Injection molding conditions

A comparison of the mechanical and physical properties of PTT, PET and PBT [67], measured from injection molded American Society of Testing Methods (ASTM) Type II samples, is given in Table 11.4. The mechanical properties of PET and PTT are highly dependent on injection molding conditions due to... 

Another important variable to consider is the fiber orientation. This is affected by many variables such as the injection molding conditions, fiber length, resin viscosity and part thickness. The fiber orientation can be determined experimentally by optical methods [44], or it can be estimated from the modulus of the molded part as follows [45-47] ... 

Table III. Injection Molding Conditions (Van Dorn 6 oz. Screw-Type Machine)...

Typical physical properties for an injection-molded transparent acrylic polyblend resin are given in Table II. The injection molding conditions used are given in Table III. Tensile, flexural, and impact properties are within the range reported for typical ABS and high impact polystyrene resins. Optical properties approach those of the acrylics [i.e., poly (methyl methacrylate)]. The strength properties are on the low side of those reported in the first paper for the transparent diene... 

Many investigators have studied the relationship between injection molding conditions and the mechanical properties of the polymer (13, 14, 15). Factors such as polymer molecular weight, degree of supercooling, and melt shear conditions significantly contribute to the observed results (16). Current observations are consistent with these reports. 

The polyarylsulfone thermoplastic exhibits essentially the same heat resistance of the polyarylstdfone based on bis-(4-chlorophenyl)sulfone and 2,2-bis(4-hydroxyphenyl)pro-pane, along with the added plus of a lower melt viscosity at equivalent processing temperatures. The flow improvement is demonstrated by comparison with Brabender data, injection-molding conditions, and melt-viscosity data. 

The significant improvement in flow properties of resin IV vs. V is evident from the data. First, the torque from Brabender mixing indicates that resin IV is an easier-flowing material (Table II). The lower torque values for IV indicate the necessity of a lower-energy input to mix the polymer melt. This lower rotational force therefore indicates the polymer melt has a lower melt viscosity. Secondly, injection-molding conditions demonstrate the improved processability of resin IV (Table III) in comparison with resin V. At the same injection cylinder temperatures, the injection pressure for the tensile bar and Izod/heat distortion bar molds is lowered by 300 psi and 250 psi, respectively. 

Table 6.28 lists injection molding conditions for a number of compounds of different fluoropolymers. 

Table 6.28. Injection Molding Conditions for Compounds of Fluoropolymers ...

Injection molding conditions of blends of polyolefin resins and other commodity resins are listed respectively in Tables 10.25 and 10.26. The conditions represent an average for each type of blend. They usually vary slightly from one grade to another. Recommended practices and specific comments are discussed below for each type of blend. 

Table 10.25a. Injection molding conditions for polyolefin-based blends — Part A...

Table 10.26b. Injection molding conditions of blends of other commodity resins — Part B...

Injection molding conditions for selected blends of engineering resins are listed in Tables 10.28 to... 

Blends based on specialty resins used routinely in injection molding applications include PEI/PC (Ultem LTX), PPS/PPE (D/C PPS), PEEJC/ LCP (Sumiploy EK) or PEEJC/PES (Sumiploy SK). Injection molding conditions for these systems are hsted in Table 10.33. 

Due to the miscibility of these blends, injection molded samples of the blends are transparent even though the poly(aryl ether ketone) is opaque under normal injection molding conditions. However, with proper annealing, opacity due to crystallization of the poly(aryl ether ketone) can be accomplished. 

Several injection molding operating parameters must be optimized in order to produce a microfluidic device with a high degree of feature fidelity. Figure 4 presents the impact of the feature fidelity of different micron-sized post features as a function of barrel temperature and injection velocity. It is also important to note that computational modeling can be employed to predict optimal injection molding conditions. 

The strength of weld lines in injection-molded articles is generally weaker than that of the bulk. This is due to the incomplete entanglement of polymer chains at the two impinging fountain flow fronts in the mold cavity. When the two flow fronts meet in the cold cavity, the molecular orientation at the interface remains parallel to the weld line as evidenced by the frozen-in molecular orientation found in the molded article under proper injection-molding conditions... 

Tables 3.6 and 3.7 show, respectively, injection molding conditions and a troubleshooting guide for various TPEs. However, one should contact the material supplier to obtain detailed information for the process.

Jang et al. (24-27) studied extensively craze formation in semicrystalline polymers, namely in virgin and rubber-modified polypropylene. They studied the effects of injection-molding conditions on PP morphology and its relation to crazing at low temperatures and high strain rates. Their investigation characterized... 

---