Thermal Insulating and Mechanical Properties of Cellulose Nanofibrils Modified Polyurethane Foam Composite as Structural Insulated Material

Abstract

Cellulose nanofibrils (CNF) modified polyurethane foam (PUF) has great potential as a structural insulated material in wood construction industry. In this study, PUF modified with spray-dried CNF was fabricated and the physical and mechanical performance were studied. Results showed that CNF had an impact on the foam microstructure by increasing the precursor viscosity and imposing resistant strength upon foaming. In addition, the intrinsic high mechanical strength of CNF imparted an extra resistant force against cells expansion during the foaming process and formed smaller cells which reduced the chance of creating defective cells. The mechanical performance of the foam composite was significantly improved by introducing CNF into the PUF matrix. Compared with the PUF control, the specific bending strength, specific tensile strength, and specific compression strength increased up to three-fold for the CNF modified PUF. The thermal conductivity of PUF composite was mainly influenced by the closed cell size. The introduction of CNF improved thermal insulating performance, with a decreased thermal conductivity from 0.0439 W/mK to 0.02724 W/mK.

Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams

“…Considerably higher loadings of cellulose nanofibrils (CNF), 20 wt % and 30 wt % of the combined polyol and CNF weight, were applied for filling rigid low-density PU foams in [ 45 ]. Thus, the weight fraction of CNF in foams, according to the formulation presented in [ 45 ], amounted to 10.3 wt % and 15.4 wt %.…”

“…The variability of stiffness reinforcement efficiency among different loading modes seen in Figure 5 a is likely to reflect the inter-batch variability of foams, the rate of growth of the bending and compressive stiffness with CNF loading being similar. However, the specific tensile stiffness at the highest filler loading was reported to increase by a factor of 10 [ 45 ], which appears to be inconsistent with the rest of data; hence, the respective data point was excluded from further analysis as an outlier. The reinforcement efficiency for strength, Figure 5 b, exhibits marked scatter, tensile strength of foams benefiting from filler the least and compressive strength - the most.…”

High Functionality Bio-Polyols from Tall Oil and Rigid Polyurethane Foams Formulated Solely Using Bio-Polyols

“…Polyurethane is the sixth most used polymer on a global scale with an annual production of more than 18 million tons [54]. The majority of produced PU materials are flexible and rigid foams that are applied in various industries.…”

“…The main application of rigid PU foam is as thermal insulation material in civil engineering and refrigerator appliances. Closed cell rigid PU foam thermal insulation applied in civil engineering usually has an apparent density of 40-60 kg/m 3 with thermal conductivity of 20-30 mW/(m•K) [22,54,55]. Various sustainable feedstocks have been successfully used to develop rigid PU foams with low thermal conductivity wales, such as rapeseed oil [28,56], soybean oil [57], lignin [58], and recycled polyethylene terephthalate (PET) waste [53,59].…”

Wood Productions and Renewable Materials: The Future Is Now

“…An example of this is the formulation of a nanocellulose aerogel from Poplar (Populus tomentosa) Catkin fiber [13]. The use of cellulose nanofibrils modified polyurethane foam composite as structural insulated material is another example of the use of an additive for advanced materials from renewable materials [14].…”