Use of PP Grafted with Itaconic Acid as a New Compatibilizer for PP/Clay Nanocomposites

SEBS-Grafted Itaconic Acid as Compatibilizer for Elastomer Nanocomposites Based on BaTiO3 Particles

Itaconic acid (IA) is an organic acid produced by the fermentation of sugars with aspergillus. It has been identified as one of the top 12 building-block chemicals. Here, we report the use of IA as a possible substitute to petroleum-based compatibilizers in polymer composite. We applied this study to thermoplastic elastomers based on styrene copolymers, since they are commonly used in blends and composites. Poly(styrene-b-ethylene-butylene-b-styrene) (SEBS) was grafted with 2.6 wt.% of itaconic acid (SEBS-g-IA) prepared by a reactive melt-mixing process, and was subsequently used to prepare composites filled with BaTiO₃.). IA was successfully grafted as demonstrated by FTIR and XRD. SEBS-g-IA composites presented better mechanical properties, achieving an increase of Young modulus up to 80% compared with the neat polymer. This was ascribed to better dispersion and compatibility with the filler. Additionally, SEBS-g-IA showed increased dielectric permittivity, i.e., showed increased polarity, which indicates that it could potentially be used as a modifier for specialized polymers.

Compatibilizer Polarity Parameters as Tools for Predicting Organoclay Dispersion in Polyolefin Nanocomposites

Nanocomposites give an innovative method to increase the mechanical, thermal, and barrier performance of polymers. However, properly dispersing the nanoparticles in the polymer matrix is often key in achieving high performance, especially in the case of hydrophilic nanoparticles and hydrophobic polymers. For that purpose, nanoparticles may be functionalized with organic groups to increase their affinity with the polymer matrix. Compatibilizing agents may also be included in the nanocomposite formulation. This paper aims at identifying parameters relative to the compatibilizer polarity that would allow predicting nanoparticle dispersion in the polymer nanocomposite. The analysis used published data on nanocomposite samples combining clay nanoparticles, polyolefins, and various compatibilizing agents. We studied the correlations between the nanoclay exfoliation ratio and five different parameters describing the compatibilizer hydrophilic-lipophilic balance: the acid value, the mole, and weight fraction of polar groups, the number of polymer chain units per polar group, and the number of moles of polar groups per mole of compatibilizer. The best correlation was observed with the number of polymer chain units per polar group in the compatibilizer. This parameter could be used as a tool to predict the dispersion of organoclay nanoparticles in polyolefins. Another important result of the study is that, among the compatibilizers investigated, those with a low acid value provided a better nanoclay exfoliation compared to those with a high acid value. This may indicate the existence of a maximum in the nanoclay exfoliation/compatibilizer polarity curve, which would open new perspectives for nanocomposite performance optimization.

Application of the Experimental Results to the Modified Halpin-Tsai Micromechanical Model to Evaluate the Clay Dispersion in Clay-Reinforced Polyethylene Nanocomposites

Low-density polyethylene (LDPE)- and linear low-density polyethylene (LLDPE)-based polymer nanocomposites (PNC) containing organically modified montmorillonite (MMT) were prepared by melt mixing process. Itaconic acid (IA) and monomethyl itaconate (MMI) grafted polyethylene (PE) were used as compatibilizers. Na-MMT was modified by dodecyl-, hexadecyl-, and octadecyl-ammonium chlorides and then the compatibilizers were synthesized in solution reaction. 5 wt% organoclay and different concentration of compatibilizers (5, 10, and 15 wt%) were used for the PNC preparations to compare the effects of compatibilizers. The interlayer spacings, d001, and the mechanical properties of samples were measured by XRD analysis and universal testing machine, respectively. The experimental tensile moduli were used in Halpin-Tsai micro mechanical model to obtain “l/t” ratios and the results were compared experimental d001 values obtained from XRD data. It was found that the experimental results are in good agreement with the calculated results.