This work reports on the development of a novel polymer blend with thermally triggered shape memory and self-healing properties. Blends were prepared by mixing a self-healing ionomer (Surlyn 9520) and polycyclooctene (with and without crosslinking agent) in different ratios. The regions of thermal activation were determined by thermogravimetric analysis, differential scanning calorimetry and oscillatory shear rheology. Consecutively, the shape memory and self-healing behaviour were investigated by a torsion procedure and tensile testing respectively. It was found that ionomer/crosslinked polycyclooctene blends of 70/30 wt% lead to polymers showing partial macroscopic healing and repeatable shape memory characteristics. The new polymer system shows both dual and triple shape memory behaviour and a near to 100% stiffness recovery after healing of crosscuts at standard ionomer healing conditions. Furthermore, the relation between terminal relaxation and self-healing in blends is shown. This study introduces a triple shape memory polymer with self-healing properties by a blending strategy thereby clearing the path for more durable materials based on shape memory properties.

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We report the development of an intrinsic healing glass fibre reinforced polymer (GFRP) composite based on a disulphide-containing organic-inorganic thermoset matrix. Thermomechanical experiments showed that the newly developed matrix has a combination of a Young's modulus value in the range of (800–1200 MPa), the ability to multiple thermally induced healing delamination (70–85 °C), and processability by conventional vacuum infusion process that is not yet reported in literature. The composite mechanical properties and the extent of healing were determined by flexural, fracture and low-velocity impact testing. Small sized (<cm²) damage could be partially healed multiple times using a minimal healing pressure to ensure a good alignment of the damaged interfaces. The level of healing can be enhanced, even for large (>cm²) damage, by increasing the healing pressure provided the location of the primary damage is concentrated within the matrix phase. The polymer matrix composite introduced here represents a significant step forward from the often mechanically inferior intrinsically self-healing composites towards structural self-healing composites.

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Over the past decade, many different strategies were developed to introduce selfhealing properties in structural polymer composite materials. Although many of the investigated routes show promising results on an academic scale, the first commercially feasible self-healing structural polymer composite has yet to be developed. The main objective of this thesis is to contribute to the gap closure between the academic concept of structural self-healing composites and its fully implemented industrial applications. As such, each chapter targeted one of the existing scientific issues, within some of the most promising healing strategies available, that are currently preventing the industrial acceptance of self-healing polymer composites. @en

A comparative study is performed on the monitoring of delamination healing in CFRP-ionomer sandwich composites by non-destructive techniques and destructive compression testing. Artificial delaminations of various areal dimensions and nature were introduced during production of the composites. The extent of the delamination and the healing thereof was monitored in both air and water-coupled ultrasonic C-scan experiments as well as by the frequency shift of the local defect resonance (LDR). It is shown that the LDR approach can be used to detect the early stage healing of the delaminations while ultrasonic C-scanning techniques are very effective to determine the extent of healing in the final stages of the repair process. A quasi-linear relation was observed between the delaminated area measured with ultrasonic C-scan and the compressive failure strength in destructive testing. This correlation shows the beneficial effect on the compression strength of the delaminated area reduction by on-demand healing.@en

This article presents development of a novel self-healing technology for asphalt pavements, where asphalt binder rejuvenator is encapsulated within the compartmented alginate fibres. The key objective of the study was to optimise the compartmented alginate fibre design, i.e., maximising amount of rejuvenator encapsulated within the fibre. The results demonstrate that optimum rejuvenator content in the alginate fibre is of 70:30 rejuvenator/alginate ratio. The fibres are of sufficient thermal and mechanical strength to survive harsh asphalt mixing and compaction processes. Furthermore, results illustrate that zeer open asfalt beton (ZOAB) asphalt mix containing 5% of 70:30 rejuvenator/alginate ratio compartmented alginate fibres has higher strength, stiffness and better healing properties in comparison to the control asphalt mix, i.e., mix without fibres, and mix containing fibres with lower rejuvenator content. These results show that compartmented alginate fibres encapsulating bitumen rejuvenator present a promising new approach for the development of self-healing asphalt pavement systems.

