Upcycling of Poly(Lactic Acid) by Reactive Extrusion with Recycled Polycarbonate: Morphological and Mechanical Properties of Blends

Poly(lactic acid) (PLA) is one of the most promising renewable polymers to be employed to foster ecological and renewable materials in many fields of application. To develop high-performance products, however, the thermal resistance and the impact properties should be improved. At the same time, it is also necessary to consider the end of life through the exploration of property assessment, following reprocessing. In this context the aim of the paper is to develop PLA/PC blends, obtained from recycled materials, in particular scraps from secondary processing, to close the recycling loop. Indeed, the blending of PLA with polycarbonate (PC) was demonstrated to be a successful strategy to improve thermomechanical properties that happens after several work cycles. The correlation between the compositions and properties was then investigated by considering the morphology of the blends; in addition, the reactive extrusions resulting in the formation of a PLA-PC co-polymer were investigated. The materials obtained are then examined by means of a dynamic-mechanical analysis (DMTA) to study the relaxations and transitions.


Introduction
Recycling plastics is one of the best opportunities available to reduce pollution, save raw materials, store carbon and protect ourselves from the negative effects of waste dispersion in nature and in the sea [1]. This assumption is also confirmed by the European Community directives that, starting from 2015, adopted an action plan aimed at fostering Europe's transition into a circular economy, in which waste is not simply disposed of but transformed into a valuable secondary raw material for further production [2]. There are a lot of reasons to incentivize and encourage plastic recycling, including limiting the use of landfills, optimising resources, limiting CO 2 emissions related to plastic production processes into the atmosphere and nurturing virtuous supply chains that can create sustainable employment [3].
In this framework, it is of great interest, both scientifically and in terms of industrial upscaling, to succeed in designing 'circular-by-design' materials, i.e., materials that can have such characteristics as to be recyclable after use, especially for high value-added applications. In addition, a topical challenge is to introduce in the recycling lines, renewable polymers, making them attractive for even high-performance applications through modifications and blending with other polymers. In this respect, the feasibility of a large window of production processes has guaranteed that poly(lactic acid) (PLA) is attractive for this purpose [4]. However, PLA is an extremely brittle material, it has a low toughness, it shows a low thermal resistance and it is relatively hydrophobic (with a static contact angle with water of 80 • ) [5]. To compensate for these defects (and above all to increase the impact properties) the incorporation of additives, such as inorganic particles or blending with

Processing
A conic twin-screw micro compounder (ThermoScientific HAAKE MiniLab II, Karlsruhe, Germany) was used to process and extrude the polymeric blends with and without the catalytic system. The melt filament was collected by a heated cylinder piston and fed into a mini-injection molding machine (Thermo Scientific HAAKE Minijet II, Karlsruhe, Germany), to produce specimens for the tensile tests (25 × 5 × 1 mm) and for the impact/fracture properties (80 × 10 × 4 mm). The processing temperature selected for the blends with and without CATA was 235 • C, the mold was held at 60 • C for an injection cycle of 25 s. Regarding PLA and R-PLA, the extrusion temperature was set at 190 • C, whereas for PC and R-PC, it was set at 280 • C.

Testing Methodologies
Firstly, during the micro compounding process, the torque trend over time, was closely related to the viscosity of the fluid itself, and was evaluated to understand the variations in the melt strength among the various formulations tested.
The quasi-static tensile tests were carried out at room temperature on Haake type III dog-bone tensile bars (size: 25 × 5 × 1.5 mm), at a crosshead speed of 10 mm/min by an Instron 5500R universal testing machine (Canton, MA, USA), equipped with a 1 kN load cell and interfaced with a computer, running MERLIN software (INSTRON version 4.42 S/N-14733H). The impact tests were performed on V-notched 80 × 10 × 4 mm specimens, using a 15 J Instron CEAST 9050 Charpy pendulum (INSTRON, Canton, MA, USA) following the standard procedure ISO 179.
The dynamic mechanical thermal analysis (DMTA) was performed on a on a Gabo Eplexor ® 100N (Gabo Qualimeter GmbH, Ahlden, Germany). The test bars were of a size of 10 × 5 × 1.5 mm and placed on a tensile geometry configuration. The temperature used in the experiment ranged from −100 • C to 200 • C with a heating rate of 2 • C/min and a frequency of 1 Hz. The properties measured under this oscillating loading are the storage modulus (E ) and tan δ. The E value represents the stiffness of a viscoelastic material and is proportional to the energy stored during a loading cycle; tan delta is the ratio between the loss and storage modulus.
The morphology of the composites was studied by scanning electron microscopy (SEM) using JSM-5600LV (JEOL, Tokyo, Japan) and by analyzing the fractured surfaces of the samples obtained by breaking them in liquid nitrogen. Prior to the SEM analysis, all of the surfaces were sputtered with gold.

