Mechanical and dielectric relaxations of epoxide resins containing the spiro‐ring structure. II. Effect of the introduction of methoxy branches on low‐temperature relaxations of epoxide resins

Abstract

SynopsisMechanisms for low-temperature relaxations of three spiro-ring-type epoxide resin systems with and without methoxy branches were investigated by comparison with those of a bisphenol A-type resin system. In the spiro-ring-type epoxi.de resin systems, two well-defined relaxation peaks, denoted as the 8 and 8' relaxations, and a shoulder peak were observed a t about -70, + 60, and OOC, respectively. The magnitude of the relaxation was decreased by the introduction of methoxy branches on the phenylene group. This phenomenon could be interpreted as a result of the formation of hydrogen bonds between the hydroxy-ether group and methoxy branch.Moreover, it was concluded that the 8' relaxation and the shoulder peak are due to the motion of the p-phenylene group adjacent to the spiro-ring and of the hydroxy-ether group blocked by the hydrogen bond, respectively. that the p' relaxation, which is observed from +50 to + 100°C, is due to the motion of the phenylene group in the n e t w~r k . '~*~ In this paper the effect of the epoxide resin structure on the low-temperature relaxation of cured resins is studied by comparing the relaxation behavior of a bisphenol A-type and three spiro-ring-type resins. The relaxation mechanisms for the cured spiro-ring-type epoxide resins are discussed in detail.

A discussion of the molecular mechanisms of moisture transport in epoxy resins

“…Both groups observe coincident flips of the bisphenol A phenyl rings on a timescale approximately one order of magnitude faster than the OCH 2 OCHOHOCH 2 OOO and OCH 2 ONO motions. However, it is doubtful that flips alone can account for the ␤ relaxation because epoxies where such motions are impossible (e.g., epoxies with a locked ring structure 14 or epoxies based on an asymmetric 1,3 substitution of the phenyl rings as opposed to the symmetric 1,4 substitution of the DGEBA 8 ) still exhibit sim- ilar ␤-relaxation behavior. Regardless of the true foundations for the ␤ relaxation, the OCH 2 O CHOHOCH 2 OOO and OCH 2 ONO segments contain the polar amines and hydroxyls and are mobile.…”

Mechanical properties of epoxy networks based on DGEBA and aliphatic amines

“…[23][24][25] For epoxy/amine networks, most authors [26][27][28][29][30][31][32] associate the b relaxation (between 280 and 2408C) with motion contributions of diphenylpropane groups and glyceryl units: Spectra for six networks are shown in Figure 6 and their characteristics (T b 5 temperature of tan d max , S b 5 area under the tan d curve) are reported in Table IV. Results presented in Table IV are not easy to rationalize.…”

Structures and properties of polycarbonate-modified epoxies from two different blending processes

“…41 relaxation can be suppressed by the formation of hydrogen bonds to other groups. 41,42,46 Indeed, in the present system the carbonate group of PC chains can form the hydrogen bonding with this 2-hydroxypropyl ether. Therefore, strong hydrogen bonding as well as the PC crystallites restricted the segmental motion and depressed the ␤-relaxation peak.…”