Contents

Plastics Industry
The Practical Guide to Surface Science (2026)

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Written by
Dr Amit Pratap Singh
PhD, Delhi University Post Doc - AIST Japan
Guest Author
Read More
alidad
Reviewed by
Dr Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
Read More
D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Written By

Dr Amit Pratap Singh

Guest Author

PhD, Delhi University

Post Doc - AIST Japan

alidad
Reviewed By

Dr Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

This is a practical guide to Surface Science for researchers working in the Plastics Industry.

In this all-new guide you’ll learn all about:

  • Crucial surface science principles
  • The significance of surface science measurements for the Plastics industry
  • Applicable ASTM Standards & Guidelines

Let’s dive right in.

Plastics

Contents

measurement

Contact Angle Measurement

tension

Surface Tension Measurement

energy

Surface Energy Measurement

sliding angle

Sliding Angle Measurement

realworld

Real World Applications

standardand guide

Standards and Guidelines

Executive Summary

What it covers: How plastics processors, converters and R&D teams use contact angle, surface free energy, surface tension and sliding angle. Each measurement is tied to a real problem, such as corona treatment, ink adhesion, bonding polypropylene or medical tubing QC.
Key insights: Most commodity plastics have low surface energy, so inks, coatings and adhesives wet them poorly until the surface is treated. Water contact angle puts a number on treatment level where a dyne test gives a visual call. Zeus ran its own Gage R&R on the Dropometer and it passed.
Business value: Checking treatment level at the line catches a weak corona or flame step before film is printed, laminated or bonded. One portable kit covers contact angle, surface tension, surface free energy and sliding angle, so it can move between the line and the lab.
Standards to follow: ASTM D5946 and ISO 15989 describe water contact angle on corona treated film. ASTM D2578 and ISO 8296 describe wetting tension with graded test solutions, and ASTM D7541 describes critical surface tension by the Zisman method. ISO 1409 covers surface tension of polymer dispersions and latices by the ring method.
Bottom line: Measure water contact angle after every surface treatment, and surface free energy when a new ink, coating or adhesive fails. Start with the step where parts fail, then book a 15 minute demo to try it on your own film or parts.

Chapter 1: Introduction

In plastics, many quality problems start at the surface. Polyethylene and polypropylene wet poorly until they are treated, so ink beads up and adhesives peel. A corona or flame step that drifts between runs gives film or parts that look fine but fail at the printer or the bonding station.

These are the places where wetting decides yield in plastics work:

The Dropometer contact angle and surface energy kit measures contact angle, surface tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.

We use the following surface properties to understand the behavior of Plastics products and improve their quality.

Chapter 2: Contact Angle Measurement

The contact angle quantifies the wettability of a surface by representing the angle between a liquid’s surface and a solid surface.
Dropletlab Research

Sample Image taken from Droplet Lab Tensiometer.

Young – Laplace Method

  • 1. This method uses the whole drop profile to calculate the contact angle value.
  • 2. This method is only compatible with an axisymmetric drop, which is not always seen in practice because a needle is typically inserted into the drop to increase or decrease the drop volume.
  • 3. This method yields more consistent results than the polynomial fitting method.

Polynomial Method

  • 1. This method uses only a portion of the drop profile to calculate the contact angle value.
  • 2. This method is compatible with both axisymmetric and non-axisymmetric drops.
  • 3. The measurement results of this method are less consistent, as they can be influenced by local surface imperfections.
Dynamic Contact Angle

Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.

Dynamic Contact Angle versus Static Contact Angle

Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.

In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.

This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.

Learn how Contact Angle measurement is done on our Tensiometer

For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide

Contact Angle measurement: The Definitive Guide

Open Benchmark Data: Contact Angle & Surface Energy

These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.

Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.

Glass - DI Water
Glass - DI Water
Nylon - DI Water
Nylon - DI Water
PMMA - DI Water
PMMA - DI Water
Teflon - DI Water
Teflon - DI Water

The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:

● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details

Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.

Explore the full benchmark datasets (contact angle + surface energy)

Measurements were performed with the Droplet Lab Dropometer under controlled laboratory conditions. Treat these values as sanity checks and starting points for your own process targets, not as product specifications.

Chapter 3: Surface Tension Measurement

This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.

Surface Tension Measurement

Sample Image taken from Droplet Lab Tensiometer

Dynamic Surface Tension

Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).

Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.

When to use Dynamic Surface Tension Measurement

Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.

Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.

Learn how Surface Tension measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide

Surface Tension measurement: The Definitive Guide

Chapter 4: Surface Energy Measurement

Surface energy refers to the energy required to create a unit area of a new surface.
231

Sample Image taken from Droplet Lab Tensiometer

Learn how Surface Energy measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide

Surface Energy measurement: The Definitive Guide

For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.

