Sustainable Fire-Retardant, Thermal Insulating Biomass-Derived Foams for Green Buildings

Video Transcript:

Hi, my name is Mika Wan and in my project, I created a novel lignocellulose based foam with six main objectives: mechanical strength, fire retardancy, biodegradability, thermal insulation, hydrophobicity, and scalability.

I used fibres, aspen and hemp, as well as additives, nanoclay and silane never used in this combination before to create foams for real world application.

Testing with various weight percentages, I found the most optimal sample combination through empirical, density, and volume shrinkage rate tests.

To ensure that the final foam met regulatory compliances of building insulation foams, the foam samples went through rigorous standardized testing to prove that the original six objectives were met.

My project is important because current petroleum-based insulation foams make up a substantial portion of the global insulation market, yet they are killing the environment. Current biobased alternatives that are up to 50% more expensive than conventional ones have a multitude of understudied chemical and mechanical problems that makes them unreliable proxies.

I was able to successfully target this problem.

Growing Insulation Foam Market

The United Nations reported that the global production of polymeric insulation foams continues to grow at a rate of 3.9% per year, with 29 million tonnes of building insulation material produced solely in 2024[4].

Problems with Conventional Foams

Non-biodegradable, petroleum-based insulation foams make up a large portion of the insulation foam market, but they cause extensive environmental challenges: the release of volatile organic compounds, the use of blowing agents (high global warming potential), and the emission of microplastics after disposal. 8 million tonnes of waste generated by these foams are sent to the landfill annually[2].

Currently, there are two types of bio-based alternatives. First is nanocellulose, which requires an energy-intensive, multistep process for its extraction and refinement, making it an expensive solution. The other type is lignocellulose (developing field in research), which has understudied chemical and mechanical limitations[21]. Lignocellulose fibres still have high potential to be used in building insulation material due to their low cost.

Objectives

This project’s objectives are to create lignocellulose-derived foam…

With enhanced mechanical and chemical properties

Scalable for production (inexpensive fabrication method/biomaterials used)

Specific foam aims were developed because for real-world application, insulation materials must meet certain criteria. This should be proved by standardized testing specific to insulation foams.

Mechanical Strength → Young’s Modulus

Fire Retardancy → UL-94 Flammability Test, Limiting Oxygen Index

Hydrophobicity → Sessile Drop Method (Static Contact Angle)

Biodegradability → stimulation

Thermal Insulation → Thermal Conductivity, R-Value

Scalability (limiting cost of production as much as possible) → simplified techno-economic analysis

Manipulating Biomaterials

Lignocellulose Fibres

Hemp is one of the fastest growing plants on Earth, generating millions of tons of natural waste per year. Hemp insulation boards exist, but have major problems like moisture sensitivity and low mechanical integrity[1]. They are often ~$1.50 more costly than petroleum-based options per board foot[9]. Aspen-derived insulation foams are not widely studied. However, aspen serves as a promising biomaterial, producing similar amounts of waste annually as hemp[15]. As lignocellulose, it has high mechanical strength.

Additives

Nanoclay serves as a reinforcing filler for petroleum-based foams currently, but in the experiments conducted in this project, it can also increase physical strength and fire retardancy[5]. Silane, which creates a nonpolar, low surface energy barrier that is “incompatible” with water, increases hydrophobicity[14].

No published studies were found on the combination of the aforementioned biomaterials to produce insulation foams. Due to their low cost and availability, they were used as the main components of the foams created in addition to other ingredients (see Figure 6). Different weight-percentage combinations of these materials were used to derive the most desired sample, selected based on empirical observations (of exterior surfaces) and density and volume shrinkage rate measurements.

Fabrication Methodology

In research, innumerable fabrication methods exist to produce biobased foams. However, many require expensive chemical processing, making them unrealistic for pilot-scale manufacturing[7]. The fabrication methodology used in this project (proposed by experts at the Biomass and Biorefinery Research Laboratory then modified for optimal foam production) involves abundant, low-cost materials, such as sodium dodecyl sulfate.

Overview of the Process

Step 1: Foaming allows all ingredients (water, lignocellulose, additives, surfactants) to be evenly dispersed together.

Step 2: Stabilization involves processing (crosslinking) to strengthen bonds between particles to withstand drying without collapse.

Step 3: Air-drying under ambient conditions transforms wet to dry foam (preserving structure).

Testing different weight-percentage combinations of aspen, hemp, nanoclay, and silane led to the most optimal sample: 3.0 wt% hemp + 2.0 wt% aspen + 2.5 wt% nanoclay + 1.0 wt% silane. With this sample, standardized testing was conducted to prove that the foam created fulfilled regulatory compliance of market insulation foams.

Mechanical Strength

Mechanical strength was determined by using a Universal Testing Machine compression test. A 2cm thick foam had a Young’s Modulus of 2.6 MPa and maximum stress of 1.44 MPa. Control samples included expanded polystyrene (EPS), which had a comparable range from 1.2 to 3.5 MPa[19].