Results
Firstly, a preliminary study was performed, aimed at understanding whether PLA and PC recycled (R-PLA and R-PC) from industrial scraps kept rheological, processed and mechanical properties similar to virgin polymers. For this purpose, the measurements of the torque during the mixing time, the quasi-static tensile tests and the impact tests were carried out and discussed.

Torque Analysis
It is accurate to assert that the viscous torque is a measure of the resistance that a fluid offers to the rotational motion of the conic twin screws and it is a function of the viscosity of the fluid itself [31]. By completely filling the micro compounder chamber (6 g), it can be observed that the higher the torque value, the higher the viscosity of the polymer. In Figure 1, the torque/time curves were recorded at 190 • C for PLA and R-PLA, over the extrusion time; the trend observed showed that for PLA, at time zero, the torque value turned out to be slightly higher than that of R-PLA, thus demonstrating the liability of the shorter chains after cleavages induced by the compounding, thermoforming and the second extrusion process suffered by R-PLA. Nevertheless, the difference tapers off as the mixing process advances, reaching similar torque values for PLA and R-PLA after 60 s. While the virgin PLA meets a continuous decrease in torque, associated with the chains breakage that is occurring for the first time as it not was not processed previously. R-PLA, instead, displayed a non-constant decrease, indeed after 40 s there is the presence of a plateau and, thus, the stabilization of the process conditions. The appropriate extrusion time to obtain the molten material to be transferred into the injection press lasted 60 s, however, we wanted to push the mixing time up to 100 s, in order to understand the torque trend, confirming that the torque of R-PLA remained stable up to 100 s, thus it was not going to encounter further cleaving or degradation; on the contrary, PLA continued to decrease its torque value for almost the entire test time.
The shape of the trend is mirrored in Figure 2 at 280 • C, regarding PC and R-PC. At their congenial extrusion temperature, they showed an almost continuous and constant decrease, concerning the virgin PC, basically matching what was reported by Chiu et al. [32], while the achievement of the torque stabilization was registered for R-PC, which started, as did R-PLA, from a relatively lower value than the virgin one, but it stabilized after 25 s and recorded a plateau. In the past, the decrease in the molecular weight of melt processed polycarbonate, was evidenced in different papers [33,34]. Similar papers were published about the PLA processing, proving the occurrence of a chain scission and the consequent decrease in the molecular weight [35,36]; indeed the rheological properties and the solution viscosity are very sensitive to the molecular weight changes and the correlations between the molecular weight and viscosity [37,38]. published about the PLA processing, proving the occurrence of a chain scission and the consequent decrease in the molecular weight [35,36]; indeed the rheological properties and the solution viscosity are very sensitive to the molecular weight changes and the correlations between the molecular weight and viscosity [37,38].

Mechanical Properties
Starting from the PLA/R-PLA comparison, from the point of view of the tensile properties (two representative stress/strain graphs in Figure 3), except for the elongation at break, there are no substantial differences. These results can probably be ascribed to the struggle between some phenomena that occur contemporarily during the reprocessing, as the decrease of viscosity (registered by the torque decrement) is probably due to the molecular chain scission [39,40]. This is crucial feedback, because it allows for the reuse of the material for subsequent processing, as it has similar properties. Definitely, the PLA matrix blends are fragile and show a low elongation at break, whereas the bi-continuous blends, including a continuous PC phase, are better and show an improved elongation at break. published about the PLA processing, proving the occurrence of a chain scission and the consequent decrease in the molecular weight [35,36]; indeed the rheological properties and the solution viscosity are very sensitive to the molecular weight changes and the correlations between the molecular weight and viscosity [37,38].

Mechanical Properties
Starting from the PLA/R-PLA comparison, from the point of view of the tensile properties (two representative stress/strain graphs in Figure 3), except for the elongation at break, there are no substantial differences. These results can probably be ascribed to the struggle between some phenomena that occur contemporarily during the reprocessing, as the decrease of viscosity (registered by the torque decrement) is probably due to the molecular chain scission [39,40]. This is crucial feedback, because it allows for the reuse of the material for subsequent processing, as it has similar properties. Definitely, the PLA matrix blends are fragile and show a low elongation at break, whereas the bi-continuous blends, including a continuous PC phase, are better and show an improved elongation at break.

