The paper describes the fabrication of cast acrylic sheets by copolymerizing a prepolymer syrup of methyl methacrylate (MMA) with varying amounts (1 -20 wt.-To) of 2-ethylhexyl methacrylate (EHMA), n-hexyl methacrylate (HMA), 2-ethylhexyl acrylate (EHA) and n-hexyl acrylate (HA). The effect of structure of copolymer on light transmittance, density and mechanical properties was evaluated. Tensile strength and storage modulus decreased with increasing comonomer content. Strain increased significantly in the case of MMA/EHA and MMA/HA copolymer sheets having 15 and 20 wt.-% of comonomer. Softening temperature of copolymer samples was determined using dynamic mechanical thermal analysis. Heat deflection temperature under flexural load and softening temperature decreased with increasing comonomer content in copolymer.
ZUSAMMENFASSUNG:Methylmethacrylat (MMA) mit einem Prepolymergehalt von 6-8% wurde mit unterschiedlichen Anteilen (1 -20%) 2-Ethylhexylmethacrylat (EMMA), n-Hexylmethacrylat (HMA), 2-Ethylhexylacrylat (EHA) oder n-Hexylacrylat (HA) copolymerisiert. Aus den erhaltenen Copolymeren wurden Folien hergestellt, an denen der Ein-fluR der Copolymerstruktur auf Lichtdurchlassigkeit, Dichte und mechanische Eigenschaften ermittelt wurde. Zugfestigkeit und Speichermodul nahmen mit zunehmendem Comonomergehalt ab. Die Dehnung stieg im Fall von MMA/EHA-und MMA/HA-Copolymerfolien mit 15 und 20 Gew.-Yo Comonomeranteil merklich an. Mittels DMTA wurde die Erweichungstemperatur der Copolymeren bestimmt. Die HDT und die Erweichungstemperatur nahmen unter Biegebelastung rnit steigendem Comonomergehalt der Copolymeren ab.
Five copolymer samples containing different mole fractions of methyl methacrylate (MMA) and 2-ethylhexyl methacrylate (EHMA) were prepared by hulk polymerisation at 70~ usin~ 0.2% bcnzoyl peroxide as an initiator. The copolymer composition was determined by H NMR spectroscopy. Molecular weight of copolymers was determined by gel permeation chromatography and viscosity measurements. Thermogravimctric experiments were conducted to evaluate activation energy for the degradation of copolymers. Two to four reaction stages for the weight loss were observed in the eopolymers. A decrease in thermal stability was observed by an increase in EHMA content.Poly(methyl methacrylate) (PMMA) is a versatile, hard, rigid, transparent plastic material having extremely good weathering resistance. In order to extend the potential application areas of PMMA in building and construction and outdoor applications, considerable work has been done to improve fire resistance, impact behaviour and heat distortion temperature. Copolymerisation of methyl methacrylate (MMA) with suitable vinyl monomers such as alkyl methacrylates has been carried out for modifying the properties of the polymer [1][2][3][4]. The length of alkyl group in these alkyl methaerylate has a pronounced effect on the flexibility of methacrylate polymers. Whereas the usual effect of increasing the side chain length in the esters derived from straight chain alcohol is to soften the polymer and to make it more flexible, the branched chain alcohols have the opposite effects [5]. The presence of eomonomers in PMMA backbone may also affect its thermal behaviour.Although significant amount of work has been carried out on thermal and oxidative degradation of PMMA [6][7][8][9][10][11][12], only little attention has been
John Wiley & Sons Limited, ChichesterAkad~miai lOadt, Budapest
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