Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The ongoing trend in papermaking industries is to lower production costs by increasing
the low cost filler content in the sheets. However, the disruption of inter-fibre bonding is
accompanied by a deterioration of paper stiffness and mechanical properties if filler content
exceeds 18 wt%. Polysaccharide solutions, such as starch, are often used as a low cost
biodegradable additive to improve internal sheet strength when added to the wet-end of
production. The amount of starch that can be added is however limited as only a small percentage
will be retained in the paper web.
A dual additive multifunctional polysaccharide system was developed to allow higher
filler loading levels without detrimental deterioration in paper properties. In order to achieve a
larger surface area for fibre/filler interaction and to reduce drainage losses, at least one of these
additives was in particulate form. Anionic, cationic, and unsaturated derivatives were prepared
using sodium monochloroacetate, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and
allyl bromide, respectively. The degree of substitution was determined by 1H-NMR spectroscopy
and back titration methods and the interaction of the ionic modified derivatives with paper
components was determined using fluorescence microscopy.
Anionic modified polysaccharide particles were prepared using techniques such as
macrogel ultrasonification, water-in-water emulsification, and in-situ cross-linking and
carboxymethylation of granular starch. A process of adding sequential layers of oppositely
charged polyelectrolyte layers onto the filler particles was also investigated. A novel approach of
preparing modified particles with tailored size and distribution using microfluidics was studied
and modelled using response surface methodology.
Hand sheets were prepared using the dual additive system and improvements in stiffness,
tear resistance, breaking length, and folding endurance were observed. The modified granular
maize starch particles had a pre-eminent effect on improving stiffness at higher filler loadings
(14% improvement at 30 wt% filler loading), while bulky particles prepared using microfluidics
showed a more consistent improvement (between 6% and 10%) across the loading range.
Overall improvements gained by the introduction of multi-layered soluble polymers onto
fillers suggest that the introduction of nanotechnology to the papermaking process should be of
potential benefit to the industry. Furthermore, the dual additive system developed during the
course of this study should also be tested on a continuous pilot plant papermaking process. / AFRIKAANSE OPSOMMING: Die papierindustrie neig voortdurend daarna om produksiekostes te verlaag deur die
persentasie lae koste vulstof wat gebruik word te verhoog. Aangesien die vulstof vesel kontak
belemmer, gaan hoër vlakke (> 18 wt%) egter gepaard met ’n verlaging in papier styfheid en
meganiese eienskappe. Polisakkaried oplossings, soos byvoorbeeld stysel, word dikwels gebruik
as lae koste vergaanbare bymiddel om papier intern te versterk wanneer dit voor die
vormingsproses bygevoeg word. Slegs ’n beperkte hoeveelheid stysel word egter behou in die
papier matriks en oormatige oplossings ontsnap tydens dreinering in die afvalwater.
’n Dubbele multi-funksionele polisakkaried bymiddelsisteem was ontwikkel wat
ongewensde verwakking in papiereienskappe verminder tydens vulstof verhogings. Ten minste
een van die bymiddels was in partikelvorm om sodoende ’n groter oppervlak te bied vir
vesel/vulstof interaksie en om dreineringsverliese te verminder. Anioniese, kationiese, sowel as
onversadigde derivate was berei deur onderskeidelik gebruik te maak van natrium
monochloroasetaat, 3-chloro-2-hidroksiepropieltrimetielammonium chloried, en alliel bromied.
Die graad van substitutiese was bepaal met behulp van 1H-KMR spektroskopie sowel as titrasie
tegnieke terwyl die ioniese interaksie van die gemodifiseerde stysels met die papierkomponente
ondersoek was met behulp van fluoressensie mikroskopie.
Anioniese polisakkaried partikels was berei met tegnieke soos makro-jel ultrasonifikasie,
water-in-water emulsifikasie, en in-situ kruisbinding en karboksiemetielasie van stysel granulate.
’n Proses was ook ondersoek waar vulstof partikels omhul was in verskeie lae poliëlektroliet
oplossings. ’n Nuwe benadering was toegepas waar gemodifiseerde partikels met voorafbepaalde
grootte en verspreiding berei is deur gebruik te maak van mikrofluïdika en gemodelleer met
behulp van oppervlakte ontwerp metodeleer.
Papier toetse was uitgevoer met die bymiddelsisteem en algehele verbetering in styfheid,
skeurweerstand, breeklengte, en voulydsaamheid is waargeneem. Die gemodifiseerde stysel
granulate het die grootste verbetering in styfheid by hoë vulstofladings getoon (14% verbetering
by 30 wt% vulstoflading) terwyl die groter mikrofluïdika-bereide partikels algehele verbetering
(tussen 6% en 10%) getoon het oor die hele vulstoflading reeks.
Die verbeteringe in styfheid sowel as meganiese eienskappe van papier voorberei met
poliëlektroliet omhulde vulstof toon dat aanwending van nanotegnologie in hierdie bedryf
potensieel voordelig kan wees. Opskalering van die polisakkaried bymiddels ontwikkel
gedurende hierdie studie behoort uitgevoer te word vir verdere toetse op ’n kontinue papier
loodsaanleg.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5376 |
| Date | 12 1900 |
| Creators | Terblanche, Johannes C |
| Contributors | Knoetze, J. H., Sanderson, R. D., University of Stellenbosch. Faculty of Engineering. Dept. of Process Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 206 p. : ill. |
| Rights | University of Stellenbosch |
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