Commonly Used Transparent Injection Molding Materials

Transparent injection molding is an indispensable process in modern manufacturing, widely applied in fields such as electronic and electrical appliances, automotive parts, medical devices, and packaging containers. Its core advantage lies in realizing the integrated molding of complex structures through the injection molding process while maintaining the material's excellent light transmittance, mechanical properties, and chemical stability. Selecting the appropriate transparent injection molding material directly determines the product's appearance texture, service performance, and production cost. This article will elaborate on the mainstream transparent injection molding materials currently available in the market, providing professional references for enterprises in material selection.

1. Polymethyl Methacrylate (PMMA, commonly known as Acrylic)

· Core Properties: Extremely high light transmittance (92%-93%), close to glass, with excellent gloss; moderate mechanical strength, outstanding weather resistance (UV aging resistance), easy to dye and process; however, poor toughness, weak impact resistance, and not resistant to organic solvents.

· Molding Key Points: Medium melt fluidity; injection temperature (210℃-250℃) and mold temperature (40℃-80℃) need to be controlled to avoid silver streaks and bubbles; low shrinkage rate (0.5%-0.8%) and good dimensional stability.

· Typical Applications: Lamp shades, instrument panel panels, display racks, cosmetic packaging, optical lenses (non-high precision).

2. Polycarbonate (PC)

· Core Properties: Light transmittance reaches 88%-90%, extremely strong impact resistance (20-30 times that of PMMA), wide temperature resistance range (-40℃-120℃), high mechanical strength, and excellent flame retardancy; however, poor scratch resistance, slightly lower processing fluidity than PMMA, and prone to stress cracking.

· Molding Key Points: High injection temperature (260℃-320℃); mold temperature should be controlled at 80℃-120℃; raw materials need to be fully dried (moisture content ≤0.02%) to avoid hydrolysis; shrinkage rate (0.5%-0.7%), suitable for molding complex structural parts.

· Typical Applications: Automotive lamp shades, baby bottles, medical devices (syringes, infusion sets), electronic device housings (mobile phones, computers), security camera lenses.

3. Polystyrene (PS, including GPPS, HIPS)

· Core Properties: GPPS (General Purpose Polystyrene) has a light transmittance of 80%-85%, low cost, good processing fluidity, and high rigidity; but it is brittle and has poor impact resistance. HIPS (High Impact Polystyrene) improves impact resistance through modification, with a slightly lower light transmittance than GPPS (75%-80%) and high cost-performance ratio.

· Molding Key Points: Low injection temperature (170℃-220℃), mold temperature (20℃-50℃), short molding cycle, suitable for mass production; shrinkage rate (0.4%-0.7%), easy to control dimensional accuracy.

· Typical Applications: GPPS is used for food packaging (yogurt cups, disposable tableware), toys, decorative parts; HIPS is used for home appliance housings (refrigerator liners, washing machine panels), office supplies (file folders, pen holders), automotive interior parts.

4. Polyethylene Terephthalate (PET/PETG)

· Core Properties: PET has a light transmittance of 85%-88%, high mechanical strength, good wear resistance, strong chemical corrosion resistance (acid and alkali resistance, oil resistance), and is environmentally friendly and recyclable; but it has a high molding temperature and slow crystallization rate. PETG (Amorphous PET) improves the processing performance of PET, with light transmittance increased to 90%-91%, good toughness, no stress cracking problem, and better weather resistance than PET.

· Molding Key Points: PET injection temperature (260℃-300℃), mold temperature (80℃-120℃), strict drying required (moisture content ≤0.03%); PETG injection temperature (230℃-280℃), mold temperature (40℃-80℃), lower processing difficulty.

· Typical Applications: PET is used for beverage bottles, food packaging containers, electronic component housings; PETG is used for cosmetic packaging (perfume bottles, lotion bottles), medical devices (contact lens cases), building decoration materials (lighting panels).

5. Transparent ABS

· Core Properties: Light transmittance of 70%-80%, combining the high impact resistance, rigidity and processing fluidity of ABS, good surface gloss, and can be subjected to secondary processing such as painting and electroplating; however, general weather resistance, and prone to yellowing when exposed to sunlight for a long time.

· Molding Key Points: Injection temperature (200℃-250℃), mold temperature (50℃-80℃), shrinkage rate (0.5%-0.8%), suitable for products with complex structures that need to balance strength and light transmittance.

· Typical Applications: Home appliance housings (air conditioner panels, microwave oven doors), automotive interior parts (instrument panel trim strips, door handles), electronic equipment accessories (printer housings, router housings).

1. Light Transmittance Requirements: For high-precision optical products (lenses, optical components), PMMA or PC is preferred; for general decorative parts, PS or Transparent ABS can be selected; for food packaging that requires both light transmittance and safety, PET or PETG is prioritized.

2. Mechanical Performance Requirements: Choose PC for products with high impact resistance requirements (e.g., automotive parts, medical devices); select GPPS for applications requiring high rigidity and cost sensitivity; opt for PETG or Transparent ABS when balancing toughness and strength is needed.

3. Service Environment: For outdoor products requiring weather resistance (UV resistance, high-temperature resistance), PMMA, PC, or PETG is suitable; for products in contact with food/pharmaceuticals (complying with standards such as FDA and GB 4806), choose PC, PET, PETG, or GPPS; for products exposed to organic solvents (e.g., cosmetics, cleaning agents), PC or PET is recommended.

4. Processing Conditions: For small-batch production or complex structural parts, select PS or PETG with good processing fluidity; for mass production requiring shortened cycles, PS or PMMA is ideal; high-crystallinity materials (e.g., PET) require specialized molds and drying equipment.

5.Cost Budget: PS or GPPS is suitable for low-cost requirements; PMMA, PC, or PETG is used for mid-to-high-end products; HIPS or Transparent ABS offers a high cost-performance ratio.

1. Poor Light Transmittance & Surface Hazing:

· Insufficient drying of raw materials (increase drying time/temperature);

· Low mold temperature (raise mold temperature);

· Slow injection speed (optimize injection parameters);

· Insufficient mold surface finish (polish the mold cavity).

2. Stress Cracking:

· Excessive moisture content in raw materials (dry the raw materials);

· Overly high injection pressure (reduce pressure);

· Uneven mold cooling (optimize the cooling system);

· Select stress-crack-resistant materials (e.g., replace PET with PETG).

3. Bubbles & Silver Streaks:

· Moisture-absorbed raw materials (fully dry the materials);

· Overly high injection temperature (lower the temperature);

· Poor mold venting (add vent grooves).

4. Dimensional Instability:

· Improper shrinkage rate control (adjust mold dimensions based on material properties);

· Fluctuations in injection parameters (standardize process parameters);

Insufficient mold precision (optimize mold design).

Conclusion

The selection of transparent injection molding materials requires comprehensive consideration of product performance requirements, service scenarios, processing conditions, and cost budgets. As mainstream materials in the market, PMMA, PC, PS, PET/PETG, and Transparent ABS each have unique advantages, covering various application needs from low-end to high-end products and from simple parts to complex structural components. With the continuous innovation of material technology, transparent injection molding materials will develop towards higher light transmittance, stronger mechanical properties, better environmental friendliness, and easier processability, providing strong support for the upgrading of the manufacturing industry.

If you need material selection solutions or technical support for specific products, please feel free to contact our professional team for customized solutions.