Contact Angle

What Is Contact Angle?

A contact angle is the angle formed where a liquid droplet meets a solid surface. It reflects the balance of interfacial forces and indicates how well the liquid wets the surface.

In general:

Low contact angle = good wetting (more hydrophilic)
High contact angle = poor wetting (more hydrophobic)

Because wettability strongly affects adhesion and coating uniformity, contact angle measurement is often used as a quick indicator of surface readiness for bonding, painting, printing, or coating.

What Contact Angle Testing Measures

Contact angle testing can provide:

Static contact angle (basic wettability assessment)
Advancing and receding angles (hysteresis; surface heterogeneity and contamination sensitivity)
Surface energy estimation (commonly using multiple liquids and established models)
Surface uniformity comparison across locations or batches
Before/after evaluation for surface treatments (plasma, corona, flame, chemical treatment)

Why Contact Angle Matters

Small changes in surface chemistry can cause major performance issues. Contact angle helps you detect and control problems such as:

poor adhesion or delamination risk
coating defects, craters, orange peel, or poor leveling
inconsistent printing or ink spread
contamination from oils, mold release agents, additives, fingerprints, or cleaning residues
aging or surface recovery after plasma/corona treatment
differences between suppliers or production lots

Typical Application Scenarios

Adhesion & Bonding Readiness

Evaluate whether a substrate is ready for bonding, lamination, or sealing
Compare “good vs. bad” surfaces to identify wetting-related root causes
Verify cleaning effectiveness before assembly or coating

Coatings, Paints & Surface Treatments

Confirm the effect of plasma/corona/flame treatment
Check surface activation stability over time (aging)
Monitor coating uniformity and wetting behavior on different substrates

Printing & Packaging

Verify surface wettability for inks and coatings
Assess film and packaging substrates for printability
Supplier qualification and batch-to-batch consistency checks

Medical Devices & Biocompatible Surfaces

Evaluate hydrophilicity/hydrophobicity for device performance
Verify surface modification or functional coating processes
Support process validation and consistency

Electronics & Precision Components

Monitor surface cleanliness and process residues
Evaluate wetting for conformal coatings, encapsulants, and adhesives
Identify surface conditions that lead to voiding or poor coverage

Common Sample Types

Contact angle measurement is commonly performed on:

polymers and plastic parts (films, sheets, molded components)
coated surfaces (paint, functional coatings, primers)
metals and treated metals
glass and ceramics
membranes and composite surfaces (case-dependent)

Best results require surfaces that are reasonably clean and flat at the measurement spot. Xinbodi can advise on sample preparation and handling to minimize contamination.

What You Will Receive

Every contact angle project is delivered with a clear, structured report that supports engineering and production decisions. A typical deliverable includes:

test objective and sample description
measurement conditions and method (static / advancing-receding, liquids used)
contact angle values (average, range, and repeatability)
images of droplets and measurement locations (as applicable)
surface energy results (when requested)
comparison summary (before vs. after treatment, batch vs. batch, supplier A vs. B)
interpretation and recommendations for process improvement or follow-up testing

Why Choose Xinbodi for Contact Angle Testing?

Practical, application-driven testing strategy (not just numbers)
Experience across coatings, polymers, adhesion, and surface treatment workflows
Support for comparisons and process validation (before/after, lot-to-lot)
Clear reporting and actionable conclusions
Confidential handling of proprietary materials and customer data

FAQs

What is a “good” contact angle?

It depends on the application and liquid. For bonding, coating, or printing, lower angles often indicate improved wetting, but target ranges should be defined based on your materials and process.

Can contact angle identify what the contaminant is?

Contact angle can indicate the presence of contamination or surface change, but it typically does not identify the chemical nature. If identification is needed, Xinbodi may recommend complementary techniques such as FTIR, XPS, or TOF-SIMS.

Do you provide surface energy results?

Yes. Surface energy estimation is available when multiple probe liquids are tested and an appropriate calculation model is used.

How do plasma or corona treatments affect contact angle?

Such treatments often increase surface energy and reduce contact angle (better wetting). However, surfaces can “recover” over time, so stability testing may be valuable.

Have additional questions?