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Graphene-based nanoparticles are suitable to enhance toughness related to impact, fracture and fatigue of epoxy nanocomposites to make them able to meet industrial requirements. The increase in the mechanical performance of graphene-based films is well known in the literature. This paper highlights an additional beneficial effect of graphene-based nanoparticles, which is related to the increase of the photooxidative resistance of polymeric films. Graphene Nanoplatelets (GNPs) have been incorporated, at different weight percentages, in the epoxy films. Unfilled and nanofilled films (30 ± 1.5 μm thick) have been subjected to the accelerated photo-oxidative degradation by exposing them to UV-A radiation (295–380 nm). AFM-Harmonix modulus maps at the micro and nanoscale level have been detected to investigate the effect of graphene nanoparticle on the mechanical properties of untreated and UV treated unfilled and nanofilled samples. SEM analysis has been used to analyse the effect of graphene on morphological features of the film surface. UV irradiation determines relevant damages of the mechanical properties and morphological feature of the unfilled sample. The experiments carried out on the nanofilled films show that GNPs, dispersed in the epoxy-based films, determine a strong decrease in the entity of the damages of the film surfaces.

Purpose: The purpose of this paper is to highlight the relevant role of the stereochemistry of two Ruthenium catalysts on the self-healing efficiency of aeronautical resins. Design/methodology/approach: Here, a very detailed evaluation on the stereochemistry of two new ruthenium catalysts evidences the crucial role of the spatial orientation of phenyl groups in the N-heterocyclic carbene ligands in determining the temperature range within the curing cycles is feasible without deactivating the self-healing mechanisms (ring-opening metathesis polymerization reactions) inside the thermosetting resin. The exceptional activity and thermal stability of the HG2MesPhSyncatalyst, with the syn orientation of phenyl groups, highlight the relevant potentiality and the future perspectives of this complex for the activation of the self-healing function in aeronautical resins. Findings: The HG2MesPhSyncomplex, with the syn orientation of the phenyl groups, is able to activate metathesis reactions within the highly reactive environment of the epoxy thermosetting resins, cured up to 180°C, while the other stereoisomer, with the anti-orientation of the phenyl groups, does not preserve its catalytic activity in these conditions. Originality/value: In this paper, a comparison between the self-healing functionality of two catalytic systems has been performed, using metathesis tests and FTIR spectroscopy. In the field of the design of catalytic systems for self-healing structural materials, a very relevant result has been found: a slight difference in the molecular stereochemistry plays a key role in the development of self-healing materials for aeronautical and aerospace applications.

A stable initiator for ROMP reactions, suitably designed to be embedded in structural resins, has been synthetized. It rapidly polymerizes cyclic olefins in reactive environments. The thermal stability and chemical inertness towards oxirane rings allow its employment in the form of molecular complex in epoxy precursors thus reducing the amount of initiator in structural self-healing materials of 90% wt/wt, simultaneously preserving the catalytic activity at high temperatures (180–200 °C) also in presence of the aromatic primary amine (DDS). NMR and FTIR spectroscopy highlighted a relevant initiator stability able to fulfill industrial requirements. Self-healing efficiency has been found to be 103%. [ABSTRACT FROM AUTHOR]

In this paper, we report the study and characterization of a multifunctional autonomically healing composite containing solid particles of Grubbs’ first generation catalyst and poly(urea-formaldehyde) microcapsules filled with liquid DCPD. This system, already reported in literature, in some respects shows great potential for epoxy structural composites: however, other aspects have to be explored in order to put to use in advanced applications. Here, we have determined the curing process to obtain the best mechanical performance without deactivating the self-repair activity of the material. It has been found that, for the same curing cycle, the presence of catalyst powder causes a slight decrease in the elastic modulus value with respect to the epoxy matrix. A large recovery in this performance is gained for the self-healing specimen, proving that the microcapsules contribute to improve the mechanical characteristics of the self-healing sample.

In this work constant cooling rate crystallization experiments were carried out by a DSC, working with an iPP and using a very little amount of material, to minimize the heat transfer resistance in the mass of the sample. The resulting data were corrected to take into account also for the external heat transfer resistance. The corrected data were compared with data produced in the past, working with larger amounts of the same resin in a less accurate DSC apparatus, confirming that in the field of polymer crystallization kinetics the calorimeter has to be used carefully. The data were also used to check a kinetic model previously tuned under isothermal conditions. Up to 10 °C/min (0.167 K/s) the isothermal model is accurate enough, but faster tests requires an improvement of the model.

