In recent years, the growing focus on green building practices has led to increased attention on indoor environmental quality, particularly in terms of acoustics and thermal comfort. As urban areas become more densely populated and energy efficiency standards rise, developers and architects face mounting pressure to create structures that effectively manage sound transmission and heat transfer. A team of researchers from China has risen to this challenge by developing an innovative porous sphere foam system that promises to revolutionize both acoustic and thermal insulation in green buildings.
The novel system, detailed in a recent publication in Scientific Reports, combines a specially designed base acoustic insulation board with foam particle acoustic balls. This unique configuration allows for superior sound absorption and thermal insulation properties compared to traditional materials. The base board features uniformly arranged circular holes, into which the foam particle acoustic balls are nested. This structure creates a complex network of air pockets and sound-absorbing surfaces that effectively dampen vibrations and block sound transmission.
The composition of the foam system is a carefully balanced mixture of various materials, each chosen for its specific properties. The base acoustic insulation board incorporates HB polymer cement-based JS-II type, carbon powder, wood chip powder, high-temperature-resistant phenol-formaldehyde resin, high-temperature-resistant glass beads, and ultrafine inorganic rock wool fibers. These components are combined with distilled water and a specialized foaming agent to create a paste that is then molded and cured. The foam particle acoustic balls are made from a similar mixture, with slight variations in proportions to optimize their performance.
One of the key innovations in this system is the use of carbon fiber wave mesh inlay technology. This technique involves using 1-1.5 mm carbon fibers arranged in a diagonal wave pattern to fix the foam particle acoustic balls within the cavities of the base board. This not only secures the balls in place but also creates additional sound-absorbing surfaces and air pockets, further enhancing the system's acoustic performance.
The acoustic principles behind this system are based on the microscopic structure of the foam particle acoustic balls. The surface of these balls is covered in tiny holes, which act as resonators when sound waves strike them. As noise enters these holes, it undergoes frequency collisions, converting acoustic energy into heat. Additionally, the irregular bonding of particles within the balls creates a network of microscopic pores that increase air resistance. When sound waves propagate through these pores, the vibration of air molecules and friction against pore walls further dissipates acoustic energy.
From a thermal insulation perspective, the system benefits from the inherently low thermal conductivity of its constituent materials. The combination of HB polymer cement, activated carbon fiber, wood chip powder, phenolic resin, glass beads, and rock wool fibers creates a composite with excellent heat-resistant properties. The foamed structure of the system also contributes to its thermal performance by trapping air and reducing heat transfer through conduction and convection.
The researchers have demonstrated that the thickness of the insulation system plays a crucial role in its performance. When the material thickness is less than 20 mm, the compressive elastic modulus can be less than 0.5 MPa. For thicknesses of 20 mm or greater, the compressive elastic modulus can be up to 1.2 MPa. This elasticity is key to the system's vibration-damping capabilities, as it forms an elastic core between the floor and underlying structure, effectively reducing impact noise and vibrations transmitted to lower floors.
The development of this porous sphere foam system represents a significant advancement in green building technology. By addressing both acoustic and thermal insulation needs with a single, integrated solution, it has the potential to simplify construction processes while improving overall building performance. As urban populations continue to grow and environmental regulations become more stringent, innovations like this will play a crucial role in creating sustainable, comfortable living spaces for future generations.
