The effect of titanium dioxide surface modification on the dispersion, morphology, and mechanical properties of recycled PP/PET/TiO2 PBNANOs

Titanium dioxide (TiO2) nanoparticles have recently appeared in PET waste because of the introduction of opaque PET bottles. We prepare polymer blend nanocomposites (PBNANOs) by adding hydrophilic (hphi), hydrophobic (hpho), and hydrophobically modified (hphoM) titanium dioxide (TiO2) nanoparticles to 80rPP/20rPET recycled blends. Contact angle measurements show that the degree of hydrophilicity of TiO2 decreases in the order hphi > hpho > hphoM. A reduction of rPET droplet size occurs with the addition of TiO2 nanoparticles. The hydrophilic/hydrophobic balance controls the nanoparticles location. Transmission electron microscopy (TEM_ shows that hphi TiO2 preferentially locates inside the PET droplets and hpho at both the interface and PP matrix. HphoM also locates within the PP matrix and at the interface, but large loadings (12%) can completely cover the surfaces of the droplets forming a physical barrier that avoids coalescence, leading to the formation of smaller droplets. A good correlation is found between the crystallization rate of PET (determined by DSC) and nanoparticles location, where hphi TiO2 induces the highest PET crystallization rate. PET lamellar morphology (revealed by TEM) is also dependent on particle location. The mechanical behavior improves in the elastic regime with TiO2 addition, but the plastic deformation of the material is limited and strongly depends on the type of TiO2 employed

Structure and Properties of Reactively Extruded Opaque Post-Consumer Recycled PET

The recyclability of opaque PET, which contains TiO2 nanoparticles, has not been as well-studied as that of transparent PET. The objective of this work is to recycle post-consumer opaque PET through reactive extrusion with Joncryl. The effect of the reactive extrusion process on the molecular structure and on the thermal/mechanical/rheological properties of recycling post-consumer opaque PET (r-PET) has been analyzed. A 1% w/w Joncryl addition caused a moderate increase in the molecular weight. A moderate increase in chain length could not explain a decrease in the overall crystallization rate. This result is probably due to the presence of branches interrupting the crystallizable sequences in reactive extruded r-PET (REX-r-PET). A rheological investigation performed by SAOS/LAOS/elongational studies detected important structural modifications in REX-r-PET with respect to linear r-PET or a reference virgin PET. REX-r-PET is characterized by a slow relaxation process with enlarged elastic behaviors that are characteristic of a long-chain branched material. The mechanical properties of REX-r-PET increased because of the addition of the chain extender without a significant loss of elongation at the break. The reactive extrusion process is a suitable way to recycle opaque PET into a material with enhanced rheological properties (thanks to the production of a chain extension and long-chain branches) with mechanical properties that are comparable to those of a typical virgin PET sample.We would like to acknowledge funding by the EU Interreg H2020 program through project POCTEFA EFA329/19. This work also received funding from the Basque Government, grant IT1309-19

Structure and properties of reactively extruded opaque post-consumer recycled PET

This article belongs to the Special Issue Recycling and Resource Recovery from Polymers.The recyclability of opaque PET, which contains TiO2 nanoparticles, has not been as well-studied as that of transparent PET. The objective of this work is to recycle post-consumer opaque PET through reactive extrusion with Joncryl. The effect of the reactive extrusion process on the molecular structure and on the thermal/mechanical/rheological properties of recycling post-consumer opaque PET (r-PET) has been analyzed. A 1% w/w Joncryl addition caused a moderate increase in the molecular weight. A moderate increase in chain length could not explain a decrease in the overall crystallization rate. This result is probably due to the presence of branches interrupting the crystallizable sequences in reactive extruded r-PET (REX-r-PET). A rheological investigation performed by SAOS/LAOS/elongational studies detected important structural modifications in REX-r-PET with respect to linear r-PET or a reference virgin PET. REX-r-PET is characterized by a slow relaxation process with enlarged elastic behaviors that are characteristic of a long-chain branched material. The mechanical properties of REX-r-PET increased because of the addition of the chain extender without a significant loss of elongation at the break. The reactive extrusion process is a suitable way to recycle opaque PET into a material with enhanced rheological properties (thanks to the production of a chain extension and long-chain branches) with mechanical properties that are comparable to those of a typical virgin PET sample.We would like to acknowledge funding by the EU Interreg H2020 program through project POCTEFA EFA329/19. This work also received funding from the Basque Government, grant IT1309-19.Peer reviewe

