--- title: "Plastic Material Selection for Injection Molding: The Engineer's Guide | Plastics.com" description: Injection molding is a high-volume process. Material selection decisions made at the prototype stage get locked in when tooling is cut. The cost of getting it wrong scales with volume. Getting material selection right early isn't just good engineering — it's risk management. --- topnavbar Material Selection 12 min read # Plastic Material Selection for Injection Molding: The Engineer's Guide Choosing the wrong resin for an injection molded part doesn't show up in CAD — it shows up in warped parts, failed qualification tests, and tooling that has to be reworked. This guide covers the properties that matter, the five material families that dominate injection molding, where they're used, and the eight mistakes engineers most commonly make. [Search 20,000+ IM Materials →](https://plastics.com/authenticate) [Ask Herman AI](https://plastics.com/authenticate/) ## Why Injection Molding Material Selection Is Different **Injection molding material selection requires satisfying two sets of constraints simultaneously:** the part's performance requirements (mechanical, thermal, chemical, regulatory) and the process requirements of the mold itself (melt flow, shrinkage, cycle time, tooling compatibility). A material that meets every performance spec but has the wrong melt flow for your mold geometry will produce defects no amount of process adjustment can fix. Most general material selection guides treat the manufacturing process as a secondary consideration — something to address after performance requirements are defined. For injection molding, that sequence leads to expensive mistakes. The mold is a fixed asset. If you select a material early in development based on performance properties alone, then discover during tooling that it requires barrel temperatures or injection pressures your equipment can't achieve, you've built cost and delay into the project from the start. The other factor that makes injection molding selection distinctive is the role of geometry. A material that fills a 3mm-wall component easily may not fill a 0.8mm-wall component without weld-line failures or short shots — even at the same injection speed and temperature. Wall thickness, flow length, gate location, and part complexity all interact with material properties in ways that aren't visible in a datasheet comparison. This is why process-specific filtering — not just property filtering — is the right starting point. Finally, injection molding is a high-volume process. Material selection decisions made at the prototype stage get locked in when tooling is cut. Changing material after tooling requires re-validating shrinkage, adjusting processing parameters, and often reworking the mold. The cost of getting it wrong scales with volume. Getting material selection right early isn't just good engineering — it's risk management. --- ## The Key Properties That Govern Injection Molding Material Selection Not all material properties matter equally for injection molding. Six property groups drive the majority of material selection decisions. ### Melt Flow Index (MFI / MFR) Melt Flow Index — also called Melt Flow Rate (MFR) — measures how easily a polymer flows in the molten state, expressed in grams per 10 minutes (g/10 min) under a standardized load and temperature. It is the most process-critical property in injection molding material selection. **High MFI** (≥ 10 g/10 min): Better flow, easier to fill complex geometries, thin walls, and long flow paths. Lower injection pressures required. Typically associated with lower molecular weight and reduced impact strength. **Low MFI** (≤ 5 g/10 min): Higher molecular weight, generally stronger and tougher, but requires higher injection pressures and temperatures. Better suited to thicker parts and simpler geometries. ⚠️ **Don't treat MFI as a ranking.** Higher is not always better. Thin-wall packaging might require an MFI of 20–40 g/10 min. A structural automotive bracket might call for 3–6 g/10 min. The right MFI depends entirely on your part geometry and tooling design. ### Mold Shrinkage Mold shrinkage is the difference between mold cavity dimensions and the final part dimensions after cooling, expressed as a percentage. It directly determines whether your part meets dimensional tolerances — and whether it warps. Shrinkage rates vary significantly across material families and are further affected by glass-fiber reinforcement, processing conditions (injection speed, mold temperature, packing pressure), and part geometry. Semi-crystalline polymers (PP, PA6, PA66, PBT) generally shrink more than amorphous polymers (PC, ABS) and exhibit anisotropic shrinkage — different rates in the flow direction vs. the transverse direction — which is the primary cause of warpage. Mold shrinkage must be provided to the toolmaker before the mold is machined. It cannot be corrected after tooling is built without remachining the cavity — a costly and avoidable outcome. ### Thermal Properties Three thermal properties drive most selection decisions: **Heat Deflection