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Views: 0 Author: Site Editor Publish Time: 2025-07-15 Origin: Site
| Table of Contents |
1. Introduction |
| 2. What Is Polycarbonate (PC)? |
| 3. Material Grades and Additives |
| 4. Comparison: Polycarbonate vs. Other Transparent Plastics |
| 5. Applications of Polycarbonate Injection Molding |
| 6. Design Tips for Polycarbonate Parts |
| 7. Processing Conditions for Polycarbonate Injection Molding |
| 8. Succeeding with Polycarbonate Injection Molding |
Polycarbonate (PC) injection molding is an efficient manufacturing process used to produce durable, transparent, and impact-resistant plastic parts with excellent dimensional stability and optical clarity. This process is ideal for applications that demand both high performance and attractive appearance—such as clear medical housings, automotive headlamp lenses, and premium electronic enclosures—while offering design flexibility and long-lasting durability.
This guide is designed for product designers, mechanical engineers, project managers, buyers, and anyone involved in plastic part development. Whether you’re exploring polycarbonate injection molding for a new project or aiming to improve your existing product’s performance, this article covers everything you need to know—from essential material properties to practical design tips and optimal processing conditions.
Polycarbonate (PC) is a high-performance engineering thermoplastic known for its exceptional impact strength, optical clarity, thermal resistance, and dimensional stability. As an amorphous polymer containing carbonate groups in its molecular structure, PC offers a unique combination of toughness and transparency. Unlike crystalline plastics, it delivers consistent mechanical properties without the need for post-processing, making it ideal for injection molding applications that demand both strength and aesthetics.
PC plastic molding delivers impact strength far beyond many other plastics—up to 850–950 J/m—and maintains toughness even at low temperatures. This resistance to cracking, shattering, and deformation makes it ideal for parts requiring durability and safety.
With light transmittance reaching up to 90%, polycarbonate is perfect for manufacturing clear or translucent components. Unlike acrylic, it also retains toughness in thin-wall designs.
PC molded parts maintain their shape and size consistently, even under mechanical stress or temperature fluctuations, ensuring tight tolerance control.
PC features a high heat deflection temperature (HDT) of around 130°C, supporting long-term use in heat-exposed applications without compromising performance.
PC resin offers excellent flow characteristics—especially in high-flow grades—enabling complex geometries, snap-fit features, and insert molding with ease.
Flame-retardant grades (e.g., UL 94 V-0) and UV-stabilized versions are available, making PC suitable for outdoor environments and safety-critical components.
PC provides high dielectric strength, making it ideal for housings and covers in electronic applications requiring reliable insulation.
PC is hygroscopic, meaning it absorbs moisture from the air. It must be dried at 120°C for 3–4 hours before molding to prevent surface defects such as splay, bubbles, or streaks.
PC has limited resistance to strong alkalis, solvents, and certain hydrocarbons. Design and material selection should take into account the end-use chemical environment.
With a typical price of $3.5–4.5/kg, polycarbonate is more expensive than general-purpose plastics like ABS, which may impact cost-sensitive projects.
Standard PC will yellow and degrade under long-term UV exposure unless protected with UV stabilizers or coatings. For outdoor use, always select UV-resistant grades.
Choosing the right PC material grade is essential for ensuring the performance, durability, and safety of injection-molded parts. Polycarbonate resins come in a wide range of grades, each tailored for specific mechanical, optical, thermal, or environmental requirements. Selecting the proper polycarbonate resin and any necessary additives depends largely on the intended application.
This is the most widely used grade in PC plastic molding, known for its excellent impact resistance, transparency, and dimensional stability. It is ideal for general-purpose enclosures, safety guards, covers, and consumer products.
UV-resistant PC includes additives or coatings that protect the material from yellowing, cracking, or degradation when exposed to sunlight or outdoor environments. This grade is commonly used in lighting covers, outdoor panels, and automotive applications.
For applications that demand fire safety, such as electrical housings, battery covers, or connectors, flame retardant PC is essential. It contains additives that slow down ignition and reduce flame propagation while retaining PC’s mechanical strength.
This grade offers superior clarity and minimal birefringence, making it suitable for lenses, medical device windows, light guides, and transparent shields. In polycarbonate injection molding, it requires highly polished molds and tight temperature control to achieve defect-free parts.
Blends such as PC+ABS combine the impact strength and heat resistance of PC with the improved processability and cost-effectiveness of ABS. These modified PC grades are widely used in automotive interiors, electronics housings, and handheld devices where high mechanical strength and good surface finish are needed.
When choosing the right PC material grade for your polycarbonate injection molding project, consider the following key factors:
Outdoor Use: Select UV-stabilized polycarbonate to ensure excellent weather resistance and prevent yellowing or degradation when exposed to sunlight.
