| Summary: | Thesis (MSc)--Stellenbosch University, 2004. === ENGLISH ABSTRACT: This study describes the design, building and optimization of a fully functional
preparative TREF (Prep-TREF) apparatus. This apparatus allows for the fractionation of semicrystalline
polyolefins according to the crystallizability of the molecules. Various factors, such as
the sample cooling rate and the effect of on-support and off-support crystallization, are
investigated.
The preparative TREF is used to fractionate a commercial low-density polyethylene
(LOPE), two commercially available plastomers (polyethylene-l-octene copolymers), as well as
blends of the LOPE and the respective plastomers. It is shown that in each case the samples
fractionated by crystallizability. The fractions recovered from the Prep-TREF were characterized
by CRYSTAF, OSC and NMR analysis. It is shown how the results of this preparative
fractionation allow for a better understanding of the molecular heterogeneity in the LOPE and
plastomers.
New ways of presenting the data from the preparative fractionation, in terms of 3-
dimensional plots, are also investigated. These plots offer a novel way of presenting the
molecular heterogeneity in the samples in terms of the molecular crystallizability. These plots
highlight features that are difficult to detect in the conventional two-dimensional plots.
In conclusion, the influences of various blending ratios of LOPE and plastomer on the
morphological and physical properties of the blends, such as haze, clarity, and tear-and impact
strength are determined. === AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die ontwikkeling en optimisering van 'n ten volle
funksionerende TREF. Hierdie tegniek word gebruik om polimeermengsels te fraksioneer deur
gebruik te maak van die kristaliseerbaarheid van polimere. Verskeie faktore soos die afkoel
spoed en die effect van met en sonder 'n ondersteuning(seesand) vir kristaliseering was
ondersoek.
Hierna is navorsing gedoen om 'n beter begrip ten opsigte van die meganiese, fisiese en
optiese eienskappe van lae-digtheid poliëtileen (LDPE) te ontwikkel. Hierdie LDPE is met die
affiniteitsreeks plastomere van die maatskappy, Dow Chemicals, gemeng om tendense in die
gefraksioneerde polimere te indentifiseer.
Een van Sasol se kommersiële LDPE produkte en twee van Dow Chemicals se
plastomere is individueel gefraksioneer. Die mengsel van die twee ongefraksioneerde LDPE en
plastomere is nog nooit voorheen op 'n molekulêre basis ondersoek nie. Dit is in hierdie studie
gedoen deur van TREF gebruik te maak.
Nuwe maniere is ontwikkel om data op 'n nuwe manier voor te stel deur middel van 3
Dimensionele grafieke te skep om resultate voor te stel wat andersins baie moelilik was om
voor te stel in een dimensie agv die hoeveelheid data wat geinterpreteer word.
Ten slotte is die invloed van die verskillende mengverhoudings van LDPE en plastomere
op die morfologiese en fisiese eienskappe soos deursigtigheid, helderheid, skeur- en
impaksterkte, ook ondersoek.
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