Dataset Hub

Chapter 5: Sliding Angle Measurement

The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.

sliding angle 1

Sample Image taken from Droplet Lab Tensiometer

Learn how Sliding Angle measurement is done on our Tensiometer

For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide

Sliding Angle Measurement: The Definitive Guide

Chapter 6: Real-World Applications

Within the Plastics industry, several case studies exemplify the advantages of conducting surface property measurements.

UV Responsive, Bottlebrush Structured Silicone Elastomers: Synthesis, Healing, and Application

This study reports a family of bottlebrush-structured silicone elastomers produced via a solvent-free synthesis combining hydrosilylation and thiol-ene chemistry. Using thiol-functional PDMS helps suppress unwanted side reactions involving Si-H during hydrosilylation. The materials incorporate dynamic covalent C-S bonds that reversibly cleave under UV light, enabling rapid forming and self-healing when illuminated. Despite being ultrasoft, the elastomers can heal in seconds and recover toughness to as high as 86% of the original value. The synthesis also enables efficient grafting of small silane molecules as “spacers” on the polymer backbone; spacer steric effects tune stiffness, while functional spacers (e.g., fluorinated groups) tune surface properties. The authors illustrate potential uses including DLP 3D printing, UV-triggered healing, and recycling.

Role of the Droplet Lab Goniometer

The Droplet Lab Dropometer was used to quantify how small-molecule spacer chemistry changes the silicone elastomer’s surface wetting behavior via water sessile contact angle measurements. Specifically:

  • Films of fluorinated-spacer elastomers (DMFS series) and amine-containing spacer elastomers (TMAS series) were tested to compare hydrophobicity vs. hydrophilicity.
  • The instrument captured droplet profiles and computed contact angles using Droplet Lab Sessile software “smart mode” (Young-Laplace + polynomial fitting), providing an objective metric for surface modification effects (Section 2.2.7, page 2).

This is the paper’s primary quantitative surface-property measurement, supporting claims about self-cleaning and repellency (Figure 4b-c, pages 5-7).

Key Findings

  • Spacer chemistry can tune silicone elastomer surface wetting measurably, even at very low functional group incorporation.
  • Adding a fluorinated spacer (DMFS) increases water contact angle substantially:
    • baseline (no fluorine) reported at ~98.4°,
    • ~118° with 0.32% fluorine graft ratio,
    • up to ~125° at 1.56% fluorine graft ratio (discussion around Figure 4c).
  • Adding an amine-containing spacer (TMAS) shifts the surface toward greater hydrophilicity, with the highest TMAS content decreasing contact angle by ~10° compared with the non-functional reference (discussion around Figure 4c).
  • A qualitative self-cleaning demonstration supports the wetting results: milk droplets left visible traces on a fluorine-free surface (TES-1) but not on the fluorinated sample (DMFS-1) (Figure 4b).
  • Beyond surface tuning, the material platform also combines UV-triggered softening, rapid self-healing, and printability, enabling manufacturing-friendly routes for soft polymer parts.

Why It Matters

For plastics and elastomer manufacturers, this work shows a practical route to engineer silicone-based polymer surfaces without changing the base polymer family, using modular spacer grafting and then verifying performance with contact angle as a fast, QC-friendly metric. Being able to dial wetting behavior upward (more hydrophobic) or downward (more hydrophilic) supports real decisions such as surface specification setting, self-cleaning/anti-fouling design, compatibility with adhesives/coatings/inks, and process optimization for UV-curable, additive-manufactured elastomer components.

Method Snapshot

  • Sample: Blade-cast elastomer films on glass, ~100 µm thick (fluorinated DMFS and amine TMAS spacer variants).
  • Droplet & angle type: ~5 µL DI water, static sessile contact angle measured from captured droplet shape using Droplet Lab Sessile software (“smart mode”).
  • Temperature / surface tension: Not explicitly stated (ambient assumed); water surface tension not reported/measured in the paper.

Data Note

Figure 4c (page 5) reports the water contact angle trends for TES-1 vs. DMFS- and TMAS-modified elastomers (data generated using the Droplet Lab Dropometer, per Section 2.2.7 on page 2).

Figure

Citation (APA Format)

Huo, M., & Clarke, D. R. (2025). UV responsive, bottlebrush structured silicone elastomers: Synthesis, healing, and application. Macromolecules. Advance online publication.

View Publication →

Packaging film performance

Packaging film must take ink, adhesive and coatings at line speed. Water contact angle on corona treated film, as described in ASTM D5946 and ISO 15989, gives a treatment number you can trend by roll and by shift.