Temperature (HDT)** — the temperature at which a standard bar deflects under a specified load, indicating structural performance at elevated temperature; **Vicat Softening Point** — the temperature at which a needle penetrates the material, a useful proxy for surface stability; and **Continuous Use Temperature** — the long-term service temperature the material can withstand without significant property degradation. For automotive underhood, appliance, and industrial applications, thermal properties are often the primary filter that eliminates material families from consideration. ### Mechanical Properties Tensile strength, flexural modulus, elongation at break, and notched Izod impact strength are the four mechanical properties that most commonly appear as minimum requirements in engineering specifications. Flexural modulus — stiffness — is particularly important for injection molded parts because most structural failure in plastic components is deflection-limited, not strength-limited. Impact strength drives the selection of toughened or rubber-modified grades, especially for parts subject to assembly stresses or drop impact. ### Chemical and Environmental Resistance Chemical resistance must be evaluated for the specific media the part will contact — not for "chemicals" in general. PA6 has excellent resistance to hydrocarbons but poor resistance to strong acids. PP resists a wide range of chemicals but is susceptible to aromatic hydrocarbons and chlorinated solvents. PC is excellent mechanically but sensitive to many cleaning agents, fuels, and certain lubricants. Environmental factors — UV exposure, humidity, temperature cycling — also affect long-term performance and must be specified upfront, particularly for outdoor or automotive applications. ### Regulatory and Certification Requirements Regulatory compliance is not a downstream consideration — it is a primary filter in many applications. UL 94 flammability ratings (V-0, V-1, V-2, HB) are mandatory for most electrical enclosures, connectors, and appliance components. FDA 21 CFR compliance is required for food-contact and medical applications. REACH and RoHS compliance are mandatory for products sold in the EU. Specifying certification requirements at the start of material selection eliminates a large number of otherwise-viable grades from the screening list and prevents late-stage compliance failures. #### Filter by any of these properties on Plastics.com The platform supports filtering across all six property groups — MFI range, shrinkage, thermal performance, mechanical minimums, chemical resistance, and certifications — simultaneously, across 20,000+ injection molding-compatible grades. [Search injection molding materials →](https://plastics.com/authenticate) --- ## The 5 Material Families That Dominate Injection Molding While hundreds of polymer families can be injection molded, five families account for the vast majority of global injection molding volume. Understanding their profiles — strengths, limitations, and the applications where they're preferred — is the foundation of IM material selection. PP ### Polypropylene The most widely used thermoplastic in injection molding globally MFI Range 2–100+ g/10 min Mold Shrinkage 1.0–2.5% HDT (0.45 MPa) 100–150°C Density 0.89–0.91 g/cm³ PP's combination of low density, good chemical resistance, excellent moisture resistance, and competitive cost makes it the default choice for high-volume commodity applications. Glass-filled grades offer improved stiffness and HDT for semi-structural applications. Talc-filled grades provide excellent stiffness-to-weight ratio at lower cost than glass. Select PP when: - Cost efficiency is a primary driver - Chemical resistance (acids, bases, most solvents) is required - Low density is important (automotive weight reduction) - Living hinges are part of the design - Food-contact compliance is needed (FDA grades available) Watch out for: - High shrinkage and warpage tendency, especially in unfilled grades - Poor UV resistance without stabilizer additives - Low service temperature in structural applications - Difficult to bond — surface treatment required for adhesives or paint PC ### Polycarbonate The benchmark for optical clarity and impact resistance MFI Range 4–30 g/10 min Mold Shrinkage 0.5–0.7% HDT (0.45 MPa) 130–145°C Density 1.20 g/cm³ Polycarbonate's defining properties are its exceptional impact strength (10–15× higher than most other thermoplastics at equivalent thickness) and optical transparency. It is an amorphous polymer with low, predictable shrinkage — which simplifies mold design and improves dimensional accuracy. PC is notch-sensitive; avoid sharp corners and V-grooves in part design. Select PC when: - High impact resistance at all temperatures (including sub-zero) is required - Optical clarity or transparency is needed (lenses, light guides, covers) - Tight dimensional tolerances are specified - Higher service temperatures than ABS can provide Watch out for: - Sensitivity to many chemicals, cleaning agents, and fuels (stress cracking) - High processing temperatures requiring adequate drying (100–120°C, 4–6 hrs) - Higher cost than commodity resins - UV degradation in outdoor applications without stabilization PA6 ### Polyamide 6 (Nylon 6) The workhorse structural polymer for demanding mechanical applications MFI Range 8–80 g/10 min Mold Shrinkage 0.6–1.5% (dry) HDT (1.8 MPa) 60–200°C (GF grades) Density 1.12–1.40 g/cm³ PA6 offers an excellent balance of toughness, fatigue resistance, and wear performance. It is naturally self-lubricating and outperforms metals in many sliding and rotating contact applications. The critical variable in PA6 processing and performance is moisture: polyamides are hygroscopic, and moisture content affects both processing (splay, voids, reduced molecular weight) and performance (dimensional change, property reduction). PA6 must be dried to <0.2% moisture before molding. Glass-fiber reinforced grades (PA6-GF30, GF50) offer significantly improved stiffness and HDT. Select PA6 when: - Good mechanical strength with toughness is needed - Wear, friction, and bearing applications - Chemical resistance to oils, greases, and hydrocarbons - Cost-sensitive structural applications (PA6 is typically less expensive than PA66) Watch out for: - Moisture absorption affects dimensions and properties — critical for precision parts - High shrinkage anisotropy in glass-filled grades causes warpage - Poor resistance to strong acids and polar solvents PA66 ### Polyamide 66 (Nylon 66) Higher heat resistance and stiffness than PA6 — the automotive and connector standard MFI Range 5–60 g/10 min Mold Shrinkage 0.5–1.5% (dry) HDT (1.8 MPa) 70–250°C (GF grades) Density 1.13–1.40 g/cm³ PA66 has a higher melting point (255–265°C vs. 220°C for PA6) and higher crystallinity, giving it better thermal performance and stiffness at elevated temperature. It is the dominant material in automotive underhood components, electrical connectors, and any application where thermal performance above 120°C is required. Like PA6, it is hygroscopic and must be dried before processing — typically 80–90°C for 4–12 hours. Select PA66 when: - Service temperatures above 120°C are required (underhood, appliance heating elements) - Electrical connector and housing applications (UL-rated grades widely available) - Higher stiffness and creep resistance than PA6 can provide - OEM automotive specifications call for it by name Watch out for: - Higher processing temperature increases energy cost and requires careful thermal management - More brittle than PA6 in impact applications - Higher cost than PA6; supply chain tighter in some grades PBT ### Polybutylene Terephthalate The preferred choice for electrical, electronic, and precision connector applications MFI Range 10–60 g/10 min Mold Shrinkage 0.5–2.2% HDT (1.8 MPa) 55–210°C (GF grades) Density 1.30–1.56 g/cm³ PBT is a semi-crystalline polyester with fast crystallization kinetics — it is one of the easiest engineering thermoplastics to process in injection molding. It offers excellent dimensional stability, low moisture absorption (making it more dimensionally stable than PA under humid conditions), good dielectric properties across a wide frequency range, and broad chemical resistance. Glass-reinforced PBT is a standard material in electrical connectors, switches, and SMT (surface-mount technology) components. Select PBT when: - Electrical and electronic connectors, sockets, housing (excellent dielectric properties) - Dimensional stability under humidity is required (lower moisture absorption than PA) - SMT solder reflow compatibility needed (high-Tg GF grades available) - Good chemical resistance to fuels, oils, and many solvents Watch out for: - Susceptible to hydrolysis at elevated temperature and humidity — critical for outdoor/automotive - Notch-sensitive in unfilled grades; glass reinforcement required for most structural uses - Must be dried before processing (120°C, 4 hrs) 💡 **Not seeing your material family?** These five families cover the majority of injection molding volume, but the platform includes hundreds of additional families — PEEK, PPS, LCP, TPE, TPU, POM, PMMA, and more. Use the process method filter on Plastics.com to see all 20,000+ injection molding-compatible grades across all families. --- ## Applications by Industry The same material families appear across industries, but the grade requirements differ significantly. Understanding which properties drive selection in each application area helps narrow the shortlist faster. ### Automotive Automotive injection molding spans two very different environments: **interior/exterior** (UV resistance, scratch resistance, low gloss, color consistency) and **underhood** (heat resistance, chemical resistance to coolants and fuels, dimensional stability at 120–150°C+). Interior trim uses high-MFI PP with talc fill or ABS/PC blends. Underhood applications — air intake manifolds, cooling fan modules, sensor housings — require PA66-GF30/50 or PBT-GF30, with some applications moving to PPA or PPS as temperatures push higher. Connector systems are dominated by PA66-GF25 and PA46 for high-temperature requirements. ### Electrical & Electronics The primary drivers in E&E