Search results for "foam"

The foaming properties of camel and bovine whey: The impact of pH and heat treatment

2018

International audience; he effect of heat treatment (70 degrees C or 90 degrees C for 30 min) on the foaming and interfacial properties of acid and sweet whey obtained from bovine and camel fresh milk was examined. The maximum foamability and foam stability were observed for acid whey when compared to sweet whey for both milks, with higher values for the camel whey. This behavior for acid whey was explained by the proximity of the pI of whey protein (4.9-5.2), where proteins were found to carry the lowest negative charge as confirmed by the zeta potential measurements. Interfacial properties of acid camel whey and acid bovine whey were preserved at air water interface even after a heat trea…

Study of acoustic properties and impact behavior of porous materials homogeneous type metal foams and inhomogeneous

2015

This work is concerned with the theoretical and experimental study of the acoustical properties of macroscopically homogenous and inhomogeneous porous media as well as their mechanical response to impacts. The model of Johnson - Champoux - Allard appeared adapted for the acoustical modeling. This model, associated with a recently developed approach involving the concept of parallel transfer matrices has lead to a new approach of macroscopically inhomogeneous porous materials based on “mixtures of materials”. Furthermore, a parametric study of the absorption coefficient as a function of porosity and frequency has been proposed. The maximums of absorption as well as the envelop of the absorpt…

USE OF BIODEGRADABLE POLYMERS FOR FOAM EXTRUSION

2013

Pathogenesis of Atherosclerosis: The Alternative Hypothesis

1998

The concept that oxidation is the major single event underlying the transformation of LDL to a proinflammatory molecule dominates the world literature. An alternative hypothesis on the pathogenesis of atherosclerosis will be presented here. We have found that nonoxidative, enzymatic modification of LDL with ubiquitous enzymes also transforms the molecule to an atherogenic moiety. Enzymatically altered LDL (E-LDL) shares major properties in common with lipoproteins that have been isolated from atherosclerotic lesions. It activates complement and is recognized by a scavenger receptor on human macrophages, thus inducing foam cell formation. Uptake of E-LDL is accompanied by induction of MCP−1 …

Aqueous foam as the carrier phase in the deposition of fibre networks

2015

Reinforcement Efficiency of Cellulose Microfibers for the Tensile Stiffness and Strength of Rigid Low-Density Polyurethane Foams

2020

Rigid low-density closed-cell polyurethane (PU) foams are widely used in both thermal insulation and structural applications. The sustainability of PU foam production can be increased by using bio-based components and fillers that ensure both enhanced mechanical properties and higher renewable material content. Such bio-based foams were produced using polyols derived from rapeseed oil and microcrystalline cellulose (MCC) fibers as filler. The effect of MCC fiber loading of up to 10 wt % on the morphology, tensile stiffness, and strength of foams has been evaluated. For estimation of the mechanical reinforcement efficiency of foams, a model allowing for the partial alignment of filler fibers…

Rheological Behavior Under Shear and Non-Isothermal Elongational Flow of Biodegradable Polymers for Foam Extrusion

2013

The production of many items, in particular for food packaging applications, is based on foam extrusion and thermoforming. These operations require the use of polymers which can grant some specific rheological properties, both under shear and elongational flow. In this work, the behavior of some biodegradable polymers [Mater-Bi® and poly(lactic acid)] under shear and non-isothermal elongational flow was investigated and compared with a traditional, non-biodegradable polymer, in order to assess their suitability for industrial-scale foam extrusion and thermoforming. The rheological characterization evidenced the differences between the different biodegradable polymers and the reference polys…

Open Cell Al-Si Foams by a Sintering and Dissolution Process

2014

Open cell foams from AlSi12 alloy were successfully fabricated by the Sintering and Dissolution Process, using NaCl as space holder (60 %). The size of the aluminum alloy powder is less than 45 μm, while the space holder powder size is 315-500 μm, 630-800 μm and 800-1250 μm respectively. The appropriate quantities of alloy powder and salt were mixed and cold pressed at 250 MPa. The sintering process was done at 500 °C and 545 °C, in vacuum (10-5 torr) for 10, 20 and 30 minutes respectively. The space holder was eliminated by holding the sintered samples in running hot water (70 °C). After the salt was dissolved, the samples were dried and the mass loss was analyzed. Keywords: Aluminum foam…

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…

Airflow and aerosol transport modeling with applications to Covid-19 aerosol reduction indoors

2022

Pēdējo pāris gadu laikā Covid-19 infekcijas slimība ir izraisījusi lielu kaitējumu cilvēkiem visā pasaulē, kas ir licis zinātniskajai kopienai apsvērt pieejas infekcijas mazināšanai, tostarp skaitliskās modelēšanas pieejas. Šī darba mērķis ir modelēt Covid-19 aerosola pārnesi un tā samazināšanu iekštelpās. Skaitliskās hidrodinamikas risināšanai tiek izmantota Reinoldsa vidējotā Navjē Stoksa modelēšanas pieeja kopā ar turbulentās difūzijas modeli aerosola pārnesei. Darbs sākas ar konkrētas telpas gaisa plūsmas modelēšanu un skaitlisko aprēķina parametru izpēti. Nākamajā daļā tiek izveidots gaisa attīrīšanas iekārtas matemātiskais modelis, kas tiek skaitliski ieviests un pārbaudīts izmantojot…