be treated as separate material grades, not as interchangeable versions of “polycarbonate.”
PC/ABS occupies a useful middle range for electronic housings, vehicle interiors, instrument panels, and equipment enclosures. The blend can provide more heat resistance than many standard ABS grades while remaining easier to process than some pure PC grades. Flame-retardant formulations may also be specified for electrical products, where the exact commercial grade and applicable UL rating matter more than the generic resin abbreviation.
Nylon introduces a different issue because PA6 and PA66 are hygroscopic. Moisture affects viscosity, molecular weight, dimensions, and final mechanical performance. A professional molding operation therefore uses controlled drying and closed material handling instead of leaving opened resin beside the press for an entire shift.
Glass reinforcement changes nylon again. PA6-GF30 and PA66-GF30 contain about 30% glass fiber by weight, raising stiffness and reducing creep while increasing abrasion inside the molding system. Screws, barrels, nozzles, gates, runners, and cavity surfaces can wear faster, especially during high-volume production, so hardened steels and wear-resistant components may be specified.
Fiber orientation also changes dimensional behavior. Fibers tend to align with melt flow, creating different shrinkage in the flow and transverse directions. A 0.2 mm flatness requirement on a long glass-filled bracket therefore needs attention to gate position, packing profile, cooling layout, wall transitions, rib design, and fiber direction before steel is cut.
| Material | Typical processing concern | Common application |
|---|---|---|
| PP | 1.0–2.5% approximate shrinkage range | Caps, housings, automotive trim |
| ABS | Moisture and cosmetic surface control | Electronics, appliances |
| PC | High melt temperature and drying | Transparent covers, housings |
| PA66-GF30 | 30% glass fiber and tool wear | Brackets, connectors |
| POM | Thermal residence-time control | Gears, clips, mechanisms |
| PBT-GF30 | Drying and fiber orientation | Electrical connectors |
| PMMA | Contamination and gate stress | Lenses, light guides |
| TPU | Moisture and overmold adhesion | Grips, seals, protective parts |
POM is often selected after nylon when friction and dimensional stability matter more than moisture resistance. It is common in gears, latches, sliders, valve components, clips, and precision mechanisms. Because POM can degrade when exposed to excessive temperature or residence time, barrel temperature, shot size, cycle interruptions, and purge procedures need controlled operating limits rather than broad trial-and-error settings.
Polyesters such as PBT and PET also require effective drying before processing. Glass-filled PBT grades with 20–30% reinforcement are widely used for connectors, switches, sensor housings, coil bobbins, and automotive electrical components because they combine stiffness, electrical insulation, and dimensional stability. Hydrolysis during processing can reduce molecular weight, so appearance alone is not a reliable acceptance test for poorly dried resin.
That requirement leads directly to material-preparation equipment. Hygroscopic polymers are normally dried with dehumidified air rather than simple ambient hot air. Resin suppliers specify their own time, temperature, and acceptable moisture limits, and a capable molder records those conditions by material lot when traceability is required.
PMMA introduces another set of controls. Optical acrylic can transmit more than 90% of visible light in suitable grades and thicknesses, but the finished molded part may still fail visually because of contamination, silver streaks, weld lines, gate blush, stress, or scratches. Highly polished cavities, stable mold temperature, clean conveying, controlled ejection, and protected post-molding handling matter as much as nominal transparency.
Flexible materials require yet another machine setup. TPE and TPU are used for grips, seals, buttons, protective edges, wheels, footwear parts, and soft-touch overmolds. Commercial TPE grades can range from below Shore A 30 to much harder formulations, so “TPE” alone is not enough information for tooling or parameter planning.
Overmolding adds a compatibility question. A soft TPE that bonds well to ABS may not bond adequately to PP without a compatible formulation or mechanical retention feature. Surface contamination, substrate temperature, first-shot cooling time, gate location, and second-shot pressure can affect adhesion; prototype trials are often more useful than assuming that two thermoplastics will chemically bond.
Higher-temperature polymers show the largest equipment gap between molding suppliers. PPS is regularly supplied with 30–40% glass or mineral reinforcement for electrical, automotive, pump, sensor, and thermal-management components. High mold temperatures, abrasive fillers, narrow processing practices, and dimensional requirements make its production less forgiving than molding unfilled PP.
PEEK raises the requirement further. Victrex processing data for several PEEK grades specify drying at 120–150°C for 3–5 hours, residual moisture below 0.02%, barrel or nozzle settings roughly in the 355–395°C range, and mold temperatures commonly around 170–210°C depending on grade. Those temperatures require a molding cell designed for sustained high-temperature operation, not simply a press capable of reaching the required injection pressure.
Victrex also recommends tool temperatures around 170°C for PEEK and higher values for some related high-temperature grades when crystalline molded components are required. A mold controller designed mainly for 80–100°C production may therefore be unsuitable for the job.
Reinforcement extends beyond glass fiber. Commercial compounds can contain carbon fiber, mineral filler, glass beads, PTFE, conductive additives, flame-retardant packages, UV stabilizers, or combinations of several additives. A 30% carbon-fiber PEEK grade will not fill, shrink, wear tooling, or conduct heat like unfilled PEEK, even though both belong to the same polymer family.
Recycled materials also need grade-level review. PCR or PIR versions of PP, ABS, PC, and PC/ABS can be molded successfully, but recycled content can change melt-flow rate, odor, color consistency, contamination level, and mechanical properties. A product using 30% PCR material should therefore be qualified against the actual compound rather than against data generated from 100% virgin resin.
Material capability is tied to mold design because shrinkage, viscosity, reinforcement, crystallinity, and operating temperature affect steel dimensions before production begins. Gate area controls shear and fiber orientation; cooling-channel placement influences warpage; vent depth affects trapped gas; draft affects ejection; abrasive compounds influence steel grade and surface treatment.
A thin-wall PC housing and a thick POM gear may also need different injection-unit sizes even when their shot weights are similar. Excessively large barrels increase residence time, while an undersized injection unit may lack the shot capacity or pressure stability required for the part. Machine tonnage alone therefore provides incomplete information about material capability.
Production documentation provides another useful screening point when choosing a Reliable injection molding partner. Ask whether the plant records the resin manufacturer, exact grade, lot number, colorant, drying condition, machine, mold, cycle parameters, and inspection batch. Programs launched in 2026 may also require customer-specific records for recycled content, flame ratings, medical use, food contact, or automotive material declarations.
For a new project, the supplier should receive the exact resin grade whenever one has already been selected. If no grade exists yet, the useful inputs are operating temperature, chemical exposure, expected load, impact requirement, dimensional tolerance, UV exposure, appearance standard, flame requirement, annual volume, and target service life.
A specification such as “PA66, black” leaves too much open. “PA66-GF30, 120°C short-term operating temperature, UL94 V-0 requirement, ±0.10 mm mounting feature tolerance, 250,000 parts per year” gives the molding engineer enough information to compare commercial grades, evaluate tool wear, estimate shrinkage, choose drying equipment, and plan validation before mold manufacturing begins.