are dielectric properties, UL 94 flammability rating, and dimensional stability. PBT-GF15/30 and PA66-GF30 are the workhorses for connectors and housings. UL 94 V-0 is the standard requirement for most enclosed equipment. Thin-wall connector housings require high-MFI grades — some connector specifications call for MFI > 30 g/10 min to fill 0.3–0.5mm walls. LED lighting components often require high-temperature PBT or PPS for SMT compatibility. For printed circuit board connectors, dimensional precision is critical: low shrinkage grades and annealing protocols matter. ### Industrial & Machinery Industrial applications demand durability over appearance. Wear-resistant grades of PA6 and POM (acetal) are used for gears, cams, bushings, and bearing surfaces. Chemical exposure varies widely — a chemical pump component may see acids that rule out PA entirely and require PVDF or PP. Enclosures for industrial electronics need UL 94 V-0 and impact resistance for tool-prone environments. Glass-filled PP and glass-filled PA66 are common for brackets, housings, and covers. For extreme temperature applications, PPS or PEEK may be specified. ### Connectors & Components Precision connectors have some of the tightest dimensional tolerances in injection molding — often ±0.05mm or tighter on mating features. Low shrinkage, isotropic shrinkage behavior, and minimal moisture sensitivity drive material selection here. PBT, LCP (Liquid Crystal Polymer), and PA66 dominate. LCP is increasingly specified for fine-pitch connectors where both dimensional precision and high-temperature performance (SMT reflow) are required. Flame retardant additives are nearly always required — specify the FR grade explicitly, not just the base polymer. ### Appliances Appliance components span a wide performance range. Outer housings — washer lids, vacuum cleaner bodies, coffee maker shells — are typically PP or ABS, selected for surface quality, colorability, and UV stability. Components near heat sources (inside ovens, around heating elements) require PA66 or PPS. Pump and valve components require chemical resistance to detergents and cleaning agents — glass-filled PP or PA66 depending on temperature. White goods in Europe face RoHS and REACH compliance requirements that must be verified at the grade level, not just the polymer family level. --- ## Property Comparison: The 5 Dominant IM Families This table provides a first-pass comparison across the most common selection criteria. Always validate against specific grade datasheets — property values vary significantly across grades within the same family. | Property | PP | PC | PA6 | PA66 | PBT | | --- | --- | --- | --- | --- | --- | | Mold Shrinkage | 1.0–2.5% | 0.5–0.7% | 0.6–1.5% | 0.5–1.5% | 0.5–2.2% | | HDT @ 0.45 MPa | 100–150°C | 130–145°C | 160–190°C | 200–250°C | 160–200°C | | Tensile Strength | 25–60 MPa | 55–70 MPa | 55–180 MPa | 60–200 MPa | 50–170 MPa | | Impact Resistance | Fair | Excellent | Good | Fair | Fair | | Chemical Resistance | Excellent | Poor (solvents) | Good (oils/HC) | Good (oils/HC) | Good | | Moisture Absorption | < 0.02% | 0.15–0.35% | 2.5–3.5% (equil.) | 2.5–3.5% (equil.) | 0.08–0.12% | | Electrical / Dielectric | Good | Moderate | Moderate | Moderate | Excellent | | Processing Ease | Very Easy | Moderate | Moderate | Moderate | Easy | | Relative Cost | Low | Medium–High | Medium | Medium | Medium | | UL 94 Grades Available | Yes (V-2, V-0 FR) | Yes (V-0, V-2) | Yes (V-0 FR) | Yes (V-0 FR) | Yes (V-0, V-2) | --- ## 8 Mistakes Engineers Make When Selecting Injection Molding Materials These aren't theoretical errors — they are the selection mistakes that recur most often in injection molded part development, each with a predictable failure mode. - 1 #### Choosing Material Only by Price The cheapest resin that appears to meet spec often fails to account for total cost: higher reject rates, more rework, shorter tool life, field failures, or regulatory re-qualification. PP may be 40% cheaper than PA66 by weight, but if the part fails at operating temperature, the cost comparison is irrelevant. Evaluate total cost of ownership — material cost per part plus processing cost, scrap rate, and field reliability — not unit price. - 2 #### Ignoring the Manufacturing Process During Selection Selecting a material based purely on performance properties — without verifying it can be processed on the target equipment at the target geometry — is the most common upstream error. A low-MFI structural grade may require injection pressures the machine can't achieve for a complex geometry. Barrel temperature ranges may exceed the mold's thermal capacity. Material selection and mold design must be developed in parallel, not sequentially. - 3 #### Overlooking Shrinkage and Warpage Semi-crystalline polymers — PP, PA6, PA66, PBT, POM — have higher and more anisotropic shrinkage than amorphous polymers. Engineers who select these materials without flagging shrinkage behavior to the toolmaker end up with molds that don't hold dimensional tolerance or parts that warp on ejection. Glass reinforcement helps reduce total shrinkage but increases