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The study is to investigate the properties of methacrylate
modified polyurethane. The PU prepolymer is prepared by
polypropylene glycol(PPG),trimethylolpropane(TMP) and
toluene-2,4-diisocyanate(TDI) as the basic structure of
oligomers, and then reacted with 2-hydroxyethyl methacrylate(
HEMA)or 2-hydroxyethyl acrylate(HEA) to form a free radical
polymerizable oligomers.After mixed with initiator(MEKPO),
catalyst(CoN) and reactive solvent, themixture is cured by heat.
The cured sheets have good mechanical properties.The discussion
is divided into several subgroups including investigations ofthe
gel content, curing time and mechanical properties of the cured
sheets :(1) Different amount of initiator and catalyst
(2) Different amount of TMP(3.15, 5.05, 6.33 wt%) (3)
Different molecule weight of PPG(PPG 1000, 2000, 3000) (4)
Different composition and amount of reactive solvent
(5) Different acrylate monomers(HEMA, HEA)
(6) Different NCO index of PU prepolymer
From the experimental data, higher dosage of initiator and
catalyst result lowergel content, ultimate stress and Young's
modulus, and higher elongation, due tolower density of
crosslinking. Higher content of TMP or TDI in the PU
prepolymerincrease the stress and modulus and decrease the
elongation. Higher moleculeweight of PPG results in lower
mechanical properties and modulus. Adding reactive solvent
improves the degree of curing and mechanical properties,
andreduces the viscosity of oligomers. Products which is using
MMA as reactivesolvent are tougher than using SM.
Furthermore, the differential scanning calorimeter(DSC) and
thermogravimetricanalyzer(TGA) have been used to analyze Tg and
cracking temperature of thecured sheets. Tg increases when the
gel content increases. The Tg of theprepolymer reacts with HEA
is higher than that reacts with HEMA. Two crackingtemperatures
have been observed,and cracking temperatures of the
prepolymersreact with HEA are higher than that react with HEMA.
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