Stretch blow molding process

Fig. 14.19 Thermomechanical histories of the two variants of the injection stretch blow molding process (a) the two-step, and (b) the less common one-step.

Fig. 14.20 Schematic representation of the injection stretch blow-molding process. Step (1) producing preforms may be carried out in different location from the stretch blow molding process. [Reprinted by permission from Schmidt et al., Experimental Study and Numerical Simulation of the Injection Stretch/Blow Molding Process, Polym. Eng. Sci., 38, 1399 (1998).]...

Fig. 14.21 Schematic representation of the crystallization behavior of PET relative to the stretch blow molding process. [J. S. Schaul, Drying and Injection Molding PET for Beverage Bottle Preform, SPE ANTEC Tech. Papers, 26, 534 (1980).]...

S. Wang, A. Makinouchi, and T. Nakagawa, Three-dimensional Viscoplastic FEM Simulation of a Stretch Blow Molding Process, Adv. Polym. Technol., 17, 189-202 (1998). 

A soak time is used in preform heating for some stretch blow molding processes. Would you expect this to more likely be needed for thick or for thin preforms Explain. 

In contrast, PEN meets the requirements, but more complex forming techniques are needed. PEN bottles cannot be produced by simple extrusion blow molding. PEN requires the use of the more complex two-step injection stretch blow molding process. In this process, a preform is first injection molded and then stretch blow molded to produce the final bottle. This is the same process used to produce bottles of the related polyester, PET. 

Table 4-8. Stretch Blow Molding Processing Characteristics.

Schematic of stretch blow-molding process (from Osswald and Hernandez-Ortiz, 2006). 

Fig. 37. Basic stretch blow mold process. Courtesy of Jerome S. Schaul.

Polylactic acid can be blow molded into bottles with an injection stretch blow molding process (NatureWorks LLC 2012). The mechanical properties of blow molding grade are listed in Table 4.12 (NatureWorks LLC 2013). 

Injection stretch blow molding processes use hollow preforms produced by injection molding. The preform is short and thick-walled relative to the finished blown article. The neck profile complete with screw thread is entirely formed by injection molding and is not modified by the blowing process. The other end of the preform is closed and typically dome shaped. 

The stretch-blow-molding process leads to a biaxial orientation of the macromolecules resulting in better mechanical properties and lowering the gas permeation of bottles. 

Figure 4.47 Schematic representation of the injection stretch blow-molding process [147].

Schmidt, F.M., Agassant, J.F., Bellet, M., and Desoutter, L. (1996) Viscoelastic simulation of PET stretch/blow molding process. J. Non-Newtonian Fluid Mech., 64, 19-42. 

Wang, S., Makinouchi, A., and Nakagawa, T. (1998) Three-dimensional viscoplastic FEM simulation of a stretch blow molding process. Adv. Polym. Technol, 17,189-202. 

---