Many converters still use test solutions under ASTM D2578 or ISO 8296. Contact angle is an alternative to those solutions, not the same method, so correlate the two on your own film first. When ink beads up even on treated film, check the ink as well; see ink beading and viscosity troubleshooting.

Packaging film performance

Medical device plastics and biocompatibility

Medical tubing, catheters and elastomer parts often need a coating or bond to stick, or a surface that controls how fluids meet it. Contact angle checks the surface state before those steps. It is a surface check, not a biocompatibility test.

Zeus, a US polymer extrusion and custom tubing maker, uses the Dropometer for contact angle on extruded tubing. Zeus ran its own Gage R&R on the Dropometer and it passed; see the Zeus polymer extrusion case study. At the Harvard shared facility, water contact angle on UV responsive silicone elastomers rose with fluorine content; our self healing elastomer use case covers similar materials.

Medical device plastics and biocompatibility

Hydrophobic micro textured plastic parts

Micro features machined or molded into a plastic surface can make it repel water far more than the flat polymer. Contact angle and sliding angle show whether drops sit on top of the texture or soak into it.

Client studies show the effect. Electrospun polystyrene fiber mats read as highly hydrophobic, and the authors link higher angles to rougher fibers. In a University of Toronto thesis, most polypropylene mask layers read higher than flat polypropylene.

Hydrophobic micro textured plastic parts

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Chapter 7: Standards and Guidelines

In an industry where precision reigns supreme, how can Plastics manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.

ASTM D2578, Wetting Tension of Polyolefin Films (Dyne Pen / Dyne Solution Method)

What it is

Standard test method for determining wetting tension (dynes/cm ≈ mN/m) of polyethylene (PE) and polypropylene (PP) film surfaces in air by applying liquids of known surface tension and identifying the highest value that “just wets” the surface within a defined time. Use it as the official discrete “dyne level” gate, and (if desired) pair it with separately reported fixed-time contact angle / surface free energy trending for a continuous numeric early-warning signal

When to use it

Production dyne spec verification

Use as the QA/QC decision method when PE/PP film “dyne level” is the line spec tied to print, coating wet-out, or lamination reliability.

Calibration anchor for supplemental trending

Use periodic D2578 checks to calibrate and validate any continuous contact-angle/SFE measurements you run between dyne checks (so you don’t replace the standard with a different method).

In-scope / Out-of-scope

In scope
  • PE and PP films evaluated in air
  • Wetting tension determination using dyne solutions (often implemented via dyne pen/swab practices)
  • “Just wets” judgment based on whether the applied solution remains a continuous film vs retracts/beads within a defined dwell time
  • Discrete reporting as a dyne level (e.g., highest passing dyne, or pass/fail versus a specified dyne requirement)
Out of scope
  • Contact angle measurements (sessile-drop, advancing/receding) and surface free energy (SFE) modeling; report these as supplemental methods, not as D2578 results
  • Predicting end-use performance (ink adhesion, coating defects, lamination bond strength) without product-specific correlation testing
  • Non-polyolefin substrates (or test conditions outside the method intent, such as testing in liquids or non-ambient environments)
  • Web mapping/uniformity metrics as formal D2578 requirements (you can add mapping internally, but it’s not the D2578 determination)

Minimum you must report (checklist)

  • Film identification: PE/PP type/grade (if known), construction, thickness, and any relevant additive/treatment history
  • Treatment details: corona/plasma/flame type and key process conditions (if available) + time since treatment at test
  • Dyne solutions: nominal dyne values used, manufacturer/lot, and storage/expiration status
  • Application method: pen/swab/drop technique and any controlled technique notes (stroke length, pressure guidance, etc.)
  • Dwell-time criterion: the hold time used for the “just wets” decision (e.g., ~2 s)
  • Pass/fail definition: what “just wets” means in your SOP (continuous film vs beads/breaks) and how the final result is chosen (highest passing dyne)
  • Replication & locations: number of test spots and where on the web/roll they were taken (edges/center/splice zones; mapped vs single-point)
  • Results & context: highest passing dyne (or pass/fail versus spec), plus date/time, operator, and any anomalies/retests

ASTM D2578 results come only from the dyne-solution “just wets” determination; do not label contact angle or SFE numbers as “ASTM D2578.” If you use contact angle/SFE tools as a companion, document them as a supplemental method (fixed timestamp + defined liquids/model) and keep them correlated to D2578 and downstream outcomes

How to interpret results (guardrails)