anisotropy. Provide shrinkage values in both flow and transverse directions to the toolmaker. Run mold flow simulation before cutting steel. - 4 #### Ignoring Environmental Conditions in Service Most lab datasheets are measured at 23°C and 50% relative humidity — conditions that rarely match actual service. A PA6 part operating at 80°C absorbs moisture and loses stiffness. A PC enclosure in a cleaning environment stress-cracks on contact with certain disinfectants. An outdoor PP automotive cover without UV stabilization chalks and embrittles within 18 months. Define the actual service environment — temperature range, humidity, UV exposure, chemical contact — before shortlisting candidates. - 5 #### Over-Engineering the Material Specifying PEEK for an application where PA66-GF30 meets all requirements adds significant cost with no performance benefit. Over-engineering often happens when engineers copy material specifications from previous, more demanding designs without re-evaluating requirements. It also happens when "high-performance" is treated as inherently safer. Match the material to the requirements, not to the engineer's comfort level with familiar high-end grades. - 6 #### Not Considering Regulatory Requirements Regulatory requirements are often discovered late in development — after a material has been selected, tooling designed, and samples made. Discovering that the selected grade lacks UL 94 V-0 certification, or that it contains a substance restricted under REACH, at qualification stage forces material changes with all downstream consequences. Establish regulatory requirements in the specification document before starting material selection. Filter by certification type at the start, not the end. - 7 #### Ignoring Supply Chain Availability A material that cannot be consistently sourced is not a viable material selection. This is especially true for specialty grades — specific flame-retardant formulations, colored compounds, or low-volume engineering grades that may have minimum order quantities, long lead times, or single-source supply. The 2021 resin shortage demonstrated how quickly supply assumptions can be invalidated. Check stock availability and lead times as part of the selection process, not as an afterthought. Consider alternate grades from multiple suppliers from the start. - 8 #### Not Validating with Prototyping Before Committing to Tooling Running first-article samples from a hardened production tool in a material that hasn't been validated is high-risk. Prototype injection molded parts — from soft tooling, 3D printed molds, or bridge tooling — allow validation of material behavior in the actual geometry before committing to hard tooling. Properties from a flat tensile bar don't reflect weld-line performance, sink marks, gate vestige behavior, or processing windows in your specific geometry. Prototyping is cheap insurance against reworking a production tool. --- ## Find the Right Injection Molding Material Faster The traditional approach to injection molding material selection — downloading PDF datasheets from manufacturer websites, building comparison spreadsheets, and cross-referencing regulatory compliance documents — takes days or weeks and is susceptible to errors from outdated or inconsistent data sources. Plastics.com provides access to over **20,000 injection molding-compatible materials** from leading global suppliers including SABIC, LyondellBasell, DOMO Chemicals, RTP Company, Teknor Apex, Envalior, Radici Group, and MOCOM — all searchable, filterable, and ranked through a single platform. 20,000+ IM-Compatible Materials 14 Property Filter Categories 45,000+ Total Materials on Platform ### Herman AI: Material Selection That Understands Context Herman AI — Plastics.com's domain-trained AI — doesn't return a generic list of materials when you describe an application. It asks clarifying questions: What's the operating temperature? What chemical exposure? What certifications are required? What's the wall thickness? It uses those answers to surface the most relevant candidates, ranked by fit — not by supplier advertising spend. Unlike general-purpose AI, Herman AI is trained on plastics-specific data: material datasheets, supplier documentation, application guides, and processing standards. It won't confabulate a tensile strength value or recommend a material family without accounting for your processing method. Herman AI — Plastics.com Suitability Analysis 1. **Mechanical Properties:** The material exhibits high tensile and flexural modulus, indicating good stiffness, which is beneficial for structural components in automotive applications. Its notched impact strength suggests moderate resistance to impact. 2. **Thermal Properties:** The DTUL values indicate that the material can withstand temperatures up to 200°C under load, making it suitable for under-the-hood applications or other high-temperature environments within vehicles. 