Molecular mobility and relaxation processes in an epoxy matrix 2. effects of weathering in humid subtropical climate

Natural Climatic Aging of Epoxy Polymers Taking into Account the Seasonality Impact

“…Quantitative values of the glass transition temperature determined using the method of dynamic mechanical analysis, as well as the duration of the accumulated time intervals depending on the season are given in Table 1. Along with quantitative environmental parameters, the moisture content of the samples at the time of direct testing is considered as a factor that has a direct impact on the mechanical strength of epoxy polymers [5,6,13,14]. In particular, it is known that in the process of full-scale climatic aging, the mass of the exposed polymer samples irreversible increases which is described by some researchers from the point of view of eliminating the initial structural disequilibrium [2,[14][15][16].…”

The Influence of Internal Stresses on the Aging of Polymer Composite Materials: a Review

“…The polymer matrices of PCMs are moderately hydrophilic systems and are able to absorb up to 3-5% of water [1,2,8,14,15,17,38]. Therefore, to clarify the effect of internal stresses on the aging of PCMs, it is important to analyze the thermal cycling of moisture-saturated PCMs.…”

“…A comparison of the research results obtained in [23,56,57] shows that, if the thermal cycling is carried out in the range of positive and negative temperatures, wet PCMs deteriorate their mechanical characteristics with a higher probability than dry ones. This process is facilitated by the internal stresses caused by both swelling (7), (8) and transition to the glassy state of water in the free volume of polymer matrices by the mechanism considered in [58].…”

“…The examples considered illustrate the noticeable effect of internal stresses on changes in the mechanical parameters of PCMs at the initial stages of aging (thermal [24, 25, 53-55, 66, 74], thermal and humid [25,[61][62][63][64][65]67], climatic [8][9][10][11][12][13][14][15][16][17], [23,27], and in open space [72]), when the threshold number N 0 of thermal cycles was exceeded. However, due to relaxation of internal stresses at later stages, a certain limiting state of physicochemical transformations and microfaults is reached [49], and then the change in the indices of material characteristics is significantly reduced.…”

“…When considering the causes for aging of polymer composite materials (PCMs) based on thermosetting binders mentioned in the foreign [1][2][3][4][5][6][7] and domestic [8][9][10][11][12][13][14][15][16][17] literature, the influence of temperature, humidity, solar radiation, oxygen, chemically active substances, erosion, precipitation on condition of matrices, reinforcing fillers, polymer-filler interfaces are discussed. Under the influence of these factors, destruction, hydrolysis, additional hardening, swelling, plasticization, structural relaxation and other physicochemical transformations occur in them, which accelerate or slow down the changes in their mechanical parameters [16].…”