Fire Retardancy

The vertical UL-94 flammability test found that the sample with clay had minimal weight loss, a short char length, and burning time of only 10 seconds, proving self-extinguishing behavior in the presence of necessary additives. The Limiting Oxygen Index (LOI) for the sample with nanoclay was about 32% and the one without nanoclay was 23%.

Hydrophobicity

A Contact Angle Meter was used to measure the contact angle of the samples. The angle was zero degrees for the one without silane and 104 degrees for the one with silane. A contact angle between 90 and 120 degrees is desirable for insulation foams[24].

Biodegradability

A stimulated soil environment was created wherein samples of EPS, PU, non-additive foam, clay-containing foam, and silane-containing foam were buried for 70 days. After the 70 days, about 1% of its original weight was retained by the non-additive foam, while the clay and silane-containing foams had 64% and 61% weight loss respectively.

Thermal Insulation

A Modified Transient Plane Source was used to deduce the thermal conductivity value of samples containing nanoclay (0.0326 W/mK) and not containing nanoclay (0.0316 W/mK). Using the thermal conductivity values, the R-Value could be calculated for the 2 cm sample: with clay had R-0.613 (m²ᐧK/W) while the non-clay sample had R-0.633 (m²ᐧK/W). The samples had an R-Values that are comparable to conventional petroleum-based foams, including EPS and PU foams which have R-Values of around 0.556 (m²ᐧK/W) and 0.800 (m²ᐧK/W), respectively[28]. A stimulation was also created to test the temperature change of a model house with the foam sample as the roof insulation. It had a smaller net change in temperature compared to the PU foam sample over a two hour period.

Scalability

With the assistance from experts at the Biomass and Biorefinery Research Lab, a simplified techno-economic analysis was conducted wherein the cost of lab-scale production was found to be $150-200 per cubic meter. After scale-up, pilot-scale manufacturing would average $30-50 per cubic meter, which is significantly lower than current biobased foams that are roughly $130-175 per cubic meter[23].

Results Summary

In comparison to existing bio-based foams in scientific literature, the foams created exhibited enhanced properties including a positive difference of about 1.1 MPa for Young's Modulus, 3.6% higher LOI, and 0.02 W/mK lower thermal conductivity.

Final Foam Sample: 3 wt% Hemp + 2 wt% Aspen + 2.5 wt% Nanoclay + 1 wt% Silane

With millions of tonnes of thermal insulation foams produced annually, foams play a vital role in reducing energy consumption in buildings. In the developing research field of lignocellulose foams, there are extensive issues that restrict it from replacing conventional petroleum-based options that are non-degradable (taking around 500 years to break down into microplastics) and require the use of blowing agents (potent greenhouse gases) which cause global warming.

Practical Functionality in Real-World Application

The biobased, fire-retardant foams developed in this project were primarily designed for building insulation, specifically wall, floor, and roof panels. Due to their excellent mechanical and chemical properties, proven by the series of standardized tests, they have high potential to become sustainable construction material alternatives. Compared to conventional expanded polystyrene and polyurethane foams, the samples exhibited similar characteristics that are crucial for high performance in real-world settings.

Impacts of this Project

An innovative foam fabrication methodology using inexpensive, abundant, and biobased materials was successfully employed to create sustainable, fire-retardant thermally insulating foams.

The biomaterials used to create the foams have not been used in this combination before, but were inspired by previous researchers who used them for similar purposes.

Conclusion

All the objectives listed at the beginning of the project were met. It is important to note that there is still extensive testing that must be done to create foams with even more enhanced properties that can increase the performance further.

Enhancing Foam Properties Further

Testing different chemicals of crosslinkers and surfactants to optimize density and volume shrinkage rates.

Modifying the foam fabrication methodology (utilizing other previous research methods) further to yield enhanced foam production.

Experimenting with more variation in types of lignocellulose fibres and additives to create foams with different mechanical and chemical properties.

Future Directions

To scale up from lab-scale manufacturing to pilot-scale manufacturing to evaluate performance consistency, cost efficiency, and industrial feasibility.

To validate the foams in simulated building environments and real world conditions to assess long-term thermal performance, durability, fire resistance, and adaptability for practical construction applications.

During this project, I received much support from my teachers, Dr. Beatriz Garcia-Diaz and Mrs. Madhavi Kale. I appreciate my school, Webber Academy, for giving me the wonderful opportunity of exploring my passion for materials science and engineering.

Thank you deeply to the Biomass and Biorefinery Research Lab at the University of Calgary wherein they allowed me to use their facilities to conduct my experiments.

Thank you to the Calgary Youth Science Fair and Youth Science Canada for giving such amazing opportunities for students interested in STEM. Specifically, I would like to acknowledge Alex Gierus, Shannon Lord, and Beth Pinckston from the Team Calgary delegation for giving me guidance.

And lastly, I could not have done it without my amazing family and friends who are my everyday cheerleaders.

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