Electrical and Structural Properties of HDPE/MWCNT/PE-g-MAH Nanocomposites Prepared Using Solution Mixing and Hot Compaction Two-Step Approach

Background: MWCNTs tend to form agglomerates in nonpolar polymers due to their small size and high surface area. A promising approach to facilitate their dispersion within the polymeric matrix is based on employing a compatibilizer agent. Objective: The current study aimed to investigate the effect of a compatibilizer agent based on maleic anhydride grafted HDPE (PE-g-MAH) on the electrical and morphology properties of high density polyethylene/multi wall carbon nanotubes nanocomposites (HDPE/MWCNT/PE-g-MAH) prepared by solution mixing and hot compaction two-step approach. Methods: A two-step approach based on solvent mixing and hot compaction was used to prepare nanocomposites of HDPE/MWCNT/PE-g-MAH with different MWCNTs and PE-g-MAH contents. The electrical, morphology and HDPE crystalline structure properties of the nanocomposites were characterized by impedance spectroscopy, high resolution field emmision scanning electron microscopy and X-ray diffraction, respectively. Results: The results confirm the positive role of the PE-g-MAH compatibilizer in enhancing the dispersion of the MWCNTs and in turn the formation of more conductive pathways at low MWCNTs content in the nanocomposites. Adding 2 wt% of the compatibilizer to the nanocomposite of 1 wt% MWCNTs increases the electrical conductivity more than three orders of magnitude. Increasing the MWCNTs concentration more than 1 wt% leads to a limited enhancement in conductivity of the nanocomposite prepared using 2 wt% of PE-g-MAH compatibilizer. Meanwhile, the morphological characterization revealed that the limited increase in conductivity of nanocomposites with only 1 wt% compatibilizer is related to a substantial increase in the HDPE crystallinity (from 14.8 to 43.9%) induced by the enhanced nucleating effect of the dispersed MWCNTs. The excess HDPE crystalline regions suppress the formation of effective MWCNTs conducting pathways due to their confinement into smaller inter-crystallite regions in the nanocomposite. Conclusion: Therefore, a balanced role of the compatibilizer between dispersion of the MWCNTs and the nucleation of more HDPE crystallites has to be achieved by carefully selecting the compatibilizer type and concentration.

Protective Low-Density Polyethylene Residues from Prepreg for the Development of New Nanocomposites with Montmorillonite: Recycling and Characterization

A sustainable alternative to the destination of polyethylene (PE) residue from the prepreg package was established. This work intends to develop nanocomposites for packaging containing neat low-density polyethylene (LDPE), a compatibilizer agent (maleic anhydride grafted-LDPE, LDPE-g-MA), recycled LDPE obtained from the protective films of prepreg (rLDPE) and montmorillonite (MMT). The rLDPE, from the prepreg shield, has a primary role during the transport and storage of prepreg, which can be composed of epoxy resin and carbon fiber or glass fiber. However, this rLDPE is withdrawn and discarded, besides, it is estimated that tons of this material are discarded monthly by the company Alltec Materiais Compostos Ltd. (São José dos Campos-SP, Brazil). Due to several factors, including the lack of technology for recycling, the majority of this material is incinerated. In this context, this work presents a technical and ecologically viable alternative for the use of this discarded material. Nanocomposites of LDPE/rLDPE blends and montmorillonite (MMT) with different contents (0.0, 1.0, and 3.0 wt%) and with the addition of compatibilizer agent (LDPE-g-MA) were prepared by extrusion process. Test specimens were obtained by hot pressing in a hydropneumatic press followed by die-cutting. The nanocomposites produced using rLDPE presented good mechanical, thermal, and morphological properties, being the ideal concentration of 1 wt% MMT. Thus, the results obtained confirmed the viability of recycling LDPE from the prepreg package which contributes to the reduction of waste and the use of this material in technological applications.

Optimization of Maleinized Linseed Oil Loading as a Biobased Compatibilizer in Poly(Butylene Succinate) Composites with Almond Shell Flour

Green composites of poly(butylene succinate) (PBS) were manufactured with almond shell flour (ASF) by reactive compatibilization with maleinized linseed oil *MLO) by extrusion and subsequent injection molding. ASF was kept constant at 30 wt %, while the effect of different MLO loading on mechanical, thermal, thermomechanical, and morphology properties was studied. Uncompatibilized PBS/ASF composites show a remarkable decrease in mechanical properties due to the nonexistent polymer‒filler interaction, as evidenced by field emission scanning electron microscopy (FESEM). MLO provides a plasticization effect on PBS/ASF composites but, in addition, acts as a compatibilizer agent since the maleic anhydride groups contained in MLO are likely to react with hydroxyl groups in both PBS end chains and ASF particles. This compatibilizing effect is observed by FESEM with a reduction of the gap between the filler particles and the surrounding PBS matrix. In addition, the Tg of PBS increases from −28 °C to −12 °C with an MLO content of 10 wt %, thus indicating compatibilization. MLO has been validated as an environmentally friendly additive to PBS/ASF composites to give materials with high environmental efficiency.

KAJIAN MODIFIKASI KIMIA SECARA KOPOLIMERISASI CANGKOK PADA PEMBUATAN KARET ALAM TERMOPLASTIK

Modifikasi diperlukan untuk memperbaiki kelemahan karet alam sehingga dapat memperluas aplikasinya dalam industri. Salah satu modifikasi kimiawi pada lateks karet alam terdeproteinisasi dapat dilakukan secara kopolimerisasi cangkok dengan monomer termoplastik golongan vinilik (metil metakrilat dan stirena) untuk menghasilkan karet alam termoplastik yang bersifat kuat, keras, kaku, mudah diproses, dan tahan terhadap oksidasi. Kopolimerisasi cangkok umumnya dilakukan dengan teknik polimerisasi emulsi mekanisme radikal bebas. Keberhasilan reaksi kopolimeriasi cangkok yang ditunjukkan dengan efisiensi cangkok yang tinggi dipengaruhi oleh rasio karet terhadap monomer, serta pemilihan jenis dan dosis inisator maupun emulsifier. Hasil kopolimer yang terbentuk dapat dikonfirmasi melalui analisis kualitatif maupun kuantitatif. Dalam industri kopolimer karet alam dengan monomer vinilik dapat digunakan sebagai perekat atau adhesif, compatibilizer agent, surface modified agent, hardness modifier, serta industri alas kaki. Oleh karena itu penelitian dan pengembangan tentang kopolimerisasi cangkok karet alam dapat mendukung kemajuan agroindustri karet alam nasional.