Mechanical Properties
Starting from the PLA/R-PLA comparison, from the point of view of the tensile properties (two representative stress/strain graphs in Figure 3), except for the elongation at break, there are no substantial differences. These results can probably be ascribed to the struggle between some phenomena that occur contemporarily during the reprocessing, as the decrease of viscosity (registered by the torque decrement) is probably due to the molecular chain scission [39,40]. This is crucial feedback, because it allows for the reuse of the material for subsequent processing, as it has similar properties. Definitely, the PLA matrix blends are fragile and show a low elongation at break, whereas the bi-continuous blends, including a continuous PC phase, are better and show an improved elongation at break.  Furthermore, regarding the PC/R-PC comparison (where two representative curves are depicted in Figure 4), there is a slight lowering of the stress at break and elongation at break, again caused by reprocessing. A 3% degree decrease of the mechanical strength and stiffness of polycarbonate, after two reprocessing steps, is in line with what was found by Perez et al. [41] and more recently, by Reich et al. [42], in their studies on the mechanical property variations of polycarbonate after successive stages of extrusion/molding. The results of the Charpy tests, shown in Table 2, reveal that the impact strength of the virgin PLA is slightly higher than the impact resistance of the recycled polymer; a reduction of around 5 percent in this property after the subsequent rework is what was also evaluated by Aguero et al. [43], who reprocessed PLA up to six times, at which point the lowering of the impact properties reached almost 50%. This progressive decrease in the energy absorption capacity can be linked with the degradation process on PLA. A 15% decrease has been evaluated for the impact resistance of R-PC, with respect to PC; but the value still turns out to be very useful for blending it with R-PLA and improving its impact resistance. Furthermore, regarding the PC/R-PC comparison (where two representative curves are depicted in Figure 4), there is a slight lowering of the stress at break and elongation at break, again caused by reprocessing. A 3% degree decrease of the mechanical strength and stiffness of polycarbonate, after two reprocessing steps, is in line with what was found by Perez et al. [41] and more recently, by Reich et al. [42], in their studies on the mechanical property variations of polycarbonate after successive stages of extrusion/molding.  Furthermore, regarding the PC/R-PC comparison (where two representative curves are depicted in Figure 4), there is a slight lowering of the stress at break and elongation at break, again caused by reprocessing. A 3% degree decrease of the mechanical strength and stiffness of polycarbonate, after two reprocessing steps, is in line with what was found by Perez et al. [41] and more recently, by Reich et al. [42], in their studies on the mechanical property variations of polycarbonate after successive stages of extrusion/molding. The results of the Charpy tests, shown in Table 2, reveal that the impact strength of the virgin PLA is slightly higher than the impact resistance of the recycled polymer; a reduction of around 5 percent in this property after the subsequent rework is what was also evaluated by Aguero et al. [43], who reprocessed PLA up to six times, at which point the lowering of the impact properties reached almost 50%. This progressive decrease in the energy absorption capacity can be linked with the degradation process on PLA. A 15% decrease has been evaluated for the impact resistance of R-PC, with respect to PC; but the value still turns out to be very useful for blending it with R-PLA and improving its impact resistance. The results of the Charpy tests, shown in Table 2, reveal that the impact strength of the virgin PLA is slightly higher than the impact resistance of the recycled polymer; a reduction of around 5 percent in this property after the subsequent rework is what was also evaluated by Aguero et al. [43], who reprocessed PLA up to six times, at which point the lowering of the impact properties reached almost 50%. This progressive decrease in the energy absorption capacity can be linked with the degradation process on PLA. A 15% decrease has been evaluated for the impact resistance of R-PC, with respect to PC; but the value still turns out to be very useful for blending it with R-PLA and improving its impact resistance. Tests for the torque evaluation were performed on the studied blends at the same extrusion temperature ( Figure 5). As for the pure polymers, a decrease in viscosity is shown for all blends with the increase of the dwell time in the micro compounder recirculation chamber. The trend decreased abruptly in the first 20 s, then a stabilization of the fluidity was registered.