  • Higher passing dyne generally = higher wettability/more process margin, but it remains a proxy; downstream adhesion/bond strength still needs confirmation for your materials and inks/adhesives.
  • Borderline results are sensitive to operator technique and timing; standardize dwell time, training, lighting/handling controls, and use replicate spots to reduce subjectivity.
  • Keep D2578 as the official spec gate; use fixed-time contact angle (e.g., [email protected] s median + IQR) and optional SFE trends as an early drift alarm, reported separately and only used as a gate after internal calibration.
  • If dyne stays “passing” but numeric trends drift (WCA rising and/or IQR widening), treat it as an early warning for dose drift, non-uniformity, or contamination; then confirm with a D2578 check and application-relevant testing.
Read our ASTM D2578 page View the official ASTM D2578 Standard

Now It’s Your Turn

We hope this guide showed you how to apply surface science in the Plastics industry.

Now we’d like to turn it over to you: 

  • What’s the #1 real-world application from this post that you want to try first?
  • Perhaps we missed a relevant industry standard.
  • Or maybe you have a question about something you read.

Feel free to leave a comment below—we’d love to hear from you.

Frequently asked questions

Which surface measurement should a plastics lab start with?

Start with water contact angle after every surface treatment, since it shows treatment level quickly. Add surface free energy when a new ink, coating or adhesive fails. Use surface tension for inks, coatings and latices, and sliding angle for textured or repellent parts. Our contact angle and surface energy guides explain each method.

Can contact angle replace dyne pens or test solutions?

Not as the same test. ASTM D2578 finds the strongest test solution that stays wet on the film, which gives a dyne level. The Dropometer does not run that swab test. It gives a water contact angle on the same film, which is a number rather than a visual call. If a customer requires a D2578 result, run a correlation study on your own film first.

How do I check corona treatment level on film?

Measure water contact angle on the treated side, as described in ASTM D5946 and ISO 15989. A lower angle means stronger treatment. Test several spots across the web, since treatment can vary from edge to centre. Recheck stored rolls before printing, because treatment can fade over time. Our corona treatment use case sets out the test plan.

How do I work out the surface free energy of a plastic?

Measure contact angles of two or more probe liquids, usually one polar and one apolar, then calculate surface free energy from them. Our contact angle to surface energy calculator does the sums. ASTM D7541 describes a related value, the critical surface tension, from a Zisman plot of several liquids. Keep the same liquids and model when you compare results.

Which standards apply to plastics wetting and surface tension?

ASTM D5946 and ISO 15989 cover water contact angle on corona treated film. ASTM D8597 covers contact angle with portable goniometers. ASTM D2578 and ISO 8296 use test solutions, and ISO 1409 uses the ring method for latices. The Dropometer uses sessile drop and pendant drop, so check which method your specification names.

Can contact angle help with polymer microfluidic devices?

Yes. Channel walls must wet or repel the liquid as the design needs, and treatment or bonding steps can change that. Contact angle on a flat coupon of the same polymer and treatment gives a practical proxy. A University of Alberta thesis used a Droplet Lab instrument to follow a drop before and after electrowetting in a polyethylene microfluidic camouflage study. See polymer microfluidic channel wettability.

How accurate is the Dropometer?

The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. Automatic edge and baseline detection gives the same reading from the same image. See our validation papers.

Is the Dropometer used in plastics production?

Yes. Zeus, a polymer extrusion and custom tubing maker, uses it for contact angle on extruded tubing. Zeus ran its own Gage R&R on the Dropometer and it passed. The Zeus case study has the details. To compare instruments for production QC, see our buying guides.

Standards, evidence and resources

1. Industry standards Use cases Case studies
  • Harvard University shared facility (CNS): One shared Dropometer measured water contact angle on silicone elastomers, rising from 98.4° to 125° with fluorine content, plus chitosan and silk films for packaging.
  • University of Alberta electrowetting lab: Contact angle of a surfactant water drop under oil on metalized polyester fell from 133° at 0 V to 15° at 3.6 V, for a low voltage electrowetting device.
  • University of Calgary electrospun fibre lab: Water contact angle on twelve electrospun polystyrene mats ranged from 130.1° to 143.2°, linking solvent ratio and spinning voltage to the hydrophobicity of porous plastic fibres.
  • University of Toronto, two campuses: Contact angle on face mask layers found the polypropylene outer layer of one medical mask near 114°, against about 78° for its PET inner layer.
  • Zeus polymer extrusion and tubing maker: Zeus moved polymer tubing QC from eye read crosshairs to automatic edge detection, and Zeus ran its own Gage R&R on the Dropometer and it passed.
Client citations (our analysis of each paper) Use case collections Further resources