Elsevier

Thermochimica Acta

Volume 562, 20 June 2013, Pages 11-21
Thermochimica Acta

Model free kinetics—Thermal degradation of bisphenol A based polybismaleimide–cloisite 15a nanocomposites

https://doi.org/10.1016/j.tca.2013.03.037Get rights and content

Highlights

  • Bismaleimide nanocomposites were prepared using cloisite 15a (1,2,3,4,5,7 and 9 wt%).

  • From FTIR, cloisite 15a interacts with the imide and ether parts of bismaleimide.

  • Microcomposites are formed at higher levels of clay loading.

  • Trend in variation of apparent Ea for degradation depends on the clay loading.

  • The Ea values are attributed to the formation of CO, CO2, amine and isocyanate.

Abstract

Bismaleimide (2,2-bis[4-(4-maleimidophenoxy phenyl)]propane) is prepared, blended with cloisite 15a (1, 2, 3, 4, 5, 7 and 9 wt%) by ultrasonically and thermally polymerized. The FTIR studies reveal that the clay particles affect the maleimide ring and ether linkage of the polybismaleimide. Thermogravimetric studies of cured materials show that the incorporation of clay particles does not affect the degradation temperature values at low levels of clay loading. At higher loadings, the degradation temperature decreases compared to pure polybismaleimide. Degradation kinetics is performed using Vyazovkin and Friedman methods. At lower loadings of clays the apparent activation energy for thermal degradation is nearly constant (α = 0.1–0.8) and at higher loadings the trend is similar to pure polybismaleimide, but the values are lower. This is due to the aggregation of nanoclays leading to microcomposites. The clay particles are well dispersed in the polybismaleimide matrix as evidenced by SEM and TEM studies of the nanocomposites.

Introduction

Inorganic/organic hybrid materials are used in the polymeric matrix systems to achieve unique properties. The materials have both the advantages of inorganic material (rigidity, high thermal stability) and the organic polymer (flexibility, dielectric, ductility and processability) and overcome the disadvantages of these two materials [1]. Only a small amount of these particles drastically enhances the properties of the polymer matrix. Nanoclays is one of the important filler used in the polymer matrix to improve the thermal stability of the polymer matrix systems. Of the different polyimides, bismaleimides are one of the addition polymers having excellent properties such as thermo-oxidative stability, high mechanical strength, high modulus, excellent chemical and corrosion resistance, hot-wet performance and electrical properties [2].

The technical and commercial importance of a polymer is in part based on the thermal stability of the material. Hence, kinetic analysis of the thermal degradation of polymeric materials plays an important role in assessing the reliability of the materials for high temperature applications. A thermal analysis method, mainly thermogravimetric method is extensively used to study the thermal degradation of the polymers. The kinetic parameters [activation energy (Ea), pre exponential factor (A) and reaction model (n)] of thermal degradation of polymers give an idea regarding the decomposition mechanism of the materials [3], [4]. In the beginning, researchers are using single heating rate kinetic methods for evaluating the kinetic parameters of the materials and it gives only a single set of kinetic triplets [5]. The International Confederation of Thermal Analysis and Calorimetry project (ICTAC) 2000, ruled out the single heating rate process and suggests the multiple heating rate processes for evaluating the kinetic triplets [6].

Model fitting kinetic methods are used to determine the kinetic triplets using multiple heating rate programs and the kinetic triplet obtained from these methods for non-isothermal condition is highly uncertain and cannot be compared with the kinetics triplet obtained from isothermal condition [5], [7]. Vyazovkin model free approach through use of isoconversion method leads to a trust worthy way of obtaining reliable and consistent kinetic information from non-isothermal data from DSC and TG studies. The variation of the activation energy with the extent of conversion helps to reveal the complexity of multiple reactions taking place during thermal degradation of materials [5], [8], [9], [10], [11].

In our previous investigations, different types of 3% weight of nanoclays are incorporated into the bismaleimide, 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane and the curing and thermal stability of these materials was investigated. Among the clays, cloisite 15a nanoclay reduces the curing exotherm window and imparts excellent thermal stability to the cured nanocomposite [12]. From these results, different weight levels (1, 2, 3, 4, 5, 7 and 9%) of cloisite 15a (C) were incorporated into the bismaleimide matrix system and the curing behavior of these materials were investigated by DSC and the apparent activation energy for the polymerization of these materials was obtained using three model free kinetic [Flynn–Wall–Ozawa (FWO), Vyazovkin (VYZ), Friedman (FRD)] methods. The added nanoclay particles influence the thermal curing behavior of the bismaleimide material and the variation in the trend of change in the apparent activation energy [13]. Hence in the present work it is intended to investigate the variation in the apparent activation energy for the thermal degradation of the thermally cured bisphenol A based bismaleimide having different loading of nanoclay (cloisite 15a). The two model free kinetic methods (VYZ and FRD) are used to evaluate the apparent activation energies and the results are presented and discussed.

Section snippets

Preparation of bismaleimide (BMIX)

The synthetic procedure (Scheme 1) for the preparation of bismaleimide, 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane, is already presented in detail in the previous work [12].

Organoclay, cloisite 15a

Cloisite 15a is an organically modified montmorillonite system in which the clay layers are modified with dimethyldihydrogenated tallow quaternary ammonium salt. The hydrogenated tallow consists of about 65% C18, about 30% C16, and about 5% C14. It should be mentioned that 100% of Na+ ions in natural montmorillonite have

FTIR studies

The FTIR spectra of the thermally cured bismaleimide (BMIX) and its cloisite 15a nanocomposites are shown in Fig. 1. The thermally cured BMIX shows bands at 1157, 1396 and 1713 cm−1 which correspond to the stretching of single bondCsingle bondOsingle bondCsingle bond group, Cdouble bondC bonds in the phenyl nucleus and the cyclic imide ring (single bondNsingle bond(COsingle bond)2) respectively and this confirms the structure of the thermally cured BMIX. The absence of band at 1635 cm−1(Cdouble bondC imide double bond) [13] confirms the complete polymerization of BMIX.