High Heat Environments: For applications requiring durability under elevated temperatures, opt for high heat resistant or flame-retardant PC grades that meet safety standards.
Clear or Optical Parts: Use optical-grade polycarbonate combined with precise molding controls to achieve superior clarity and minimal defects in transparent components.
High Impact with Cost Control: A PC+ABS blend offers a balanced solution, delivering strong impact resistance and improved processability at a competitive cost.
Regulated Industries: For medical, food contact, or safety-critical products, ensure the selected PC grade complies with UL, FDA, or ISO certifications to meet regulatory requirements.
With Alpine Mold’s 23 years of experience in custom polycarbonate injection moulding, we assist customers in choosing the most suitable PC grade for their application—whether it’s for impact resistance, clarity, chemical resistance, or flame retardancy.
Here is the comparison table for Polycarbonate (PC) vs. PMMA (Acrylic) vs. PETG across key properties:
Property | Polycarbonate (PC) | PMMA (Acrylic) | PETG | Key Comparison |
Transparency/Optical Clarity | High (≈90%), slight yellow tint | Excellent (≈92%), glass-like | High (≈90%), no inherent tint | PMMA > PETG ≈ PC |
Impact Resistance | Exceptional (≈850 J/m) | Poor (brittle, shatters easily) | Good (≈100–200 J/m) | PC > PETG (4–8x) > PMMA |
Weather Resistance | Good (requires UV coating to prevent yellowing) | Excellent (UV-resistant, 10+ years outdoor) | Good (better UV resistance than PC) | PMMA > PETG > PC (uncoated) |
Heat Resistance | High (HDT ≈135–140°C) | Moderate (HDT ≈90–105°C) | Low (HDT ≈70–80°C) | PC > PMMA > PETG |
Chemical Resistance | Poor (sensitive to solvents, alkalis) | Poor (attacked by alcohols, ketones) | Excellent (resists oils, disinfectants, weak acids/bases) | PETG > PMMA ≈ PC |
Processability | Difficult (high-temp molding, stress cracking) | Moderate (easy cutting/thermoforming, poor flow) | Easy (thermoforms, bonds, prints well) | PETG > PMMA > PC |
Cost | High (≈$3.5–4.5/kg) | Moderate (≈$2.0–3.0/kg) | Low (≈$1.5–2.5/kg) | PC > PMMA > PETG |
Primary Applications | Safety gear, bullet-resistant glazing, automotive parts | Displays, signage, lenses, aquariums | Food packaging, medical devices, point-of-sale displays | PC: Strength/heat |
Thanks to its unique balance of strength, clarity, and heat resistance, polycarbonate is widely used across various sectors through injection molding. Below are some of the most common and emerging application areas of PC plastic molding:
Industry | Specific Applications | Key Properties Utilized |
Automotive | Headlight lenses, taillight covers, instrument cluster lenses | High transparency, heat resistance (130°C+), impact safety |
Medical | Surgical instrument housings, IV connectors, transparent dialysis components | Sterilizability (autoclavable), clarity, chemical resistance |
Electrical & Electronics | Power socket covers, switch panels, circuit breaker housings | UL94 V-0 flame retardancy, dielectric strength, creep resistance |
Consumer Electronics | Smartphone cases, camera lens mounts, drone propeller guards | Lightweight, impact absorption, dimensional stability |
Industrial & Safety | Machine safety shields, riot helmets/face shields, respirator components | Bullet/impact resistance (ISO 16933), optical clarity, durability |
Emerging Fields | EV battery housings, AR/VR visors, biometric device windows | EMI/RF shielding (when coated), optical precision, thin-wall molding capability |
Designing parts for polycarbonate injection molding requires more than just mechanical understanding—it demands a deep awareness of how PC behaves during the molding process. Due to its rigidity, optical clarity, and moisture sensitivity, poor PC component design can lead to internal stress, warpage, or cosmetic defects. Here are key design tips to ensure your polycarbonate plastic molding projects achieve optimal performance:
In PC plastic molding, uneven wall thickness can lead to warping, voids, or visible sink marks—especially in clear parts. Aim for a wall thickness between 1.0 mm and 3.8 mm and transition gradually if changes are unavoidable. Smooth transitions help maintain dimensional stability and flow consistency during polycarbonate part molding.
Sharp corners concentrate stress and reduce material strength, particularly in high-impact applications. In polycarbonate molding design, use fillets with a minimum radius of 0.5–1.0 mm to improve material flow and reduce the risk of cracking. This also enhances part aesthetics in clear PC components.
Because polycarbonate injection moulding parts can stick to vertical mold walls, apply a draft angle of at least 1–2° on all vertical faces. For textured surfaces, increase the draft to 2–5° to allow smooth ejection and prevent drag marks. Proper draft design improves cycle time and protects part surface quality.
