Syntactic foams are lightweight, porous composites usually used in marine designs owing to their floating nature and low moisture absorption. Since the last few decades, researchers have been exploring various new types of syntactic foams for making them suitable for a wide array of applications. With the growing research and development in the syntactic foams arena, several novel applications have been evolved owing to their improved performance capabilities.

Lightweight but sturdy materials have great importance in industrial applications ranging from marine to aerospace sectors. One such lightweight material having amazing applications is syntactic foam. It is self-healing in behavior, lighter than water, and possesses amazing properties.  

The name “syntactic foam” was given by Bakelite in 1955. This compound is not what a usual foam looks like; syntactic foam is a class of material produced using pre-formed hollow spheres (generally made of ceramic, glass, polymer, or even metals) bound together with a polymer. Although the concept of syntactic foams is several decades old, it is proving to be a game-changing technology for a broad spectrum of industries and applications in the recent years.

Syntactic foams are lightweight, porous composites usually used in marine designs owing to their floating nature and low moisture absorption. Since the last few decades, researchers have been exploring various types of syntactic foams for making them suitable for a wide array of applications.

The customizable nature, quality features, and remarkable applications of syntactic foams in diverse technological applications have grabbed the interest of several researchers and industrialists. Moreover, properties such as light weight and low density of syntactic foams have proved to be favorable in weight-sensitive aircraft designs. In addition, syntactic foams have propelled the performance confines for composites and empowered the improvement of machines for travelling even in deep oceans and to other faraway planets. The high level of porosity of syntactic foam also makes it ideal for thermal insulation of pipelines in the oil & gas industries. 

Here are few points that every industrialist should know about syntactic foam; and why it should be on the list of materials for an upcoming design project.

Amazing Features of Syntactic Foam that are Worth Making a Note of:

• Low density
• Thermally insulating
• Better rigidity 
• Enhanced compressive strength 
• Buoyant

What are the Perks of Using Syntactic Foam?

Since the invention of syntactic foams, it was pondered to have numerous inherent characteristics and benefits. For instance, in marine product designs for obtaining buoyancy without absorbing huge quantities of water. Moreover, automated as well as manned automobiles can travel for longer periods at increased distances with the help of syntactic foams.

This light weight substance has proved useful in an extensive spectrum of applications owing to various reasons:

1. Low Density

The higher compressive strength and low density of syntactic foams as compared to other foams make them highly suitable in various applications. An equilibrium between microsphere volume fraction and wall thickness is vital to obtain the expected density and this can be obtained using syntactic foams.

2. Low Weight

Syntactic foam is nearly 50% porous, as it is made using hollow fillers. Low porosity helps in achieving considerable weight reduction of the resultant product. Even though all types of foams are porous in nature, they are not as stiff, strong, and durable as syntactic foams.

3. High Strength

Syntactic foam sheets possess high degrees of compressive strength. This strength can be increased by optimizing raw materials, altering formulations, and processing. Compressive strength is imperative for foams used in heavy load or hydrostatic pressure applications. However, syntactic foams are relatively less tensile, as the hollow fillers are usually unbonded. The tensile strength of syntactic foams can be enhanced by processing its particles with a chemical surface treatment and/or by adding fibrous fillers. An advantage of having spherical fillers in syntactic foam, for instance: microballoons, is that the components formed are isotropic and have the same strength as well as all other thermal & mechanical properties.

4. Enhanced Insulation

Syntactic foam is a naturally good insulator and has low thermal conductivity owing to its highly porous design. They provide substantial engineering as well as monetary benefits as compared to traditional insulation materials.

5. Easy Customization

Syntactic foams can be easily customized as per the needs of an application. This is because:

• The matrix material can be picked from nearly any type of polymer, metal, or ceramic. 
• Microspheres are available in varied sizes and material types. 

Adjusting the size, distribution, diameter, and wall thickness of the microspheres can enable several possible variations to customize the properties of syntactic foam. Moreover, choosing suitable gas, which has to be enclosed within the hollow particles is one more design specification that can be customized as per needs. Other factors such as particle diameter, matrix material, and volume fraction can also be tailored. It is imperative to remember that minor alterations in the structure of syntactic foams can significantly impact compressive properties, porosity, density, coefficient of thermal expansion, water absorption, and thermal conductivity.

What are the Different Applications of Syntactic Foams?

With growing research and development in the syntactic foams arena, several novel applications have been evolved owing to their improved performance capabilities. Some of them are:

• Rigid pipe insulation for deep-water oil & gas investigation
• Autonomous underwater vehicles (AUVs)
• Core products for sandwich composites
• Remotely operated underwater vehicles (ROVs)
• Soccer ball
• Automotive underhood parts
• Airplane radomes
• Boat hulls
• Spacecraft

For example, 

• In 2014, a Bluefin autonomous underwater vehicle (AUV) was used in the deep-water research for investigating the remnants of the Malaysia MH370 aircraft.
• In 2012, the Deepsea Challenger was a man-operated submersible controlled by James Cameron to reach the deepest part of the sea in the Mariana Trench at a distance of seven miles. 
• Even the Brazuca soccer ball, designed by Adidas for the 2014 World Cup in Brazil, was made using syntactic foam. This ball was capable of returning to its original shape after being kicked, thus offering better precision and improved goal rates. Later models of the ball still use syntactic foam.
• The USS Zumwalt Navy destroyer, developed in 2008, has syntactic foam all through its design to reduce and maintain low weight. 

Can Syntactic Foams Replace Traditional Materials?

Syntactic foams hold the potential of replacing a wide range of conventional materials such as natural and synthetic foams, balsa wood, PVC, fiber-reinforced-plastics as well as metals. Legacy materials alone cannot provide the same level of density, strength, and weight savings owing to the temperature as well as the moisture content in them. For instance, a typical microsphere shell is able to bear a pressure of over 25,000 pounds per square inch before cracking, which is more than five times the compressive strength of a traditional concrete road.

Heading toward the Future of Syntactic Foams

Nowadays, even theoretical presentations and results of several research studies on syntactic foams have become available. Scientists hope that the future years are going to witness a significant surge in the improvement or optimization of syntactic foam structures, mainly at the molecular level. Currently, research studies focused on resins with higher strength, lower water absorption, better heat resistance, and microspheres having specific chemistries that enhance properties are under development. Surface treatments that enhance bonding or guarantee debonding are also under process. In brief, the applications of syntactic foams are anticipated to spur in the upcoming years as the researches in science & technology of these materials are ongoing and evolving at an accelerated pace.