3. **Water Absorption:** The material has a relatively high water absorption rate, which could affect its dimensional stability and mechanical properties over time, especially in humid or wet conditions. Automotive Applications The database context indicates that Durethan BKV130 000000 is used in various automotive applications, including General Automotive Applications, Interior, Powertrain & UTH, and Exterior & Body components. Conclusion Durethan BKV130 000000 can be considered suitable for automotive applications due to its favorable mechanical and thermal properties. However, its high water absorption rate should be taken into account when designing components, potentially requiring additional protective measures or design considerations to mitigate the effects of moisture. #### Refine Your Results Select one or more filters to narrow your results Require a specific polymer family? Polyamide (401) Polyamide 6 (3742) Require fillers or reinforcement? Fiber Glass Fiber (10699) Prefer a specific manufacturer? What are you building? (End Use) Automotive Applications General Automotive Applications (7209) Exterior & Body (6905) Powertrain & UTH (5992) Interior (7284) Building & Construction Structural Components (338) Looking for a specific brand? 1 1 ### Filter Across 14 Property Categories Once you've identified candidate material families, the platform's filter system lets you narrow down to the right grade with precision. Property filters span 14 categories: #### Property Filters Physical Mechanical Thermal Electrical Flammability Optical Process RTI Rheology Fill Analysis Sustainability Elastomer Film Storage #### Category Filters Process Method (Injection Molding) Certifications Chemical Resistance Flame Ratings Families Manufacturers Additives Fillers Color Verified UV Protection Availability Filter by MFI range, shrink rate, HDT minimum, UL 94 rating, FDA compliance, chemical resistance profile, and supplier — simultaneously, across 20,000+ IM-compatible grades. Plastics Marketplace Reset Filters 80 materials match your search and filter criteria Delivery: All Products Molding (1) ✕ Tensile Strength (Break): 0 – 6,960 MPa ✕ Tensile Creep Modulus (1000hr): 182 – 3,661.5 MPa ✕ Tensile Creep Modulus (MPa) 182 MPa 3,661.5 Makrolon 2807 Covestro Polycarbonate (PC) Polycarbonate RoHS UL-94 IEC 60695-2-12 IEC 60695-2-13 Tensile: 70 MPa Flame: UL-HB General-purpose, medium-viscosity polycarbonate offering excellent impact resistance and optical clarity for injection molding. Order Now ✓ Ships in 24 hrs DELRIN 500P NC010 Delrin USA, LLC Polyacetal Homopolymer (POM-H) Acetal Ford GM Stellantis UL-94 IEC 60695-11-10 Tensile: 60.82 MPa Flame: UL-HB General-purpose acetal (POM) homopolymer known for good mold release, processability, and balance of stiffness and toughness. Request Info Makrolon 2258 Covestro Polycarbonate (PC) USP-Class-VI RoHS UL-94 ISO-10993 Tensile: 60 MPa Flame: UL-HB Medical-grade polycarbonate with low viscosity, easy mold filling, and USP Class VI compliance for injection molding. Order Now ✓ Ships in 24 hrs Hytrel ECO-B 6356 ECO-B 252 Celanese Copolyester Elastomer (COPE) Elastomer ISCC Mercedes-Benz VW UL-94 FMVSS 302 Tensile: 22.27 MPa Flame: UL-HB Medium modulus, plasticizer-free copolyester elastomer with bio-based content, suited for flexible injection-molded components. Request Info Makrolon 6485 Covestro Polycarbonate (PC) Polycarbonate RoHS UL-94 IEC 60695-2-12 IEC 60695-2-13 Tensile: 65 MPa Flame: UL-V-1 Flame-retardant, medium-viscosity polycarbonate with a good balance of flow and impact resistance for injection molding. Order Now ✓ Ships in 24 hrs Makrolon 6265 X Covestro Polycarbonate (PC) Polycarbonate RoHS UL-94 IEC 60695-2-12 IEC 60695-2-13 Tensile: 65 MPa Flame: UL-V-0 Flame-retardant, low-viscosity PC with UL 94 V-0 rating at 1.5 mm and high flow for complex injection-molded geometries. Request Info ### MaterialRank: Scored Without Bias Every material on Plastics.com is scored by MaterialRank — Plastics.com's proprietary algorithm that evaluates data completeness, property coverage, regulatory documentation, and technical relevance to your application. Materials rank higher because they have better data and better fit — not because a supplier paid for premium placement. This means shortlists reflect actual technical suitability, not database economics. ### Supplier Access Built In The platform includes suppliers across the full material spectrum: SABIC LyondellBasell DOMO Chemicals Envalior RTP Company Teknor Apex Radici Group MOCOM + many more #### Start with Herman AI — describe your application Tell Herman AI what you're designing, what it needs to do, and what environment it will operate in. It will ask the right clarifying questions and return a ranked shortlist — ready to filter, compare, and source from. [Sign up free and start searching →](https://plastics.com/authenticate) ## Frequently Asked Questions What is the most important property to consider when selecting a plastic for injection molding? Melt Flow Index (MFI) is the most process-critical property — it determines whether the material can fill your mold geometry without defects. However, the most important property overall depends on your application. For structural parts, mechanical properties (tensile strength, impact resistance) dominate. For