基于MuCell的聚丙烯微孔注塑成型及其力学性能研究

发布时间：2018-01-19 09:58

本文关键词： MuCell 聚丙烯微孔发泡复合材料力学性能泡孔形貌　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚丙烯(PP)发泡材料具有优良的力学性能、较好的环境适应性及耐热性,广泛应用于车辆和航空航天等领域。然而,PP属于半结晶聚合物,熔体强度较差,不利于均匀细密泡孔结构的形成,而且其冲击韧性较低,限制了PP微孔发泡材料的应用。为优化PP微孔发泡材料的泡孔形貌和力学性能,扩展PP微孔发泡材料的应用领域,本文基于MuCell微孔注塑成型技术进行了如下研究:首先,采用单因素实验法,研究了熔体温度、注射速度、背压和超临界流体(SCF)含量等微孔注塑成型工艺条件对纯PP微孔发泡材料发泡行为(泡孔尺寸和泡孔密度)和力学性能(拉伸、冲击和弯曲强度)的影响,结果表明,在减重均为10%的前提下,纯PP发泡试样相同位置处的表观密度在不同工艺组合下没有明显变化,充填近端均维持在0.775g/cm3左右,而充填远端在0.65-0.69g/cm3之间。随熔体温度升高,泡孔尺寸有先增后减的趋势,泡孔密度则呈现相反规律,充填远端泡孔密度普遍高于充填近端。随着注射速度和背压的增加,充填近端和远端的泡孔尺寸均有减小的趋势,而泡孔数量会有所增加;随着SCF含量的提高,泡孔尺寸明显降低,泡孔密度有增大的趋势。不同工艺条件下,未发泡试样的拉伸强度均保持在30MPa左右,发泡试样的拉伸强度在16-19 MPa之间,相对于未发泡试样,发泡试样拉伸强度下降比例可达36%-45%。发泡试样和未发泡试样的缺口冲击强度和弯曲强度分别维持在3 KJ/m2左右和31-34.3MPa之间,且发泡试样的冲击强度和弯曲强度一般大于未发泡试样。而后研究了POE、滑石粉对于PP复合微孔发泡材料发泡行为和力学性能的影响。加入POE后,PP/POE共混物的粘度增大,熔体流动速率下降,PP的熔体强度得到提升,改善了PP的发泡效果。随POE含量的提高,共混物发泡试样的泡孔平均直径呈先降低后增大的趋势,而泡孔密度呈相反趋势,当POE含量为15%时,泡孔的平均直径降至73.8μm,泡孔密度则达到13.1×105个/cm3,是其它组分下泡孔密度的5-7倍,且泡孔分布均匀,无明显合并和塌陷。发泡和未发泡试样的拉伸强度和弯曲强度均呈连续下降趋势,发泡试样的冲击强度在POE含量为25%时达到最大值18.24 MPa,而未添加POE时发泡试样的冲击强度仅有3.08 MPa。对于PP/POE/滑石粉共混物,滑石粉的加入对PP/POE共混物发泡效果的改善作用有限,但其整体发泡效果仍好于纯PP,在滑石粉含量为10%时,泡孔平均直径为142.7μm,泡孔密度为1.33×105个/cm3,泡孔形貌优于其它组分。此时发泡试样的拉伸强度达到最大值17.5MPa,随滑石粉含量提高,共混物发泡和未发泡试样的弯曲强度则有较大提升,分别可达33.57MPa和34.44MPa,而冲击强度均持续下降,但仍大于纯PP发泡试样的冲击强度。
[Abstract]:Polypropylene (PP) foamed materials have excellent mechanical properties, good environmental adaptability and heat resistance, and are widely used in vehicle, aerospace and other fields. However, PP is a semi-crystalline polymer. The poor melt strength is not conducive to the formation of homogeneous and dense foam structure, and its impact toughness is low, which limits the application of PP microcellular foaming materials. In order to optimize the morphology and mechanical properties of PP microporous foaming materials. In order to expand the application field of PP microcellular foaming material, the following research was done based on MuCell micropore injection molding technology: firstly, the melt temperature and injection rate were studied by single factor experiment method. The effects of back pressure and SCF content on the foaming behavior (size and density) and mechanical properties (tensile) of pure PP microcellular foamed materials were investigated. The results showed that the apparent density of pure PP foamed specimen at the same position had no obvious change under the condition of weight loss of 10%. The proximal end of filling was maintained at about 0.775g / cm ~ 3, while the distal end of filling was between 0.65-0.69 g / cm ~ 3. With the increase of melt temperature, the pore size increased first and then decreased. The density of bubble pore in distal filling was higher than that in proximal end of filling. With the increase of injection speed and back pressure, the size of bubble hole at proximal end and distal end of filling had a tendency to decrease. However, the number of vesicles will increase. With the increase of SCF content, the size of foam decreased obviously, and the density of foam increased. The tensile strength of unfoamed samples remained about 30MPa under different processing conditions. The tensile strength of the foamed samples ranged from 16 to 19 MPa, compared with the unfoamed samples. The tensile strength of foamed specimens can decrease by 36% to 45%. The notched impact strength and bending strength of foamed and unfoamed specimens are maintained at 3. 5% respectively. Between KJ/m2 and 31-34.3MPa. The impact strength and bending strength of the foamed sample were generally higher than that of the unfoamed sample. Then the influence of Poe and talc powder on the foaming behavior and mechanical properties of PP composite microporous foamed material was studied. After adding POE. The viscosity of PP/POE blends increased and the melt flow rate decreased. The melt strength of PP was improved and the foaming effect of PP was improved with the increase of POE content. The average diameter of foamed sample decreased first and then increased, but the density of foam increased. When the content of POE was 15, the average diameter of foam decreased to 73.8 渭 m. The bubble density is 13.1 脳 105 / cm ~ (-3), which is 5-7 times of that of the other fractions, and the bubble pore distribution is uniform. The tensile strength and flexural strength of foamed and unfoamed samples decreased continuously. The impact strength of foamed samples reached a maximum of 18.24 MPa when the content of POE was 25. However, the impact strength of foamed samples without POE was only 3.08 MPa. for PP- / Poe / talc blends. The effect of talcum powder on the foaming effect of PP/POE blends was limited, but the overall foaming effect was still better than that of pure PPP.When the talc content was 10, the average diameter of the foam pore was 142.7 渭 m. The bubble density is 1.33 脳 10 ~ 5 / cm ~ (-3), and the morphology of foam is better than that of other components. The tensile strength of foamed sample reaches the maximum value of 17.5 MPA, which increases with the content of talc powder. The flexural strength of foamed and unfoamed blends increased to 33.57 MPA and 34.44 MPA, respectively, while the impact strength decreased continuously. But it is still higher than the impact strength of pure PP foamed sample.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ325.14

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