Ribs and bosses strengthen parts without adding excessive weight, but they must be carefully proportioned. In PC plastic part design, rib thickness should be 50–60% of the adjacent wall to avoid sink marks. Bosses should be supported with gussets and have radiused bases to avoid stress concentration in the molding process.
PC has excellent stiffness but limited flexibility compared to materials like PP. When integrating snap-fit features into polycarbonate injection molded parts, allow adequate deflection distance and avoid sharp locking features. This prevents stress whitening or cracking and ensures a longer product lifespan.
For large or complex PC molded components, gate positioning is critical to avoiding weld lines or flow hesitation. Use mold flow analysis tools during early polycarbonate molding design stages to identify ideal gate locations that ensure balanced filling and minimal internal stress.
Design Aspect | Guideline | Purpose |
Wall Thickness | 1.0–3.8 mm | Balanced flow, cooling, structural integrity |
Rib Design | 50–60% thickness; ≤3× wall height | Reinforces strength without sink issues |
Corner Radius | ≥3 mm | Reduces stress concentration & improves mold fill |
Draft Angle | 0.5–1° standard, up to 3° with texture | Eases demolding and prevents surface damage |
Gate Placement | Use simulation tools | Ensures even flow, fewer weld lines & stress points |
Surface Finish | Gloss or matte with extra draft for texture | Balances visual appeal and functionality |
Polycarbonate (PC) is a robust and versatile engineering plastic, but its successful molding depends on strict control of processing parameters. Due to its moisture sensitivity, high melt viscosity, and optical applications, PC plastic molding requires proper drying, optimized temperatures, and precise injection control.
Inadequate control of polycarbonate molding conditions can result in warpage, internal stress, or surface defects like splay and bubbles. For optical-grade PC or high-precision parts, these conditions become even more critical.
Here are the standard polycarbonate injection parameters that Injection molders should follow during the molding process:
Recommended Processing Parameters for PC Injection Molding | ||
Parameter | Recommended Range | Purpose / Notes |
Material Drying | 100–120 °C for 3–4 hrs | Dry to moisture <0.02% using dehumidifying dryer; critical to prevent hydrolysis |
Melt Temperature | 260–310 °C | Avoid exceeding 320 °C to prevent degradation and yellowing |
Mold Temperature | 90–120 °C | Improves flow, clarity, and reduces internal stress; optical PC may require >100 °C |
Injection Pressure | 80–120 MPa (≈800–1200 bar) | Adjust based on part thickness and gating; excessive pressure may induce stress |
Injection Speed | Medium to High | Moderate speed avoids jetting; adjust for thick/thin wall sections |
Back Pressure | 5–15 MPa (≈50–150 bar) | Helps melt homogeneity and air removal |
Screw Speed | 30–80 rpm | Slower speeds reduce shear heating and degradation |
Clamping Force | 4–5 tons/in⊃2; of projected area | Too low causes flash, too high may deform thin-wall PC parts |
Cooling Time | 12–25 sec, depending on wall thickness | Overcooling increases cycle time without improving quality |
Regrind Use | Max 10–20% (must be dried) | Recycled PC should be clean and dry to avoid cosmetic and structural defects |
Purging Material | HDPE or PMMA | Clear purge materials prevent carbon deposits in barrel and nozzle |
Always dry PC pellets thoroughly before molding. Even trace moisture can cause hydrolysis, leading to brittleness or visible surface defects.
Use mold temperature controllers to keep tooling above 80 °C, especially for optical parts like lenses or covers in polycarbonate injection moulding.
Avoid long residence times at high melt temperatures to reduce the risk of yellowing or degradation.
Consider mold-flow simulation for gating and venting design—especially for thick-wall or complex polycarbonate molded parts.
For transparent parts, use polished mold cavities and maintain tight control over all thermal zones.
Succeeding in PC injection molding requires not only selecting the right polycarbonate material but also expert polycarbonate injection mold design and precise control of processing conditions—such as thorough moisture drying, accurate melt and mold temperatures, proper injection speed and pressure, and careful cycle time management. These critical factors ensure dimensional stability, optical clarity, and mechanical strength. Poor control can lead to defects like warpage, surface blemishes, or internal stresses during the polycarbonate plastic molding process.
With over 23 years of experience, Alpine Mold is a trusted plastic mold supplier and injection molding partner offering end-to-end solutions—from detailed DFM analysis to precise molding control. Whether your project involves optical-grade parts or high-impact components, working with an experienced mold maker ensures consistent quality and faster time-to-market. Alpine Mold is ready to support your success in polycarbonate molding with expert knowledge and full technical assistance, contact us today!
