Phthalonitrile polymers: Cure behavior and properties

Abstract

This article compares the cure behavior and properties of phthalonitrile polymers derived from three different monomers, namely, 4,4Ј-bis(3,4-dicyanophenoxy)biphenyl, 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]hexafluoropropane and 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]propane. Rheometric measurements with monomer melt in the presence of an aromatic diamine curing agent reveal that the rate of the cure reaction differs for the three monomers. The rate is dependent on the concentration of the curing agent. The glass transition temperature advances with increasing extent of cure and disappears upon postcure at temperatures in excess of 350°C. Based on thermogravimetric analysis, the thermal stability of all three polymers are comparable, whereas the fluorine-containing resin shows the best oxidative stability at elevated temperatures. Microscale calorimetric studies on all three polymers reveal that the char yields are high and the total heat release upon exposure to 50 kW/m 2 flux for each polymer is low, compared to other thermosets. Flexural strength ranges between 80 -120 MPa. The water uptake under ambient conditions is less than 3% by weight after submersion in water for seven months.

A Molecular Dynamics Study of Crosslinked Phthalonitrile Polymers: The Effect of Crosslink Density on Thermomechanical and Dielectric Properties

“…The non-bonded van der The initial uncrosslinked molecular model structure was established using a procedure similar to that used by Varshney et al [12]. In accordance with experimental measurements conducted by Keller et al [13] a molar ratio of 28:1 (BPh:m-APB) with a density of 1.2 g/cm 3 is selected in this study. Image of the initial uncrosslinked structure along with a 3D molecular structure of the cross-linking agent and monomer are shown in Figure 2 below.…”

Self-promoted curing phthalonitrile with high glass transition temperature for advanced composites

“…The exothermic transition peaked at 239°C and the enthalpy of cure was 179.3 J/g, which were a result of self-promoted curing reaction of the 3-APN monomer between the amino group and phthalonitrile units. For these phthalonitrile monomers [9][10][11][12][13][14][15][16][17][18][19][20][21], the polymerization reaction occurs through the nitrile groups of the phthalonitrile units in the presence of aromatic diamine curing agents and these exothermic transitions of the cure reaction peaked at 250-270°C. In addition, the maximum processing temperature was up to 425°C and the heat-treatment time was very long (> 10 h) due to the low reactivity of the phthalonitriles.…”

“…Therefore, tremendous interests has been focused on initiating the curing process and shortening the curing time of phthalonitrile resins at the present of various curing additives such as phenols [15], organic amines [16], strong organic amines [17] and strong organic acid/amine salts [18]. Thus, the research efforts were concerned mainly with aromatic amines such as bis [4(4-aminophenoxy)phenyl]sulfone (p-BAPS), 1,3-bis(3-aminophenoxy)benzene (m-APB) and 1,4-bis(4-aminophenoxy)benzene (p-APB) [13,19].…”

Low-melting siloxane-bridged phthalonitriles for heat-resistant matrices

“…Since 1950s the a considerable amount of researches dedicated to development of polymer matrices possessing high thermal stability, convenient processability and good mechanical properties had been conducted. According to these requirements several types of resins had been developed, including polyimides [1][2][3] and modified phenolic resins [4,5], phthalonitriles [6][7][8][9][10] and others.…”

“…In 1958 Marvel and Martin first attempted to introduce a phthalocyanine moiety in the polymer structure however the resulting polymer had a low molecular weight [12]. The rapid development of the phthalonitrile-based matrices began in 1980s and since they have been gradually established as one of the most prospective resins for the composite materials due to high glass transition temperature, outstanding thermal and thermo-oxidative stability, excellent mechanical properties, good moisture resistance and superior fire resistance [6][7][8][9][10]. Nevertheless phthalonitriles had disadvantages such as high softening points (180-250°C) which raised and narrowed the processing window due to the start of polymerization shortly after melting (around 230°C) which caused the viscosity growth.…”