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Bio-Implants Derived from Biocompatible and Biodegradable Biopolymeric Materials
Published in P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas, Advanced Studies in Experimental and Clinical Medicine, 2021
Microcapsules were added to PLA to form a composite material with self-healing property. The microcapsules are filled with additives for healing. It can function when cracked and releasing the self-healing additives to fractured areas. This can also function as nucleating agents to improve the PLA composite’s temperature resistance. Self-healing microcapsules can be created by encapsulating the dicyclopentadiene and Grubbs catalyst. It is then released into damage volumes and undergoing polymerization by the chemical reaction of the catalyst. This technique helps in the recovery of the polymer composite’s toughness towards facture.
Modified self-healing cementitious materials based on epoxy and calcium nitrate microencapsulation
Published in Journal of Microencapsulation, 2021
Fahimeh Farshi Azhar, Aylin Ahmadinia, Alireza Mohammadjafari Sadeghi
For protection of healing agent from environmental conditions, a practical container (shell) such as phenol–formaldehyde (PF) resins (Jadhav et al.2011, Leyang et al.2016), urea–formaldehyde (UF) resins (Xing and Ni 2013, Dong et al.2016, Wenting et al.2016), and melamine–formaldehyde (MF) resins (Liu et al.</em, Li et al.2016) were developed. Among these materials, poly (urea-formaldehyde) (PUF) is widely used as a shell because of its unique properties such as good seal performances, flexibility, penetration resistance, high strength and impermeability. In addition, PUF microcapsules have controllable size and shell thickness. The encapsulation process starts by reaction of the urea and formaldehyde in the water phase and in the continue, formation of the colloidal cross-linked particles around the emulsified healing agent droplets. Therefore, the healing agent, as the core, is covered by the PUF shell wall (Çömlekçi and Ulutan 2018 ). Up to now, microencapsulation of PUF shell and different healing agents such as dicyclopentadiene (DCPD) (White et al.2001), epoxy (Yin et al.2007, Yuan et al.2008, Wang et al.2009, Jin et al.2012, Dong et al.2016), linseed oil (Suryanarayana et al.2008) and diglycidyl tetrahydro-o-phthalate (DTP) (Yuan et al. 2008) has been investigated.
Influence of synthesis parameters on properties and characteristics of poly (urea-formaldehyde) microcapsules for self-healing applications
Published in Journal of Microencapsulation, 2019
Ana Cláudia Medeiros de Carvalho, Evans Paiva da Costa Ferreira, Mauricio Bomio, José Daniel Diniz Melo, Ana Paula Cysne Barbosa, Maria Carolina Burgos Costa
Endo-dicyclopentadiene (DCPD) (Sigma-Aldrich, St. Louis, MO, USA) with a melting point of 33 °C was used as self-healing agent (core material). Grubbs catalyst first generation (Sigma-Aldrich, St. Louis, MO, USA, P.A. 97%) was used as catalyst of the self-healing system. Epoxy monomer Ar260 (Barracuda) and hardener AH260 (Barracuda) were used as epoxy matrix.
Investigation on the mechanical properties of polyurea (PU)/melamine formaldehyde (MF) microcapsules prepared with different chain extenders
Published in Journal of Microencapsulation, 2018
Jianfeng Hu, Xiaotong Zhang, Jinqing Qu
Compared with other self-healing systems, like dicyclopentadiene (DCPD)-Grubbs catalyst, isocyanate offers advantages since it is one-component and catalyst free self-healing system (Koh et al. 2013, He et al.2014, Khun et al. 2014, Koh et al. 2014), which can be cured by moisture. In isocyanate serials, isophorone diisocyanate (IPDI) is a good choice because of its low viscosity and enough reactivity with water (Sardon et al. 2009). Yang et al. (2008) encapsulated IPDI with polyurethane for the first time. Then, Credico et al. (2013) used polyurethane and polyurethane/urea formaldehyde (UF) to encapsulate it and studied the morphology, thermal stability and core fraction. In 2014, Wang et al. (2014a, 2014b) demonstrated the mechanism of self-healing process of IPDI microcapsules with a UF shell through measurements using a scanning micro-reference electrode (SMRE) technique and electrochemical impedance spectroscopy (EIS). After that, Yi et al. (2015) formulated the microcapsules made of IPDI-loaded multilayers, which showed outstanding performances in thermal and solution resistance. Considering the mechanism of microcapsule-based self-healing materials, the core material is one of the key factors to affect the self-healing efficiency (Ming et al. 2016). Furthermore, the mechanical properties of self-healing microcapsules are crucial, which should be optimised since they cannot be too weak or too strong (Hu et al. 2009). Adjusting the shell thickness can change the mechanical properties of microcapsules. However, preparation of moisture-curing microcapsules with a core of isocyanate, like IPDI, normally requires preparation of an oil (O)/water (W) emulsion, followed by chemical reaction for a period of time. The core material has high reactivity with water. It is not always desirable to prepare a thicker shell of microcapsules using a longer reacting time since water can be trapped in the core, which reduces their storage stability (Hu et al. 2009, Ming et al. 2016). It has been found that the mechanical strengths of microcapsules made of different shell materials including melamine formaldehyde (MF) and UF, characterised by a micromanipulation technique (Zhang et al. 1999, Sun and Zhang 2001, 2002), were significantly different. MF microcapsules were stronger and ruptured at larger deformations than UF for a given size and shell thickness (Sun and Zhang 2002). It is likely that the mechanical strength and deformability of microcapsules depend on their formulation and processing conditions.