Recently, there is a growing interest in the functionalization of polymers to impart self-healing capability to polymer products in which damages can be repaired by stimuli. The self-healing polymeric materials are prepared based on the principle of recovering damages by enabling molecular movement ...
Recently, there is a growing interest in the functionalization of polymers to impart self-healing capability to polymer products in which damages can be repaired by stimuli. The self-healing polymeric materials are prepared based on the principle of recovering damages by enabling molecular movement by external stimuli. However, self-healing in composite materials of organic polymers containing inorganic reinforcements or fillers is very limited due to the difficulty of molecular movement of organic polymers hindered by the inorganic reinforcements or fillers. Cross-linked polyurethanes (PUs) are widely used for coatings, adhesives, or foams and often used as a composite material in which inorganic reinforcing materials or fillers are incorporated. In this study, the effects of inorganic components and coupling agents on the self-healing crosslinked PUs were investigated. PU prepolymers were prepared from commercially available toluene diisocyanate (TDI-80) and polypropylene glycol (PPG) diol / triol mixtures and chain extended with hydroxyethyl disulfide (HEDS) to impart self-healing capability to the crosslinked PUs by disulfide metathesis. The PPG diol / triol (8/2 by weight) mixture showed the best mechanical properties due to the proper microphase separation of the soft and hard segment domains in the crosslinked PUs. It was confirmed that the cross-linked PUs showed self-healing properties for the scratches on the surface via the metathesis reaction of disulfide groups in HEDS. The cross-linked PU composites containing 0.2, 0.4, 0.6, and 0.8 phr of graphene nanoplates (GNP) were prepared and characterized. It was observed that the mechanical strengths of the composites increased significantly at low contents of GNPs, but self-healing properties were restricted. The addition of furfuryl mercaptan (FM) as a coupling agent of the PU and GNP was studied as the furfuryl group of FM can undergo Diels-Alder reaction with GNP reversibly and mercaptan group can participate in the disulfide metathesis reactions. By incorporating FM into the composites of PU and GNP, the composites showed scratch healing at elevated temperatures. FM was observed mainly on the graphene surface and exhibited the Diels-Alder reaction. In addition, mercaptan groups participated in disulfide metathesis, resulting in lowering the crosslinking density and mechanical strength of the PU composites. Cross-linked polyurethane composites containing 10, 20, 30, or 40 phr of calcium carbonate (CaCO3), which is frequently used in industrial products, were prepared and characterized. In PU/CaCO3 composites, mercaptopropionic acid (MA) was studied as a coupling agent as the acid group has affinities with calcium carbonate via acid-base interactions and the mercaptan can undergo metatheses with PUs chain extended with HEDS. It was confirmed that the addition of the coupling agent could restore the self-healing properties of the cross-linked PU/CaCO3 composites while the composites without the coupling agents could not repair the scratch. However, it was found that increasing the loading of calcium carbonate more than 10 phr makes the composites difficult to implement self-healing properties through the addition of coupling agents. It is inferred that the incorporation of coupling agents designed properly for the composites resulted in the improvement of self-healing capability of cross-linked PU composites.
Recently, there is a growing interest in the functionalization of polymers to impart self-healing capability to polymer products in which damages can be repaired by stimuli. The self-healing polymeric materials are prepared based on the principle of recovering damages by enabling molecular movement by external stimuli. However, self-healing in composite materials of organic polymers containing inorganic reinforcements or fillers is very limited due to the difficulty of molecular movement of organic polymers hindered by the inorganic reinforcements or fillers. Cross-linked polyurethanes (PUs) are widely used for coatings, adhesives, or foams and often used as a composite material in which inorganic reinforcing materials or fillers are incorporated. In this study, the effects of inorganic components and coupling agents on the self-healing crosslinked PUs were investigated. PU prepolymers were prepared from commercially available toluene diisocyanate (TDI-80) and polypropylene glycol (PPG) diol / triol mixtures and chain extended with hydroxyethyl disulfide (HEDS) to impart self-healing capability to the crosslinked PUs by disulfide metathesis. The PPG diol / triol (8/2 by weight) mixture showed the best mechanical properties due to the proper microphase separation of the soft and hard segment domains in the crosslinked PUs. It was confirmed that the cross-linked PUs showed self-healing properties for the scratches on the surface via the metathesis reaction of disulfide groups in HEDS. The cross-linked PU composites containing 0.2, 0.4, 0.6, and 0.8 phr of graphene nanoplates (GNP) were prepared and characterized. It was observed that the mechanical strengths of the composites increased significantly at low contents of GNPs, but self-healing properties were restricted. The addition of furfuryl mercaptan (FM) as a coupling agent of the PU and GNP was studied as the furfuryl group of FM can undergo Diels-Alder reaction with GNP reversibly and mercaptan group can participate in the disulfide metathesis reactions. By incorporating FM into the composites of PU and GNP, the composites showed scratch healing at elevated temperatures. FM was observed mainly on the graphene surface and exhibited the Diels-Alder reaction. In addition, mercaptan groups participated in disulfide metathesis, resulting in lowering the crosslinking density and mechanical strength of the PU composites. Cross-linked polyurethane composites containing 10, 20, 30, or 40 phr of calcium carbonate (CaCO3), which is frequently used in industrial products, were prepared and characterized. In PU/CaCO3 composites, mercaptopropionic acid (MA) was studied as a coupling agent as the acid group has affinities with calcium carbonate via acid-base interactions and the mercaptan can undergo metatheses with PUs chain extended with HEDS. It was confirmed that the addition of the coupling agent could restore the self-healing properties of the cross-linked PU/CaCO3 composites while the composites without the coupling agents could not repair the scratch. However, it was found that increasing the loading of calcium carbonate more than 10 phr makes the composites difficult to implement self-healing properties through the addition of coupling agents. It is inferred that the incorporation of coupling agents designed properly for the composites resulted in the improvement of self-healing capability of cross-linked PU composites.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.