Blow moulding PEF, a
Blow moulding PEF, a biobased polyester with a great future Avantium is a technology company which has established a leading market position in providing advanced catalysis services and systems to companies in the oil, gas, chemical, and renewable industry sectors. From 2005 onwards, Avantium has used its capabilities to develop its own novel proprietary process and product platform for renewable plastics and chemicals under the name YXY. More recently, it started to undertake similar development projects into breakthrough technologies for renewable chemistry in its business unit New Chemistries. Avantium’s YXY technology comprises the catalytical conversion of plant based sugars into furan-2,5- dicarboxylic acid (FDCA) and its polymerization to poly(ethylene furanoate), PEF. PEF is a novel polyester with a unique performance and sustainability profile. PEF is often compared to PET due to its similar chemistry; both polyesters are produced from the monomers ethylene glycol (MEG) and an aromatic diacid (FDCA or PTA respectively). Despite this similarity, however, PEF’s small molecular difference gives rise to a number of different properties. PEF is found to have a higher oxygen and CO 2 barrier than PET (10x) and a higher water vapour barrier (2x). Also the glass transition temperature (+12 °C) and modulus of PEF (+60 %) are higher than for PET. These advantageous properties enable novel packaging opportunities and additional functionality for brand owners, retailers and consumers, where PET often does not meet the requirements. This article will first dive deeper into the physical properties of PEF, before discussing specific application areas, and the value PEF brings to brand owners and consumers. A small change in bond angle, a big difference in properties Recently, a PhD thesis at the Georgia Institute of Technology has taken a fundamental look into the difference in properties between PEF and PET, and has for the first time provided scientific evidence of their origin. It was found that the shorter bond length and the angle of the aromatic bond in PEF gives rise to a much more rigid and densely packed polymer chain, which is at the heart of many of PEF’s properties [1]. Both the dense packing and the chain rigidity of PEF are the likely causes of the higher density of PEF and an intrinsically higher stiffness (Young’s Modulus) and maximum load before deformation starts (Yield stress). Also the increased glass transition can be explained in this way, since a higher temperature is needed to get the more rigid PEF chains into motion. At the same time, the lack of motion slows down the process of crystallization, too high crystallization rates can cause haziness in many applications where transparency is desired. However, the most astonishing finding was that the rigidity of the chains is the main mechanism of inhibiting gasses from passing through the material. The result: a 10 times higher barrier to both oxygen and carbon dioxide for PEF compared to PET, intrinsic to the material without any stretching or forming process. Figure 1: Chemical structure of PEF (top) and PET (bottom), displaying the shorter overall repeating unit length of PEF and the rotation freedom of the benzene ring over the straight bond angle in PET, which is absent in PEF and gives the chain more rigidity Table 1: Intrinsic properties of amorphous PET and PEF O H Property PET PEF Density 1.36 g/cm 3 1.43 g/cm 3 O 2 permeability* BIF = 1 [2] BIF = 11 [2] CO 2 permeability* BIF = 1 [3] BIF = 13 – 19 [3] T g 76 °C 88 °C T m 250 – 270 °C 210 – 230 °C E-modulus 2.1 – 2.2 GPa [4] 3.1 – 3.3 GPa [4] Yield strength 50 – 60 MPa [4] 90 – 100 MPa [4] *BIF = Barrier Improvement Factor compared to PET HO O O O O O HO O O H O 16 bioplastics MAGAZINE [04/15] Vol. 10
Blow moulding PEF as a packaging material – design by orientation Packaging seems a logical application for a material which is both more sustainable (more details below) and has a gas barrier that is an order of magnitude higher than PET. The main areas of packaging are bottles, trays, cups, films and laminates, all of them existing in many different forms dependent on the end-use applications. One thing that most of these forms have in common is that the material typically undergoes a stretching or forming process as part of the production. This allows plastics to become oriented, and some plastics – like PET and PEF – to develop strain induced crystallinity. Both orientation and strain induced crystallinity have benefits to the final product properties. In the development of PEF, controlled biaxial orientation is one of the key methods to evaluate the applicability of PEF resins in certain packaging applications. Biaxial orientation studies have highlighted that PEF requires different processing conditions than PET, such as temperature and stretch rate, and exhibits different behavior under these conditions. Both of these aspects should be accommodated in the design of a product and the set-up of a production process. Furthermore, the studies bring to light how changes in the PEF production method can change the stretching behavior and the resulting oriented properties. The oriented properties of a basic PEF grade such as PEF A are shown in table 2 and table 3. Behavior such as PEF B can be achieved by increasing the molecular weight or the polymer chain architecture. Controlling the PEF production method to achieve the right behavior for the right application is one of the key aspects of the YXY technology. PEF, a drop-in with a twist Despite the differences between PEF and PET, their chemical similarity results in very similar production steps and quality control methods to PET and other Oxygen (O 2 ) 10x Carbon dioxide (CO 2 ) 4x By: Nathan Kemeling Business Development Director and Jesper van Berkel Technical Application Manager Avantium Amsterdam, The Netherlands Water vapour (H 2 O) 2x Figure 2: Biaxial orientation behavior of two PEF materials at two conditions, compared to PET 80 70 60 Bottle grade PET typical conditions PEF B condition 2 Force (N) 50 40 30 20 PEF B condition 1 PEF A condition 2 10 0 1 2 4 6 9 12 16 20 Areal stretch ratio PEF A condition 1 25 30 bioplastics MAGAZINE [04/15] Vol. 10 17