Torque Analysis
Tests for the torque evaluation were performed on the studied blends at the same extrusion temperature ( Figure 5). As for the pure polymers, a decrease in viscosity is shown for all blends with the increase of the dwell time in the micro compounder recirculation chamber. The trend decreased abruptly in the first 20 s, then a stabilization of the fluidity was registered. The significant data concerning all of the materials, is that the addition of the catalytic system decreases the torque value with respect to the relative counterparts without TA and TBATPB; the reason is to be found in the typical process of the chain scission in the presence of a catalyst that polymers undergo during the transesterification reaction in the melt, with a decrease in the molecular weight and, consequently, of the torque value [44]. This difference is more pronounced for blends in which there is a higher amount of PC. These considerations should be related to the morphology of the blends that are analyzed in the following section. The significant data concerning all of the materials, is that the addition of the catalytic system decreases the torque value with respect to the relative counterparts without TA and TBATPB; the reason is to be found in the typical process of the chain scission in the presence of a catalyst that polymers undergo during the transesterification reaction in the melt, with a decrease in the molecular weight and, consequently, of the torque value [44]. This difference is more pronounced for blends in which there is a higher amount of PC. These considerations should be related to the morphology of the blends that are analyzed in the following section.

Morphological Structure and the Mechanical Results
The fluidity of the polymeric melts, assessed indirectly by means of the torque measurement, necessarily goes to influence the morphological structures of these blends, which, in turn, influence the mechanical properties that are closely related. The micrographs presented in Figure 6a-d are explanatory: it can be seen in the 4000× magnifications, that the R-PLA60/R-PC40 blend (Figure 6a) is characterized by a co-continuity of phases, while the corresponding blend with the addition of TA and TBATPB (Figure 6c) shows rarefied areas of bi-continuity, but especially areas where the presence of the deformed ellipsoidal particles of PC, as dispersed phase in the PLA, is observed. The fluidity of the polymeric melts, assessed indirectly by means of the torque measurement, necessarily goes to influence the morphological structures of these blends, which, in turn, influence the mechanical properties that are closely related. The micrographs presented in Figure 6a-d are explanatory: it can be seen in the 4000× magnifications, that the R-PLA60/R-PC40 blend (Figure 6a) is characterized by a cocontinuity of phases, while the corresponding blend with the addition of TA and TBATPB (Figure 6c) shows rarefied areas of bi-continuity, but especially areas where the presence of the deformed ellipsoidal particles of PC, as dispersed phase in the PLA, is observed. In contrast, in the case of the R-PLA40/R-PC60 blend, a PC matrix structure with spheroidal inclusions of PLA, is seen (Figure 6b), nevertheless the addition of the catalytic system caused the formation of a bi-continuous morphological structure (Figure 6d).
In the literature, it is well known that immiscible polymers, such as the PLA/PC systems, are characterized by heterogeneous morphologies achievable during the melting. The types and dimensions of the morphology determine the properties of the blend, depending on the interfacial tension, viscosities and compatibilizers [45,46]. The co- In contrast, in the case of the R-PLA40/R-PC60 blend, a PC matrix structure with spheroidal inclusions of PLA, is seen (Figure 6b), nevertheless the addition of the catalytic system caused the formation of a bi-continuous morphological structure (Figure 6d).
In the literature, it is well known that immiscible polymers, such as the PLA/PC systems, are characterized by heterogeneous morphologies achievable during the melting. The types and dimensions of the morphology determine the properties of the blend, depending on the interfacial tension, viscosities and compatibilizers [45,46]. The co-continuous structures can be considered as the coexistence of at least two adjacent structures within the same volume. The mixtures with a co-continuous structure can favorably combine the properties of both components [47] and the concept of the phase inversion must be taken into account.
Phase inversion is a phenomenon that occurs when within a mixture, as the composition changes, the polymer that had the continuous phase changes to a dispersed phase, and vice versa [48], but why is such a morphology obtained at different percentages of PLA with and without a catalyst? According to Avgeroupolos et al. [49], phase inversion occurs when the ratios of the torques and volume fractions of the components of a blend are equal. For blends without CATA, in this paper, therefore, the phase inversion point is reached for larger quantities of PLA, than for the compatibilized blends. The motivation we propose is that the lowering of the viscosity generated by the catalyst flattening the torque values to similar values, identifies the phase inversion around 50/50 between R-PLA and R-PC, for such systems causing the different behaviors, in response to the tensile stress.
