Plastic Melting Temperature Chart: A Complete Guide for Injection Molding and Material Selection

Last Thursday, a production line in Dongguan ground to a halt three hours into a scheduled run. The culprit was not a contaminated resin batch or a damaged mold. The temperature controller on the injection unit was set 20°C below the recommended melt range for the PA66 GF30 loaded into the hopper. The result was a cascade of short shots, degraded material, and four hours of unplanned downtime that cost the manufacturer more than the material itself.

If you process engineering plastics, you have faced a version of this scenario. Temperature is the invisible variable that governs flow, surface finish, mechanical properties, and cycle economics. Yet many processors still rely on rough estimates or outdated references when setting barrel and mold temperatures.

This guide delivers a complete plastic melting temperature chart for the thermoplastics that drive modern manufacturing. You will find processing ranges for ABS, PC, PA6, PA66, POM, PP, PE, PBT, and PMMA, along with practical guidance on how to apply this data to material selection, machine setup, and quality control. Whether you are qualifying a new grade or troubleshooting a processing issue, this chart belongs in your technical library.

Why Melting Temperature Is the Foundation of Successful Processing

Every injection molding operation is a controlled exercise in heat management. The polymer must absorb enough thermal energy to transition from a solid pellet to a homogeneous melt with the viscosity required to fill the mold cavity. Too little heat, and the material will not flow completely. Too much heat, and molecular chains begin to degrade, producing volatile byproducts, discoloration, and weakened parts.

The relationship between temperature and material behavior is not uniform across thermoplastics. Crystalline materials such as PA66, PP, and POM exhibit sharp melting points where the crystalline lattice breaks down. Amorphous materials such as ABS, PC, and PMMA do not have a discrete melting point. Instead, they soften gradually as temperature increases past the glass transition temperature (Tg). This fundamental distinction determines how you interpret any plastic melting temperature chart and how you set processing windows on your shop floor.

Beyond simple flow, temperature affects shrinkage, warpage, crystallinity, and weld line strength. A mold temperature set 20°C too low for PA6 can reduce crystalline content and produce a part with lower stiffness and higher moisture absorption than the design assumes. A PC melt held at 320°C for an extended residence time will yellow and lose impact strength before it ever reaches the cavity.

Technical Note: Always distinguish between the material's melting point (a physical property) and the recommended processing temperature range (an operational parameter). The processing range is typically 20-40°C above the melting point for crystalline materials, and 60-100°C above Tg for amorphous materials, to achieve injection-molding viscosity.

Need grade-specific processing parameters for your current project? Request a Technical Data Sheet for detailed melt temperature, mold temperature, and drying requirements for any grade in our portfolio.

Complete Plastic Melting Temperature Chart

The following chart summarizes melting points and recommended injection molding processing temperatures for the core engineering and commodity plastics used in automotive, electronics, appliance, and industrial applications. Values represent typical ranges for unfilled grades. Glass-filled and modified compounds often require adjustments, which are noted below the table.

* Amorphous materials do not exhibit a true melting point. The value shown represents the approximate upper softening or processing initiation range. Glass transition temperatures are lower: ABS (~105°C), PC (~145°C), PMMA (~105°C).

Adjustments for Reinforced and Modified Grades

Glass fiber reinforcement increases the effective heat input required for homogeneous melting. As a general rule, raise the processing temperature by 5-10°C for glass-filled grades compared to their unfilled counterparts. For example:

• PA66 GF30: Process at 290-310°C (unfilled PA66 processes at 280-300°C)

• PP GF30: Process at 220-260°C (unfilled PP processes at 200-250°C)

• PC GF20: Process at 290-330°C (unfilled PC processes at 280-320°C)

Flame-retardant additives can reduce thermal stability. FR-ABS and FR-PC grades often require processing at the lower end of the standard range to prevent additive degradation and surface defects. Always consult the supplier's TDS for exact recommendations.