A comparison of the mechanical behaviour of natural rubber-based blends using waste rubber particles obtained by cryogrinding and high-shear mixing

The influence of the type of mechanical recycling of waste rubber particles on the tensile properties of waste/natural rubber blends has been investigated. The wastes originating from ground tyre rubber (GTR) had been treated by two distinct processes: cryo-grinding and high shear mixing (HSM). For both processes, the resulting composites show enhanced stiffness and strength for all strain rates and temperatures tested. This is attributed to both the reinforcing effect of the waste as well as the nucleation ability of the wastes on strain induced crystallization (SIC) in the natural rubber (NR) matrix. Cryo-grinding was shown to provide the finest particle size with an average diameter of 34 μm, while the HSM process was found to show an elastic modulus of aggregated GTR powder of 7 MPa at 1 Hz at room temperature. Within these characteristics, the NR/GTR blends using the HSM process show the best tensile performance under single loading, with the highest strength and highest ability to crystallize under strain. Under cyclic loading, NR/GTR blends using cryo-ground GTR particles show the best performance, which we ascribed to their ability to better distribute and accommodate the stress from one cycle to another owing to their finest size. Both explored recycling techniques provide the natural/waste rubber blends interesting properties such as mechanical reinforcement and strain-induced crystallization ability under various testing conditions

Epoxy coupling agent for PLA and PHB copolymer-based cotton fabric bio-composites

Epoxy coupling agent was deposited on cotton fabric used for the manufacture of film stacked composites based on poly(lactic acid) (PLA) or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB copolymer) matrices. The additive confined on the fabric surface allowed it to be reactive in the heating stage of the composite production right at the interface between fibres and matrix. The resulting composites were tensile tested comparing the data with the neat matrices and the composites with untreated fabric. A discussion to explain the mechanical results taking in consideration the density, porosity and crystallinity as well as exploiting some micro-mechanical models is presented. The ability of the additive to increase the adhesion between cotton and both matrices is verified and is essential to lighten the structures and to reach application requirements

Multilayer cotton fabric bio-composites based on PLA and PHB copolymer for industrial load carrying applications

The thermo-mechanical and impact behavior of bio-based polymers reinforced with a multilayer cotton fabric were determined and assessed for the potential use in building, furniture or automotive applications. The measured properties were compared to other composites with similar natural fabric content or to international standard requirements. Flexural properties of PLA composites fully satisfied the requirements for heavy duty load-bearing boards in humid condition (EN 312 standard), while the PHB copolymer composites still satisfied the conditions for load-bearing boards. The HDT evaluation through the dynamic mechanical thermal analysis revealed the great increase (+53 °C) in the temperature for PHB composites that reached 123 °C, potentially extending their application fields to automotive applications. For this focus, the Charpy impact strengths were also investigated. One of the highest values reported in the literature (54.5 kJ/m2) was reached with PHB, superior to what is commercially used for the interior part of the cars. Furthermore, an epoxy functional additive was employed and was found to reduce the void content and increase the flexural properties and the impact strength

Bio-polyamides (PA10.10 and PA6.10) montmorillonite composites: properties and Essential Work of Fracture (EWF)