In this context Veenstra et al. [50] stated that the co-continuous morphology improves the characteristics of both polymer components, with respect to all possible morphologies. This assumption is confirmed by the quasi-static tensile properties (Figure 7 and Table 3) in which the bi-continuous blends (R-PLA60/R-PC40 and R-PLA40/R-PC60 + CATA) exhibit a much higher ductility, with elongations at break, even exceeding those of the pure PC, without decreasing in tensile strength. In contrast, the other two blends show a comparable ultimate tensile strength but with an evident brittleness. What drives the achievement of the improved properties over the pure PLA is the accomplishment of a co-continuous morphology during the processing. continuous structures can be considered as the coexistence of at least two adjacent structures within the same volume. The mixtures with a co-continuous structure can favorably combine the properties of both components [47] and the concept of the phase inversion must be taken into account. Phase inversion is a phenomenon that occurs when within a mixture, as the composition changes, the polymer that had the continuous phase changes to a dispersed phase, and vice versa [48], but why is such a morphology obtained at different percentages of PLA with and without a catalyst? According to Avgeroupolos et al. [49], phase inversion occurs when the ratios of the torques and volume fractions of the components of a blend are equal. For blends without CATA, in this paper, therefore, the phase inversion point is reached for larger quantities of PLA, than for the compatibilized blends. The motivation we propose is that the lowering of the viscosity generated by the catalyst flattening the torque values to similar values, identifies the phase inversion around 50/50 between R-PLA and R-PC, for such systems causing the different behaviors, in response to the tensile stress.
In this context Veenstra et al. [50] stated that the co-continuous morphology improves the characteristics of both polymer components, with respect to all possible morphologies. This assumption is confirmed by the quasi-static tensile properties ( Figure  7 and Table 3) in which the bi-continuous blends (R-PLA60/R-PC40 and R-PLA40/R-PC60 + CATA) exhibit a much higher ductility, with elongations at break, even exceeding those of the pure PC, without decreasing in tensile strength. In contrast, the other two blends show a comparable ultimate tensile strength but with an evident brittleness. What drives the achievement of the improved properties over the pure PLA is the accomplishment of a co-continuous morphology during the processing. The elastic modulus exhibits higher values for the mixtures with CATA; this is due to the formation of bonds, due to the interchange reaction between the components. In a previous study [22], it was seen that, after the quasi-static tests, the elongations at break, even greater than 120%, were achieved, but always with polycarbonate amounts of at least 60%; in the present work, with the recycled polymers, it is possible to state that this range  The elastic modulus exhibits higher values for the mixtures with CATA; this is due to the formation of bonds, due to the interchange reaction between the components. In a previous study [22], it was seen that, after the quasi-static tests, the elongations at break, even greater than 120%, were achieved, but always with polycarbonate amounts of at least 60%; in the present work, with the recycled polymers, it is possible to state that this range of bi-continuity is much wider, allowing even blends with 60% PLA to have a co-continuous morphology, resulting in its ductile behavior.
This strong relationship between the phase morphology and the elongation at break values for the studied blends, has been highlighted in Figure 8. of bi-continuity is much wider, allowing even blends with 60% PLA to have a cocontinuous morphology, resulting in its ductile behavior. This strong relationship between the phase morphology and the elongation at break values for the studied blends, has been highlighted in Figure 8. Conversely, when these materials were examined at high-speeds, through the impact tests, it has been noticed that what increases the toughness is the amount of R-PC in the compound, rather than the morphology; in fact, the trend is almost linear for both blends without and with a catalyst (Figure 9). This difference, in response to the slow test, versus the fast test, has also been found in other polymer systems, such as PLA/PBAT [51] or PLA/POE-g-GMA [52].
The catalytic system, operating through the chain rupture, did not favor the achievement of the impact strengths equivalent to the blends without a catalyst.
Definitely, as a result of the mechanical response in the slow test, specifically the tensile toughness is increased when a bi-continuous structure has been achieved during the processing, while in the fast test (impact test) it is the higher PC content that causes high value of energy absorbed before the crack propagation. Conversely, when these materials were examined at high-speeds, through the impact tests, it has been noticed that what increases the toughness is the amount of R-PC in the compound, rather than the morphology; in fact, the trend is almost linear for both blends without and with a catalyst (Figure 9). This difference, in response to the slow test, versus the fast test, has also been found in other polymer systems, such as PLA/PBAT [51] or PLA/POE-g-GMA [52].   Figure 9. Trend of the Charpy impact strength over the R-PC quantity in the blend.
The catalytic system, operating through the chain rupture, did not favor the achievement of the impact strengths equivalent to the blends without a catalyst.
Definitely, as a result of the mechanical response in the slow test, specifically the tensile toughness is increased when a bi-continuous structure has been achieved during the processing, while in the fast test (impact test) it is the higher PC content that causes high value of energy absorbed before the crack propagation.

