Mango Seed Bioplastic Film Strength and Decay

ISEF Category: Materials Science

Subcategory: Polymers  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Plastic can last for centuries. A mango seed can become a film that acts more like a leaf than a bottle. Your job is to see how much glycerol changes that behavior. You will measure both strength and how fast the film breaks down in soil.

What Is It?

This project looks at bioplastic films made from mango-seed starch mixed with glycerol. Starch is a natural polymer, which means it is made of long sugar chains. Glycerol is a plasticizer, which means it slips between those chains and makes them move more easily. That usually makes a film more flexible, but it can also make it weaker and easier for microbes and water to break apart.

Think of the starch network like a pile of cooked spaghetti. If the noodles stick together too tightly, the sheet can crack. If you add too much sauce, the pile slides around and loses shape. Glycerol works like that sauce. The core question is how much you need before the film stops acting like a useful material.

You can test two big outputs at once. One is tensile strength, which tells you how much pulling force the film can handle before it tears. The other is biodegradation rate, which you can estimate by burying samples in soil and tracking mass loss over time. That gives you a simple materials science story, one property for performance, and one for end-of-life.

Why This Is a Good Topic

This is a strong science fair topic because you can change one ingredient and measure two real material properties. That gives you clear cause and effect. The project connects to plastic waste, food byproducts, and sustainable packaging, so the real-world angle is easy to explain. You can learn how to build a fair test, make repeatable film samples, collect quantitative data, and compare tradeoffs between strength and biodegradability.

Research Questions

• How does glycerol ratio affect the tensile strength of mango-seed starch films?
• How does glycerol ratio affect the percent mass loss of mango-seed starch films buried in soil?
• What is the effect of glycerol ratio on the flexibility of mango-seed starch films before cracking?
• Does glycerol ratio change the balance between strength and biodegradation in mango-seed starch films?
• To what extent does soil moisture change the mass-loss rate of mango-seed starch films at a fixed glycerol ratio?
• Which glycerol ratio gives the best compromise between tensile strength and biodegradation for a packaging use case?

Basic Materials

• Mango seeds or mango-seed starch source, cleaned and dried.
• Food-grade glycerol.
• Distilled water.
• Kitchen blender or grinder.
• Digital kitchen scale with 0.1 g accuracy.
• Measuring cups or graduated cylinders.
• Hot plate or stove-safe heating setup.
• Saucepan or beaker.
• Flat casting trays or petri dishes.
• Ruler or calipers.
• Paper clips, binder clips, or a simple pull-test setup.
• Soil-filled containers with lids or trays.
• Mesh bags or labeled sample envelopes for burial trials.
• Notebook or spreadsheet for data tracking.

Advanced Materials

• Universal testing machine or force gauge with sample grips.
• Thickness gauge or digital micrometer.
• Controlled humidity chamber or sealed conditioning boxes.
• Analytical balance with 0.001 g accuracy.
• Soil incubation containers with temperature and moisture monitoring.
• Sieve set for starch isolation and sample cleanup.
• Fourier transform infrared spectroscopy access for functional group checks.
• Scanning electron microscopy access for fracture surface imaging.
• Differential scanning calorimetry access for thermal property comparison.
• Texture analyzer for puncture or elongation testing.

Software & Tools

• Google Sheets: Organizes strength, mass-loss, and thickness data, and helps you graph trends.
• ImageJ: Measures film width, crack length, and sample area from photos.
• Python: Handles curve fitting, summary statistics, and cleaner data plots.
• RStudio: Runs statistical tests and compares multiple glycerol ratios.
• BioRender: Makes clean diagrams of your sample design and soil burial setup.

Experiment Steps

1. Define the exact sample series by choosing the glycerol ratios you will compare and the property you want to optimize.
2. Plan how you will keep film thickness, drying conditions, and sample size as even as possible across all groups.
3. Design a strength test that gives you a numeric failure point, not just a yes-or-no result.
4. Build a soil burial plan that tracks sample identity, burial depth, and recovery schedule without mixing groups.
5. Decide how you will normalize mass-loss data for thickness, starting mass, or surface area so the comparison stays fair.
6. Prepare a statistics plan before you start, including which graph, test, or regression will answer your main question.

Common Pitfalls

• Making films with uneven thickness, which changes strength and biodegradation more than the glycerol ratio does.
• Mixing up moisture loss with true biodegradation, which makes buried samples look like they vanished faster than they really did.
• Pulling samples by hand without a fixed setup, which gives noisy tensile data that cannot be compared.
• Letting soil samples dry out or stay waterlogged, which changes microbial activity and skews mass loss.
• Comparing films with different starch purity or seed prep, which adds a hidden variable to every result.

What Makes This Competitive

A strong version of this project does more than compare a few recipes. You can test whether the same glycerol trend holds across strength, elongation, and biodegradation, then look for the tradeoff point. You can also control thickness, soil conditions, and sample aging so your data look clean. If you add a simple model or statistical test that predicts the best formulation, your work starts to feel like real materials screening.

Project Variations

• Use cassava, corn, or potato starch instead of mango-seed starch and compare whether the plasticizer trend stays the same.
• Swap the soil burial method for compost burial or water immersion to compare different breakdown environments.
• Add a second plasticizer, such as sorbitol, and test whether it changes the strength-to-biodegradation tradeoff.

Learn More

• PubMed: Search review articles on starch-based bioplastics and plasticizers to learn the field’s common methods and limitations.
• USDA National Agricultural Library: Search for starch extraction, biodegradable plastics, and agricultural byproduct use.
• NOAA Office for Coastal Management: Use background on plastic pollution and material persistence to frame the environmental need.
• MIT OpenCourseWare: Search materials science or polymer lecture notes for basics on stress, strain, and polymer behavior.
• Polymer Testing: Search recent peer-reviewed papers on tensile testing and biodegradation of starch films through your school library or journal portal.