Choosing the right injection molding material starts with how the finished part will actually be used—not simply resin price or which plastic looks strongest on a datasheet.
As a practical starting point, ABS works well for many general housings, PC is often considered when impact resistance matters, PP for chemical resistance and flexibility, nylon for structural and wear applications, and POM for low-friction mechanical parts.
These are starting points, not fixed recommendations. The final resin grade should be selected against the actual operating temperature, mechanical load, chemical exposure, dimensional requirements, appearance, and assembly conditions.
Why Material Selection Matters in Injection Molding
Two molded parts with similar geometry can behave very differently when produced from different polymers.
Before selecting a resin, define what the component will experience:
- Mechanical load
- Operating temperature
- Chemical or solvent exposure
- Moisture
- Impact
- Wear and friction
- Dimensional requirements
- Surface appearance
- Assembly method
- Flame-rating requirements where applicable
Material choice also affects manufacturing. Different polymers have different shrinkage, flow behavior, processing temperatures, moisture sensitivity, and tooling considerations.
This is why material and geometry should be considered together. Our [Injection Molding DFM Guide] explains how wall thickness, draft, ribs, bosses, undercuts, tolerances, and material requirements interact before tooling begins.
FSD Precision’s Injection Molding Service supports custom plastic components from DFM and tooling through molded-part production.
ABS: A Practical Choice for General Housings
ABS (Acrylonitrile Butadiene Styrene) offers a useful balance of toughness, rigidity, surface appearance, moldability, and cost.
It is commonly considered for:
- Electronic housings
- Equipment covers
- Control enclosures
- Structural plastic brackets
ABS is a practical starting point for many general components, but demanding heat or chemical exposure may require a different grade or material.
PC: When Impact Resistance Matters
Polycarbonate (PC) is often considered when toughness and impact resistance are important.
Common applications include protective components, technical housings, electrical parts, and suitable transparent parts.
Depending on the grade, PC may offer higher impact and temperature performance than general-purpose ABS, but chemical compatibility, processing conditions, and molded-in stress should also be considered.
PC/ABS blends are another option when a project needs a different balance of toughness, processing behavior, appearance, and cost.
PP: Lightweight, Flexible and Chemically Resistant
Polypropylene (PP) is widely used where low density, chemical resistance, or flexibility is important.
Typical applications include:
- Fluid-related components
- Covers and clips
- Chemical-contact parts
- Living hinges with suitable grades
A key consideration is dimensional behavior. PP shrinkage combined with large flat areas or uneven walls can contribute to warpage, so geometry and tolerance requirements should be reviewed together with the selected grade.
Nylon (PA): Watch Moisture as Well as Strength
Polyamide (PA / nylon) is commonly used for structural and mechanical components where strength, fatigue resistance, and wear performance matter.
Typical applications include brackets, gears, clips, and bushings.
One important consideration is moisture absorption. Moisture can affect both mechanical properties and dimensions, which deserves additional attention when a component has tight fits or dimensional requirements.
Glass-filled nylon can provide additional stiffness for some applications, but filled grades also introduce different shrinkage, surface, flow, and tooling considerations.
POM: Low Friction for Mechanical Components
POM (Polyoxymethylene / Acetal) is often considered for gears, bushings, guides, and sliding mechanisms because of its low friction, wear resistance, and useful dimensional stability.
Typical applications include:
- Gears
- Bushings
- Sliding components
- Mechanical guides
- Precision mechanisms
These properties make POM useful for many moving components, but wall thickness, shrinkage, gate strategy, tolerance requirements, and the specific grade still influence molding consistency.
Quick Injection Molding Material Comparison
| Material | Primary Advantage | Heat Performance | Chemical Resistance | Key Consideration | Typical Applications |
|---|---|---|---|---|---|
| ABS | Balanced toughness, cost and appearance | Moderate | Application-dependent | Heat and chemical exposure | Housings, covers |
| PC | High impact resistance | Good for many grades | Application-dependent | Chemical compatibility and molded-in stress | Protective and technical parts |
| PP | Chemical resistance and low density | Moderate | Good for many applications | Shrinkage and warpage | Clips, fluid-related parts |
| PA / Nylon | Strength and wear resistance | Good for many grades | Application-dependent | Moisture absorption | Brackets, gears, bushings |
| POM | Low friction and dimensional stability | Good for many grades | Application-dependent | Grade, geometry and processing | Gears, guides, sliding parts |
This table is an early selection reference, not a final material specification. Performance varies by resin grade, fillers, additives, temperature, environment, and part geometry.
Material Family vs. Specific Resin Grade
Selecting a polymer family is only the first step.
