• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • Tagged with
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

SHORT TERM CHARACTERISTICS AND ENVIRONMENTAL AGING OF BIO-RESIN GFRP TESTED IN TENSION AND FOR CONFINEMENT OF CONCRETE CYLINDERS

Eldridge, AMANDA 26 August 2013 (has links)
Conventional fiber reinforced polymers (FRPs) require polymers such as epoxies that are not biodegradable, which have a significant impact on the environment. The first phase of the thesis aims at replacing conventional polymers with sustainable bio-polymers. The tensile mechanical properties of glass-FRP (GFRP) laminates using two types of organic furfuryl alcohol bio-resins extracted from renewable resources, such as corncobs, were investigated. Results are compared to control specimens fabricated using conventional epoxy resin. It was shown that by careful selection of viscosity of bio-resin, and type and dosage of catalyst, similar mechanical properties to epoxy-GFRP can be achieved. The second and third phases consisted of durability testing of the bio-resin GFRP. A total of 160 tension coupons and 81 unconfined and confined concrete cylinders wrapped with bio-resin-GFRP were studied. Conditioning was achieved by immersion of the specimens in saline solutions with 3% salt concentration, at 23, 40 and 55 degrees Celcius, for up to 300 days. Specimens were compared to epoxy-GFRP specimens aged in the same environment. Deterioration was quantified by tensile testing of the coupons and compression testing of the cylinders at various stages of exposure. The bio-resin-GFRP showed 33% less tensile strength retention than the epoxy-GFRP. The epoxy-GFRP and bio-resin-GFRP wrapped cylinders had the same un-aged confined axial compressive strength (fcc’), essentially a strengthening ratio (fcc’/fc’) of 2.24. After 300 days, the (fcc’/fc’) ratio retentions for the bio-resin-GFRP was 73% at all temperatures. Using the Arrhenius model, it was predicted that 61% retention in tensile strength of the bio-resin-GFRP and 65% retention of the compressive strength of wrapped cylinders would occur after 100 years in an environment with a mean annual temperatures of 10 degrees Celcius. / Thesis (Master, Civil Engineering) -- Queen's University, 2013-08-24 00:02:25.683
2

Exploring the sustainability potential of an algae-based wood adhesive : Comparative and explorative environmental life cycle assessment of algae- vs. formaldehyde- based adhesives for particleboard production

Rasche, Charlotte January 2020 (has links)
Adhesives used for wood composites such as particleboard are conventionally of petrochemical nature with formaldehyde as a base substance and represent a pain point in the industry due their toxic emissions. Consequently, adhesives are subject to an agenda to develop more benign, low-impact alternatives. On the one hand, the issue has been addressed by means of optimisation of composition and amounts, and on the other hand, development of biobased adhesives from different renewable feedstock has been taking place over the past decades. Yet, these bio-adhesives remain a niche segment as renewability or lower toxicity alone is widely not enough despite increasingly strict regulations on formaldehyde emissions. Emphasis on a more comprehensive set of beneficial properties of ‘green’ adhesives is needed for successful adoption in the market. In this context, this study investigates the holistic sustainability potential of a yet untapped bio- adhesive feedstock: macroalgae. Current research on an algae-based adhesive from cultivated biomass in Sweden suggests suitable adhesive properties for particleboard manufacture. Complementing these promising findings on material properties, this study assesses sustainability of using an algae-based adhesive in a particleboard production system as opposed to conventional formaldehyde-based resins. A comparative cradle-to-gate life cycle assessment of different scenarios was conducted, with the specific aim to explore changes in toxicity, climate change impacts and eutrophication due to the known benefits of cultivated macroalgae in these areas. A considerably better performance for algae-based adhesives was found across impact categories (CML baseline method) compared to formaldehyde-based scenarios, as well as a similar pattern with respect to cumulative energy demand. Particularly under a low-impact preservation method for the algal biomass, relative impacts were substantially lower without exception. Furthermore, a potential for carbon sequestration and replacing of fossil with biogenic carbon flows was identified, as well as bioremediation of location eutrophication through nutrient uptake of the biomass during cultivation. Despite the early stage and the need for further research, the results point to a promising potential for macroalgae as a feedstock for biobased wood adhesives which go beyond renewability. / Lim som vanligtvis används för träkomponenter som exempelvis spånskivor är konventionellt från petrokemiska källor med formaldehyd som basämne, och anses vara en utmaning för branschen på grund av dess giftiga utsläpp. Därav är det av intresse för branschen att utveckla bättre alternativ med mindre miljöpåverkan. Utvecklingen har dels skett genom optimering av sammansättning och proportioner, men under det senaste decennierna har även utveckling av biobaserade lim från olika förnyelsebara råvaror tagit fart. Dessa biobaserade lim är dock fortfarande ett nischat område, att enbart arbeta med förnybara råvaror som ger lägre toxicitet verkar inte vara tillräckligt, trots allt striktare bestämmelser om formaldehydutsläpp. Därför krävs det tydliga bevis av miljövinsterna med lim av förnyelsebara råvaror för att denna metod ska bli mer framgångsrik på marknaden. I detta sammanhang undersöker denna uppsats, genom ett holistiskt perspektiv, potentialen med lim gjort på det ännu outnyttjade förnyelsebara materialet makroalger. Aktuell forskning på algbaserat lim från odlad biomassa i Sverige har uppvisat lämpliga limegenskaper för användning inom spånskivetillverkning. Som ett komplement för dessa potentiella fördelaktiga egenskaper, bedömer denna uppsats miljönyttan med användandet av ett algbaserat lim i produktionssystem av spånskivor, i relation till det konventionella formaldehydbaserade limmet. Därmed görs en jämförande livscykelanalys från vaggan till grinden av olika scenarier, med syftet att undersöka förändringar i toxicitet, klimatpåverkan och övergödning, i och med att dessa tre påverkanskategorier redan har visat på kända miljöfördelar. Resultatet visade att det algbaserade limmet hade betydligt bättre miljöprestanda i alla påverkanskategorier undersökt med metoden CML baseline i jämförelse med det formaldehydbaserade limmet, vilket även visades för kategorin kumulativt energibehov. När en konserveringsmetod används för att processa algbiomassan, är skillnaden i miljöpåverkan av dom två limmen lägre inom alla påverkanskategorier. Slutligen identifierades potential för kolbindning och utbyte av biogena och fossila kolflöden, även bioremediering av lokal övergödning genom att biomassan upptog näringsämnen under odling. Trots det tidiga stadiet och behovet av fortsatt forskning så visar dessa resultat en fortsatt potential för makroalger som ett råmaterial för biobaserade trälim som tar förbybarhet ett steg längre.

Page generated in 0.0357 seconds