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This study shows the feasibility of clay reinforced alginate-based compartmented fibers as healing agent carriers for the autonomous healing of glass fiber reinforced polymer composites. First we report on the effect of montmorillonite (MMT) clay on the fiber tensile and vacuole lateral compression properties. It is found that the fiber tensile properties are enhanced with increasing MMT concentration, while the effects on the vacuole lateral compression properties are seemingly negligible. The second part of this work shows the proof of concept of healing by compartmented fibers in glass fiber reinforced polymer (GFRP) composites. A single- and a double-healing agent configuration, both based on epoxy–thiol chemistry, were compared in these model GFRP composites. The healing phenomena were quantified by mechanical characterization (interlaminar fracture and flexural testing) and nondestructive testing techniques (X-ray microtomography and air-coupled ultrasonic C-scanning). It is found that a configuration with one healing agent is favorable over a system with two separate agents and that further exploitation of the compartmented fiber concept should focus on the healing of matrix damage as the loss of mechanical integrity because of glass fiber fracture cannot be overcome. POLYM. COMPOS., 2017@en

This paper explores the potential use of compartmented alginate fibres as a new method of incorporating rejuvenators into asphalt pavement mixtures. The compartmented fibres are employed to locally distribute the rejuvenator and to overcome the problems associated with spherical capsules and hollow fibres. The work presents proof of concept of the encapsulation process which involved embedding the fibres into the asphalt mastic mixture and the survival rate of fibres in the asphalt mixture. To prove the effectiveness of the alginate as a rejuvenator encapsulating material and to demonstrate its ability survive asphalt production process, the fibres containing the rejuvenator were prepared and subjected to thermogravimetric analysis and uniaxial tensile test. The test results demonstrated that fibres have suitable thermal and mechanical strength to survive the asphalt mixing and compaction process. The CT scan of an asphalt mortar mix containing fibres demonstrated that fibres are present in the mix in their full length, undamaged, providing confirmation that the fibres survived the asphalt production process. In order to investigate the fibres physiological properties and ability to release the rejuvenator into cracks in the asphalt mastic, the environmental scanning electron microscope and optical microscope analysis were employed. To prove its success as an asphalt healing system, compartmented alginate fibres containing rejuvenator were embedded in asphalt mastic mix. The three point bend tests were performed on the asphalt mastic test samples and the degree to which the samples began to self-heal in response was measured and quantified. The research findings indicate that alginate fibres present a promising new approach for the development of self-healing asphalt pavement systems.@en

This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe3O4 nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading. The initiated damage was healed upon localized inductive heating of the embedded nanoparticles by exposure of the particulate composite to an alternating magnetic field. It is here demonstrated that healing of this early stage damage in ionomer particulate composites occurs in two different steps. First, the deformation is restored by the free-shrinkage of the polymer at temperatures below the melt temperature. At these temperatures, the polymer network is recovered thereby resetting the fatigue induced strain hardening. Then, at temperatures above the melting point of the polymer phase, fatigue-induced microcracks are sealed, hereby preventing crack propagation upon further loading. It is shown that the thermally induced free-shrinkage of these polymers does not depend on the presence of ionic clusters, but that the ability to heal cracks by localized melting while maintaining sufficient mechanical integrity is reserved for ionomers that contain a sufficient amount of ionic clusters guaranteeing an acceptable level of mechanical stability during healing.@en

When the cracks within the surface layer of the asphalt pavement are still in an early phase, it is possible to prevent further crack propagation and pavement failure by spraying rejuvenator over the surface of the asphalt pavement. Such a process may increase the life span of the asphalt pavement by several years. However, this method only impacts on the top centimetres of the pavement, cracks originating at the bottom of the asphalt layer will not be healed. The inclusion of encapsulated rejuvenators into the asphalt pavement mix presents an opportunity to overcome these problems to heal the entire pavement. The principle behind this approach is that the fracture energy at the tip of the cracks generated in the pavement will break open the capsules, and release the contained rejuvenator. The rejuvenator will then diffuse within the asphalt binder, thereby sealing the cracks and preventing their further propagation. This paper explores the potential use of compartmented sodium alginate fibres as a new method for incorporating rejuvenators into asphalt pavement mixtures. Such an approach potentially offers the following advantages over spherical microcapsules: due to the high aspect ratio of the compartments in the alginate compartmented fibres there is a higher potential that the containers will encounter a fracture enabling the release of higher amounts of healing agent or rejuvenator), alginate is an organic material and poses no environmental/leaching risks, if not opened via fracture contact, alginate fibres will degrade over time, releasing the healing agent rejuvenator and presenting a secondary self-healing trigger mechanism. This work presents the proof of concept of the encapsulation process, embedding of the fibres in asphalt mixtures and the survival rate of fibres in the asphalt mixture. The research findings support the hypothesis that sodium alginate fibres are another step in the development of self-healing asphalt pavement systems.@en