Polycarbonate (PC) is the “workhorse” of clear industrial plastics. Valued for its exceptional impact resistance, optical clarity, and thermal stability, it is a staple in medical devices, automotive lenses, and protective electronic housings.
However, bonding polycarbonate presents a unique set of technical hurdles. Its amorphous structure makes it susceptible to stress cracking (crazing) when exposed to certain chemicals, and its high coefficient of thermal expansion can lead to joint failure if the wrong adhesive is selected.
This guide explores the optimal bonding solutions for polycarbonate and how Incure’s technical expertise ensures a fail-safe assembly.
Understanding the Polycarbonate Bonding Challenge
To achieve a structural, long-lasting bond with polycarbonate, engineers must account for three primary factors:
1. Chemical Sensitivity and Crazing
Polycarbonate is an amorphous polymer. When it comes into contact with aggressive solvents or certain monomers found in standard adhesives, the polymer chains can begin to separate, leading to “crazing”—microscopic cracks that compromise both the aesthetics and the structural integrity of the part.
2. Thermal Expansion Differential
Polycarbonate has a high Coefficient of Thermal Expansion (CTE), typically around 70×10−6 m/(m⋅K). If you are bonding PC to a metal (which has a much lower CTE), the adhesive must be flexible enough to absorb the movement as the materials expand and contract at different rates.
3. Surface Energy and Wetting
While PC has a relatively high surface energy (≈42 dynes/cm) compared to plastics like Polypropylene, it still requires an adhesive with excellent “wetting” capabilities to ensure a void-free bond line, especially in optical applications.
Top Industrial Bonding Technologies for PC
| Technology | Why it’s used for Polycarbonate | Key Limitation |
| UV/Visible Light Curable | The Industry Standard. Offers “on-demand” curing in seconds and prevents stress cracking by minimizing monomer exposure time. | Requires at least one substrate to be light-transmissive (clear). |
| Cyanoacrylates (CAs) | Excellent for rapid fixturing of small components. | Can cause “blooming” (white frost) and may induce stress cracking if over-applied. |
| Structural Epoxies | Used for heavy-duty, opaque assemblies requiring maximum chemical resistance. | Long cure times; requires careful formulation to avoid exothermic heat damage. |
How Incure Helps You Select the Right Solution
At Incure, we move beyond “off-the-shelf” recommendations. We utilize a data-driven approach to ensure the adhesive system matches your specific polycarbonate grade and production environment.
1. The “Stress-Free” Product Selection
We prioritize acid-free and low-stress formulations. Our Uni-Weld™ series is specifically engineered to be “PC-friendly,” meaning the monomers are selected to provide maximum adhesion without penetrating the polymer matrix and causing crazing.
2. Matching Flexibility to Substrate
If your assembly involves bonding polycarbonate to stainless steel or aluminum, we recommend high-elongation adhesives.
- Incure Uni-Weld™ 1471 offers an elongation of 310%, acting as a shock-absorbing bridge that prevents delamination during thermal cycling.
3. Optimization for Optical Clarity
For medical or electronic displays, any distortion is a failure.
- Incure Uni-Weld™ 1465 is designed with ultra-low linear shrinkage (≈0.20%). This ensures that as the adhesive cures, it does not “pull” on the polycarbonate, preventing optical distortion or part warping.
4. Integrated Curing Validation
Incure doesn’t just provide the glue; we provide the UV/LED Curing System. We help you determine the exact Joules (J/cm2) and Intensity (W/cm2) required to reach 100% cross-linking, ensuring no residual uncured monomer is left to attack the polycarbonate surface over time.
Featured Incure Solutions for Polycarbonate
- For High-Speed Automated Lines: Uni-Weld™ 1054 – Ultra-fast curing with a high tensile strength of 10,800 psi on PC.
- For Flexible/Medical Tubing: Uni-Weld™ 1471 – ISO 10993 certified, perfect for PC-to-PVC or PC-to-Metal joints.
- For Electronic Potting: Incure Epo-Weld™ – Low-exotherm epoxies for deep-section bonding without heat-distortion.
Industrial Note: Always ensure the polycarbonate surface is free from mold release agents and oils. We recommend a simple Isopropyl Alcohol (IPA) wipe prior to bonding for most Incure products.