Glass fibres slowly degrade due to dissolution when exposed to water. Such environmental aging results in the deterioration of the mechanical properties. In structural offshore and marine applications, as well as in the wind energy sector, R-glass fibre composites are continuously exposed to water and humid environments for decades, with a typical design lifetime being around 25 years or more. During this lifetime, these materials are affected by various temperatures, acidity levels, and mechanical loads. A Dissolving Cylinder Zero-Order Kinetic (DCZOK) model was able to explain the long-term dissolution of R-glass fibres, considering the influence of the pH, temperature, and stress corrosion. The effects of these environmental conditions on the dissolution rate constants and activation energies of dissolution were obtained. Experimentally, dissolution was measured using High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). For stress corrosion, a custom rig was designed and used. The temperature showed an Arrhenius-type influence on the kinetics, increasing the rate of dissolution exponentially with increasing temperature. In comparison with neutral conditions, basic and acidic aqueous environments showed an increase in the dissolution rates, affecting the lifetime of glass fibres negatively. External loads also increased glass dissolution rates due to stress corrosion. The model was able to capture all of these effects.

Glass fibers are degraded when they are exposed to water. In this work, a model is developed that uses zero-order kinetics for predicting a decreasing glass fiber radius. The model is used to describe experimental test results of almost half a year long-term dissolution of R-glass fibers. The model is able to predict both mass loss and radius reduction kinetics using the same four parameters: initial fiber radius (r0), rate constants for both short-term degradation $\left( K_{0}^{I} \right)$and steady-state degradation $\left( K_{0}^{II} \right)$and the time when steady-state kinetics are reached (tst). All parameters can be easily determined from initial radius measurements and mass loss evolution in time. Elements released and detected during degradation were Na, K, Ca, Mg, Fe, Al, Si and Cl. Rate constants were obtained for individual ion release and for the total mass loss. The contribution of Si to the total mass loss was the largest (56.1% by mass). It governed the dissolution process. The kinetics of radius reduction are also reported. The radius reduction was found to be linear with time during the steady-state dissolution. The zero-order kinetic constant and the density of the glass describe the rate (proportionality) of the dissolution.

Epoxies are often exposed to water due to rain and humid air environments. Epoxy yellows during its service time under these conditions, even when protected from UV radiation. The material’s color is not regained upon redrying, indicating irreversible aging mechanisms. Understanding what causes a discoloration is of importance for applications where the visual aspect of the material is significant. In this work, irreversible aging mechanisms and the cause of yellowing were identified. Experiments were performed using a combination of FT-NIR, ATR-FT-IR, EDX, HR-ICP-MS, pH measurements, optical microscopy, SEM, and DMTA. Such extensive material characterization and structured logic of investigation, provided the necessary evidence to investigate the long-term changes. No chain scission (hydrolysis or oxidation-induced) was present in the studied common DGEBA/HDDGE/IPDA/POPA epoxy, whilst it was found that thermo-oxidation and leaching occurred. Thermo-oxidation involved evolution of carbonyl groups in the polymeric carbon–carbon backbone, via nucleophilic radical attack and minor crosslinking of the HDDGE segments. Four probable reactive sites were identified, and respective reactions were proposed. Compounds involved in leaching were identified to be epichlorohydrin and inorganic impurities but were found to be unrelated to yellowing. Carbonyl formation in the epoxy backbone due to thermo-oxidation was the cause for the yellowing of the material.

Hydrolytic degradation at elevated temperatures is a key reason for failure in offshore flexible risers. In this article, the aging of polyamide 11 in deoxygenated water at 90 C and 120 C was studied. Tensile and dynamic mechanical thermal analysis tests were performed to measure changes in mechanical properties. Viscometry, gravimetric measurements, differential scanning calorimetry, and thermogravimetric analysis were used to link these properties with morphological changes. General trends are increased stiffness, tensile strength, and glass transition temperature as well as decreased glassy state damping efficiency with increased aging times. Changes can be initially ascribed to plasticizer depletion and then to interplay between molecular weight decrease and crystallinity increase. Viscosity at hydrolysis equilibrium indicates that brittle failure typically involves oxidation or UV exposure. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41971.

The present study is about the enzymatic modification of thermomechanical pulp (TMP) fibers for reduction of water uptake and their use in bio-based filaments for 3D printing. Additionally, TMP was used as a fiber reinforcing material and poly­(lactic acid) (PLA) as the polymer matrix. The hydrophilic TMP fibers were treated via laccase-assisted grafting of octyl gallate (OG) or lauryl gallate (LG) onto the fiber surface. The modified TMP fibers showed remarkable hydrophobic properties, as demonstrated by water contact angle measurements. Filaments reinforced with OG-treated fibers exhibited the lowest water absorption and the best interfacial adhesion with the PLA matrix. Such higher chemical compatibility between the OG-treated fibers and the PLA enabled better stress transfer from the matrix to the fibers during mechanical testing, which led to the manufacture of strong filaments for 3D printing. All of the manufactured filaments were 3D-printable, although the filaments containing OG-treated fibers yielded the best results. Hence, laccase-mediated grafting of OG onto TMP fibers is a sustainable and environmentally friendly pathway for the manufacture of fully bio-based filaments for 3D printing.