No abstract

Single fibre tensile testing of thermally conditioned water sized and γ – aminopropyltriethoxysilane (APS) sized boron-free E-glass has been carried out. The fibres were produced from identical melts following which bare fibre had only water applied to it before winding whereas the sized fibre had a solution containing only APS applied to its surface. Both fibre types experience a loss of room temperature tensile strength after exposure to elevated temperature. By application of a novel method of single fibre thermal conditioning it was demonstrated that the tensile strength of heat treated glass fibre can be significantly underestimated. Strength loss was found, in most cases, to be caused by a combination of thermal effect and mechanical handling damage. The latter is found to be influenced by thermal loading of the fibre. The onset of mechanical handling damage in APS sized fibre was found to be controlled by the thermal degradation of the silane sizing. This suggests that silane-based coatings, even when they are present as only a relatively thin surface layer, can protect fibres from the development or growth of critical surface flaws. The relative contribution to overall fibre strength loss from mechanical handling damage highlights the need to minimise processes which may cause fibre mechanical damage during glass fibre recycling procedures

Abstract:The recovery and reuse of glass fibres from manufacturing waste and end-of-life composites in an environmentally-friendly, cost-effective manner is one of the most important challenges facing the thermosetting polymer composites industry. A number of processes for recycling fibres from such materials are available or under development. However, nearly all options deliver recycled glass fibres that are not cost-performance competitive due to the huge drop in strength of recycled glass fibre compared to its original state. A breakthrough in the regeneration of recycled glass fibre performance has the potential to totally transform the economics of recycling such composites. This paper reviews the available knowledge of the thermally-induced strength loss in glass fibres, discusses some of the phenomena that are potentially related and presents the status of research into processes to regenerate the strength and value of such weak recycled glass fibres.

The strength loss of glass fibres (GF) following exposure to elevated temperatures is a long-established phenomenon, yet the mechanism or mechanisms responsible for the strength decrease are not fully understood, aside from acknowledgement that surface flaws must become more severe by some means. As disposal of GF based composite materials by landfill has become untenable in many regions, interest in composite recyclability has increased. Separation of GFs from thermosetting polymers generally requires the use of high temperatures, which produces very weak fibres with minimal commercial value. In this context an understanding of the strength loss mechanisms is of importance in terms of efforts to mitigate fibre damage or to recover the strength of previously heated fibres. In addition to fibre strength loss, numerous other physical and chemical changes to heat treated (HT) or recycled GF have been described in the literature

Amphiphilic polymer conetworks (APCNs) are polymer networks composed of hydrophilic and hydrophobic chain segments. Their applications range from soft contact lenses to membranes and biomaterials. APCNs based on polydimethylsiloxane (PDMS) and poly(2‐hydroxyethyl acrylate) are flexible and elastic in the dry and swollen state. However, they are not good at resisting deformation under load, i.e., their toughness is low. A bio‐inspired approach to reinforce APCNs is presented based on the incorporation of poly(β‐benzyl‐L‐aspartate) (PBLA) blocks between cross‐linking points and PDMS chain segments. The mechanical properties of the resulting peptide‐reinforced APCNs can be tailored by the secondary structure of the peptide chains (β‐sheets or a mixture of α‐helices and β‐sheets). Compared to non‐reinforced APCNs, the peptide‐reinforced networks have higher extensibility (53 vs. up to 341%), strength (0.71 ± 0.16 vs. 22.28 ± 2.81 MPa), and toughness (0.10 ± 0.04 vs. up to 4.85 ± 1.32 MJ m−3), as measured in their dry state. The PBLA peptides reversibly toughen and reinforce the APCNs, while other key material properties of APCNs are retained, such as optical transparency and swellability in water and organic solvents. This paves the way for applications of APCNs that benefit from significantly increased mechanical properties.