Silicone rubber mold making and urethane resin casting are applied polymer chemistry. The materials involved — platinum-cure silicones, two-component polyurethanes — exhibit behaviors that are scientifically measurable and that produce genuinely interesting experimental results when investigated rigorously.

For students who are already making molds and casting props, the jump to a science fair project is smaller than it might look. The materials are already in the workshop. The question is how to frame the work as systematic scientific investigation rather than craft.

What Makes a Good Science Fair Project

Science fair judges evaluate:

  1. Clear research question — a specific, testable hypothesis
  2. Controlled variables — isolating one variable while holding others constant
  3. Measurable outcomes — quantitative data, not just qualitative judgment
  4. Analysis — does the data support or refute the hypothesis?
  5. Methodology transparency — could someone else replicate your experiment?

A project that demonstrates “I made a mold and it worked” fails all these criteria. A project that tests “How does temperature during cure affect Shore A hardness in urethane resin?” passes all of them.

Viable Project Concepts

Effect of Temperature on Cure Properties

Research question: How does ambient temperature during cure affect final Shore A hardness in urethane resin?

Setup:

  • Cure identical samples (same resin, same mix ratio, same mold geometry) at three or more temperatures (60°F, 70°F, 80°F, 90°F) using a temperature-controlled environment (coolers with ice, heating pads, or a temperature-controlled cabinet)
  • Control: same humidity, same ratio, same cure time before testing
  • Measure: Shore A durometer readings at 24-hour intervals for 72 hours

Science involved: Reaction kinetics (temperature effects on polymerization rate), polymer network formation, testing methodology

Ratio Deviation and Mechanical Properties

Research question: How do deviations from the manufacturer’s mix ratio affect tensile strength in silicone rubber?

Setup:

  • Mix platinum-cure silicone at manufacturer ratio (e.g., 100A:10B) and at deliberate deviations (95A:10B, 100A:8B, 100A:12B)
  • Cast identical dog-bone-shaped test specimens (ASTM D412 geometry is standard but simplified versions work for a student project)
  • Test: stretch each to failure with a measured load (a simple tensile test rig can be built from inexpensive hardware)
  • Record break force and elongation at break

Science involved: Stoichiometry, cross-linking chemistry, mechanical testing, data analysis

Inhibition Testing of Platinum-Cure Silicone

Research question: Which commonly used clay types inhibit platinum-cure silicone, and to what degree?

Setup:

  • Test platinum-cure silicone against multiple clay types: Roma Plastilina No. 1 (contains sulfur), Chavant NSP Medium (sulfur-free), oil-based clay from a craft store, water-based clay, polymer clay
  • Apply fresh silicone to each clay surface; record cure time and completeness at 6-hour intervals
  • Rating: fully cured / partially cured / uncured after 24 hours

Science involved: Catalyst inhibition chemistry, experimental design, classification methodology

This experiment has direct practical application — the results tell prop builders which materials are safe to use against platinum silicone. See choosing silicone rubber for molds for the professional knowledge this connects to.

Humidity Effects on Urethane Resin

Research question: Does relative humidity during cure cause measurable surface defects in urethane resin castings?

Setup:

  • Cast identical samples at controlled relative humidity levels (use a hygrometer and a small tent with silica gel or a humidifier to control RH)
  • Levels: ~30% RH, ~50% RH, ~70% RH, ~85% RH
  • Evaluate: surface bubble count and depth, final hardness, visual appearance

Science involved: Moisture chemistry in isocyanate reactions, controlled environment methodology, quantitative visual analysis

Framing the Project for Judges

The judges who score science fair projects may not be familiar with silicone mold making. Frame the background and significance sections to explain:

  1. Why these materials matter (industrial applications: medical device molding, aerospace composites, entertainment prop making)
  2. Why the specific variable matters (e.g., temperature sensitivity affects whether commercial production can happen in an uncontrolled environment)
  3. How the experiment variables map to real-world decisions a practitioner makes

A clear significance statement turns “I tested some rubber” into “This investigation informs material selection decisions in industries that depend on consistent polymer properties.”

Equipment and Safety

Most of the experiments above require:

  • The materials themselves (silicone, urethane — available from Smooth-On or Reynolds Advanced Materials)
  • A digital shore durometer (Shore A type, available for $50–100)
  • Accurate graduated cylinders or a digital scale
  • A thermometer and/or hygrometer
  • Standard safety equipment: nitrile gloves, safety glasses, ventilation

PPE and handling requirements for these materials are covered in the urethane resin beginner’s guide. These are manageable materials for student use with appropriate adult supervision and ventilation.

Beyond the Fair

Science fair projects that investigate material properties can be entered into competitions beyond the school level — county, regional, state, and national science fairs. Projects with rigorous methodology and genuine data travel further in competition than impressive-looking demonstrations without scientific substance.

For students who develop serious interest in polymer materials through this kind of project work, materials science and chemical engineering are natural academic paths. The practical experience with polymer systems is unusual among applicants and worth highlighting in college applications and scholarship submissions.

Melicreview.com maintains a directory of student competitions and scholarships, including science and engineering awards for middle school, high school, and university students. If a science fair project yields strong results, submitting it to appropriate competition programs can extend its reach.