Thermal expansion instability and creep in amine‐cured epoxy resins

Abstract

Similar thermal expansion instabilities, consisting of isothermal, time‐dependent changes in thermal expansion after a rapid change in temperature, were observed in epoxy resins with different degrees of cross‐linking. Creep experiments performed at different stages of expansion show decreases in tensile creep rate with decreased expansion. The role of changes in moisture content as a possible cause of the dimensional instability is examined for epoxy resins and a highly cross‐linked polyurethane. Results indicate that the state of expansion is the primary cause of changes in creep rate rather than temperature or moisture content.

Copper Hydroxide Ethanedisulfonate: A Cationic Inorganic Layered Material for High‐Capacity Anion Exchange

“…The exchange gave a decrease of d-spacing from 9.6 to 7.2 for malonate and to 8.6 for succinate. The intercalation of glutarate between the [Cu 4 (OH) 6 ] 2+ layers was also successful and resulted an increase of d-spacing from 9.6 to 11.1 . The completeness of each anion exchange is 100 % for malonate, 98.7 % for succinate, and 92.4 % for glutarate based on the intensity of (001) 1300s (cm À1 ): CÀO, Figure S3].…”

“…Synchrotron single-crystal X-ray diffraction reveals that the structure consists of a cationic copper hydroxide layer with EDS as interlamellar charge-balancing anion ( Figure 1 and Figure 2). The [Cu 4 (OH) 6 ] 2+ layer has two crystallographically independent Cu centers with similar octahedral coordination environments ( Figure 1 and Figure 3). Four oxygens in the positively charged layer define a square-plane around Cu1, while one oxygen (O1) of two separate EDS molecules (one above the given layer, one below) weakly bond to complete the octahedral geometry.…”

“…The other copper atom (Cu2) has the same square-planar connectivity to four intralayer oxygens, with an axial connection to an intralayer hydroxy group and another weak bond to O1 of EDS. All oxygens in the [Cu 4 (OH) 6 ] 2+ layer are protonated and triply bridge to metal centers as for LDHs, with the proton of each pyramidal OCu 3 center pointing towards the interlamellar region. [24] Indeed, CSSD indicates that 92 % of CuÀO bonds are shorter than 2.4 , even with the Jahn-Teller effect.…”

“…[5] Chlorination can lead to even more toxic compounds, such as monohalogenated or oxidized by-products. [6] The typical approach to trap these intrinsically anionic pollutants remains ion exchange resins, though these organic polymers possess limited thermal and chemical stability and thus longevity. [7] Cationic inorganic layered materials are 2-D extended architectures where the positively charged layers are held together electrostatically by charge-balancing anions.…”

A Hexameric Cationic Copper(II) Metallacrown as a Pertechnetate and Perrhenate Scavenger

“…[3] Nevertheless, the relativelyl arge size andl ow charged ensity of TcO 4 À are responsible for small binding constantsa nd small enthalpy of complexation, both of which make recognition and immobilization of this oxoanion difficult. [8,9] Unfortunately,m ost of these methods are based on the use of polymericm aterials (although macrocyclic receptors have also been tested;s ee, for example, ref. An importantg roup of approaches is basedo nm ethods involvings olvent extraction (including the use of multicrown dendrimers [7] )o ri on exchange from aqueousm edia.…”