Use of UV-Curing Adhesive Systems on Non-transparent Joining Parts by Using Sidelight Activated Polymer Optical Fibres

An Overview on Methods for Producing Side-Emitting Polymer Optical Fibers

“…Continuous perforations are also possible, e.g., one or more notches running in a spiraling manner along the fiber axis (cf. Figure 5g) [13,68]. With regard to the fiber axis, microperforated or notched fibers have locally variable cross-sections.…”

“…In so-called side-emitting POF (SE-POF), as a special form of POF, total internal reflection (TIR) is deliberately hindered and, thus, light leakage via the cladding of the fiber is induced [2]. This enables the use of POF for illumination purposes in which emitting light at the end of the fiber is not sufficient (e.g., in automotive or decorative lighting [3,4]) as well as innovative applications in the fields of medicine (e.g., antimicrobial applications for disinfection reasons and phototherapy [5][6][7][8]), security and military technology (e.g., protective waistcoats with localization of projectile entry or smart police uniforms [4,9]), fiber-optical sensing (e.g., fluid level sensors and MRI-compatible motion detection [10,11]) as well as for UV curing resins and adhesives [12,13]. As can be seen from the mentioned applications, SE-POF stand out from conventional lighting systems, such as LEDs or injection-molded light guides, due to various advantages: textile drapability and bendability, immunity to electromagnetic interferences, small required installation space due to low light guide thickness as well as the separation of light source and light emission [14,15].…”

“…Accordingly, there are basically three ways to prevent total internal reflection: increase the cladding refractive index, decrease the core refractive index or change the angle θ [37]. In practice, however, usually only the change of the angle is used: The approaches to change the reflection angle can be categorized as follows [13]:…”

Extra thin sidelight-emitting polymer optical fiber narrow fabrics for UV structural adhesive joints: design, preparation and performance experiments

“…6 Strategies to counteract this effect include a gradually increasing surface modification density, 4 simultaneous light in-coupling from both fiber ends 7,8 or variation in weft density, if the POFs are used as warp in a woven fabric. 9,10 As described by Seewald et al, 11 SE-POFs can be used to cure ultraviolet-curable adhesives (UV adhesives) by transmitting the UV light of an external light source into an adhesive joint which enables bonding of nontransparent parts with UV adhesives. UV adhesives are radiation-curing adhesives which, in case of widely used acrylate-based radical curing systems, contain photoinitiators.…”

“…18 However, their biggest drawback is the limitation to joints with at least one transparent adherend to allow for uniform exposition of the adhesive by the external light source. 19 In the study 11 exploring the feasibility of substrateindependent UV curing, the usage of single POFs for curing was found to be unsuitable for most industrial applications, as the UV absorption within the adhesive only allowed for a range of about 2.5 mm around the POF to be cured when using POFs with a diameter of 1.0 mm. Moreover, introducing POFs with such a high diameter into the adhesive joint increases the thickness of the adhesive layer above established industry standards and comes at the cost of reduced mechanical properties.…”