DMTA Analysis
The development of such blends, based on polylactic acid and polycarbonate, could have a higher impact if the studied catalytic system could form copolymers during the reactive extrusion. Even polymers suffered in the industrial recycling process. In this regard, the DMTA analysis guarantees the possibility, through the study of tan delta peaks generated by a tensile test carried out at a certain frequency and in temperature sweeps, to evaluate the formation of copolymers, as demonstrated by Liu et al. [18] As shown in Figure 10, the energy released by the viscous motion of the polymer chains is reflected in the relaxation peak of tan δ, whose maximum can be considered an expression of Tg. Since the immiscible blends are those without CATA, a clear phase separation structure occurs, as revealed by two maxima in the tan δ curve. The small intermediate peaks of the blends without catalyst (red and black dots in Figure 10) are explained as the occurrence of the crystallization of the material; moreover, the more evident and significant ones (circled in yellow in Figure 10) that are present in the curves, concerning the blends with a catalyst are attributable to the formation of a copolymer that has, as Tg, a temperature intermediate between those of PLA and PC. This finding also confirms the data obtained with the virgin polymers, by Phuong et al. [22], namely that the presence of a new species is represented by the tan δ peak at around 110 • C.

Conclusions
The development of materials that are environmentally friendly and recyclable, that also have good mechanical properties (comparable to benchmarks), compatible with affordable price and capable to replace petroleum derivatives, is the path currently pursued in polymer research. Moreover, it can be noticed that the blends with the catalyst system exhibit a glass transition that starts at lower temperatures; this is probably due to the viscosity decrease caused by TA. The modulus storage E' is higher for the mixtures with CATA, when high temperatures are reached; this is due to the bond formation because of the interchange reaction between the components.

Conclusions
The development of materials that are environmentally friendly and recyclable, that also have good mechanical properties (comparable to benchmarks), compatible with affordable price and capable to replace petroleum derivatives, is the path currently pursued in polymer research.
In this paper, the melt viscosity and mechanical properties of the virgin PLA and PC were first compared with the corresponding materials that had undergone extrusion, thermoforming processes and were recovered as production scraps. Such processing was seen to decrease the properties, but always in an acceptable range of values that guaranteed their reuse and subsequent compounding.
For this purpose, the blends with 40 and 60% wt. of recycled PLA (R-PLA) were processed by studying whether a system of compatibilizers (successfully tested on the virgin polymers in a previous paper) would also work for the blends obtained from the recycled polymers. An interesting phenomenon was seen, as a result of the mechanical response in the slow test, specifically, the tensile toughness is increased when a bi-continuous structure has been achieved during the processing, while in the fast test (impact test), it is the higher PC content that causes the high value of energy absorbed before the crack propagation. The catalytic system, through the DMTA analysis, was seen to be able to induce the formation of the PLA-PC copolymers, since the presence of a peak of the tan delta at an intermediate temperature, with respect to PLA and PC, an α-transition has been registered.
The R-PLA/RPC blends with an improved ductility, with respect to the pure recycled PLA, were obtained in the present work, thanks to the achieved R-PC phase continuity, thus suggesting the methodologies to foster the use of recycled renewable polymers in a wider range of durable applications, such as in automotive and electronic equipment, where recyclability is requested.
With respect to the blends produced by using the virgin PLA and PC [22] where 60 wt.% of PC was necessary to observe blends with a good ductility, the use of recycled polymers allowed to obtain blends with an improved ductility, using only 40% of R-PC, thus allowing to increase the renewable content (and thus the carbon storage potential) of the developed secondary material). Such compounds, therefore, represent a great opportunity because they combine a good technical potential, a high renewable content, eco-sustainability, recyclability and can be a viable solution to post-consumer disposal problems, which are increasingly burdensome in both economic and environmental terms. The challenge that needs to be addressed concerns logistics, i.e., ensuring the suitable recycling lines for materials of this type and the widespread possibility of implementing the circular-by-design concept.