In the thermally cured

Conclusions

The nitro compound, 2,2-bis(4-nitrophenoxy phenyl)propane was obtained from bisphenol-A and p-chloronitrobenzene, which on reduction in ethanol medium gave 2,2-bis(4-aminophenoxyphenyl)propane. The imidization of bisamic acid derived from the diamine using acetic anhydride and anhydrous sodium acteate in acetone lead to 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane. Nanoclay, cloisite15a (1, 2, 3, 4, 5, 7 and 9 wt%) was blended with bismaleimide by ultrasonically and thermally polymerized. The

Acknowledgements

The authors express their sincere thanks to Directorate of Extramural Research & Intellectual Property Rights (ER&IPR), Defence Research & Development Organization, Ministry of Defence, Government of India, New Delhi 110 105 for financially supporting this work under the grant ERIP/ER/0704359/M/01/1101 dated 12-12-2008. The authors wish to express sincere thanks to Dr. W. Selvamurthy for his keen interest in this research work. The authors would like to thank the Principal and Management of the

References (39)

  • K. Chrissafis et al.

    Can nanocomposites really enhance thermal stability of polymers? Part I. An overview on thermal decomposition of addition polymers

    Thermochim. Acta

    (2011)
  • D. Bikiaris

    Can nanocomposites really enhance thermal stability of polymers? Part II. An overview on thermal decomposition of polycondensation polymers

    Thermochim. Acta

    (2011)
  • B. Jankovic et al.

    Application of model-fitting and model-free kinetics to the study of non-isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel: thermogravimetric analysis

    Thermochim. Acta

    (2007)
  • P. Sivasamy et al.

    A study on the effect of para substitution on the thermal degradation of poly-N-arylmaleimides

    J. Anal. Appl. Pyrolysis

    (2003)
  • W. Xie et al.

    Thermal characterization of PMR polyimides

    Thermochim. Acta

    (2001)
  • C.T. Vijayakumar et al.

    Synthesis and polymerization of bismaleimide derived from 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane

    Polym. Plast. Technol.

    (2009)
  • K. Celis et al.

    kinetics of consecutive reactions in the solid state: thermal decomposition of oxalates

    Meas. Sci. Rev.

    (2001)
  • S. Vyazovkin

    Computational aspects of kinetic analysis: Part C. The ICTAC Kinetics Project – the light at the end of the tunnel?

    Thermochim. Acta

    (1999)
  • S. Vyazovkin et al.

    Kinetics of thermal decomposition of cubic ammonium perchlorate

    Chem. Mater.

    (1999)
  • Cited by (19)

    • Embedding low–cost 1D and 2D iron pillared nanoclay to enhance the stability of polyethersulfone membranes for the removal of bisphenol A from water

      2021, Separation and Purification Technology
      Citation Excerpt :

      The TEM morphology of FePB (Fig. 2d) showed uniquely irregular granular morphology that indicates the bentonite was pillared successfully [33]. The pristine C15A exhibited a smooth surface [45] and appeared as lath shaped (Fig. 2e). For FePC15A, the less disoriented sheets of nanoclay silicate layers observed in Fig. 2f were evidence for pillar intercalated structure.Fig. 3 shows the EDS pattern of pillared nanoclay.

    • Effect of imidazole based polymer blend electrolytes for dye-sensitized solar cells in energy harvesting window glass applications

      2019, Chinese Journal of Chemical Engineering
      Citation Excerpt :

      The TG and DTG curves for polymer blend electrolytes are shown in Fig. 4a (S1–S5). The DTG curve (Fig. 4b) of the film shows that the multi-stage degradations in the degradation system are relatively complex [35]. The onset (Ts), endset (Te), and maximum (Tmax) temperatures for the degradation and the char residue of the samples are listed in Table 1.

    • Distinguishing the combustion stage using the pre-exponential factor and preparation of low-sulfur biomass fuels

      2018, Catalysis Today
      Citation Excerpt :

      Differential scanning calorimetry (DSC) is one of the most commonly used methods to analyze the thermal behavior of biomass [8,9]. Furthermore, the model free iso-conversional Friedman method is a more popular kinetic evaluation program [10,11,12] than other strict iso-conversional rate expression methods [13] and was used to determine the apparent activation energy of sugarcane bagasse combustion [14], volatilization of sunflower oil [15], decomposition of natural fibers [16], and even the synthesis of ZnS quantum dots [17], but no research study was able to directly use the activation energy or pre-exponent factor to predict the reaction progress [18,19]. The kinetic analysis of the thermal effects is mainly done through multivariate non-linear regression [20], however that is a difficult skill to master for most engineers.

    • Kinetic analysis and characterization of an epoxy/cork adhesive

      2015, Thermochimica Acta
      Citation Excerpt :

      The fundamental assumption of the model-free method is that the reaction model f(α) is not dependent on temperature or heating rate. MFK can be used for epoxy [31] and phenolic resins [32], in curing and degradation processes [33], and in isothermal and non-isothermal curing processes [32,34]. Other empirical models can be used for dynamic kinetic studies such as Kissinger and Flynn–Wall–Ozawa models.

    View all citing articles on Scopus
    View full text