PETpla.net Insider 04 / 2012

MATERIAL / RECYCLING 14 PET planet insider Vol. 13 No. 04/12 www.petpla.net Post-wash air elutriation The next testing step is elutria- tion. While both the APR and EPBP call for this step, the APR allows for a higher elutriation loss rate than the EPBP which will aid in more thin mul- tilayer material and /or label removal. Therefore, studies involving multilayer materials or labels can be impacted by which protocol is used. Study blend compositions This is an area where the two studies have similarities but also differ. The U.S. protocol calls for com- positions of 0, 25 and 50% innovation flake blended with control flake. The European protocol allows for addi- tional percentages of 2, 5 and 10% to cover lower levels of innovation flake content. Extrusion / palletisation Extrusion of the various flake blends to pellets creating a second melt heat history is next. The tem- peratures can be different in each pro- tocol with Europe calling for a higher extrusion temperature. The U.S. protocol does not specify a particular extrusion temperature and allows for optimisation on the smaller laboratory equipment being used for the extru- sion/ palletisation step. The result is that while the higher extrusion temperatures may cause increased yellowing, they are consid- ered closer to actual production scale conditions. The U.S. protocol, with its lower temperatures, may not show problems with an innovation material that is prone to yellowing at higher temperatures. Solid-state processing Solid stating of the crystallised extruded pellets is the next testing phase called for in both protocols. Both set specific parameters for mate- rial that will be moulded into preforms and plaques. The European protocol sets a spe- cific time of eight hours for solid start- ing. This is sampled at various times to determine the IV build rate for each variable being studied. The United States protocol requires longer solid stating with measurements taken at 8 and 15h. (The 15h is to make sure the material will meet an IV requirement of 0.95 for strapping applications.) This test is also intended to measure the solid stating rate of each variable. However, both protocols specify that each variable must be solid stated to produce a quantity of mate- rial that has a final IV 0.80(+/-.02)dL/g for use in plaque melding and preform melding. Plaque melding Plaque melding simulates the third melt heat history of each of the 0.80(+/-.02)dL/g variables. In the United States, plaque melding is done with 100% of each extruded material variable. This can accentuate the co lour and haze issues in the moulded plaque. The European protocol uses a 50% blend of each variable along with virgin resin to meld the plaques, which can improve on the yellow colour. This could be considered more “real world” as the innovation material will nor- mally not be found in high concentra- tions in the rPET recycle stream. Preform and bottle testing Both protocols are very simi- lar from this point on. Each of the 0.80(+/-.02)dL/g variables are diluted with virgin resin at 50 per cent, injec- tion moulded into preforms and then blown into bottles for testing. Both organisations use a typical generic bottle and similar test protocol for bottle evaluation. Innovation recognition Because the European protocol looks at testing levels of 2, 5, 10, 25 and 50%, the innovation material can be granted approval for meeting the protocol requirements based on the anticipated market penetration at any of these lower levels. This aids in better defining the impact it may have on the recycle stream based on lim- ited introduction into the market. The United States views this dif- ferently. A recycler may receive a concentrated amount of innovation material bottles that may cause his rPET product to temporarily worsen. If that product goes on to become a commercial success, it may end up becoming a larger component of the recycle stream. Then, its effect on quality could become more notice- able. For this reason, the APR uses only 25 and 50% blend rates and does not consider the lower percent- ages for innovation recognition. Conclusion Although there are differences between the test protocols, a common goal remains. Both the U.S. and European testing approaches help maintain the current rPET recycle stream quality. They also guide bottle manufacturers and brand owners in producing PET bottles that can main- tain the flow of good usable material back into the supply chain. The nagging questions that remain include:  What will comprise future feed- stocks?  How can we produce better rPET to improve the recycle stream?  How can we collect a wider variety of high performance PET bottles and thermoforms? Plastic Technologies, Inc. (PTI) is one of only two U.S. companies approved by APR to provide testing services in conjunction with the organ- isation’s critical guidance documents. The APR and PTI are embarking on a recycle monitoring program which will evaluate current recycled PET materi- als, meld them into plaques and track their colour on a regular basis. This monitoring program will aid in deter- mining the quality of what is currently being produced and how the quality may change over time. There is no shortage of applica- tions for high quality rPET. PET recy- cling in the United States and Europe can increase and prosper if the quality of the bottles being recycled can be kept high. Organisations such as the APR and the EPBP will be instrumen- tal in assisting PET bottle manufac- turers to improve the quality of their products. www.plastictechnologies.com