Type II plasticizers

Along with being a forgiving and functional deflocculant, MFO has other benefits to the tape casting process. These other benefits, which will be discussed in the "Organic Interactions section of this chapter, include carrier release. Type II plasticizer (lubricant), and lamination aid. 

Many acrylic polymers, specifically (poly)methyl methacrylate and (poly) ethyl methacrylate, show great strength at low concentrations in the green tape. This benefit also contributes to binder removal later in the process, since lower binder content leads to lower binder residue. Acrylic binders are also plasticized or made flexible by a wide variety of additives, which gives you the freedom to choose a plasticizer that burns out cleanly. The acrylic binders, when used as dissolved polymers, can be made flexible by both Type I and Type II plasticizers. These plasticizers are addressed in detail in Section 2.5. We have also seen the methacrylates exhibit behavior quite the reverse of "common sense. It has been seen in more than one solvent system, with different powder chemistries, that more binder can lead to denser tape. This will be discussed in Section 4.3. 

It can be seen using the mosaic tile model that relative changes in Type I and Type II plasticizer additions will cause logical and predictable changes in tape flexibility and plasticity that can be charted by or even read from a standard stress-strain diagram. 

The increased yield-to-fracture and low yield point enhanced by an added lubricant (Type II plasticizer) can help to prevent cracking in thicker green tapes during drying. As will be discussed in more detail in Section 4.3, stresses develop during the drying process due to the... 

One benefit of the Type II plasticizer that was not found in the published literature is its lubricating benefit in the tape casting slip before drying. Tape casting slips in general... 

Referring back to the mosaic tile model in Section 2.5, over time some of the rubber bands from particle to particle wrap around the particles instead. This action displaces the menhaden fish oil which then acts like a Type II plasticizer to lubricate the system. The end result of this interaction follows logically out of the mosaic tile model. Fewer rubber band ties between particles result in a weaker tape. More olive oil, or in this case fish oil, in the matrix results in greater deformation under its own weight and higher plastic deformation. As aging time increases with both PVB and MFO in proximity to the particle surface, the tape becomes weaker and floppier and can even discolor the drying surface of the tape. 

The Type II plasticizer is also discussed in Section 2.5. The Type II plasticizer does not chemically react to any great extent with the binder or with the Type I plasticizer. The only real interaction between the Type II plasticizer (lubricant) and any other component (s) in the system is mechanical. As mentioned earlier, the lubricant physically inhibits some of the polymer ties from forming and facilitates permanent, plastic motion in both the fluid slip and the dried tape. 

Curling always begins with the tape edges, where the reduced thickness of the tape does not exert as much gravitational force. One of the other stress-relief mechanisms was covered in previous sections the Type II plasticizer. The Type II plasticizer in a tape structure can act as a lubricant, facilitating motion within the tape structure in response to drying stress instead of curling. 

Flat tape, whether forced flat by mechanical constraints or held flat by gravity or good chemistry, experiences Level 2 stress and may or may not undergo Level 3 plastic deformation. We have never seen a tape that did not store residual tensile stress in the polymer matrix. This stored stress will be discussed in detail in later sections, along with methods for alleviating the stress. Plastic deformation cannot really be measured, but can be assumed when the same slip without a Type II plasticizer shows multiple Level 4 behaviors, but with the Type II plasticizer lays flat. 

The big picture in this case focuses mainly on the ability to plasticize these water-soluble polymers in the desired manner. Many plasticizers have been used and reported for both PVA and cellulose binders, but the vast majority fall into the category of Type II plasticizers. Glycerin and various glycols have been reported, and seen by the authors, to be very effective lubricants in the water-soluble tape casting systems. The earlier section on plasticizers, however, pointed out that while a Type II plasticizer is desired in some cases, the mandatory plasticizing agent found in all tapes is the Type I plasticizer or binder solvent. The requirements of a Type I plasticizer are solution of the binder polymer and low volatility. Water-soluble binders are plasticized (Type I) by water, which satisfies both of these criteria. 

Type II plasticizer An additive used to soften the green tape matrix. The Type II plasticizer is not thought to interact chemically with the binder polymer but acts mechanically to partially prevent formation of the 3-D polymer matrix. The Type II plasticizer is often oily as well, acting as a lubricant within the tape matrix. 

---