注塑成型習(xí)題及答案-wenkub.com
2025-01-05 21:34 本頁(yè)面
【正文】 特別聲明： 1：資料來(lái)源于互聯(lián)網(wǎng)，版權(quán)歸屬原作者 2：資料內(nèi)容屬于網(wǎng)絡(luò)意見(jiàn)，與本賬號(hào)立場(chǎng)無(wú)關(guān) 3：如有侵權(quán)，請(qǐng)告知，立即刪除。材料改性后，注塑成型工藝應(yīng)做哪些調(diào)整。一般較低檔的采用 475，高檔的用 ABS。 他們認(rèn)為由剪切速率減小引起的壓力和剪切粘度的上升的影響超過(guò)了弱的拉伸和剪切場(chǎng)的影響。另一方面，高的注射速度會(huì)引發(fā)強(qiáng)的拉伸和剪切場(chǎng)，引起分散相的變形和破裂，最后形成更小的微粒。注射速度的提高使皮下層的位置移到了棒表面(也就是固化層變薄了 )，使分散相粒子的拉伸比增大并且使皮下層的分散粒子的直徑減小。 Before mold filling,the preformed dispersed PC and PET droplets must have already experienced some degree of stretching in the high shear and elongational flow fields during the previous blending morphology evolution to the final solidstate structure after injection molding was determined by the flow fields experienced by the melt during mold filling, and the cooling rate during and after mold high shear and elongational fields during mold filling cause the deformation and also the break up and coalescence of the dispersed final shape and size of the injectionmolded bar is the product of the balance between deformation,breakup and the case of nonisothermal flow,the velocity distribution across the thickness has an inflection point where the shear rate reaches the maximum[27],while the shear rate is zero at the mold surface and the shear rate profile in two positions of the cross section from gate to nongate end is schematically ill ustrated in to other shear rate profiles proposed in the literature[26],it presents asolidified layer with increasing thickness along melt flow solidified layer was formed continuously until cessation of mold solidified layer shown in contained elongated dispersed the solid layer close to the gate end was thicker is understandable because of the following facts： though the same thickness forms as the melt flow front touches the cold mold surface all along the mold,the material near the initial solid layer can continue to cool to solid until the cessation of mold filling. solidified layer near the gate end experienced longer thickening time than that at the nongate end. soon as the solidified layer is formed,the shear rate in the previously solidified layer surface decreases to the maximum shear rate appears near the solidified layer surface,there exists athin melt layer where the shear rate is relatively lowsince the shear rate changes continuously from zero at the surface of the solidified layer to the maximum at apoint quite close to the solidified on the same reason,the subskin layer,mainly prised of elongated dispersed phase,turns thinner along the melt flowdirection,while the core layer containing mainly spherical domains gets thicker and thicker from gate to nongate end. The higher the melt flowrate is,the shorter the time is needed for mold filling,and the stronger the shear and elongational fields ,high injection speed promotes the deformation and the breakup of mentioned above,the final morphology is the product of the balance between deformation and Figs 3– 8(圖略 ),it was found that the deformation played apredominant role in the formation of the subskin layer since with the increase of the injection speed,the diameter of the elongated particles decreased increase of injection speed shifted the position of the subsk in layer toward the bar surface(.,the solidified layer became thinner),increased the aspect ratio of the dispersed particles,and reduced the diameter of the dispersed particles in the subskin ,for high speed injection molding,after mold filling,the melt exhibited relatively higher temperature than the case of low speed injection because the melt was exposed less time to acold mold and more heat was generated by the viscous friction during mold ,t
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