The plastics industry is increasingly oriented towards the use of polymers from natural origin (biobased) replacing plastics derived from petrol chemistry (fossil-based). Recently, some aliphatic polyamides were revalued by industries for packaging and for long-term applications but still low investigated. Moreover, nanoclays have been proven to improve mechanical and barrier performance of fossil based PAs. On the other hand, these superior properties of PA nanocomposites usually have as a "side effect" the increase of the brittleness by suppressing plastic deformation at the crack tip, which greatly limits the application of these materials. In this study two kinds of bio-polyamides were investigated: PA10.10 and PA6.10. As filler a natural montmorillonite modified with methyl hydrogenated tallow bis-2-hydroxyethyl quaternary ammonium (Cloisite®30B-Cl30B) was used. PAs were melt blended with clay using a co-rotating twin screw extruder LEISTRITZ ZSE 18/40 D. Neat polymers were also processed to have the same thermal history. Pellets obtained by the first extrusion were dried before the film extrusion. A single screw extruder (Eurotech Extrusion Machinery S.r.l.) (L=80cm D=25mm) equipped with a flat die was used. Samples for mechanical characterization were die cut and tested with a crosshead speed of 1 mm/min using a Zwick 10 universal testing machine. Specimens for EWF were prepared according to the ESIS protocol and conditioned at 33% of R.H. and room temperature. Before testing, a fresh razor blade was carefully tapped into ligament of specimen to introduce two aligned sharp pre-cracks. The free ligament length (l) was left in the range from 5 to 22 mm. The specific work of fracture (wf) was obtained by dividing the integrated area of the load-elongation curve with the initial ligament area. The essential work of fracture (we) and the plastic term (β*wp) are easily obtained from the best linear regression of a set of values represented in a graph plotting wf versus l (Figure 1a). An estimation of the shape and dimensions of the necked zone surrounding the fractured ligament was done in order to derive the wp value (Figure 1b). Clay did not significantly affect the work required for the onset of crack propagation (we) in PA6.10 while decrease in PA10.10. The plastic work (β*wp) of both PA was increased with clay. The individual nanoparticles act as stress concentration points, which promoted cavitations and thus induced relatively large local deformation. By this way, the mechanical work content necessary to generate the plastic flow is increased, leading to a higher wp value

Hydrostatic pressure dependence in tensile and compressive behavior of an acrylonitrile–butadiene–styrene copolymer

The strain-rate dependence of a commercial grade ABS copolymer has been analyzed in both compression and tension. By measuring in two loading geometries, the hydrostatic pressure-dependence on the material's deformation behavior can be established. An alternative method to determine pressure-dependence, based on the difference in strain-rate dependence for various loading geometries, has been presented. It was shown to be an effective technique, both for thermorheologically simple materials such as ABS, as well as thermorheologically complex materials, for example, PMMA. A yield criterion, based on an Eyring-type pressure-modified rate equation, has been compared to finite element simulations using the Eindhoven Glassy Polymer (EGP) constitutive model. Although both methods give quantitatively similar results for the yield stress prediction, only the fully 3D EGP model is able to represent the large-strain deformation behavior.Spanish Government (Ministry of Science and Innovation, Ministry of Economy and Competitiveness) through grant numbers RYC- 2010-07171, DPI2011-25470, and PID2019-106518RB-I00 is gratefully acknowledged

Effect of Chitin Nanocrystals on Crystallization and Properties of Poly(lactic acid)-Based Nanocomposites

The crystalline phase of poly(lactic acid) (PLA) has crucial eects on its own propertiesand nanocomposites. In this study, the isothermal crystallization of PLA, triethyl citrate-plasticizedPLA (PLA–TEC), and its nanocomposite with chitin nanocrystals (PLA–TEC–ChNC) at dierenttemperatures and times was investigated, and the resulting properties of the materials werecharacterized. Both PLA and PLA–TEC showed extremely low crystallinity at isothermal temperaturesof 135, 130, 125 ºC and times of 5 or 15 min. In contrast, the addition of 1 wt % of ChNCs significantlyimproved the crystallinity of PLA under the same conditions owing to the nucleation eect ofthe ChNCs. The samples were also crystallized at 110 ºC to reach their maximal crystallinity,and PLA–TEC–ChNC achieved 48% crystallinity within 5 min, while PLA and PLA–TEC required 40 min to reach a similar level. Moreover, X-ray diffraction analysis showed that the addition ofChNCs resulted in smaller crystallite sizes, which further influenced the barrier properties and hydrolytic degradation of the PLA. The nanocomposites had considerably lower barrier propertiesand underwent faster degradation compared to PLA–TEC110. These results confirm that the additionof ChNCs in PLA leads to promising properties for packaging applications.Validerad;2020;Nivå 2;2020-03-31 (alebob)</p