Synthesis and thermal cure of high molecular weight polybenzoxazine precursors and the properties of the thermosets

Takeichi, Tsutomu; Kano, Takuya; Agag, Tarek

doi:10.1016/j.polymer.2005.10.088

Cited by 313 publications

(262 citation statements)

References 27 publications

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“…10 The yields of various precursors were in the range of 77-87% after purification. The M w was in the range of 6,000-8,900 and M n was 2,200-2,600, showing that the molecular weight is not so high.…”

Section: High Molecular Weight Benzoxazine Precursorsmentioning

confidence: 99%

High Performance Polybenzoxazines as a Novel Type of Phenolic Resin

Takeichi

Kawauchi

Agag

2008

Polym J

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217

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Polybenzoxazines that can be obtained by the thermally induced ring-opening polymerization of cyclic benzoxazine monomers are expected as a novel type of phenolic resins. Various benzoxazine monomers are easily synthesized from mono-or diamines, mono-or bisphenols, and formaldehyde. Polybenzoxazines have not only the advantageous properties of the traditional phenolic resins such as the high thermal properties, but also other properties that are not found in the traditional phenolic resins such as the molecular design flexibility, and excellent dimensional stability. The disadvantages of the typical polybenzoxazines are high temperature needed for the cure and brittleness of the cured materials. Further enhancement of thermal properties is also expected for the applications in harsh conditions. Herein, we report on our various approaches for performance enhancement of the polybenzoxazine, including the designs of novel monomers, high molecular weight polymeric precursors, polymer alloys, and hybrids with inorganics.KEY WORDS: Thermoset / Ring-Opening Polymerization / Thermal Properties / Toughness / Polymer Alloy / Organic-Inorganic Hybrid / Nanocomposite / The traditional phenolic resins possess excellent characteristics such as good heat and chemical resistance, flame retardancy, electrical properties, low water absorption, and low cost due to the inexpensive raw materials and fabricating processes. Therefore, they are widely used in various fields such as structural materials, adhesives, paints and matrix for fiber-reinforced plastics (FRP). Nevertheless, the traditional phenolic resins has many disadvantages including poor shelf life of the precursors, the use of harsh catalyst for polymerization, evolution of volatiles during the cure leading to a large volumetric shrinkage upon cure and formation of voids, and the brittleness of the cured materials. Furthermore, the volatalization of phenol and formaldehyde into the air during the cure process causes some health concern.A series of polybenzoxazine has been developed as a novel type of phenolic resin.1 It differs from the traditional phenolics in that the phenolic moieties are connected by a Mannich base bridge [-CH 2 -N(R)-CH 2 -] instead of methylene (-CH 2 -) bridge associated with the traditional phenolics. The structure of a typical benzoxazine monomer (B-a) prepared from bisphenol-A, aniline and formaldehyde along with the structure of its polybenzoxazine (PB-a) are shown in Figure 1. The monomers for polybenzoxazines are easily prepared from phenols, primary amines and formaldehyde. The wide variations of raw materials, phenols and amines, allow tremendous molecular-design flexibility for the cyclic monomers. Polymerization proceeds through the ring-opening of the cyclic monomers only by heat treatment without the need of catalysts and without generating byproducts or volatiles, and thus offering an excellent dimensional stability for the cured product.Polybenzoxazines provide characteristics found in the traditional phenolic resins such as excellent...

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Section: High Molecular Weight Benzoxazine Precursorsmentioning

confidence: 99%

High Performance Polybenzoxazines as a Novel Type of Phenolic Resin

Takeichi

Kawauchi

Agag

2008

Polym J

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217

150

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“…However, one major disadvantage of the typical polybenzoxazines is their brittleness. Three major approaches are generally considered to overcome this problem: (1) by preparing specially designed novel monomers [26][27][28][29][30][31][32], (2) by blending with polymers or fillers and fibers [33][34][35], or (3) syhthesis of end-chain, sidechain or main-chain polybenzoxazines [36][37][38][39][40]. Among the successful approaches to overcome the inherent brittleness of the thermosets is the modification by rubber [41,42].…”

Section: Introductionmentioning

confidence: 99%

Self-Curable Benzoxazine Functional Polybutadienes Synthesized by Click Chemistry

Küküt

Kışkan

Yaǧcı

2009

Designed Monomers and Polymers

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Novel side-chain benzoxazine functional polybutadiene (PB-benzoxazine) was synthesized by using click chemistry strategy. First, some of double bonds were brominated with Br 2 in CCl 4 and subsequently converted to azido groups by using NaN 3 in DMF. Propargyl benzoxazine was prepared independently by a ring-closure reaction between p-propargyloxy aniline, paraformaldehyde and phenol. Finally, azidofunctionalized polybutadiene was coupled to propargyl benzoxazine with high efficiency by click chemistry. The spectral and thermal analysis confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that PB-benzoxazine undergoes thermally activated curing in the absence of any catalyst forming polybutadiene thermoset with high char yield.

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“…By these methods, thermal properties were improved, but often became even more brittle. To enhance toughness, alloying with elastomers [8] and the use of high molecular weight benzoxazines [9][10][11] are representative methods. Interestingly, these toughening methods often improve also thermal properties by increasing the crosslink density of polybenzoxazine [1].…”

Section: Scheme 1 Synthesis Of B-a and Pb-amentioning

confidence: 99%

Preparation of Imide-modified Benzoxazines and Characterization of Cured Films

Nagata

Kurowarabi

Kawauchi

et al. 2015

J. Photopol. Sci. Technol.

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We synthesized novel monofunctional and bifunctional benzoxazines having imide groups. Brown-colored transparent films were obtained by curing the benzoxazines up to 240 ºC. Monofunctional benzoxazine gave brittle film, but bifunctional benzoxazine gave tough film. Viscoelastic analysis revealed that glass transition temperature of the polybenzoxazine film obtained from the bifunctional benzoxazine was 289 ºC, about 90 ºC higher than that of a typical polybenzoxazine. Thermogravimetric analyses revealed that the introduction of imide groups was also effective to improve the thermal stability of polybenzoxazines.

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Synthesis and thermal cure of high molecular weight polybenzoxazine precursors and the properties of the thermosets

Cited by 313 publications

References 27 publications

High Performance Polybenzoxazines as a Novel Type of Phenolic Resin

High Performance Polybenzoxazines as a Novel Type of Phenolic Resin

Self-Curable Benzoxazine Functional Polybutadienes Synthesized by Click Chemistry

Preparation of Imide-modified Benzoxazines and Characterization of Cured Films

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