Impact of Melt Flow Index on Temperature Selection

Within a single material family, melt flow index (MFI) variations affect optimal processing temperature. High-flow grades (higher MFI) can often be processed at slightly lower temperatures because they require less thermal energy to achieve target viscosity. Low-flow grades, common in extrusion or thick-walled injection molding, may need temperatures at the upper end of the range to ensure complete cavity filling.

When Chen Wei, a process engineer at a Shenzhen electronics molder, recently switched from a general-purpose ABS with MFI 5 g/10min to a high-flow ABS with MFI 25 g/10min for a thin-wall housing, he reduced his barrel temperature by 8°C. The change eliminated silver streaking caused by overheating while maintaining fill pressure margins. The adjustment was small, but it originated from understanding that MFI and temperature are interdependent variables.

Melting Point vs. Processing Temperature: What the Chart Does Not Show

A plastic melting temperature chart is a starting point, not a complete setup guide. The gap between melting point and recommended processing temperature exists for several technical reasons that every processor should understand.

Crystalline Materials: Latent Heat of Fusion

Crystalline polymers such as PA6, PA66, POM, PP, and PBT absorb significant latent heat during the phase change from crystal to melt. The energy required to break down crystalline structures is higher than the sensible heat needed to raise temperature alone. Consequently, the barrel must deliver enough total energy to overcome both the temperature increase and the enthalpy of fusion. This is why crystalline materials typically require narrower, higher processing windows and why barrel residence time matters as much as temperature setpoint.

Amorphous Materials: Viscosity Control

Amorphous polymers such as ABS, PC, and PMMA soften over a broad range. Processing temperature is selected based on the viscosity required for the application, not on a discrete phase change. For PC, a melt temperature of 280°C might produce adequate flow for a thick-walled electrical enclosure, while a 0.8 mm thin-wall lighting lens might require 310°C to achieve complete fill. The processing chart provides the range; the part geometry and mold design determine where within that range you should operate.

Mold Temperature: The Overlooked Variable

Mold temperature influences crystallization rate, surface gloss, and residual stress. For crystalline materials, higher mold temperatures promote crystalline growth, which improves stiffness and heat deflection temperature but extends cycle time. For amorphous materials, higher mold temperatures reduce molded-in stress and improve surface appearance. The mold temperatures listed in the chart should be treated as equally important to the melt temperature.

How to Use Melting Temperature Data for Material Selection

Melting and processing temperatures are not merely operational parameters. They are selection criteria that determine whether a material is compatible with your equipment, your mold design, and your downstream assembly processes.

Machine Capability Matching

Not every injection molding machine can reach the temperatures required for high-performance engineering plastics. A general-purpose press with a maximum barrel temperature of 300°C can process ABS, PP, and PA6 comfortably, but it may struggle with PC or high-temperature PA66 grades. Before specifying a material, verify that your equipment's temperature controller, heater bands, and thermocouples can sustain the required range with adequate safety margin.

Multi-Material Assembly Considerations

Products that combine multiple plastic components must account for thermal compatibility during secondary operations. Ultrasonic welding, heat staking, and insert molding all expose one material to temperatures that could deform an adjacent component. If an ABS housing (processing temperature ~240°C) is assembled with a PP clip (melting point ~165°C), the heat staking parameters must stay below PP's softening range to prevent clip failure.

When Maria Santos, a product designer at a Brazilian appliance manufacturer, selected PC for a transparent control panel, she did so knowing the material's 310°C processing limit. However, she also had to specify a PP mounting frame with a 40°C lower continuous service temperature. By referencing the full plastic melting temperature chart for both materials, her team designed a snap-fit assembly that avoided thermal bonding and maintained structural integrity across the appliance's operating envelope.

Selecting materials for a multi-component product? Our material selection guide covers thermal compatibility, weldability, and assembly considerations for common engineering plastic combinations.

Heat Resistance vs. Processing Heat

A common misconception is that materials with high heat deflection temperatures (HDT) are always more difficult to process. While there is a general correlation, it is not absolute. POM has a relatively low melting point (~170°C) but achieves respectable HDT values in structural applications. PA66 melts at ~260°C and delivers excellent under-hood heat resistance. The chart helps you distinguish between the thermal demands of processing and the thermal performance of the finished part.