Simply specifying “ABS,” “PC,” or “nylon” may not provide enough information for a demanding OEM component because grades within the same family can vary in:
- Impact performance
- Flame rating
- Glass-fiber content
- UV resistance
- Heat performance
- Flow behavior
If a particular resin has already been approved, include the manufacturer and grade designation in the drawing or RFQ.
If the grade remains open, provide the functional requirements instead.
What Changes with Glass-Filled Plastics?
Glass-fiber reinforcement can increase stiffness, strength, dimensional stability, and temperature performance for suitable applications.
It also changes how the material behaves during molding.
Glass fibers tend to orient with material flow, so shrinkage and mechanical behavior may differ between the flow direction and the transverse direction. Depending on the material, geometry, gate location, and processing conditions, this anisotropic behavior can contribute to warpage or directional dimensional variation.
Filled materials can also influence surface appearance, weld-line behavior, flow, and tooling wear.
If a glass-filled grade is likely to be required, identify it before mold design is finalized.
Material-Related Molding Troubleshooting
| Part Issue | Possible Material-Related Factor | What to Review |
| Part warpage | High or uneven shrinkage | Material grade, wall consistency, gate/cooling strategy |
| Dimensions change after molding | Moisture absorption or conditioning | Resin behavior and operating environment |
| Sink near thick features | Localized volumetric shrinkage | Walls, ribs, bosses, packing and cooling |
| Unexpected impact failure | Grade suitability or molded-in stress | Material grade, geometry and processing |
| Visible weld lines | Flow behavior, fillers or meeting flow fronts | Gate strategy, resin/process conditions and cosmetic requirements |
Molding defects rarely have only one cause. Material, geometry, tooling, and processing conditions should be reviewed together before changing the resin.
How Material Choice Affects Tooling and DFM
Material selection should ideally be confirmed before mold manufacturing begins.
Resin characteristics can influence:
- Shrinkage allowance
- Gate design
- Cooling
- Surface requirements
- Tooling wear
For abrasive filled materials, for example, tooling wear becomes a more important consideration. This does not mean every filled-material project requires the same tooling strategy.
Reviewing material, geometry, and tooling together helps reduce late changes. These requirements can also be considered alongside Mold Manufacturing before tooling begins.
What to Send for an Injection Molding Material Review
If the resin has already been selected, provide the manufacturer and grade designation where possible.
If the material is still open, provide:
- 3D CAD model
- 2D engineering drawing
- Operating temperature
- Mechanical loads
- Chemical exposure
- Impact requirements
- Critical dimensions
- Appearance or texture requirements
- Flame-rating requirements where applicable
- Expected quantity
- Assembly information
Providing these details with the RFQ allows the material, geometry, tooling, and production requirements to be reviewed together.
If your project requires material certificates, resin compliance records, traceability, flame-rating documentation, or dimensional inspection reports, identify these requirements with the RFQ so their availability and scope can be confirmed before tooling and production.
Frequently Asked Questions
What are the most common injection molding materials?
Common thermoplastics include ABS, PC, PP, PA/nylon, POM, PE, and many modified engineering grades. The right material depends on the mechanical, environmental, dimensional, appearance, and cost requirements of the application.
Is ABS or PC better for injection molded housings?
It depends on the application. ABS is commonly considered for general housings where appearance, toughness, and cost matter. PC may be considered where higher impact or temperature performance is required, depending on the grade and environment.
Is nylon suitable for precision molded parts?
Yes, for suitable applications. Moisture absorption, resin grade, geometry, and operating conditions should be considered when dimensional stability is important.
Why is POM used for gears and moving components?
POM offers low friction, wear resistance, and good dimensional behavior for many mechanical applications, making it useful for gears, guides, bushings, and sliding components.
When should glass-filled plastics be considered?
Glass-filled grades may be considered when additional stiffness, strength, dimensional stability, or temperature performance is required. Flow behavior, anisotropic shrinkage, surface appearance, and tooling wear should also be evaluated.
Should the material be selected before mold manufacturing?
Preferably yes. Material shrinkage, flow behavior, fillers, and processing requirements can influence dimensional planning and mold design. Changing resin families after tooling is complete may require additional process or tooling review.
Need Help Selecting Material for a Custom Plastic Part?
Not sure whether ABS, PC, PP, nylon, POM, or another engineering plastic is the right fit?
Send FSD Precision your CAD model and drawing together with the operating conditions, quantity, and critical requirements. Our engineering team can review the manufacturing requirements and discuss practical material and tooling considerations as part of the quotation process.
Need help sourcing custom OEM parts?
Send drawings, samples, part numbers, material requirements, quantity, and application details for engineering review.