Micromechanical properties and thermal stability of adhesives for optical fibers based on ethylene-vinyl acetate copolymer

Abstract

Optical fibers are used for transfer of information when the reliable system was required, and in some situations it is necessary to transport optical fibers on the drums and to enable controlled and fast unwinding from the drum. Adhesives used for fixation of the optical fiber in these situations need to have defined properties regarding to adhesiveness and age resistance. Presented research contributes new approach in investigating of adhesion effects and forces between the optical fibers and adhesive, and in that aim novel experimental method was developed for fast examination of mentioned effects. Ethylene-vinyl acetate copolymers were used (EVA) and the polymer blends with the addition of poly(methyl methacrylate) (PMMA). Characterization of optical fibers was performed by optical and scanning electron microscopy in the aim of morphology examination; by tensile test for tensile strength determination; nanoindentation to obtain elastic properties of final polymer coating of optical fiber; Furrier transformed infrared spectroscopy for characterization of chemical composition of polymer coating of optical fiber, as well as obtained adhesives. In testing of adhesiveness, optical fiber with outstanding mechanical properties was used (optical fiber denoted as SFM 28+ corning). Based on the analysis of chemical composition of final polymer coating of optical fiber, it was concluded that EVA have satisfied compatibility with the optical fiber final coating, what led to opportunity for developing adhesives based on mentioned copolymer. In the aim of improving thermal stability of EVA copolymer, adhesives based on EVA/PMMA polymer blends were used, where Elvax 410 was chosen as EVA copolymer with better thermal stability. Compatibilization of EVA/PMMA polymer blends was performed using in situ free radical polymerization, where raw EVA-g- PMMA adhesive was synthesized. Controlled „living” polymerization was employed in the aim of controlling the adhesion and compatibilization by graft chain length. Characterization of polymer blends consists of chemical structure examination, determining of adhesive and thermal properties in relation to EVA copolymers and physical polymer blend EVA/PMMA. The adhesion test of optical fibers with adhesives showed that the improved adhesion was achieved by modification of physical polymer blend. The type of adhesive failure was determined by optical microscopy that showed the difference between used polymeric adhesives. Compatibilization effect was monitored on optical microscope by phase separation in polymer blends and by determining of wetting angles. Adhesive properties after accelerated aging on 60 °C after 60 and 120 hours were examined. Thermogravimetry coupled with mass spectroscopy indicated that the adhesive raw EVA-g-PMMA had improved thermal stability...

Optička vlakna se koriste za prenos informacija u situacijama kada je potreban pouzdan sistem, a u pojedinim slučajevima potrebno je vlakna transportovati na kalemima i omogućiti kontrolisano i brzo odmotavanje vlakna sa kalema. Za fiskiranje vlakana u ovim situacijama koriste se adhezivi koji moraju da imaju definisana svojstva u pogledu adhezivnosti i starenja. Prikazana istraživanja daju novi pristup u ispitivanju adhezivnih efekata i sila između optičkih vlakana i adheziva, i u ovu svrhu razvijena je eksperimentalna metoda za brzo ispitivanje. Korišćeni su adhezivi na bazi kopolimera etilena i vinil-acetata (EVA) i polimernih blendi sa dodatkom poli(metil-metakrilata) (PMMA). Karakterizacija optičkih vlakana je vršena primenom optičke i skenirajuće elektronske mikroskopije u cilju ispitivanja morfologije; test na istezanje za utvrđivanje zatezne čvrstoće optičkog vlakna; nanoindentacije za utvrđivanje elastičnih svojstava zaštitne polimerne prevlake optičkog vlakna; infracrvene spektroskopije sa Furijeovom transformacijom (FTIR) za karakterizaciju hemijskog sastava polimerne prevlake optičkog vlakna, kao i dobijenih adheziva. Za ispitivanje adhezivnosti korišćeno je optičko vlakno sa najboljim mehaničkim svojstvima (optičko vlakno pod nazivom SFM 28+ corning). Na osnovu analize hemijskog sastava polimerne prevlake na optičkom vlaknu utvrđeno je da EVA ima zadovoljavajuću kompatibilnost sa završnom prevlakom što je otvorilo mogućnost razvoja adheziva baziranih na tom polimeru. U cilju poboljšanja termičke stabilnosti EVA kopolimera, korišćeni su i adhezivi na bazi EVA/PMMA polimernih blendi, gde je Elvax 410 korišćen kao EVA kopolimer sa boljom termičkom stabilnošću. Kompatibilizacija EVA/PMMA polimerne blende je izvedena polimerizacijom u masi preko slobodnih radikala, čime je dobijen sirovi adheziv s-EVA-g-PMMA. Kontrolisana „živa” polimerizacija je korišćena za kontrolu adhezivnosti i kompatibilizacije promenom dužine kalemljenih lanaca. Karakterizacija polimernih blendi je obuhvatala ispitivanje hemijske strukture, adhezivnih i termičkih svojstava u poređenju sa EVA kopolimerima i fizičkom polimernom blendom EVA/PMMA. Adhezioni test dva spojena vlakna je pokazao da je modifikacijom fizičke blende uspostavljena poboljšana adhezija. Optičkom mikroskopijom je utvrđen tip adhezionog loma koji je ukazivao na razliku u adhezivnosti korišćenih polimernih adheziva. Efekat kompatibilizacije je praćen putem optičke mikroskopije posmatranjem izdvajanja faza polimernih blendi i određivanjem ugla kvašenja optičkog vlakna. Ispitivana su svojstva adheziva nakon ubrzanog starenja na 60 °C tokom 60 i 120 sati...