PETpla.net Insider 11 / 2016

MATERIAL / RECYCLING 12 PET planet Insider Vol. 17 No. 11/16 www.petpla.net rPET can be safely used with hot-fill packaging. A clearer view A study by Plastic Technologies, Inc, has determined that the use of rPET in hot-fill packaging has no significant impact on bottle performance at concentrations up to 50%. Above that level, the major impact is some haze or yellowing. Companies across the packaging industry are constantly seeking ways to improve the performance of their prod- uct. The focus in recent years as far as PET is concerned has been to include a higher proportion of rPET (recycled PET). As recyclate recovery and puri- fication methods have improved, the potential for raising the percentage of rPET in food and beverage packag- ing has grown. The advantage is that packagers will benefit from being seen to be environmentally sensitive, and legislative and financial impacts will be reduced by the increased use of recycled materials. The concern is that higher concentrations of PET will see decline in performance. A recent study by Plastic Technolo- gies, Inc (PTI), the American company known for its expertise in preform and package design and development, has produced results that will raise confi- dence in packaging containing quite high proportions of recycled material. It found that rPET content up to 50% has no significant effect on material perfor- mance at all. The objective While there is quite a lot of rele- vant information already available in the marketplace, PTI wanted to help provide brand owners with additional, relevant data and knowledge, which would help to facilitate the decision- making processes. Its research considered and analysed the use of rPET in a range of percentages, from fairly low (25%) to total (100%), and to determine the commercial viability of the range of recipes. The study - parameters This study was focused on evaluat- ing virgin PET and two different rPET resins, which were added to virgin PET at 25%, 50% and 100% levels. The study focused on the production and performance of a 27g commer- cial 500ml six-panel hot-fill bottle and preform. Bottles containing recycled- content variables were processed simi- larly, in order to maintain equivalent bottle wall thicknesses and maximise preform temperatures. In this way, the study could focus on the performance of rPET at various concentrations, as it would then be the only variable. The bottles were tested to determine hot-fill and top load performance, wall thick- ness, colour, haze, crystallinity and acetaldehyde (AA) content. The hot-fill testing regime the study subjected the bottles to is indicative of how the packages will perform under commercial hot-filling conditions. A vacuum is formed as the hot product cools inside the enclosed containers and this has the effect of increasing the chances of the occur- rence of ovality or bottle denting. The heat of the product with which the package is being filled also causes the PET to shrink, through relaxation of the stresses created during the blow moulding process. Ovality and shrinkage were measured in order to ensure that they met standard perfor- mance specifications (fig. 1). The study - results Table 1 summarises the results of the key performance tests. The results show that, in all of the formula- tions - the virgin, 25% and 50% - and for both recycle resins, the materials and packages performed similarly. In terms of minimum peak top load results, rPET A performed at least as well as virgin PET. Ovality results were within acceptable levels at all concentrations. The bottles measured actually showed less ovality at 25% rPET than virgin PET, in both formula- tions. With the proportion of rPET at 100%, the bottles experienced shrink- age at the bell that reached levels that almost exceeded specification. The 100% rPET A resin also showed increased shrinkage at the lower bumper. This latter result was Spec Virgin 25% rPET A 50% rPET A 100% rPET A 25% rPET B 50% rPET B 100% rPET B Min. peak top load (lbf) ≥ 44 86 87 86 91 79 79 77 Max. ovality (mm) ≤ 3 0.53 0.42 0.6 0.93 0.47 0.6 0.81 Max. diameter shrinkage (%) ≤ 2% -1.43% -1.39% -1.42% -1.99% -1.27% -1.37% -1.95% Max. volume shrinkage (%) ≤ 2% -0.91% -0.87% -0.90% -1.55% -1.08% -1.12% -1.34% Table 1: Testing summary