Main‐chain benzoxazine oligomers: Effects of molecular weight on the thermal, mechanical, and viscoelastic properties

Abstract

With the intent to study materials processing properties during the curing process, oligomeric benzoxazines of different molecular weight and distribution were obtained from 4‐tert‐butylphenol, bisphenol A, 4,4′‐diaminodiphenylmethane and paraformaldehyde by varying the amounts of phenolic compounds. Average molecular weight and distribution of prepared mixtures of polybenzoxazine precursors were determined by gel permeation chromatography analysis. By knowing the molecular weight distribution of prepared mixtures of polybenzoxazine precursors its effect on thermal, mechanical, and viscoelastic properties of the resin during processing and polymerization could be investigated. Mixtures of polybenzoxazine precursors of higher average molecular weight and broader molecular weight distribution displayed faster curing, lower curing conversions, and higher crosslinking densities of cured resins leading to polybenzoxazines with improved properties. This investigation was oriented towards the material processing aspects with the focus on the effect of molecular weights and viscoelastic properties of starting materials on the proceeding of the curing, including changes in material properties, and sample molding. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46659.

Synthesis and thermal properties of phenol- and amine-capped main-chain benzoxazine oligomers with multiple methyl substitutions

“…This is different from the solvent effect reported before 33 and may be caused by the different reaction rates of the reagents. 35 From another point of view, this result inspires us to find a new way to prepare high-quality MCBOs with narrow molecular weight distribution, which we will report in another research.…”

“…34 Krajnc’s group studied the effect of main-chain with different molecular weights on the material properties. 35 Liu’s group has done systematic research on fluorene-containing polybenzoxazines to enhance the thermal performances of the materials. 36 –39…”

Simulation, design and synthesis of polybenzoxazine with different main‐chain structures and properties: A comparative study

“…There was still a weak absorption peak at 1230 cm −1 , which may be due to the formation of ether structure in the ring‐opening process. There was no peak at 948 cm −1 in the infrared spectra of five PBZ, which proved the opening of the oxazine ring 43 …”

“…As shown in Figure 6, for the H 1 NMR spectra of Co-ddm, a was the vibrational peak of the H connected with the benzene, b was the vibrational peak of the hydrogen atom in the methylene connected with benzene and N of benzoxazine, c was the vibrational peak of the methylene between the oxazine ring, and the subsequent six consecutive peaks were due to the peak of the H on the C C of the methylene in the unsaturated fatty chain of cardanol, which were same as the results reported in the literature. 43 In addition, from the H 1 NMR spectra of (Co-BPA-ddm-Co) main , the characteristic peaks were basically the same, but it was worth noting that the b and c peaks in the H 1 NMR of (Co-BPA-ddm-Co) main were relatively wider because the oxazine ring of (Co-BPA-ddm-Co) main not only had the oxazine ring adjacent to the benzene of cardanol but also had the oxazine ring adjacent to bisphenol-A. As shown in Figure 6, the hydrogen of b* was different from that of b, and the c peak was widened.…”

Rational Design of Waterborne Polyurethane Pressure Sensitive Adhesives for Different Working Temperatures

“…Many works have been focused on the preparation of general WPU-PSAs by adjusting the crosslinking of WPU [ 2 , 4 , 19 ]. The cross-linked structures not only changed hydrogen bonds content in the polymer, but also led to a wider molecular weight distribution of the polymer, which was closely related to adhesive performances of a PSA [ 21 ]. An efficient acrylic/PU hybrid system was developed to control finely the structure networks of polymer and affected adhesive performances [ 22 , 23 ].…”