electrical components, you need to evaluate dielectric strength and flammability ratings. For automotive or outdoor applications, thermal and UV resistance drive the decision. The right approach is to first define your non-negotiable requirements, then filter by MFI and processing conditions. What is Melt Flow Index (MFI) and why does it matter for injection molding? Melt Flow Index (MFI), also called Melt Flow Rate (MFR), measures how easily a molten polymer flows under a standard load and temperature — expressed in grams per 10 minutes (g/10 min). For injection molding, higher MFI means the material flows more easily, which is critical for thin walls, long flow paths, and complex geometries. Lower MFI materials require higher injection pressures and are better suited for thicker, simpler parts. Matching MFI to your mold geometry is one of the first screening steps in injection molding material selection. What plastics are most commonly used in injection molding? The five material families that dominate injection molding are: Polypropylene (PP) — the highest volume, used in automotive interior trim, appliances, packaging, and consumer goods; Polycarbonate (PC) — used where optical clarity or high impact resistance is required; Polyamide 6 (PA6) — for structural components requiring toughness and chemical resistance; Polyamide 66 (PA66) — similar to PA6 but with higher heat resistance, used heavily in automotive and connectors; and Polybutylene Terephthalate (PBT) — preferred for electrical and electronic components due to dimensional stability and good dielectric properties. How does shrinkage affect injection molding material selection? Mold shrinkage — the difference between the mold cavity dimensions and the final part dimensions — directly affects dimensional accuracy and warpage. Shrinkage rates vary significantly by material family: PP typically shrinks 1.0–2.5%, PA6/PA66 shrinks 0.5–2.0% depending on moisture content, PC shrinks 0.5–0.7%, and PBT shrinks 0.5–2.2% depending on glass reinforcement. Anisotropic shrinkage (different rates in flow vs. transverse directions) causes warpage. Material shrinkage must be factored into mold design from the start — it cannot be corrected after tooling is built. How can I find the right injection molding material faster? The traditional approach — downloading datasheets from manufacturer websites and manually comparing properties — can take days. Plastics.com provides access to over 20,000 injection molding-compatible materials from leading suppliers including SABIC, LyondellBasell, DOMO Chemicals, RTP Company, Teknor Apex, Envalior, and MOCOM. Herman AI asks clarifying questions about your application and filters across 14 property categories — Physical, Mechanical, Thermal, Electrical, Flammability, Optical, Process, Rheology, Sustainability, and more — plus certifications, chemical resistance, and regulatory compliance. Engineers go from requirements to a ranked shortlist in minutes. What certifications should I look for when selecting a plastic for injection molding? The relevant certifications depend on your application. For electrical and electronic applications, UL 94 flammability ratings (V-0, V-1, V-2, HB) are typically required. For medical or food-contact applications, FDA compliance (21 CFR) is mandatory. For products sold in Europe, REACH and RoHS compliance are required. Automotive parts may require compliance with specific OEM standards. Plastics.com allows engineers to filter materials by certification type so only compliant grades are returned — before you invest time evaluating non-compliant options. ## Find the Right Resin for Your Injection Molded Part Search 20,000+ injection molding-compatible materials. Filter by MFI, shrinkage, HDT, certifications, chemical resistance, and supplier. Ranked by Herman AI — not by who paid more. [Sign Up Free →](https://plastics.com/authenticate) [Book a Demo](https://outlook.office.com/bookwithme/user/c59253b3deac4b01b98dae3596f41043%40plastics.com/meetingtype/f8L6I7Dt1ka1vKcr7isv1A2?anonymous&ismsaljsauthenabled) footer ```json { "@context" : "https://schema.org", "@type" : "Article", "author" : { "@type" : "Organization", "name" : "Plastics.com" }, "description" : "A comprehensive guide to selecting the right plastic material for injection molding, covering critical properties, the five dominant material families, application requirements, and the most common selection mistakes.", "headline" : "Plastic Material Selection for Injection Molding: The Engineer's Guide", "keywords" : "injection molding material selection, plastic material selection, injection molding resin, PP, PC, PA6, PA66, PBT", "mainEntityOfPage" : { "@id" : "https://plastics.com/resources/material-selection/injection-molding", "@type" : "WebPage" }, "publisher" : { "@type" : "Organization", "name" : "Plastics.com", "url" : "https://plastics.com" } } ``` ```json { "@context" : "https://schema.org", "@type" : "BreadcrumbList", "itemListElement" : [ { "@type" : "ListItem", "item" : "https://plastics.com", "name" : "Home", "position" : 1 }, { "@type" : "ListItem", "item" : "https://plastics.com/resources", "name" : "Resources", "position" : 2 }, { "@type" : "ListItem", "item" : "https://plastics.com/resources/material-selection", "name" : "Material Selection", "position" : 3 }, { "@type" : "ListItem", "item" : "https://plastics.com/resources/material-selection/injection-molding", "name" : "Injection Molding", "position" : 4 } ] } ``` ```json { "@context" : "https://schema.org", "@type" : "FAQPage", "mainEntity" : [ { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "Melt Flow Index (MFI) is the most process-critical property — it determines whether the material can fill your mold geometry without defects. However, the most important property overall depends on your application. For structural parts, mechanical properties (tensile strength, impact resistance) dominate. For electrical components, you need to evaluate dielectric strength and flammability ratings. For automotive or outdoor applications, thermal and UV resistance drive the decision. The right approach is to first define your non-negotiable requirements, then filter by MFI and processing conditions." }, "name" : "What is the most important property to consider when selecting a plastic for injection molding?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "Melt Flow Index (MFI), also called Melt Flow Rate (MFR), measures how easily a molten polymer flows under a standard load and temperature — expressed in grams per 10 minutes (g/10 min). For injection molding, higher MFI means the material flows more easily, which is critical for thin walls, long flow paths, and complex geometries. Lower MFI materials require higher injection pressures and are better suited for thicker, simpler parts. Matching MFI to your mold geometry is one of the first screening steps in injection molding material selection." }, "name" : "What is Melt Flow Index (MFI) and why does it matter for injection molding?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "The five material families that dominate injection molding are: Polypropylene (PP) — the highest volume, used in automotive interior trim, appliances, packaging, and consumer goods; Polycarbonate (PC) — used where optical clarity or high impact resistance is required, such as lenses and electronics enclosures; Polyamide 6 (PA6, Nylon 6) — for structural components requiring toughness and chemical resistance; Polyamide 66 (PA66, Nylon 66) — similar to PA6 but with higher heat resistance, used heavily in automotive and connectors; and Polybutylene Terephthalate (PBT) — preferred for electrical and electronic components due to dimensional stability and good dielectric properties." }, "name" : "What plastics are most commonly used in injection molding?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "Mold shrinkage — the difference between the mold cavity dimensions and the final part dimensions — directly affects dimensional accuracy and warpage. Shrinkage rates vary significantly by material family: PP typically shrinks 1.0–2.5%, PA6/PA66 shrinks 0.5–2.0% depending on moisture content, PC shrinks 0.5–0.7%, and PBT shrinks 0.5–2.2% depending on glass reinforcement. Anisotropic shrinkage (different rates in flow vs. transverse directions) causes warpage. This is especially critical in glass-filled grades. Material shrinkage must be factored into mold design from the start — it cannot be corrected after tooling is built." }, "name" : "How does shrinkage affect injection molding material selection?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "The traditional approach — downloading datasheets from manufacturer websites and manually comparing properties in spreadsheets — can take days. Plastics.com provides access to over 20,000 injection molding-compatible materials from leading suppliers including SABIC, LyondellBasell, DOMO Chemicals, RTP Company, Teknor Apex, Envalior, and MOCOM. Herman AI, Plastics.com's domain-trained AI, asks clarifying questions about your application and filters across 14 property categories — Physical, Mechanical, Thermal, Electrical, Flammability, Optical, Process, Rheology, Sustainability, and more — plus categorical filters for certifications, additives, chemical resistance, and regulatory compliance. Engineers go from requirements to a ranked shortlist in minutes." }, "name" : "How can I find the right injection molding material faster?" }, { "@type" : "Question", "acceptedAnswer" : { "@type" : "Answer", "text" : "The relevant certifications depend on your application. For electrical and electronic applications, UL 94 flammability ratings (V-0, V-1, V-2, HB) are typically required — many enclosures and connector bodies specify UL 94 V-0. For medical or food-contact applications, FDA compliance (21 CFR) is mandatory. Automotive parts may require compliance with specific OEM standards (e.g., USCAR for connectors). For products sold in Europe, REACH and RoHS compliance are required. Plastics.com allows engineers to filter materials by certification type so only compliant grades are returned." }, "name" : "What certifications should I look for when selecting a plastic for injection molding?" } ] } ```