Processing Temperature Ranges by Application

Different industries have developed material preferences based on a combination of regulatory requirements, performance demands, and processing economics. The following application-specific guidance connects the chart data to real manufacturing contexts.

Automotive Under-Hood Components

Under-hood applications demand materials that withstand sustained temperatures above 120°C while maintaining structural load. PA66 GF30 dominates this space due to its melting point of ~260°C and HDT exceeding 240°C. Processing temperatures of 290-310°C are standard. Mold temperatures should be held at 100-120°C to promote crystallinity and dimensional stability.

PBT GF30 is also common for electrical connectors and sensors in the engine bay. Its lower processing temperature (240-270°C) compared to PA66 can offer cycle time advantages, though HDT is typically lower.

Electronics and Electrical Housings

Consumer electronics favor ABS, PC, and PC/ABS blends. ABS processes at 220-260°C, making it compatible with most general-purpose molding equipment. PC requires higher temperatures (280-320°C) but delivers superior impact resistance and flame-retardant performance for laptop and monitor housings.

Flame-retardant grades in this category require special attention. Halogen-free FR-ABS and FR-PC formulations often have narrower processing windows. Barrel temperatures at the high end of the range can degrade flame-retardant additives, producing plate-out on molds and reduced fire performance.

Home Appliance Panels and Housings

Appliance manufacturers balance appearance, cost, and processability. High-gloss ABS grades for refrigerator and washing machine panels process at 240-260°C with mold temperatures of 60-80°C to achieve mirror-like surfaces. PP copolymers for internal structural components process at 200-240°C, offering cost savings and chemical resistance for detergent-exposed parts.

Precision Mechanical Components

POM homopolymer and copolymer grades are the material of choice for gears, bearings, and conveyor components where low friction and dimensional stability are critical. POM's low melting point (~170°C) translates to processing temperatures of 190-230°C, among the lowest of the major engineering plastics. This reduces energy consumption per part and minimizes thermal degradation risk during extended production runs.

Common Temperature-Related Processing Mistakes

Even experienced processors make errors when translating chart data into machine settings. The following mistakes account for the majority of temperature-related defects in injection molding.

Running Too Cold: Short Shots and Weld Line Failure

Setting barrel temperatures at the low end of the range to reduce cycle time or energy consumption produces melts with excessive viscosity. The material may not fill thin sections completely, or weld lines may form with insufficient strength. In extreme cases, unmelted pellets can carry through the barrel and create weak spots in the finished part.

For crystalline materials, under-temperature processing is particularly damaging because incomplete melting prevents proper crystalline development. A PA6 part processed at 230°C instead of 260°C may exhibit 20-30% lower tensile strength due to poor crystallinity, even if the part looks acceptable on visual inspection.

Running Too Hot: Degradation and Volatiles

Excessive melt temperature breaks polymer chains through thermal oxidation and hydrolysis. The visual symptoms vary by material:

• PA6 and PA66: Yellowing, reduced impact strength, and increased moisture sensitivity

• ABS and PC: Discoloration, surface splay from volatile release, and reduced mechanical properties

• POM: Formaldehyde release (detectable by odor) and severe embrittlement

• PBT: Hydrolytic degradation if moisture content exceeds 0.04% before processing

Residence time compounds the problem. A material held at 300°C for 10 minutes degrades more than the same material held at 310°C for 3 minutes. Hot runner systems and extended idle periods are common culprits.

Ignoring Mold Temperature

Focusing exclusively on melt temperature while neglecting mold temperature is like tuning an engine without checking tire pressure. Mold temperature controls cooling rate, which directly affects crystallinity, shrinkage, and warpage. For PA66 GF30, dropping mold temperature from 100°C to 60°C can increase warpage by 30-50% in large flat parts due to differential crystallization rates.

