Progress in Recycling of Composites with Polycyanurate Matrix

Abstract

Thermoset based composites are used increasingly in industry for light weight applications, mainly for aircraft, windmills and for automobiles. Fiber reinforced thermoset polymers show a number of advantages over conventional materials, like metals, especially their better performance regarding their strength-to-weight ratio. However, composite recycling is a big issue, as there are almost no established recycling methods. The authors investigate the recyclability of polycyanurate homo-and copolymers with different recycling agents under different conditions. Also the influence of the recycling process on the most important reinforcement fibers, i.e. carbon-, glass-, aramid-, and natural-fiber is investigated. The authors find that: the recycling speed is not only dependent on the temperature, but also is significantly influenced by the particular recycling agents and the polycyanurate formulation. Hence, the stability against the recycling media can be adjusted over a broad range by adjusting the polymer composition. Furthermore, the authors find that the inorganic reinforcement fibers (carbon and glass) are almost unaffected by neither recycling agent at either temperature. Aramid-fibers degrade, depending on the particular recycling agent, from slightly up to extremely strong. This leaves one with the possibility to find a combination of matrix resin and recycling agent, which does not affect the aramid-fiber significantly. In the case of natural fibers, the dependence on the particular recycling media is very strong: some media do not affect the fiber significantly; others reduce the mechanical properties (tensile strength and elongation at break) significantly, and still others even improve both mechanical properties strongly. From the Recyclate, the authors synthesize and subsequently characterize a number of new polyurethane thermosets (foamed and solid samples) with different contents of recyclate, exhibiting Tg in the range of 60˚C to 128˚C.

Thermal and mechanical properties of azomethine functionalized cyanate ester/epoxy blends

“…Fourier transform infrared (FT-IR) spectra were recorded in an ABB Bomem MB series FT-IR spectrometer using a KBr pellet. 1 H and 13 C nuclear magnetic resonance measurements were carried out with a Bruker AV III spectrometer (500 MHz). Samples were prepared in CDCl 3 or DMSO-d 6 solutions.…”

“…: 140 C. FT-IR (KBr, cm À1 ): 3395, 3371 (aromatic NH 2 ), 2945 (OCH 2 ), 835 (p-substituted aromatic). 1 2.750 g, 0.01 mol) was taken in a 250 mL round bottomed ask with 100 mL of ethanol and reuxed until it was completely dissolved in ethanol. To this 2.4662 g of 4-hydroxy benzaldehyde (0.0201 mol) in 50 mL of ethanol was added drop wise with constant stirring.…”

“…On heating or irradiation either in the presence or absence of catalyst, three units of cyanate ester monomer undergo cyclotrimerization to form a symmetric triazine ring with nitrogen and carbon atoms, where the carbon atoms are linked to an ether substituent. 1 The heat resistant character of cured cyanate esters (CE) make them more appealing for use in high thermal applications. 2 The polycyanurates exhibit low dielectric constants and low dissipation factors.…”

Preparation of POSS/Quartz fibers/cyanate ester resins laminated composites

“…The highly symmetrical crosslinked structure of triazine rings and a few polar groups result in good dielectric properties (dielectric constant of 3.0–4.0 and dielectric loss of 0.005–0.010), which reveals good stability in a wide range of temperature and electric field frequency. Furthermore, a large number of aromatic rings, aryl and heterocyclic linkages and the unique triazine rings make CE resins possess high mechanical strength, excellent heat resistance properties, and high dimensional stabilities . Therefore, CE resins display potential application in radomes and antenna system of aircrafts.…”

Matrix Decomposition of Carbon-Fiber-Reinforced Plastics via the Activation of Semiconductors

“…A local matrix decomposition of CFRP that allows for locally depleting the matrix of CFRP components without causing negative effects to the reinforcing fibers was investigated earlier [ 26 , 27 ]. However, this treatment is only suitable for specially developed resin systems based on cyanate.…”