In plastic injection molding, the choice of materials is one of the factors that most influences the technical and economic success of a project. It is not just a matter of selecting a polymer that meets the specifications for use, but of integrating multiple variables: behavior during processing, dimensional stability, interaction with the mold, compatibility with post-processing, cost, availability, and, increasingly, environmental impact.
For product engineers and industrial purchasing managers, an incorrect selection can lead to an increase in rejects, changes to molds that have already been manufactured, or inefficient production cycles. At Gestión de Compras, we have participated in a large number of injection molding projects, advising our clients on the most appropriate choice for each part, with an approach based on functional, technical, and economic requirements.
? Main Factors in Material Selection
1. Mechanical and thermal requirements of the part
The mechanical strength required by the end application is the starting point. Properties such as the following must be considered:
- Modulus of elasticity and tensile strength (PA66, PEEK, PC-GF)
- Impact resistance (PC, ABS, TPU)
- Heat deflection temperature (HDT) (PBT-GF, PPS, LCP)
? Real example: For a technical housing in the railway sector, we replaced a standard PC with a PC+ABS UL94 V0 blend to meet thermal resistance requirements and flammability regulations.
2. Geometry and design of the part
Parts with thin areas, metal inserts, ribs, or clips require materials with good flow and low shrinkage. In these cases, behavior during injection is as important as the final properties.
- Materials with low warping: PMMA, SAN, ASA
- High-flow polymers for fine details: PA6, PP copolymer, POM
? Key consideration: reinforced materials (such as PA66 GF30) improve mechanical properties but increase mold wear, so their use must be evaluated from a global cost perspective.
3. Environmental and chemical conditions
Resistance to weathering, humidity, UV rays, hydrocarbons, or chemicals is crucial in sectors such as automotive, agribusiness, or outdoor lighting.
- PP + UV additives for components exposed to sunlight
- PVDF, PBT, or PPS for contact with aggressive chemicals
- TPU or TPE elastomers for flexible parts requiring chemical resistance
? In Gestión de Compras’s projects for outdoor LED lighting, we recommend the use of ASA + PC, combining UV resistance, thermal stability, and aesthetics.
4. Compatibility with post-processing and aesthetics
Not all materials respond equally to post-processing such as painting, chrome plating, laser engraving, or ultrasonic welding.
- Chrome-plated ABS offers good adhesion for electroplating.
- PA66 with glass fiber may have limitations in surface finishes if the mold is not adjusted.
- PMMA provides excellent transparency without the need for post-processing.
? Example: in a visible appliance housing, modified high-gloss ABS was chosen to improve paint adhesion and reduce visual defects due to flow lines.
5. Costs and processing efficiency
In large volumes, the choice of material can represent between 40% and 60% of the total cost of the product. But the cheapest material is not always the most cost-effective. Consider:
- Cycle time: some polymers allow for reduced filling and cooling times.
- Mold life: abrasive fillers accelerate wear.
- Price stability and market availability.
? Frequent strategic decision: opting for a slightly more expensive material with better processability properties and a lower rejection rate is more cost-effective in the medium term.
6. Sustainability and regulatory compliance
European directives promote the use of recycled materials and biopolymers. Commercial alternatives with very good properties already exist:
- Post-industrial recycled PP or ABS for returnable packaging
- PLA or compostable biopolymers in single-use packaging
- REACH and RoHS certified polymers for regulated sectors
? At Gestión de Compras, we help our clients integrate sustainable solutions without compromising quality, validating recycled materials through comparative testing.
? Gestión de Compras’ experience in material selection
With more than 15 years of experience working in sectors such as automotive, electronics, appliances, machinery, and consumer goods, we have developed a technical approach to guide our customers in:
- Technical comparisons between alternative materials
- Evaluation of trade-offs between mechanical properties, cost, and aesthetics
- Selection of materials for multi-cavity molds and short cycles
? Featured case: In a project for industrial machinery covers, switching from standard PC+ABS to flame-retardant PC+ABS improved the UL rating and reduced the rejection rate by 17% after revising the injection gate design.
✅ Conclusion
Choosing the right material for injection molding requires a balance between technical performance, production efficiency, aesthetics, and cost. At Gestión de Compras, we accompany our customers from the design phase, proposing optimized solutions based on our experience in materials and molds.
? Are you developing a new plastic component or looking to reduce costs without compromising quality? Contact our technical team and let us help you find the best solution.