Inadequate Drying Before Processing

Hygroscopic materials such as PA6, PA66, PBT, and PC must be dried to strict moisture limits before melting. Wet pellets exposed to processing temperatures hydrolyze rapidly, producing splay, bubbles, and weakened parts. The drying requirement is related to processing temperature because higher melt temperatures accelerate hydrolysis if moisture is present.

Recommended drying conditions before processing:

• PA6 and PA66: 80°C for 4-6 hours, target moisture <0.2%

• PBT: 120°C for 3-4 hours, target moisture <0.04%

• PC: 120°C for 3-4 hours, target moisture <0.02%

• ABS: 80°C for 2-4 hours, target moisture <0.1%

When a procurement team at a Turkish automotive supplier recently onboarded a new source of PA66 GF30, they insisted on verifying the supplier's recommended drying protocol alongside the melt temperature chart. The extra step prevented a moisture-related defect that had plagued their previous supplier. Their incoming inspection now checks both pellet appearance and processing documentation before any material enters the hopper.

Looking for processing parameters tailored to your equipment and grade? Contact our technical team for material-specific drying, melting, and mold temperature recommendations.

Where to Find Grade-Specific Temperature Data

The plastic melting temperature chart in this guide provides general ranges suitable for initial material screening and machine capability assessment. For production setup, you need grade-specific data from the Technical Data Sheet (TDS).

What the TDS Provides

A complete TDS lists recommended melt temperature, mold temperature, and drying conditions for the specific grade and formulation. It also includes melt flow index tested at a standard temperature and load, which helps you relate the chart data to actual flow behavior. For modified grades such as glass-filled, flame-retardant, or UV-stabilized compounds, the TDS is the only authoritative source because additive packages can shift processing windows significantly.

Batch-to-Batch Variation

Even within a single grade, slight variations in molecular weight distribution and additive content can affect optimal processing temperature. Reputable suppliers provide a Certificate of Analysis (COA) with each batch, documenting MFI and other key properties. Comparing COA values to the TDS baseline helps processors fine-tune temperature settings for each incoming lot rather than running the same profile for six months straight.

When to Consult Your Supplier

If you are processing a grade for the first time, switching to a new supplier, or encountering defects that standard parameter adjustments cannot resolve, consult your material supplier's technical team. Application-specific factors such as wall thickness, flow length, and filler content all influence the ideal temperature profile. A supplier with genuine technical expertise can recommend starting parameters based on your part geometry and mold design, not just generic chart values.

At Shanghai Wenqin Plastics, we provide complete TDS, MSDS/SDS, and batch COA documentation for all ABS, PC, PA6, PA66, POM, PP, PE, PBT, and PMMA grades. Our technical team supports customers with processing guidance tailored to specific injection molding applications.

Conclusion

Temperature is the single variable that touches every stage of the injection molding process, from pellet melting through cavity filling to crystalline solidification. The plastic melting temperature chart provided in this guide gives you a reliable reference for the core engineering and commodity plastics that power automotive, electronics, appliance, and industrial manufacturing.

Keep these principles in mind as you apply the data:

• Crystalline materials (PA, PP, POM, PBT, PE) have sharp melting points and require precise temperature control to achieve proper crystallinity.

• Amorphous materials (ABS, PC, PMMA) soften gradually and are processed based on viscosity requirements, not discrete phase changes.

• Mold temperature is as critical as melt temperature for part quality, dimensional stability, and cycle economics.

• Grade-specific TDS values always override general chart data when setting up production.

• Proper drying of hygroscopic materials prevents hydrolytic degradation that no temperature adjustment can fix.

Use this chart as your first reference during material selection, machine qualification, and troubleshooting. When you need grade-specific data, processing support, or material samples for evaluation, our technical team is available to help you translate chart values into profitable production parameters.

Ready to put this data to work? Request a quotation for the grades you need, or contact our technical team to discuss processing parameters for your specific application. With sufficient Shanghai-based inventory across all major engineering plastics and established export logistics worldwide, we deliver the materials and documentation your production schedule demands.