The transformations of the trans‐planar mesophase of syndiotactic polypropylene (sPP) subjected to thermal, mechanical and solvent treatments, were investigated. The unoriented trans‐planar mesophase, obtained by quenching the melt at 0°C, was annealed at 80°C and the thermal transformation was investigated by X‐rays, infrared and dynamic‐mechanical analysis. The presence of the helical form II was recognized in the annealed sample. The oriented trans‐planar mesophase, obtained by drawing at room temperature and releasing the tension, was immersed in liquid dichloromethane for 24 hours. After drying the sample showed the presence of the oriented form II, although it was not possible to exclude a partial transition into form IV. On the basis of the present and literature results we suggested a scheme of the polymorphic transitions of sPP, in which the central role of the trans‐planar mesophase is enlightened.

Three syndiotactic polypropylene samples were crystallized under different conditions in order to obtain different polymorphs. A first sample was crystallized at high temperature, obtaining the helical form I; a second was crystallized from the melt at 0°C for many days obtaining the trans‐planar mesophase; a third sample was obtained by solvent induced crystallization followed by annaeling of the trans‐planar mesophase, leading to a mixture of both the helical forms I and II. In the dynamic‐mechanical analysis the helical form I showed only one peak of tan δ corresponding to the amorphous glass transition. The other polymorphs also showed this transition centered at about the same temperature. Beside the peak corresponding to the Tg, the trans‐planar mesophase was characterized by a peak appearing at 70°C, and the helical form II by a peak at 100°C. These peaks, unambiguously associated to transitions of the different forms, can be considered a distinctive evidence for the polymorphs obtained in different processing conditions.

Syndiotactic polypropylene (sPP) was cast‐extruded with a laboratory single screw extruder, obtaining a crystalline and still highly transparent film.

Syndiotactic polypropylene (sPP) was cast-extruded with a laboratory single screw extruder, obtaining a crystalline and still highly transparent film. The structural studies showed that the film crystallized at room temperature in the disordered helical form I, containing a fraction of a mesophase with the chains in trans-planar conformation. X-ray patterns, taken either along the extrusion direction (MD) or along the orthogonal directions (TD and ND), indicated a low orientation of the c axis parallel to the machine direction (MD) and a partial orientation of the a axis along the transverse direction (TD). Mechanical properties performed in either direction showed a very similar behaviour, but a different strain at the breaking point. The mechanical parameters were derived in both directions.

A syndiotactic poly(propylene) film (sPP), quenched from the melt at 0°C, was drawn at room temperature up to a draw ratio of λ= 6. The fibre was analysed under tension by X‐ray analysis and FTIR spectroscopy, showing the presence of the oriented crystalline form III described by Chatani, with the chains in trans‐planar conformation. Then it was unhooked, undergoing a large shrinkage, and reaching a length corresponding to a draw ratio of λ= 3.8. X‐ray and FTIR analysis showed that in the relaxed fibre, a conformational transition from the trans‐planar to the helical form occurred. The relaxed fibre was again submitted to increasing extensions up to λ= 6, step by step, and the elastic behaviour was analysed through the Mullins' curve and hysteresis cycles. It showed good elastic properties, which appear to be closely correlated to the conformational transition between helical and trans‐planar forms.

In this work we compare calorimetric and X‐ray diffraction experiments realized on annealed sPS in helical γ forms resulting by different treatements: From clathrate δ form and from interaction of amorphous sample with acetone. The experimental results show that the γ form obtained by acetone converts into the more ordered final α” form modification; while the γ form, obtained by thermal treatments of δ form, transforms into the poorly ordered final α' form.

Due to a typing error, the name of the second co‐author, Liberata Guadagno, was spelled incorrectly. We would like to apologize for any inconvenience this mistake may have caused!

Due to a typing error, the name of the second co-author, Liberata Guadagno, was spelled incorrectly. We would like to apologize for any inconvenience this mistake may have caused!