Preparation Of Ultrafine Particulars/RPUF And Its Structure And Properties

Used in the situation of vibration,Rigid polyurethane foams as Light rigid damping material need a balance among three properties:rigidity,toughness and damping perpormance. The main reason which prevents powder reinforced materials from being applied in RPUF is the decrease of impact strength. Good toughness and damping properties were expected by decreasing the cross linkage density of RPUF,on the other hand,the increase of elastic modulus and reducing of influence of filler in toughness were hoped through superfine particulars dispersed well. In view of the absence of jobs in detail on cell structure and mechanic properties,this paper investigated the influences o of five sorts of rigid inorganic fillers (nano-CaCOs was the central) to the structure and mechanic properties.,Four aspects of experiments were achieved:(1) dispersing of nanometer agglomerates by ultrasonic;(2) Preparation of Reinforced RPUF;(3) Image analysis of cellular structure and calculation of structure parameters;(4) Study on the quasi-static and dynamic mechanic test of RPUF. The main conclusions are listed as following:1. Dispersing tests of nano-CaCO3 and nano-SiOa in polyether polyol went on by power ultrasonic,as a result, suspensions in which 30Vol% of particulars whose grainsizes were below 100nm,and 60Vol% of particulars whose grainsizes were below 200nm were gained from two sorts of agglomerates.2. The dispersing results of nano-CaCO3 and nano-SiO2 agglomerates by ultrasonic shows two-component rule. Principles of processing in ultrasonic dispersing were analyzed by disperse degree and Kusters model. According toKapur's "self-support" hypothesis,computer simulation for the development of volume fraction -particular size curve in the process of dispersing by ultrasonic was performed ,the results show the process in dispersing by ultrasonic of nano-agglomerates directly,and represent the basic characteristics of the volume fraction -particular size curve of nano-agglomerates measured in practice.3. With a view to the effects of blow pressure on the structure and properties of RPUF,parameters of formula and processing were investigated,it is found that the dosage of blow agent is the most important factor influencing the foaming pressure. Theory model for the relation of dosage of blow agent and blow pressure has been developed and confirmed in tests,parameters of model have been fitted too,and the ultimate expression can be used in the design for the processing of RPUF. Finally,RPUF filled with five sorts of fillers (ultrafine particulars was the central) was prepared on the above job.4. Diameter,density of cellular and thick of cell wall of RPUF reinforced by several fillers were calculated through computer image analysis. The results show that the reduce of cellular diameter and cellular density follows the decrease of void fraction,but they keeps invariable when void fraction induces to a certain value (below the maximum dense stack fraction).5. The relation of Yong's modulus and compress strength of reinforced RPUF connection to the solid volume fraction follows the power law in quasi-static compress tests. The results of impact tests show that nano-CaCOs ,nano-SiO2 and hollow glass microbead influence impact strength of reinforced RPUF slightly while micrometer CaCO3 and glass fibre induce the fall of reinforced RPUF sharply. The decrease of cross linkage density of RPUF can enhance the impact strength,and RPUFs reinforced by nano-CaCO3 and nano-SiCh with the lower cross linkage density have higher impact strength than the opposite higher cross linage density,but micrometer CaCO3 has no such phenomenon.6. Dynamic thermomechanic analysis (DMA) shows that effect of CaCO3 for reinforcing RPUF have relation to void fraction. In systems with different void fraction,threshold values of fillers for enhancing Yong's modulus visibly aredifferent,the threshold value in system with higher void fraction is higher than that in system with lower void fraction. Unlike situations of quasi-compress tests...