Preparation of Polyurethane Microencapsulated Expandable Graphite, and Its Application in Ethylene Vinyl Acetate Copolymer Containing Silica-Gel Microencapsulated Ammonium Polyphosphate

Abstract

Polyurethane microencapsulated expandable graphite (PUEG) is prepared by in situ polymerization, and its structure is characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated PUEG is successfully prepared. The microencapsulated expandable graphite (EG) leads to an increase in the thermal stability and the expanded volume. The research compares the influence of an EG/ammonium polyphosphate (APP)/ethylene vinyl acetate copolymer (EVA) system and a PUEG/silica-gel microencapsulated ammonium polyphosphate (MCAPP)/EVA system on the flame retardancy and mechanical properties. The results indicated that EVA/MCAPP/PUEG composite possesses the same LOI value and UL-94 rating as those of EVA/APP/EG composite. However, the EVA/MCAPP/PUEG system can still pass a UL-94 V-0 rating after being treated with 70 °C water for 168 h, indicating excellent water resistance. Because of good interfacial adhesion between fillers and the EVA matrix, the EVA/MCAPP/PUEG composite shows better mechanical and dynamic mechanical thermal properties than those of the EVA/APP/EG composite. Moreover, the electrical property and the combustion behavior of EVA composites are investigated.

Intumescent flame retardant polyurethane/starch composites: Thermal, mechanical, and rheological properties

“…The appearance of these small holes is due to partial diffusion of water into the bulk of composite under this relatively long time, not because of MCAPP dissolution. It is worthwhile to point out APP solubility in water significantly declines after encapsulation by PU . Strong hydrogen bonding between hard segments of PU and starch is responsible for good dispersion (See section “Thermal Transition of Pure PU and IFRPU/starch composites”).…”

Effect of expandable graphite particle size on the flame retardant, mechanical, and thermal properties of water‐blown semi‐rigid polyurethane foam

“…This may be attributed to the oxidation and fragmentation process of the polymer matrix accelerated by the residual nitric acid in the EG interlayer . Moreover, the nitric acid can react with graphite at high temperature:…”

The Effect of Soluble Ammonium Polyphosphate on the Properties of Water Blown Semirigid Polyurethane Foams

“…Ammonium polyphosphate (APP), as inorganic phosphorus flame retardant with nitrogen-phosphorus synergistic intumescent effect [17][18][19][20], has the advantages of thermal stability and lasting effect. APP can also improve the mechanical properties of the material, so it is often used with other flame retardants [21][22][23], and the most common APP flame retardant studied by researchers is form II, of which the polymerization degree is greater than 1000 [24][25][26][27]. In this paper, the water blown SPUF is synthesized only with soluble ammonium polyphosphate (SAPP) with a low polymerization degree.…”