Recycled Poly (ethylene Terephthalate) Modified

As a common engineering plastic, poly(ethylene terephthalate) (PET) has been widely used in many fields in recent years. With the development of beverage industry, PET bottles are of enormously demanded. The abandoned bottles, however, have led to a serious environmental problem. Therefore, it is necessary to recycle and reuse these bottles, which is an efficient way to release environmental pressure. But rPET presents many shortcomings, such as poor flow stability and impact properties. Thus, the modification is necessary to improve the overall performance of rPET materials. In this work, rPET was toughened by methyl methacrylate-butadiene-styrene (MBS) and maleic anhydride grafted styrene-ethylene-butylenes-styrene (SEBS-g-MAH) respectively. It was also strengthened by glass fibre (GF). Four rPET materials, such as rPET/MBS blends, rPET/SEBS-g-MAH blends, binary rPET/GF composites and ternary rPET/SEBS-g-MAH/GF composites, were prepared by melt mixing. The hierarchical structure, mechanical properties, crystallization and viscoelastic behavior of those rPET materials were then studied by scanning electron microscope (SEM), dynamic mechanic thermal analyzer (DMTA), differential scanning calorimeter (DSC) and rheometer. Many mechanical models were further used to explore the relations between hierarchical structure and properties.(1) For the rPET materials toughened by elastomer: the addition of MBS could improve the toughness of rPET. At the MBS contents of 30 wt%, the izod impact strength increases by about 42% compared with that of neat rPET. But the tensile strength and Young's modulus decrease by about 26% and 9%, respectively. In contrast to MBS, the addition of SEBS-g-MAH could improve the toughness of rPET significantly, with only small decrease of yielding strength. The izod impact strength enhances by about 500% as the SEBS-g-MAH contents achieving up to 30 wt%. The better toughness of rPET/SEBS-g-MAH blends is due to the lower interface tension and higher interfacial adhesion between two components than those of in rPET/MBS blends. SEBS-g-MAH phase is well dispersed in rPET matrix, which also contributed to toughening effect.(2) For the rPET materials reinforced by GF: as the GF contents achieving up to 30 wt%, the toughness, tensile strength, bending strength, Young's modulus and bending modulus increase by about 163%, 115%, 86%, 115% and 534%, respectively. GF has evident reinforcing and toughening effects on rPET. Kerner and Nielsen equations can be well used to predict the tensile modulus of the composites. The aspect ratio and the orientation level of GF are the two important structural aspects determining the final properties of rPET/GF composites. Therefore, the mechanical properties of the composites were further studied by Halpin-Tsai, Krenchel-COX and Kelly-Tyson models, aiming at exploring how the short-term and long-term structures of GF affect the properties of composites. The effective aspect ratio of GF is ca. 5, which is far lower than the geometric aspect ratio of GF. This is because GF is flexible in rPET matrix, and as a result, it may be bent, entangled, and even broken off during melt mixing. Compared with those calculated from the Krenchel-COX equation, the values of orientation factor of GF calculated from the Kelly-Tyson equation is closer to the experimental results.(3) For the ternary rPET/SEBS-g-MAH/GF composite materials: as the GF contents achieving up to 30 wt%, the toughness (at the SEBS-g-MAH contents of 20 wt%) increases by about 445%. The tensile and bending strength show their maximum at the GF content of 15 wt%, increasing by about 88% and 63%, respectively. The presence of SEBS-g-MAH has no evident heterogeneous nucleating effect, while inhibiting crystallization process of the rPET matrix and reducing the crystallization and melting temperatures as a result. Contrarily, the presence of GF shows remarkable nucleating effect on the rPET, accelerating the melt crystallization and increasing the crystallization and melting temperatures. Therefore, with increasing loading levels, GF plays dominant role on the crystallization and melting behaviors of rPET matrix. Key words: recycled poly ethylene terephth alate (rPET); elastomer; glass fibre (GF);...