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| 2. |
- Agfors, Gunnar, et al.
(författare)
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KEMI : den gränslösa vetenskapen
- 2011
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Bok (populärvet., debatt m.m.)abstract
- Kemi – handlar inte det bara om farliga ämnen och onödiga tillsatser? Det är kanske bildenmånga har av kemi, men faktum är att utan kemi skulle vi inte ha det höga välstånd vi har i dag.Tack vare kemisk kunskap har vi tillgång till läkemedel som botar sjukdomar och lindrar smärta– med hjälp av syntetiska antibiotika kan infektionssjukdomar som tidigare var dödliga botas,magsår kan behandlas utan dyra och plågsamma operationer och många cancerformer kanframgångsrikt behandlas med syntetiska preparat. Konstgödsel och medel som hindrar skadeinsektergör att skördar kan ökas och svälten i världen därigenom begränsas. Tack vare kemin harvi även tillgång till alla de material vi behöver för att tillverka allt från kläder, rengöringsprodukteroch kosmetika till bilar, TV-apparater och reservdelar till kroppen. Det är genom kemisk syntes vikan framställa dessa och alla de övriga produkter vi behöver för vårt dagliga liv och det är keminsom visar vägen till hållbar produktion som utnyttjar förnybara råvaror och ger minimala mängderavfall. Kemisk kunskap är också oumbärlig för utveckling av nanoteknik och medicinskdiagnostik och andra till kemin angränsande områden. Kemin bidrar alltså till att finna lösningartill många av de komplexa globala problem vi står inför: hälsa, klimat, brist på råvaror, utnyttjandetav nya energikällor och tillgång till livsmedel för att föda jordens ökande befolkning. DET ÄR OM ALLT DETTA DEN HÄR BOKEN HANDLAR.
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| 3. |
- Ankerfors, Caroline, et al.
(författare)
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A comparison of polyelectrolyte complexes and multilayers : Their adsorption behaviour and use for enhancing tensile strength of paper
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:1, s. 77-86
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Tidskriftsartikel (refereegranskat)abstract
- This paper compares the adsorption behaviour and paper-strength-enhancing properties of polyelectrolyte complexes (PECs) and polyelectrolyte multilayers (PEMs) of polyallylamine hydrochloride and polyacrylic acid. Model adsorption experiments using SPAR (stagnation point adsorption reflectometry) and QCM-D (quartz crystal microbalance with dissipation) showed that the amount of complexes adsorbed was lower than the amount adsorbed when forming a multilayer using the same polymer system. From these experiments, in combination with AFM and ESEM imaging, it was concluded that the PEC adsorption stopped before full surface coverage was reached. Tensile testing of handsheets treated with PECs and PEM showed a significant increase in both tensile index and strain-at-break using both systems. The largest strength improvement was achieved with the fibres treated with the largest number of PEMs, but the largest effect per adsorbed amount of polymer was achieved by PEC treatment.
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| 6. |
- Ankerfors, Caroline, et al.
(författare)
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Using jet mixing to prepare polyelectrolyte complexes : Complex properties and their interaction with silicon oxide surfaces
- 2010
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 351:1, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- The influence of mixing procedure on the properties of polyelectrolyte complexes (PECs) was investigated using two complexation techniques, polyelectrolyte titration and jet mixing, the latter being a new method for PEC preparation. For the low-molecular-weight polyelectrolytes polyacrylic acid (PAA) and polyallyl amine hydrochloride (PAH), shorter mixing times produced smaller PECs, whereas for higher molecular weights of the same polyelectrolytes, PEC size first decreased with decreasing mixing time to a certain level, after which it started increasing again. This pattern was likely due to the diffusion-controlled formation of "pre-complexes", which, in the case of low-molecular-weight polymers, occurs sufficiently quickly to form stable complexes; when polyelectrolytes are larger, however, non-equilibrium pre-complexes, more prone to aggregation, are formed. Comparing the techniques revealed that jet mixing produced smaller complexes, allowing PEC size to be controlled by mixing time, which was not the case with polyelectrolyte titration. Higher polyelectrolyte concentration during jet mixing led to the formation of larger PECs. It was also demonstrated that PEC size could be changed after preparation: increasing the pH of the PEC dispersion led to an irreversible increase in PEC size, whereas lowering the pH did not influence PEC size. The adsorption behavior of PECs formed from weak polyelectrolytes on model substrates was studied using QCM-D, SPAR, and AFM imaging; the results indicated that increasing the pH increased the amount of PECs adsorbed to model surfaces. However, the amount of PECs adsorbed to the model surfaces was low compared with other systems in all studied cases.
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| 8. |
- Ansari, Farhan, et al.
(författare)
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Hierarchical wood cellulose fiber/epoxy biocomposites : Materials design of fiber porosity and nanostructure
- 2015
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 74, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers - at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.
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| 9. |
- Castro, Daniele Oliveira, et al.
(författare)
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The use of a pilot-scale continuous paper process for fire retardant cellulose-kaolinite nanocomposites
- 2018
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Ingår i: Composites Science And Technology. - : Elsevier Ltd. - 0266-3538 .- 1879-1050. ; 162, s. 215-224
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured materials are difficult to prepare rapidly and at large scale. Melt-processed polymer-clay nanocomposites are an exception, but the clay content is typically below 5 wt%. An approach for manufacturing of microfibrillated cellulose (MFC)/kaolinite nanocomposites is here demonstrated in pilot-scale by continuous production of hybrid nanopaper structures with thickness of around 100 μm. The colloidal nature of MFC suspensions disintegrated from chemical wood fiber pulp offers the possibility to add kaolinite clay platelet particles of nanoscale thickness. For initial lab scale optimization purposes, nanocomposite processing (dewatering, small particle retention etc) and characterization (mechanical properties, density etc) were investigated using a sheet former (Rapid Köthen). This was followed by a continuous fabrication of composite paper structures using a pilot-scale web former. Nanocomposite morphology was assessed by scanning electron microscopy (SEM). Mechanical properties were measured in uniaxial tension. The fire retardancy was evaluated by cone calorimetry. Inorganic hybrid composites with high content of in-plane oriented nanocellulose, nanoclay and wood fibers were successfully produced at pilot scale. Potential applications include fire retardant paperboard for semi structural applications and as reinforcement mats in molded thermoset biocomposites.
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