Study of the acoustic and thermal performance of composites made from recycled polyurethane foam with polypropylene fibers and micro-particles

Although ultra-low density fiberboards (ULDFs) have good sound and thermal insulation performance, formaldehyde emission in the manufacturing process and in the subsequent use of the products limits their field of application. The objective of this study was to employ an unsaturated polyester resin (UPR) in the manufacturing of the boards as a substitute of formaldehyde-based adhesives in order to develop environment-friendly ULDFs. The effects of UPR dosage, fiber treatment agent, press time and fiber consumption on the properties of fiberboards were studied. Sound absorption and thermal conductivity were also measured to ensure sound and thermal insulation properties of the fiberboards. Board density, modulus of rupture and thickness swelling in 2 h were 320 kg/m3, 4.14 MPa and 3.75%, respectively, under optimal conditions such as 12% UPR dosage, 1% fiber treatment agent, 400 g fiber consumption and 210 s press time. Noise reduction coefficient and thermal conductivity of the boards were found within a range of 0.68–0.58 and 0.038–0.048 W/(m K), respectively, while the density of boards ranged from 150 to 400 kg/m3. Therefore, sound absorption property of the fiberboards developed in this study satisfies the requirement of high-efficiency sound absorption materials, which is close to the value (0.67) of ULDF having a density of 56.3 kg/m3 obtained by a wet process. Thermal insulation property of boards was close to that of commonly used insulation materials such as rock wool [0.036 W/(m K)] and glass fiber [0.045 W/(m K)]. In conclusion, fiberboards can be used for non-structural furniture materials, sound and thermal insulation materials in buildings because of their environmental friendliness, good mechanical properties, and excellent sound and thermal insulation properties.

Among the various polymer fibers available, polypropylene (PP) fibers are often used to improve the impermeability, impact resistance, anti-wear and crack resistance of concrete. In order to improve the interfacial adhesion between PP fibers and cement a series of PP composite fibers were prepared by melt spinning with micro-silica (MSi) as a hydrophilic modifier and the structure and properties of the composite fibers were studied. The results showed that the composite fibers displayed rougher and more hydrophilic surfaces than the pure PP fibers. As revealed by single fiber pull-out tests, the interfacial adhesive strength between the PP fibers and a cement matrix increased obviously after adding the MSi to the PP fibers. The flexural strength and compressive strength of the cement mortar blended with the composite fibers were much better than those of the cement modified by pure PP fibers. The cement mortar enhanced by the composite fibers containing 10 wt.% of MSi showed the best mechanical strength, which we suggest was caused by a balance between fiber strength and interfacial adhesive strength. In general, our research indicated that the mechanical properties of PP fiber reinforced cement-based materials could be further enhanced by mixing appropriate amounts of MSi in the PP fibers which provides a novel strategy to design high-ρperformance materials for modern architecture.

Mass timber is increasingly being employed in constructing low- and mid-rise buildings. One of the primary reasons for using mass timber structures is their sustainability and ability to reduce environmental consequences in the building sector. One criticism of these structures is their lower subjective sound insulation quality. Therefore, acoustic treatments should be considered. However, acoustic solutions do not necessarily contribute to lower environmental impacts or improved thermal insulation performance. This paper discusses a design methodology that incorporates the development of a sound insulation prediction tool (using an artificial neural networks approach), life cycle assessment analysis, and thermal insulation study. A total of 112 sound insulation measurements (in one-third octave bands from 50 to 5000 Hz) are utilized to develop the network model and are also used for the LCA and thermal insulation study. They are lab-based measurements and are performed on 45 various CLT- and ribbed CLT-based assemblies. The acoustic model demonstrates satisfactory results with 1 dB differences in the prediction of airborne and impact sound indices (Rw and Ln,w). An acoustic sensitivity study and a statistical analysis are then conducted to validate the model’s results. Additionally, an LCA analysis is performed on the floor assemblies to calculate their environmental footprints. LCA categories are plotted against the acoustic performance of floors. No correlations are found, and the results emphasize that a wide range of sound insulation can be achieved with similar environmental impacts. Within each acoustic performance tier, the LCA results can be optimized for a floor assembly by selecting appropriate materials. The thermal insulation of floors is then calculated. Overall, a strong positive correlation is found between the total thermal resistance and heat loss against acoustic performance. Designers should be cognizant of the trade-offs between acoustic, thermal insulation, and environmental performance when choosing assemblies with favorable environmental impacts relative to acoustic and thermal insulation ratios.

