| Summary: | Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. === ENGLISH ABSTRACT:
Polymethacrylates are well known adhesives and can carry specific functionality, but have
the disadvantage that their flexible backbones impart limited thermal stability and mechanical
strength. Polyurethanes (PUs) are finding increasing application and use in many industries
due to their advantageous properties, such as a wide range of flexibility combined with
toughness, high chemical resistance and excellent weatherability. PUs do however have
some disadvantages, for instance, PU is considered an expensive polymer, especially when
considered for solvent based adhesives. the focus of this study was to consider a largely
unstudied area of PU chemistry, namely combining PUs with polymethacrylates.
Two types of linear urethane macromers (UMs) UM1 and UM2 were synthesized by the
polyaddition polymerization of 4,4'-methylenediphenyl diisocyanate (MDI) with ethylene
glycol (EG), and MDI with neopentylglycol (NPG), via a pre-polymer method, followed by
termination with 2-hydroxy ethylacrylate (2-HEA) and methanol (MeOH) to yield UMs having
specific urethane chain lengths, and which have to be predominantly monofunctional.
Structural identification of the UMs was verified by MALDI-TOF-MS, FTIR, 13C-NMR and 1HNMR
spectroscopy.Various percentages of the respective UMs (0_55 wt % of methacrylate monomers) were
then incorporated into polymethyl methacrylate (PMMA) and poly n-butyl methacrylate
(PnBMA) backbones via solution free-radical copolymerization. The resulting methyl
methacrylate-g-urethane and n-butyl methacrylate-g-urethane copolymers were
characterized by 1H-NMR,13C-NMR, FTIR, SEC with double detectors (UV and RI), light
scattering, UV-Vis, HPLC, TGA, DSC, DMA and TEM. Weight percentages of UM
incorporated into the methyl methacrylate-g-urethane copolymers were calculated using
FTIR, UV-Vis and 1H-NMR techniques. Phase separation which occurred between the
urethane segment and methacrylate segment in the graft copolymerization products was
investigated by DMA, DSC and TEM analysis.
Microphase separation occurred in all PMMA-g-UM1 and PnBMA-g-UM1 copolymers: two
glass transitions temperatures corresponding to the PMMA or PnBMA and UM1 fractions,
respectively, were observed. On the other hand, DMA and DSC results showed that in most
graft copolymer products the two respective component parts PMMA-g-UM2 or PnBMA-g-
UM2 were compatible, because only one Tg was observed. Two glass transitions occurred
for PMMA or PnBMA and UM2 when the amount of UM was increased to 55 wt % during
copolymerization and microphase separation was evident in DSC, DMA and TEM
measurements. Thermal stability and storage modulus (stiffness) of all the synthesized PMMA-g-urethane
and PnBMA-g-urethane copolymers increased as the concentration of urethane
macromonomer in the copolymerization feed increased, as confirmed in TGA and DMA
results. The surface and adhesive properties of the synthesized graft copolymer were studied
by measuring the static contact angle and peel strength. Adhesion increased as the content
of UMs increased in the graft copolymer. The graft copolymers prepared using a high UM2
feed for both PMMA and PnBMA showed improved in adhesion compared to the pure
methacrylate polymers. The adhesion was better for both leather and for vinyl. === AFRIKAANSE OPSOMMING:
Polimetakrilate is bekende kleefstowwe. Hulle het egter die tekortkoming dat hulle buigbare
ruggraat beperkte termiese en meganiese stabliteit besit. Poliuretane (PUs) word deesdae al
hoe meer gebruik in baie nywerhede as gevolg van hulle baie voordele, insluitend hul wye
buigsaamheid tesame met sterkte, hoë chemiese weerstand en uitstekende weerbaarheid.
PUs het egter ’n paar nadele: hulle is baie duur, veral wanneer hulle gebruik word in
oplosmiddel-gebaseerde kleefstowwe. Die doel van hierdie studie is om die kombinering van
PUs met polimetakrilate te bestudeer, 'n onderwerp wat tot dusver baie min aandag-getrek
het.
Twee tipes liniêre uretaanmakromere (UMs), UM1 en UM2, is gesintetiseer deur
gebruik te maak van poliaddisiepolimerisasie van 4,4'-metileendifeniel diisosianaat (MDI) met
etileenglikol (EG), en MDI met neopentielglikol (NPG), via ‘n prepolimeermetode, gevolg deur
terminering met 2-hidroksiëtielakrilaat (2-HEA) en metanol (MeOH). Die produk hiervan is
UMs met spesifieke kettinglengtes (hoofsaaklik monofunksioneel). Die samestelling van die
UMs is met behulp van die volgende gevorderde analitiese tegnieke bepaal: MALDI-TOFMS,
FTIR, 13C-NMR en 1H-NMR.
Verskillende hoeveelhede van die UMs (0_55 gewIing% metakrilaatmonomere) is dan
in die polimetielmetakrilaat (PMMA) en poli-n-butielmetakrilaat (PnBMA) ruggrate
geïnkorporeer deur middel van oplossing-vryradikaalpolimerisasie. Die samestelling van die
kopolimeerprodukte, metiel-metakrilaat-g-uretaan en n-butiel-metakrilaat-g-uretaan, is met
behulp van die volgende gevorderde analitiese tegnieke bepaal: 1H-NMR, 13C-NMR, FTIR,
SEC met dubbele detektors (UV en RI), ligverstrooiing UV-Vis, HPLC, TGA, DSC, DMA en
TEM. Die hoeveelheid UM geïnkorporeer in die metielmetakrilaat-g-uretaan kopolimere is
bereken deur gebruik te maak van FTIR, UV-Vis en 1H-NMR data. Die faseskeiding wat
plaasgevind het tussen die uretaansegment en die metakrilaatsegment in die produkte van
die entpolimerisasie is met behulp van DMA, DSC en TEM ondersoek.
In alle PMMA-g-UM1 en PnBMA-g-UM1 kopolimere het mikrofaseskeiding
plaasgevind: twee verskillende glasoorgangstemperature vir die PMMA of PnBMA en UM1
fraksies is waargeneem. Hierteenoor het DMA en DSC resultate getoon dat in die meeste
entkopolimeerprodukte (PMMA-g-UM2 of PnBMA-g-UM2) was die twee komponente
verenigbaar, aangesien net een Tg waargeneem is. In die geval van die kopolimere waar die
hoeveelheid UM in die kopolimerisasiereaksies tot 55 gew% verhoog is, is twee
glasoorgangstemperature vir PMMA of PnBMA, en UM2 waargeneem. Mikrofaseskeiding is
met behulp van DSC, DMA en TEM bewys.
Termiese stabiliteit en stoormodulus (styfheid) van alle gesintetiseerde PMMA-g uretaan en PnBMA-g-uretaan kopolimere het toegeneem namate die uretaankonsentrasie in
die kopolimerisasiereaksie toegeneem het soos deur middel van TGA en DMA resultate
bewys is. Die oppervlakte- en kleefeienskappe van die bereide entkopolimere is bestudeer
deur die statiese-kontakhoek en skilkrag te meet. Adhesie het toegeneem namate die UMinhoud
toegeneem het. Die entkopolimere berei met hoë PMMA en PnBMA inhoud het
uiteindelik beter adhesie getoon as die suiwer metakrilaatpolimere. Die adhesie was beter vir
beide leer en viniel.
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