Hardness Of Foams Research Articles

Cell structure and hardness evolutions of TPU foamed sheets with high hardness via a temperature rising foaming process

The foams based on TPU with high hardness were prepared by temperature rising foaming. The effects of hardness on thermal behavior, mechanical and rheological properties, gas solubility and diffusivity of TPU were discussed. It was found that TPU with higher hardness have lower CO2 solubility and smaller diffusivity. TPU foamed sheets with various expansion ratio and cellular morphology were fabricated using different foaming parameters. It was easier to prepare TPU foams with low density for TPU with higher hardness. At suitable foaming temperatures, foams with similar density but different cell sizes could be prepared by altering saturation pressures. Finally, the hardness of the foamed samples was systematically compared. It was demonstrated that the hardness of TPU foams was affected by foam density, resin hardness and cell structure.

Effect of different concentration of rapeseed‐oil‐based polyol and water on structure and mechanical properties of flexible polyurethane foams

ABSTRACTFlexible polyurethane foams (FPURFs) with varied concentration of water from 3.2 to 4.2% and rapeseed oil based polyol (ROP) in the range of 13–22% in polyol premix were obtained. Effects of changes in polyurethane (PUR) formulation on the foaming process and mechanical properties of FPURFs were analyzed. It was found that the change of water content in PUR formulation influences its foaming process. Higher water content in the PUR formulation increases the growth velocity and the temperature of reaction mixture. In the case of foams modified with ROP, an opposite effect can be observed, where higher content of that component resulted in overall downturn of the foaming process and decreases of registered temperature inside the foams core. An addition of ROP beneficially influences on foams cellular structure favoring creation of finer cells. Such modification of PUR formulation with ROP increased apparent density, reduced hardness, and resilience of flexible foams. What is more the support factor of FPURFs with ROP was higher in comparison to the reference foam. Along with higher water content in the PUR formulation, apparent density and hardness has decreased and foams ability to absorb energy has been increased. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42372.

반경질 폴리우레탄 발포체의 물성에 대한 사슬 연장제와 무기 충전제의 영향

The physical properties of polymeric foams depend on the density of foams, physical properties of base polymers, the content of open cells, and cell structures including the size and its distribution, the shape of cell, and the thickness of skin layer. The foam density is affected by the chemistry of raw materials, the concentration of crosslinking agent and the blowing agent as well as the operating parameters during production process. In this study, the basic formulations of foams are composed of polyester polyol, MDI, amine catalyst, tin catalyst, silicone surfactant, and water. Cross-linking density of polyurethane was increased by using chain extenders. Also, the mechanical properties of polyurethane foam were improved by using the inorganic fillers (silica 1,2 and talc 1,2) having different contents and particle sizes. We investigated the properties of modulus, tensile strength, compressive strength and hardness of foams obtained by changing kind of inorganic filler and chain extender, and observed the distribution of inorganic filler as well as variation of cell size within the foams by electron microscopy.

Time Dependence of Hardness of Cold Cure Molded Flexible Foams and Its Importance for System Development

The first impression made by a car seat, and thus very important for the customer, is the hardness. This can be adjusted to specific requirements or preferences. However, in practice it is found that the hardness is not constant but increases under load. This is in contrast with the results of standardized hardness measurements, where the values decrease. This time dependence should be further examined, because it is also suggested to be different for TDI- and MDI-foams. To get a first insight, standard deformation cycles were applied before and after a high constant loading over 10-20 hours

Time Dependence of Hardness of Cold Cure Molded Flexible Foams and Its Importance for System Development

The first impression made by a car seat, and thus very important for the customer, is the hardness. This can be adjusted to specific requirements or preferences. However, in practice it is found that the hardness is not constant but increases under load. This is in contrast with the results of standardized hardness measurements, where the values decrease. This time dependence should be further examined, because it is also suggested to be different for TDI- and MDI-foams. To get a first insight, standard deformation cycles were applied before and after a high constant loading over 10-20 hours

Time Dependence of Hardness of Cold Cure Molded Flexible Foams and Its Importance for System Development

Time Dependence of Hardness of Cold Cure Molded Flexible Foams and Its Importance for System Development