In this study, the acoustic properties of polyurethane (PU) foams produced with the biodegradable, easily disposable natural bamboo leaves particles (bamboo chips and bamboo stems) were investigated. Acoustical properties of PU foam composites as normal sound absorption coefficient and sound transmission loss were measured using a two‐microphone impedance tube and a four‐microphone impedance tube, respectively. The microstructures of PU foam composites were examined using scanning electron microscope (SEM) and air‐flow resistivity was also measured. The results illustrate that suitable constituents of bamboo chips and stems have significantly enhanced the sound absorption and insulation properties of the PU foam composites over the entire frequency range, especially giving rise to a considerable improvement of low‐frequency sound absorption and sound insulation characteristics. PU foam composites with 6% of bamboo stems obtain the highest NRC (noise reduction coefficient) value with 0.714 and the maximum value of the sound absorption coefficient is 0.971, achieved at 6,300 Hz. Besides, PU foam composites with 8% of 2–3 mm bamboo chips exhibit the best sound insulation with high transmission loss around 18.9 dB over the entire frequency range (100–6,300 Hz). POLYM. COMPOS., 39:1370–1381, 2018. © 2016 Society of Plastics Engineers

Production and usage of green and sustainable building materials realizes the desire to integrate more biodegradable, natural, recycled, and renewable resources into the construction industry. The aim is to replace traditionally available construction industry materials due to their environmental impacts through air emissions and waste generation. An observed trend is the production of insulation materials by recycling of industrial, agriculture, construction and demolition (C&D), and municipal solid wastes, thus reducing the environmental burdens of these wastes. While thermal insulation is important in saving energy, sound insulation has drawn much attention in recent years. There are various waste materials that have good thermal and sound properties, enabling effective replacement of traditional materials. This review investigates the use of industrial, agricultural, C&D, and municipal solid wastes to produce innovative thermal and acoustic insulating building materials. The performance of these insulating materials, and the influence of several materials parameters (density, thermal conductivity, sound absorption coefficient) on thermal and acoustic performance are reported after a brief description of each material.

The construction of concentrated infrastructures due to rapid urbanization has given rise to urban heat island (UHI) phenomenon which causes temperature of urban areas to significantly increase compared to its adjacent cooler rural areas. The absorption of heat in the form of solar radiation by infrastructures is the main contributor to UHI, which results in the rise in the ambient temperature at night. This has forced the construction industry to focus on thermal insulating building materials such as foamed concrete. Air voids in the matrix of foamed concrete allow it to reduce the thermal conductivity and dry density; however, due to its reduced density, foamed concrete is prone to microcracking which results in loss of strength. To counteract the development and propagation of microcracks, polypropylene (PP) fibres are used to reinforce the foamed concrete. Therefore, in this study, foamed concrete of density 1600 kg/m3 was reinforced using PP fibres in three percentages, 0.20%, 0.25% and 0.30%. Thermal performance, in terms of thermal conductivity and surface temperature, was conducted as well as the compressive and tensile strength was determined. It was observed that the PP fibres not only enhanced the strength but also significantly lowered the thermal conductivity and absorbed less heat.

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

The clothing and textile industry generates vast amounts of waste annually, some of which is combusted through incineration or being dumped in landfills, resulting in extensive environmental pollution. This work provides a green approach through recycling clothing and textile waste to manufacture sound-absorbing panels with a new sponge structure. Panels were formed through a blend of textile waste of different fiber diameter, tufting orientation, and porosity. Acoustic properties of the samples were characterized by sound absorption coefficient and sound transmission loss in the frequency range of 500–2000 Hz. The effects of fiber content, layer structure, and bonding process on noise reduction coefficient (NRC) and sound transmission class (STC) were studied. Outcome shows hybrid samples with multilayer sponge-like structures exhibited better acoustic performance with a maximum of 0.65 NRC values and more than 20 dB improvement in sound pressure in mid-frequencies. Hybrid samples of fiber diameters and layered layers showed maximum sound absorption with greater internal porosity and energy dissipation. Sample ID 27 possesses an NRC of 0.9175 and STC of 22.47, greater than double the values described for natural-fiber panels in the literature. In addition to greater absorption coefficients, improved sound insulation (STC > 20) is also provided. All these results clearly show the improved performance of our sponge-like hybrid material from garment textile waste. The study justifies the application of recycled textile materials in green acoustic panel design and the application of the circular economy in the textile sector.

The aim of this paper is to present the influence of the modification of polypropylene (PP) fibers on the sorption capabilities of the fibers. The physical modification of the PP fibers was made with inorganic nanoadditives in the mass, with a view to improving the properties of silicate composites used in the construction industry. The compositions of the modified PP fibers using two different nanoadditives were based on previous work, as well as the work presented in this paper. The prepared modified PP fibers were compared with pure PP fibers, and their mechanical and thermomechanical properties were evaluated. Another task of this work was to evaluate and compare the sorption capabilities of these fibers without the preparation of concrete blocks. Therefore, the Washburn method was used. However, the obtained results led us to the conclusion that the given method points to the excellent transport properties of PP fibers if such properties are used to evaluate the sorption of the fibers. However, the sorption of the prepared modified fibers could be associated with the nanoadditives used, which have a higher water sorption capacity compared to pure PP fibers, and this could also ensure the higher adhesion of the modified PP fibers with inorganic additives to the cement matrix compared to the adhesion of the hydrophobic PP fibers.

