0000000001095635
AUTHOR
Ilze Beverte
showing 9 related works from this author
Rapeseed oil-based rigid polyisocyanurate foams modified with nanoparticles of various type
2014
Polyisocyanurate foams have been developed using a polyol system partially derived from rapeseed oil (RO). The effect of nanofillers with iso-dimensional geometry (zinc oxide), nanofibers (carbon nanotubes), and nanoplatelets (organically modified montmorillonite) on stiffness and strength of the foams has been studied. It was demonstrated that the tensile properties of the filled foams are enhanced by roughly the same proportion as the stiffness and strength of monolithic filled polymers.
Polyurethane and Polyisocyanurate Foams in External Tank Cryogenic Insulation
2013
External tanks of the spacecrafts need not only efficient, but also safe cryogenic insulation materials and the issues of their development are still urgent. At present, polyurethane (PUR) or polyisocyanurate (PIR) foams’ cryogenic insulation is widely applied in the partially reusable launch systems. Factors influencing the cryogenic resistance of external thermal insulation performed of spray-on PUR or PIR foams are characterised based on a wide literature search. They include chemical structure and macromolecules’ architecture of polymeric matrix, physical and mechanical properties of foams, thermal stability and combustibility, cellular structure of foams etc. Experimental data on physi…
Water-Blown Polyisocyanurate Foams From Vegetable Oil Polyols
2008
Polyols with the hydroxyl value OHV from 290 to 318 mg KOH/g are synthesized from rapeseed, sunflower seed, flaxseed, or coconut oils by the way of their: (1) transesterification with triethanolamine or (2) amidization with diethanolamine. The influence of water as the blowing agent on the storage stability of the polyol premix system is assessed from values of the polyol premix system pH, acid value, and variations in such parameters as cream and gel time. Water-blown polyisocyanurate (PIR) foams (150 · II × 300; II—isocyanate index) characterized by good mechanical characteristics, dimensional stability at 70°C and at relative humidity RH = 95% as well as by a very low water absorbance, …
Determination of highly porous plastic foam structural characteristics by processing light microscopy images data
2013
Mathematical modelling of physical and mechanical properties of plastic foam as well as numerous practical applications requires knowledge of foam structural characteristics. A necessity exists to determine the characteristics of the spatial structure of inhomogeneous materials comprising inclusions of other material, e.g., polyurethane foam without destructing the material and analysis of each element. A methodology is elaborated for preparing highly porous plastic foam specimens and investigation of foam strut-like structure with light microscopy (LM) by taking images in three mutually perpendicular planes. A mathematical model is developed for highly porous plastic foam for the determina…
Mechanical properties of rigid polyurethane foams at room and cryogenic temperatures
2011
Studies on the effect of the foams’ polymeric matrix’ properties on the tension and compression properties of pour rigid polyurethane (PUR) foams, apparent core density 65—70 kg/m3, at 296 and 77 K were carried out. PUR foams were produced by the hand mixing method from polyol systems that comprised polyether, polyester polyols, and chain extenders. To produce PUR foams, crude MDI was used, and Solkane 365 mfc/227 ea was used as a blowing agent. The molecular weight per branching unit (Mc) of the polymeric matrix of PUR foams was varied in the range 300—1150. Cohesion energy densities of the blocks forming the polymeric matrix were calculated. The effect of Mc on the formation of hydrogen …
Polytetrafluoroethylene Films in Rigid Polyurethane Foams' Dielectric Permittivity Measurements with a One-Side Access Capacitive Sensor.
2021
As a non-metallic composite material, widely applied in industry, rigid polyurethane (PUR) foams require knowledge of their dielectric properties. In experimental determination of PUR foams’ dielectric properties protection of one-side capacitive sensor’s active area from adverse effects caused by the PUR foams’ test objects has to be ensured. In the given study, the impact of polytetrafluoroethylene (PTFE) films, thickness 0.20 mm and 0.04 mm, in covering or simulated coating the active area of one-side access capacitive sensor’ electrodes on the experimentally determined true dielectric permittivity spectra of rigid PUR foams is estimated. Penetration depth of the low frequency excitation…
An experimental method for the investigation of rigid polyurethane foams in shear
2018
Widespread applications of rigid polyurethane and plastic foams lead to shear deformations. Therefore, methods for ensuring shear using experimental investigations are necessary, including the possibility of determining the shear modulus, strength and limit angle. Therefore, a device that allows investigating the shear properties of highly porous plastic foams was developed. The proposed device comprises a clip-on extensometer, commonly exploited in uni-axial compression/tension tests, for the determination of the shear displacement directly on the foams’ sample, on a measurement zone of certain dimensions and location. An innovative construction of the extensometer’s legs is elaborated, p…
Deformation of Polypropylene Foam Neopolen® P in Compression
2004
Neopolen® P is a two-phase cellular composite foam material produced by BASF AG, Germany. In most of the practical applications, Neopolen® P works under a range of small and compressive deformations. Therefore it is necessary to determine the moduli in compression and compressive strength in the most effective way for a wide range of foam densities: 22≤ρ84≤kg/m3. Several experimental methods of different precision for deformation properties of Neopolen® P were compared. The direct measurements performed by a universal testing machine were used for the main part of the experiments. They were compared with results obtained by a more precise and time-consuming method, using an inductive exten…
Deformative Properties of Monotropic Plastic Foams with a Pronounced Strut-Like Strukture
1996
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