Mechanical and thermal properties of phenolic/glass fiber foam modified with phosphorus-containing polyurethane prepolymer

Lignin-Based Phenolic Foam Reinforced by Poplar Fiber and Isocyanate-Terminated Polyurethane Prepolymer

Phenolic foams (PFs) are lightweight (<200 kg/m³), high-quality, and inexpensive thermal insulation materials whose heat and fire resistance are much better than those of foam plastics such as polyurethane and polystyrene. They are especially suitable for use as insulation in chemical, petroleum, construction, and other fields that are prone to fires. However, PFs have poor mechanical properties, poor abrasion resistance, and easy pulverization. In this paper, a polyurethane prepolymer was treated with an isocyanate, and then the isocyanate-terminated polyurethane prepolymer and poplar powder were used to prepare modified lignin-based phenolic foams (PUPFs), which improved the abrasion resistance and decreased the pulverization of the foam. The foam composites were comprehensively evaluated by characterizing their chemical structures, surface morphologies, mechanical properties, thermal conductivities, and flame-retardant properties. The pulverization ratio was reduced by 43.5%, and the thermal insulation performance and flame-retardancy (LOI) were improved. Compared with other methods to obtain lignin-based phenolic foam composites with anti-pulverization and flame-retardant properties, the hybrid reinforcement of foam composites with an isocyanate-terminated polyurethane prepolymer and poplar powder offers a novel strategy for an environmentally friendly alternative to the use of woody fibers.

Preparation and Properties of the 3-pentadecyl-phenol In Situ Modified Foamable Phenolic Resin

In this present study, 3-pentadecyl-phenol was selected as a modifier to prepare a foamable phenolic resin with excellent performance, which was successfully prepared by in situ modification. Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (¹H NMR, 13C NMR) were used to test and characterize the molecular structure of the modified resin. The results showed that 3-pentadecyl-phenol successfully modified the molecular structure of phenolic resin with a reduction in the resin gel time. The effect of changing the added amount of 3-pentadecyl-phenol on the mechanical properties, microstructure, and flame retardancy of the modified foam was investigated. The results showed that when the amount of added 3-pentadecyl-phenol was 15% of the total amount of phenol, this resulted in the best toughness of the modified foam, which could be increased to 300% compared to the bending deflection of the unmodified phenolic foam. The cell structure showed that the modified phenolic foam formed a more regular and dense network structure and the closed cell ratio was high. Furthermore, the compressive strength, bending strength, and limited oxygen index were improved, while the water absorption rate was lowered. However, the foam density could be kept below 40 mg/cm³, which does not affect the load.

Facile synthesis of a novel magnesium amino-tris-(methylenephosphonate)-reduced graphene oxide hybrid and its high performance in mechanical strength, thermal stability, smoke suppression and flame retardancy in phenolic foam

This study presents a one-step synthesis of a magnesium amino-tris-(methylenephosphonate) (Mg-AMP)-reduced graphene oxide (Mg-rGO) hybrid involving graphene oxide (GO) reduction and growth in situ of Mg-AMP nanoparticles in the absence of a reducing agent. Mg-rGO was characterized by X-ray diffraction, X-ray photoelectron and Fourier-transform infrared spectroscopies, transmission electronic microscopy, and thermogravimetric analysis (TGA). Mg-rGO was then used to prepare flame-retardant and toughened phenolic (PF) foam. This additive was found to enhance the compressive and flexural strengths of PF foam as well as to reduce its high friability and brittleness. The limiting oxygen index of the foam with 4 phr Mg-rGO (sample PF/4Mg-rGO) increased to 41.5%, compared with the 38% of untreated foam; the peak heat release rate and total heat release of sample PF/4Mg-rGO were decreased by 28.7 and 18.4%, respectively. Also, the total smoke release and peak CO production rate of PF/4Mg-rGO were reduced by 52.5 and 38.1%, respectively. TGA results indicated that Mg-rGO clearly improved the thermal stability of PF foam.

Synthesis of CoAl-layered double hydroxide/graphene oxide nanohybrid and its reinforcing effect in phenolic foams

A graphene oxide (GO) immobilized with layered double hydroxide (CoAl-LDH/GO) nanohybrid was prepared via a hydrothermal method and characterized by transmission electron microscopy, field emission scan electronic microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis (TGA). The TGA results show that the immobilization of CoAl-LDH nanoparticles on GO surface greatly promotes the thermal stability of GO. More importantly, the incorporation of the CoAl-LDH/GO nanohybrid into PF foams leads to not only a great improvement in their mechanical strengths but also a reduction in their brittleness and friability. Specifically, compared to neat phenolic (PF) foam, at only 0.9 phr (parts per hundred of resin by mass) of CoAl-LDH/GO, the compressive and flexural strengths of the modified PF foam increase by 54.8% and 35.2%, respectively, and pulverization ratio decreases by 55.2%. The addition of the CoAl-LDH/GO nanohybrid also results in an increase in the limiting oxygen index and a decrease in the peak heat release of the modified PF foam in cone calorimeter test. Moreover, the thermal stability of the PF foam is enhanced by the addition of the nanohybrid.

One-step in situ synthesis of a novel α-zirconium phosphate/graphene oxide hybrid and its application in phenolic foam with enhanced mechanical strength, flame retardancy and thermal stability

A novel α-zirconium phosphate/graphene oxide hybrid was synthesized, and its incorporation into phenolic foam can greatly improve mechanical strengths, thermal stability and flame retardancy of the foam.

Synthesis of a cardanol-based phosphorus-containing polyurethane prepolymer and its application in phenolic foams

A cardanol-based P-containing polyurethane prepolymer (PPUP), a novel cardanol derivative, was synthesized.

Preparation of a silica nanospheres/graphene oxide hybrid and its application in phenolic foams with improved mechanical strengths, friability and flame retardancy

A silica nanospheres/graphene oxide hybrid (SGO) was synthesized, and it is found that SGO can greatly improve the mechanical strengths, thermal stability and flame retardancy of phenolic foams.