外文翻譯---礦物填充物在聚苯乙烯熔融過程的作用-其他專業(yè)(編輯修改稿)
2025-02-24 09:41 本頁面
【文章內(nèi)容簡介】 essure losses at a shear rate of 587, 1328, and 3000 s?1. Fig. 5. Determination of onset of percolation of mineral?lled polystyrene. overnight. The sample was then taken out and cut into small pieces and stored. In similar fashion samples with different volume fractions were prepared for 10–30 and up to 70%. The mineral?lled samples were subjected to capillary melt extrusion experiment at a temperature 190 ?C with a melt time of 300 s to allow air and moisture trapped in the sample barrel to evolve. The experiment was carried out using Dynisco Instruments Model 7001 LCR capillary rheometer (Mantown, PA, USA). The diameter of the dies used was 1mm and the length to diameter ratios ranged from 1 to 32. The entering angle of the dies was 180?. These experiments were used to determine the processing and recycling behavior of these polymer–mineral posite materials. 3. Results and discussion The mineral ?llers make the recycling of the posites more dif?cult by increasing the energy consumption in the melt processing process. The energy consumption is related to the total pressure drop in the melt ?ow Δp, including the end pressure losses Δpend (sum of the entry pressure drop and the exit pressure drop) and the pressure drop within the extrusion die Δpdie [5] Fig. 6. Electron microscopic view of surface sharkskin at shear rate of 1800 s?1 and 190 ?C: (a) 0% minerals, (b) 20% (volume) minerals. Fig. 7. The electron microscopic crosssection view of the extrudates: (a) 0% mineral, (b) 20% mineral. Δp = Δpend + Δpdie (2) The relationship, which governs the wall shear stress and the total pressure drop in the die extrusion, can be expressed as τw = (Δp ? Δpend)D/4L (3) where τw is the shear stress at the wall, D the diameter, L the length of the die, Δpend the end pressure losses which are determined using the Bagley plot method. The shear rate was calculated from the speed of the extrusion plunger: ˙ γ = 4R2bSp/R3c (4) where Rb is the radius of the feed barrel, Rc the radius of the die, Sp the speed of the plunger. The apparent shear viscosity ηa is de?ned as ηa = τw/˙ γa (5) Fig. 1 shows that the viscosity of the mineral?lled polystyrene increases with the volume fraction of the mineral ?llers. As expected, the shear viscosity decreases with an increase in temperature, provided they are chemically stable. This is shown in Fig. 2. At prolonged and elevated temperatures, some polymers may increase in molecular weight through gelforming or crosslinking, resulting in a rise in viscosity. Alternatively, it can break down by way of chain scission causing a larger than expected drop in viscosity with temperature. Fig. 3 is the typical Bagley plot that is used to calculate the end pressure losses. The end pressure losses are characteristic of the viscoelastic nature of the polymer melt ?owing through the changing crosssections. The end pressure losses thus obtained show a signi?cant dependence on the processing condition in terms of shear rate, as shown in Fig. 4. The increase in the end pressure losses is more rapid than linearly with the shear rate. Percol
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