Acoustic and thermal performance of polypropylene nonwoven fabrics for insulation in buildings

The current study deals with the analysis of sound absorption characteristics of foxtail millet husk powder. Noise is one the most persistent pollutants which has to be dealt seriously. Foxtail millet is a small seeded cereal cultivated across the world and its husk is less explored for its utilization in polymer composites. The husk is the outer protective covering of the seed, rich in silica and lingo-cellulose content making it suitable for sound insulation. The acoustic characterization is done for treated foxtail millet husk powder and polypropylene composite panels. The physical parameters like fiber mass content, density, and thickness of the composite panel were varied and their influence over sound absorption was mapped. The influence of porosity, airflow resistance, and tortuosity was also studied. The experimental result shows that 30-mm thick foxtail millet husk powder composite panel with 40% fiber mass content, 320 kg/m3 density showed promising sound absorption for sound frequency range above 1000 Hz. We achieved noise reduction coefficient (NRC) value of 0.54. In view to improve the performance of the panel in low-frequency range, we studied the efficiency of incorporating air gap and rigid backing material to the designed panel. We used foxtail millet husk powder panel of density 850 kg/m3 as rigid backing material with varying air gap thickness. Thus the composite of 320 kg/m3 density, 30-mm thick when provided with 35-mm air gap and backing material improved the composite’s performance in sound frequency range 250 Hz to 1000 Hz. The overall sound absorption performance was improved and the NRC value and average sound absorption coefficient (SAC) were increased to 0.7 and 0.63 respectively comparable with the commercial acoustic panels made out of the synthetic fibers. We have calculated the sound absorption coefficient values using Delany and Bezlay model (D&B model) and Johnson–Champoux–Allard model (JCA model) and compared them with the measured sound absorption values.

This study presents the development and performance assessment of six composite samples (SC1–SC6) engineered for advanced applications requiring mechanical strength, thermal insulation, and acoustic efficiency. Each composite was analyzed for thickness, tensile strength, flexural strength, impact resistance, compressive strength, thermal conductivity, and sound absorption coefficient (SAC). SC1 demonstrated modest mechanical properties, with tensile strength of 12.79 MPa and SAC of 0.74%, while SC2 offered enhanced flexural (80.90 MPa) and compressive strength (14.47 MPa), along with the lowest thermal conductivity (0.048 W/mK) and the highest SAC (0.79%), highlighting its excellent insulation potential. SC3 exhibited superior tensile (36.53 MPa) and impact strength (16.46 J/m), though it’s SAC (0.65%) and thermal conductivity (0.053 W/mK) were moderate. SC4 recorded the highest flexural (96.42 MPa) and compressive strength (19.17 MPa), with strong impact resistance (18.82 J/m) and SAC of 0.76%, but a slightly higher thermal conductivity (0.058 W/mK). SC5 showed balanced attributes across all parameters, while SC6 demonstrated high overall mechanical strength, including flexural (90.67 MPa) and impact strength (18.78 J/m), though with the highest thermal conductivity (0.065 W/mK) and a notable SAC of 0.78%. The comparative analysis highlights trade-offs between thermal conductivity and acoustic performance. SC2 stands out for thermal and sound insulation, SC3 and SC4 are well-suited for load-bearing applications, and SC6 offers a versatile profile for multi-functional use. These results underscore the potential for customizing composite properties to meet diverse engineering needs.

Experimental studies of thermal and acoustic properties of recycled aggregate crumb rubber concrete

This paper investigates the influence of adding vegetal fibers on thermal and acoustic performance based on natural hydraulic lime. Mortar samples with 10% weight of vegetal fibers were fabricated adding water to obtain easily workable mortars with good consistency; their performance was compared to mortar samples without vegetal fibers. The fibers were of different types (rice husk, spelt bran, and Khorasan (turanicum) wheat chaff) and size (as-found and ground form). Thermal performance was measured with the Small Hot Box experimental apparatus. Thermal conductivity was reduced in the 1–11% range (with Khorasan wheat chaff and rice husk); no significant reduction was found with spelled bran in the mixture. When ground, fibers were characterized by both good thermal and acoustic absorption performance; a reduction of 6–22% in thermal conductivity λ was achieved with spelled bran (λ = 0.64 W/mK) and rice husks (λ = 0.53 W/mK), whereas the Khorasan wheat chaff had the highest sound absorption average index (0.38). However, the addition of fibers reduced sound insulation properties due to their low weight densities. This reduction was limited for rice husks (transmission loss value was only 2 dB lower than the reference).

Innovative Cardboard Based Panels with Recycled Materials from the Packaging Industry: Thermal and Acoustic Performance Analysis