ASTM D1896/D1896M-10(2017)由美国材料与试验协会 US-ASTM 发布于 2010。
ASTM D1896/D1896M-10(2017) 在中国标准分类中归属于: G31 合成树脂、塑料基础标准与通用方法,在国际标准分类中归属于: 83.140.99 其他橡胶和塑料制品。
4.1 Transfer molding is particularly suited to thermosetting materials of intermediate plasticity. Fixed molding parameters cannot be specified for each type of material. Molding compounds of the same type come in many different plasticities measured in accordance with Test Methods D3123 and D3795. Consequently, for a given material type, the molding parameters required to produce satisfactory test specimens will often vary dependent on the plasticity of the specific material grade.
4.2 The mold shown in this practice provides for a set of five specimens. However, if only certain specimens are desired, the other cavities can be blocked by inserting gate blanks.
4.3 Typically, breathing of the mold is not required to release trapped volatile matter as the gas is free to flow from the vent end of the mold. This is a particular advantage for heat-resistant compounds and reduces the tendency for molded specimens to blister at high exposure temperatures.
4.4 Flow and knit lines in a molded piece are often sites of mechanical or electrical weakness and can be found in some degree of severity throughout the molded piece. The semisolid molding compound passing through the gate is subject to non-Newtonian flow and, consequently, wrinkles and folds as it travels down the mold cavity. Fibers and other reinforcements in the molding compound align with the flow pattern and, consequently, can orient perpendicular to the axis of the bar at the center and parallel at the surface of the bar. Mold temperature, thermal conductivity and plasticity of the molding compound, degree of preheat, and plunger pressure are parameters that influence the time to fill the mold cavities and the formation of knit lines.
Note 3: If the temperature of the mold is held constant and the plunger pressure varied for a designated thermosetting molding compound, two extreme characteristic conditions can be obtained. If the pressure is low, then the vent end of the cavity will not fully fill, and weld lines will form by incomplete knitting of the material. If the pressure is too high, the mold cavity will fill fast, the outside of the specimen will case harden while the pressure is still forcing material out the vent, and a ball-and-socket grain structure will be obtained. A ball-and-socket structure is an indication of the molding condition, and lower test data will result.
4.5 Thermosetting compounds containing long-fiber fillers such as glass roving, chopped cloth, or shavings can be used but are not recommended for transfer molding. These filler materials tend to break, tear, or ball in passing through the gates of the mold, thereby not optimizing their potential strength.
4.6 The Izod impact strength of transfer molded specimens of molding compounds containing short fibers will generally be lower than the values obtained using compression-molding methods. Quite often the impact strength will vary along the axis of the bar due to molding parameters, flow pattern, and fiber orientation.
4.7 The flexural and tensile stre
挤出成型挤出成型也称挤压模塑或挤塑,它是在挤出机中通过加热、加压而使物料以流动状态连续通过口模成型的方法。挤拉成型挤拉成型是热固性纤维增强塑料的成型方法之一。用于生产断面形状固定不变,长度不受限制的型材。注射成型注射成型(注塑)是使热塑性或热固性模塑料先在加热料筒中均匀塑化,而后由柱塞或移动螺杆推挤到闭合模具的模腔中成型的一种方法。...
2、相关试验标准: GB/T1043.1-2008塑料简支梁冲击性能的测定第1部分:非仪器化冲击试验 GB/T2918-1998 塑料试样状态调节和试验的标准环境 GB/T3360-1982 数据的统计处理和解释均值的估计和置信区间 GB/T 4550-2005 试验用单向纤维增强塑料平板的制备 GB/T 5471-2008 塑料 热固性塑料试样的压塑 GB/T9352...
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