Characterizations of polybenzoxazine modified with isomeric biphenyltetracarboxylic dianhydrides

Abstract

Abstract.A series of polymeric alloying films were prepared from bisphenol A/aniline-based bifunctional benzoxazine resin (BA-a) with three isomeric biphenyltetracarboxylic dianhydrides, i.e., 2,3!,3,4!-biphenyltetra carboxylic dianhydride (a-BPDA), 2,2!,3,3!-biphenyltetracarboxylic dianhydride (i-BPDA), and 3,3!,4,4!-biphenyltetracarboxylic dianhydride (s-BPDA) through fully thermal curing. Chemical structure, thermomechanical property and thermal stability of bisphenol A/aniline type polybenzoxazine (PBA-a) copolymers were evaluated. Their chemical structures analyzed via Fourier transform infrared spectroscopy reveal ester carbonyl linkage formation between hydroxyl group of the PBA-a and anhydride group in the isomeric dianhydride. Glass transition temperatures (T g s) of the dianhydride-modified PBA-a increased with PBA-a"<<"i-BPDA"<"a-BPDA"<"s-BPDA. Degradation temperatures (T d ) of the PBA-a copolymers recorded to be in the range of 365-402°C were significantly higher than that of the neat PBA-a i.e. 334°C. Finally, char yield of the PBA-a copolymers was found to be about 54-57% which is about twofold increase from that of the parent PBA-a.

Flammability and thermomechanical properties of dianhydride-modified polybenzoxazine composites reinforced with carbon fiber

“…Therefore, the flmmability characteristic of the 65 wt% carbon fiber‐reinforced BA‐a/PMDA copolymer composites can be retarded with PMDA content increased with observation of reduced burning time in Table , suggesting that an addition of the PMDA into the poly(BA‐a) matrix of the carbon fiber composites can help improve the fire resistance of the composites due to carbonaceous char barrier formation that results in blocking of available oxygen caused by the generation of combustion barriers and delay of flame propagation by adiabatic effect. This result is in good agreement with our previous work reported that the char yield value of polybenzoxazine modified with dianhydrides copolymers were much higher than that of the neat poly(BA‐a). In principle, the higher char residue of the copolymer can provide a sample with enhanced flammability because char formation can inhibit volatile products from diffusing to the flame and shield the polymer surface from heat and air .…”

“…From the results, the T g value substantially enhanced with the incorporation of PMDA into the composites. This phenomenon is due to the presence of greater aromatic content and the increased crosslink density via ester linkage between hydroxyl group of poly(BA‐a) and anhydride group of PMDA in the copolymer structures . Furthermore, loss tangent (tan δ) of 65 wt% carbon fiber‐reinforced poly(BA‐a) and 65 wt% carbon fiber‐reinforced PMDA‐modified poly(BA‐a) composites at various mol ratios of PMDA are illustrated in Fig.…”

Property enhancement of polybenzoxazine modified with monoanhydrides and dianhydrides

“…Interestingly, all alloy films of PBAa:PA, PBA-a:NA, PBA-a:PMDA and PBA-a:NTDA demonstrated significantly toughness in comparison with the neat PBA-a. The flexibility enhancement of all alloy samples is attributed to additional ester linkages, structurally flexible functional group, formed in the PBA-a network as a result quoted in previous publications [21][22][23][24].…”

“…Moreover, the free carboxylic acid vibration band occurred after thermal curing of the alloys can also be observed as a band at 1669-1651 cm −1 attributed to C=O stretching band [29]. The reaction models of those monoanhydrides and dianhydrides modified PBA-a alloys are proposed and shown in Scheme 1 as similar to our previous works [21][22][23]. The reaction was also like to the ester formation between a diglycidyl ether of bisphenol A based epoxide resin (DGEBA) and dodecyl succinic anhydride (DDSA) as reported by Ghaemy and Riahy [30].…”

Dielectric and thermal behaviors of fluorine‐containing dianhydride‐modified polybenzoxazine: A molecular design flexibility

“…The obtained copolybenzoxazine at a weight ratio of 1/1 showed a relatively low dielectric constant of 2.36, compared with the value of about 3.56 for the polybenzoxazine without fluorine atoms in its structure. The second approach to enhancing the properties of polybenzoxazine is copolymer formations of the polybenzoxazine with other resins or polymers such as polyimide, polyurethanes, epoxy, and anhydride . Recently, Jubsilp et al .…”