Study On The Relationship Between Mechanic Properties Of Structural Polyurethane Foam Plastics And Sub-cluster Scale

As is well known, the structural polyurethane foam plastic is one of the important functional foam plastics. Its smooth, high-density, tough and tensile external skin and low density score form the whole foam at the same time. Based on the reference summary on the field of polyurethane foam, the influence of cell diameter distribution on the mechanics property of foam was studied, and the foam sub-cluster scale model was found in this paper. The sub-cluster scale theory on the cell size distribution was put forward by the sub-cluster statistics in order to reveal the internal relationship between the cell microcosmic structure and macroscopic mechanics property of foam. The work is mentioned as follows:(1) Through adjusting the amount of blowing agent F11, the entire amount of ingredients in the mould and the temperature of the mould, the influence of formulation and processing technology on the density of the Polyurethane (PU) foam plastics were studied. The results indicated that the foam density increases with the addition of F11 within the certain scope, and the rate of the increase of density becomes slower and slower. The addition of the entire amount of ingredients in the mould can affect the formation of the foam cell by increasing the external pressure in foaming. Consequently, the open cell content decreases, which leads to the change of the inner density. Furthermore, the effect of the temperature inside the mould on the properties of the PU foam plastics was investigated, thus the optimal range of the temperature was obtained.(2) In this paper, the five concept: cell shape, cell sizeO, cell density(P), hole degree(E)and area of cell wall( ) together with four sub-cluster parameter R1, R2, R1 . R2,R2/ R1 were put forward to express the cell microscopic character. They foundedthe relationship between cell microscopic structure and the foam macroscopic mechanic property successfully and completely. What's more, the foundation of the foam sub-cluster scale theory provided the theoretical basis to combine the foam microscopic structure with property.(3) In this paper, the internal relationship were predicted theoretically between cell size distribution character and series of properties as hardness of surface, impact strength,bending strength, compressive strength. ln(R1 × R2) indicated the energy the foam needed when the foam get some cell size distribution, so it should has the linear relationship between ln(R1×R2) and cell density P. And also has relationshipbetween hardness of surface, impact strength, bending strength and compressive strength.(4) After a lot of experiments, the results show that the sub-cluster scale theory can successfully explain the relation of cell structure and foam mechanics property ondifferent chemical blowing agent and amount of ingredients, which classical theory cannot do. In this paper, physical meaning of R1, R2, R1識2, R2/R1 was given.R1, indicated the possibility which the hole skip the middle size hole to become a big cell; R2 indicated the possibility which the hole skip the middle size hole to become a small cell; R1?R2 indicated the well-distribution degree of cell size, itwould make the notable influence on the cell density P; R2/R1, indicated the big cell and small cell exchange possibility. Through the verification by a lot of experiment data, it showed that ln(R1識2) -cell density, In R1-hardness ofsurface had good linear relationship. This results have important contribution to foam design and understanding of the structural PU foam mechanics property.