Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Aqueous polyurethane (PU) dispersions were synthesized for the use in paper coatings.
These PUs contained a polyester polyol soft segment (content of 60-70%) and a urethane
hard segment (content of 30-40%). This was followed by grafting using four different grafting
agents. Triethylamine (TEA) was used as the neutralizing agent. The polyester polyol
segment consisted of neopentyl glycol (NPG), adipic acid, 1,4-cyclohexane dicarboxylic acid
(1,4-CHOCA) and 2-phosphonobutane-1 ,2,4- tricarboxylic acid (PSTCA), while the urethane
hard segment consisted of hydrogenated 4,4-diphenylmethane diisocyanate,
dimethylolproponic acid (OMPA), 3-hydroxypivalic acid (HPA) and hydroxyethylene
methacrylate (HEMA). The grafting agents used were lauryl methacrylate (LMA), n-butyl
methacrylate (n-SMA), methyl methacrylate (MMA) and styrene.
Two different polyester polyols were synthesized, one containing 10% phosphate and the
other none. The polyols were characterized in terms of their acid value, hydroxyl value and
molecular mass. The PUs synthesized from the polyol containing 0% phosphate were grafted
with LMA, while the phosphate-containing PUs were grafted with each of the all four grafting
agents.
The resulting dispersions were applied to paperboard, and then dried at a maximum
temperature of 100°C. The PU-coated paperboard was characterized using the moisture
vapour transmission rate (MVTR), and scanning electron microscopy (SEM) techniques.
PU films (not supported by paper, stand alone) were prepared by heating the PU dispersion
in Teflon holders up to 130°C for 6 hours. The dried films were then characterized by
thermogravimatric analysis (TGA), differential scanning calorimetry (OSC), dynamic
mechanical analysis (OMA) and Fourier transform infrared spectroscopy (FTIR).
MVTR-analysis showed that the phosphated PU coatings had a minimum MVTR-value at 0%
grafting, and that its overall MVTR-values were much lower than that of the non-phosphated
PU coatings. SEM-analysis showed that the phosphated PU coatings had no pinholes at a
maximum of 8% grafting, while the non-phosphated PU coatings showed pinholes at all
levels of grafting. OMA-analysis showed that the phosphated PU samples had higher Tg's (Tg
onset between O-S°C)than that of the non-phosphated PU samples (Tgonset below -SO°C). / AFRIKAANSE OPSOMMING: POLI-URETAAN DISPERSIES VIR PAPIER BEDEKKINGS
Waterige poli-uretaan (PU) dispersies is gesintetiseer vir gebruik as papierbedekkings.
Hierdie poli-uretane het 'n poliester poli-ol sagte segment (60-70% inhoud) en 'n uretaan
harde segment (30-40% inhoud) bevat. Die poli-uretane is met vier verskillende ent-middels
geêent. Trietielamien (TEA) is as neutraliseermiddel gebruik. Die poli-ester poli-ot segment
het bestaan uit: neopentielglikol (NPG), adipiensuur, 1,4-sikloheksaandikarboksielssuur (1,4-
SHDKS) en 2-fosfonobutaan-1 ,2,4-trikarboksielssuur (FSTKS). Die uretaan harde segment
het bestaan uit: hidrogeneerde 4,4-difenielmetaandiisosianaat, dimetielpropioonsuur
(DMPS), 3-hidroksipivaalsuur (HPS) en hidroksietileenmetakrilaat (HEMA).
Laurielmetakrilaat (LMA), n-butielmetakrilaat (n-SMA), metielmetakrilaat (MMA) en stireen is
as entmiddels gebruik.
Twee verskillende poli-ester polihidroksie verbindings is gesintetiseer: een met 10% fosfaat
en een met geen fosfaat, en gekarakteriseer in terme van hulle suurwaardes,
hidroksiwaardes en molekulêre massas. Die PUs wat vanaf die fosfaat-bevattende poli-ol
gesintetiseer is, is met LMA geêent, terwyl die fosfaat-bevattende PUs met al vier entmiddels
geêent is. Papier (Eng. paperboard) is met hierdie dispersies bedek en by 100°C gedroog.
Die PU-bedekte papier is gekarakteriseer in terme van vogdeurlaatbaarheidstransmissie
(Eng: MVTR - the moisture vapour transmission rate), en skandeerelektonmikroskopie
(SEM).
PU-films wat nie deur papier gestut is nie is ook voorberei deur die verhitting van die PU
dispersies in Teflon houers (130°C, 6 ure). Die droë films is daarna gekarakteriseer deur
middel van termogravimetriese analise (TGA), differensiêle skandeerkalorimetrie (DSC),
dinamiese meganiese analise (OMA) en Fourier-transformasie infrarooispektroskopie (FTIR).
Resultate van MVTR analises het getoon dat die fosfaat-bevattende PU bedekkings 'n
mimimum MVTR-waarde by 0% enting gehad het, en dat die totale MVTR waardes baie laer
was as die van die nie-fosfaatbevattende bedekkings. SEM het gewys dat die fosfaat-PU
bedekkings by 8% enting geen mikrogaatjies (Eng. pinholes) gehad net nie, terwyl die PU
bedekings met geen fosfaat mikrogaatjies (Eng. pinholes) by alle vlakke van enting gehad
het. OMA analises het getoon dat die monsters van die fosfaatbevattende PU hoër Tg
waardes gehad het (Tg begin tussen 0 en 5 "C) as die nie-fosfaatbevattende PU monsters
(Tg begin onder -50°C).
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53005 |
| Date | 12 1900 |
| Creators | Seboa, Sharrief |
| Contributors | Sanderson, R. D., Mequanint, K., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 106 p. : ill. |
| Rights | Stellenbosch University |
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