Achievements and prospects for the synthesis of poly(meth)acrylimide foams. Stage of the thermal imidisation of polymer precursors

Abstract

<jats:p> The review summarises the trends in the development of research on the synthesis of polymethacrylimides (PMIs) and polyacrylimides by the method of intramolecular thermal imidisation of (meth)acrylic polymers. Along with the widely used industry variant of PMI foam of the ‘Rohacell’ series based on bulk copolymers of methacrylonitrile and methacrylic acid, intensive research on alternative variants began after 2005. This review describes the main and side reactions when using polymer precursors of different structures as well as the effect of precursor composition and structure on the properties of the resulting poly(meth)acrylimides. It has been shown that the achievements of the last 15 years provide a basis for reducing the cost of poly(meth)acrylimides which will significantly expand the areas and scale of their application. </jats:p>

MWCNT-Reinforced Polymethacrylimide Foams for Broadband Electromagnetic Wave Absorption

“…After a lengthy water-bath polymerization, a random copolymer was formed, which is a hard solid. Under high-temperature atmosphere, the foaming agent decomposed to form bubble holes, and the intramolecular cyclization reaction occurred between the carboxylic group of methacrylic acid and/or the cyanide group of acrylonitrile, forming the hexamethylene imide structure, trapezoidal structure, and hexacyclic anhydride structure, ,, as seen in the reaction diagram (Figure S2). These rigid molecular structures reinforced the hole-wall strength, which is sufficient to withstand the pressure of bubble pore growth as gas increases in the pores and suppress the merging or rupture of pores.…”

“…With its cross-linked molecular structure, closed independent hole, and abundance of imide groups, polymethacrylimide (PMI) foam exhibits the benefits of heat resistance, pressure resistance, and lightweight. − The copolymerization curable-hot air method, which prepares PMI foam with methacrylic acid (MAA) and acrylonitrile (AN) as comonomers, has advantages in both production cost and material properties. ,, The controllable density and structural morphology of PMI foam can be achieved through preparation process adjustments . As a result, PMI foam is highly valued in the research and industrial production fields and has found extensive application in wind power, aerospace, rail, and other industries.…”

Lightweight and High-Performance Polymethacrylimide Foams for Complex-Shaped Applications Based on the Highly Foamable Precursor Beads

“…Polymethacrylimide (PMI) foams are a kind of high-performance polymeric rigid foam containing closed-celled structures. − Thanks to the abundant hexatomic imide rings in the main chains and cross-linked structures between the main chains, the PMI foams exhibit excellent mechanical properties and high heat resistance. Since the first development of PMI foams by the Evonik company in the 1972s, there have been more than 15 series and 60 brands of PMI foam products for different applications.…”

Flame-retardant polymethacrylimide foams modified by grafting with amino-terminated phosphorous polyborosiloxane

“…The dispersion of APP in PMI, however, was heterogeneous, even with a certain amount of thickener added. Further incorporation of an antiwear agent was observed to be favorable to overcome this issue, but greatly increased the cost and degraded the structure and properties of the polymer matrix [14,15]. These are the common byproducts of physical addition to improve the flame retardancy of PMI foams [16][17][18].…”