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The low-frequency Raman scattering (2-200 cm -1 range) of poly(methyl methacrylate) (PMMA) specimens plastically deformed in pure shear is compared to that of non-deformed specimens. The main experimental feature is an excess of Raman scattering in the 30-50 cm -1 spectral range induced by plastic deformation. This excess appears to be strongly anisotropic and is maximum...
Structural relaxation of poly(methyl methacrylate) has been studied by differential scanning calorimetric (d.s.c.) and dynamic mechanical techniques, and the effect of temperature of ageing has been investigated. Isothermal ageings at temperatures between T g - 30 K and T g - 100 K lead to d.s.c. pre-peaks and a diminution of the mechanical loss tangent. The β relaxation is not affected...
A new test, known as antistress relaxation, allows us to study, exclusively, the anelastic deformation, i.e. one which is recoverable with time, of various polymers over a wide range of stresses and temperatures until the yield flow point is reached. In the linear regime, this test is linked with certain viscoelastic properties, such as the loss tangent, tan φ and the loss dynamic compliance, J″,...
Various maleimide-containing copolymers have been studied with respect to their miscibility behaviour towards poly(methyl methacrylate) (PMMA) by differential scanning calorimetry (d.s.c.). Poly(styrene-co-N-maleimide)s (NMIs) with maleimide contents between 8 and 21 wt% were shown to be completely miscible with PMMA, whereas a blend containing 45 wt% maleimide in the NMI was not miscible with PMMA...
I.r. and high-resolution solid-state 13 C n.m.r. spectra, as well as proton relaxation times T H1 andT H1ρ of poly(ethylene oxide) (PEO)/atactic poly(methyl methacrylate) (a-PMMA) blends in the solid state, with PEO weight fractions of 10, 30, 50 and 70% were measured. Infra-red spectra of pure PEO with various molecular weights were also measured. The...
The surface enrichment of blend films of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) cast from various solvents has been investigated by contact angle, X-ray photoelectron spectroscopic and attenuated total reflection Fourier transform infra-red spectroscopic measurements. The composition of each component was fixed at 50 wt%. The surfaces of miscible PMMA/PVAc blend films are...
Highly isotactic (it-) and highly syndiotactic (st-) poly(methyl methacrylate)s (PMMAs) were fractionated into the individual homologues (uniform polymers) from the 13mer to the 50mer by means of supercritical fluid chromatography. The glass transition temperature (T g ) and crystalline melting temperature of the uniform PMMA samples were determined by differential scanning calorimetry. ...
The photophysical behaviour of benzophenone (BP) in poly(methyl methacrylate) (PMMA) has been studied as a function of temperature. Time-resolved phosphorescence data reveal that at no temperature between 77 and 420 K can the decay behaviour of the triplet state of BP in PMMA be described adequately by a single exponential function. This contrasts with the phosphorescence behaviour of BP in low temperature,...
Composition dependences of the glass transition temperature (T g ), the molecular weight between entanglements (M e ) and the thin film deformation behaviour have been studied in two series of methyl methacrylate-based random copolymers. When the comonomer is styrene, increases in both M e and brittle behaviour accompany the decrease of T g . When the comonomer is...
Matrix-assisted laser desorption/ionization mass spectrometry (m.a.l.d.i.-m.s.) is shown to be a unique method for the determination of the functional heterogeneity of poly(methyl methacrylate)s. In group-transfer polymerization of methyl methacrylate, oligomers with cyclic end-groups are formed in addition to the expected linear oligomers. The cyclics are identified via preparative separation of...
We report measurements of the hydrostatic pressure dependence of the elastic constants of poly(methyl methacrylate) using high resolution Brillouin spectroscopy. We have measured the density ρ(p) up to 500 MPa, and the longitudinal and transverse sound velocities up to 300 MPa. We have calculated the bulk modulus, Youngs modulus, shear modulus and Poisson's ratio. Initially there is a strong increase...
Methanol transport in crosslinked poly(methyl methacrylate) (PMMA) was studied. Four thicknesses were considered: 0.6, 1.0, 1.5 and 1.9 mm. The front velocity is independent of thickness. The front velocity obeys the Arrhenius equation and the activation energy is 20 kcal mol -1 . Comparing the crosslinked and uncrosslinked PMMA, the front velocity of the crosslinked PMMA is smaller...
Enthalpic ageing data for poly(methyl methacrylate) are reanalysed in terms of a modified version of the Cowie-Ferguson model which takes account of a time-dependent characteristic time, t c . In terms of describing the time evolution of enthalpy changes occurring upon ageing, no significant improvement in the fits to the data were found when compared with the original linear model.
Microdeformation in thin films of rubber modified poly(methyl methacrylate) has been investigated using TEM. The effects of two-layer core-shell particles with rubbery cores, and three-layer particles with glassy cores are compared. While the former undergo relatively coarse cavitation and may act to block fibril drawing in matrix crazes, the rubber shell of the three-layer particles tends to fibrillate,...
Certain styrene/maleic anhydride copolymers (SMA) are completely miscible with poly(methyl methacrylate) (PMMA). This paper explores the solubilization of SMA copolymers in the grafted PMMA shell layer of emulsion-made core-shell impact modifiers by examining glass transition behaviour and morphology of SMA/core-shell modifier blends. There appears to be a single, composition-dependent hard phase...
Melt blends of poly(methyl methacrylate) (PMMA) with a phenoxy (polyhydroxy ether of bisphenol A) have been prepared over the complete composition range using a single-screw extruder. Injection-moulded specimens of the blends were transparent, and differential scanning calorimetry and rheological measurements gave a single glass transition temperature (T g ), indicating miscibility of the...
Plaques (2 mm thick) of atactic, bulk polymerized poly(methyl methacrylate) (PMMA) were exposed to γ-rays (dose rate 2.5 kGy h -1 , doses ranging from 5 to 10 kGy), at ambient temperature in a nitrogen atmosphere. Tensile-loaded samples (stress: 47 MPa) were exposed together with unloaded ones. The molecular weight distribution was studied before and after irradiation by size exclusion...
Experimental data from thermo-stimulated creep (TSCr) spectrometry display a retardation mode in poly(methyl methacrylate) (PMMA) at T > T g (glass transition temperature). In this work an attempt is made to relate the restoring force involved during TSCr measurements beyond the glass transition zone to the viscoelastic behaviour of the polymeric chains flowing in the entangled network...
Based on the process of polymerization, an interpenetrating cell model was proposed for poly(methyl methacrylate) (PMMA). This model was used to account for the presence of dimples on the fracture surface of PMMA when voids are present. PMMA was treated by various methods including mixtures of methanol and chlorophyll, gamma irradiation, at different crosshead speeds and after warm drawing. Micrographs...
The changes in sensitivity of a cellulose triacetate (CTA) film dosimeter is reported as a function of linear energy transfer (LET). The change in molecular weight of poly(methyl methacrylate) (PMMA) is also reported. For both materials, little or no LET effect was observed up to a threshold LET, but the sensitivity or radiation yield decreased with increasing LET above this threshold level. The...
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