Abstract
For adjusting the optical properties of surfaces, fibrous
structures and mould products, pigments and fillers find
uses e.g. in paper and board, plastics, surface
treatments and paints. Recyclability of the products may
be impaired by the mineral pigments and increased
proportions of incombustible and non-degradable residues
are formed. To substitute mineral and synthetic
petroleum-derived fillers and pigments, modified
polysaccharide-based materials are proposed. The
particular advantages of polysaccharide-based (e.g.
starch-based) derivatives are that they are based on a
renewable raw-material source and can easily be recycled.
The opacity and brightness and especially the light
scattering capacity of the pigmented or filled structures
are affected by the size, shape, packing and optical
character of the constituent components and possible
pores. Light reflects partially from surfaces that differ
from their surroundings by their refractive index (RI),
which derives from the molecular structure, density and
atomic polarizability of a material. Also the light
absorption character of the material affects the
refractive index. Thus, in a coating or paper structure
an improved light scattering potential is associated with
pigmenting materials that possess higher values of RI
than that of the surrounding materials, e.g. fibres,
binders (and air in the pores). The refractive indices of
organic pigmenting materials inherently are close to that
of cellulosic papermaking fibres, i.e. close to 1.5.
Improved optical response of (poly)saccharide-based
pigmenting materials is based on incorporated organic
aromatic side groups in order to modify the
conformational structure of (poly)saccharides and to
introduce portions of higher optical density to the
material. Aromatic substitution also increases the
hydrophobicity of saccharide-based materials, improving
their suitability for filler and pigment use. For these
purposes, ester derivatives such as benzoyl,
diphenylacetyl and naphthoyl have been prepared of
starch, sucrose, cellulose and xylan. Dispersions and
particulate products of the substituted polysaccharides
suitable for pigmenting and filler use can be prepared by
precipitation as well as grinding. The derivatives were
characterized for RI using immersion techniques and for
filler performance in paper.
Original language | English |
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Publication status | Published - 2009 |
MoE publication type | Not Eligible |
Event | Polysaccharides as a Source of Advanced Materials - Turku, Finland Duration: 21 Sept 2009 → 24 Sept 2009 |
Seminar
Seminar | Polysaccharides as a Source of Advanced Materials |
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Country/Territory | Finland |
City | Turku |
Period | 21/09/09 → 24/09/09 |