Effects of Molecular Structure of Modifiers on the Thermodynamics of Phenolic Blends:  An Entropic Factor Complementing PCAM

Abstract

Different thermodynamics in phenolic blends with different polymeric modifiers, i.e., phenoxy, poly(decamethylene adipate), poly(ethylene oxide), and poly(vinyl alcohol), calculated by the Painter and Coleman association model (PCAM) are examined. The thermodynamics is calculated based upon the equilibrium constants derived experimentally from infrared spectroscopies of low molecular weight analogues with similar hydrogen-bonding formation. The discrepancies between the PCAM predictions and the experimentally observed T g and free volume variation with blending composition are attributed to the additional entropic effects introduced by the long repeated units of modifiers. The structural characteristics and hydrogen-bonding heterogeneity as derived from solid-state NMR and IR spectra support the notion that the length and size of the modifier repeated unit are responsible for such discrepancies. These observed nonidealities can be interpreted as competition between inter- and intraassociations (ΔH m favored), which depend on the entropy rise associated with the amount of increase of the breaking off of the self-association in phenolic and modifiers within blends. While PCAM is based on “true” miscibility, however, minor modification is required to better describe the thermodynamics for “real” blends where microdomain heterogeneity with size greater than that defined by thermodynamic criteria may be present.

Structure and dynamic properties of nitrile‐butadiene rubber/hindered phenol composites

“…Because rubber has excellent damping properties, rubber-based damping materials are used in a variety of applications including transportation, civil construction, precision instruments, and military equipment. 2,3 Homopolymers or random copolymers generally have a glass transition region of 20-30 C, therefore the effective damping temperature range for these materials is also 20-30 C. 4 Because rubber generally has a low T g , and its effective damping temperature range is narrow, pure rubber can satisfy few application requirements without modification. At present, methods like blending, filler reinforcement, and interpenetrating network are used to enhance the rubber damping performance.…”

The Interassociation Equilibrium Constant and Thermodynamic Properties of Phenolic Resin/Polyamide 6 Blend

“…The association equilibrium constant of OH1 amide is much higher than those of OH1OH (l120), OH1 ester (l90), and then OH1 ether (l67). [7] Enthalpies of 2,4-xylenol/NPAA interassociation are estimated from the difference (Dm OH = 217 cm -1 ) between associated and free OH band shifts, described as follows: [11] -Dh (kcal N mol -1 ) = 2.564 + 0.0122 Dm OH (cm -1 ) (2) It shows that the enthalpy of 2,4-xylenol/NPAA interassociation is -5.21 Kcal/mol. Table 3 summarizes the values of the interassociation constants and enthalpies between phenolic resin and polyamide 6 resin.…”

“…This high K A value encouraged us to calculate the thermodynamic properties of phenolic resin/polyamide 6 blend correctly as reported in previous papers. [5,7] There is a series of characteristic data (the inherent properties of polymer, i. e. molar volume, molecular weight of repeated unit, degree of polymerization, and solubility parameters of the neat polymer at 25 8C) are required to calculate the thermodynamic properties of the blends by using MG & PC software. [6] Except for the degree of polymerization and molar volume, which are measured directly, the other polymer properties are estimated by the MG & PC software.…”

“…[1][2][3][4] The Painter-Coleman association model is capable of describing the change of thermodynamic properties that occurs as a result of forming a hydrogen bond with one another. [5][6][7][8][9] Through a number of reports, there has been clear evidence given indicating that PCAM can well be used in polymer blend to predict its thermodynamic properties. [5 -7] The OH group exhibits various interassociation equilibrium constants, K A , when it is hydrogen bonded to a guest functional group.…”

“…The K A value of OH is dependent on the type of guest functional group, and the order is the following: hydroxyl, ester, and then ether group. [7] A high K A value implies the blend system would be miscible and it is convenient for further construction of polymer blends.…”