Poly(urethane‐co‐benzoxazine)s via reaction of phenol terminated urethane prepolymers and benzoxazine monomer and investigation of their properties

Abstract

In the present work, a new method was developed for the combination of polyurethanes (PUs) and polybenzoxazine (PBz) to obtain novel thermoset poly(urethane-co-benzoxazine)s with good thermal, mechanical, and electrical properties as well as low temperature curing profile. Knowing the catalytic effect of compounds possessing free phenolic groups on ring opening polymerization of benzoxazine monomers, preparation of phenol terminated urethane oligomers (PTPU) as the macroinitiator for a benzoxazine monomer (Ba) was considered. Firstly, NCOterminated urethane prepolymers were prepared from the reaction of poly(tetramethyleneether glycol), and 2,4-tolylene diisocyanate, and then end functionalized with bisphenol-A under proper condition. DSC, DMTA, and gel content measurements were applied to find optimum ring opening polymerization condition (170-C for 1 hr and 200-C for 15 min). Various kinds of thermoset polymers were prepared by the reaction of PTPU at different molecular weights with variable contents of Ba. All of monomeric and polymeric materials were characterized by conventional spectroscopic methods and their thermal, mechanical, viscoelastic, and electrical properties were measured and properties were correlated to their structure. Due to the interesting properties of these new materials, the possibility of using them as electrical insulators with higher service temperature in comparison to common PUs were examined and their potential applicability was confirmed.

Preparation and properties of cardanol‐based polybenzoxazine/SiO2 hybrids by sol‐gel technique

“…Figure 9 represents FT‐IR spectra of PCBZ and cardanol‐based polybenzoxazine/SiO 2 hybrids. Compared with the FT‐IR spectroscopy of CBZ, for all samples (PCBZ, PCBZT1, PCBZT2, and PCBZT3), the peaks at 937 cm −1 disappeared and the new absorption peak appeared at 1461 cm −1 due to the tetra substituted benzene ring, which confirmed the ring‐opening polymerization of CBZ 5–8. In addition, the absorption peak at 1084 cm −1 confirmed the formation of –Si–O–Si–linkage due to the hydrolysis reaction of TEOS and the following condensation reactions of Si‐OH.…”

“…But the major shortcoming of polybenzoxazines is their brittleness and need for high curing temperature, which limits their application. Various efforts have been made to improve the properties of polybenzoxazines via the formation of copolymer, polymer alloys, fiber reinforced composites, nanocomposites, etc 5–8…”

Chemorheology and thermomechanical characteristics of benzoxazine‐urethane copolymers

“…Thermal stability of the resulting networks was improved by increasing PU molecular weight as well as BA‐a content. 13 Interesting characteristics of some, benzoxazine‐urethane alloy systems were also observed by Rimdusit et al According to this report, benzoxazine resin (BA‐a) was alloyed with isophorone diisocyanate/polyether polyol (Mw 2000) based PU. The obtained alloys not only provided expected enhancement on their flexibility but also exhibited synergism in glass transition temperature ( T g ).…”

A novel hyperbranched polyborazine and its reactive blend with benzoxazine thermosets

“…Polybenzoxazine is a novel type of addition‐cure phenolic system and it has gained immense interest due to its potential to overcome several shortcomings of the traditional resole‐type phenolic resins while retaining such benefits as near zero volumetric upon cure, low water absorption, no strong acid catalysts required for curing, and no byproduct released during curing, etc. [21–27]. However, polybenzoxazines require somewhat higher polymerization temperature and monomer‐based polybenzoxazines are brittle as is the case for all other thermosetting resins.…”