Introduction

Bio-based polymers are of the highest interest to researchers and industry worldwide, because of their environmental friendliness. They offer the possibility of replacing common plastics and reducing the overall pollution level caused by polymers, which has been so significant in recent decades. Biodegradable materials, in comparison to regular ones, usually exhibit rather limited properties. Among their main drawbacks, the following crucial ones can be distinguished: deteriorated mechanical properties, insufficient thermal resistance and the risk of premature decomposition during the exploitation time. Therefore, any attempts to overcome their limitations and adjust the characteristics of biodegradable polymers are essential for the development of these materials.

One of the options is to prepare biodegradable polymeric blends. One of the most popularized examples is poly(lactic acid) (PLA) that can be merged with more ductile polymers to overcome its brittleness, namely: polycaprolactone (PCL), poly(propylene carbonate) (PPC), poly (butylene succinate) (PBS), poly(butylene-succinate-co-adipate) (PBSA), poly(butyleneadipate-co-terephthalate) (PBAT), thermoplastic starch (TPS) and polyamide 11(PA11) [1, 2]. This work will focus on PLA blends with PBS, PBAT and TPS.

PBS is widely used as an addition to PLA, mainly due to its high strength and moderate plastic properties, which allows PLA to retain high flow stress, while noticeably improving its elongation [3]. PLA/PBS blends evolve with the PBS content—when it is low, PBS disperses in PLA matrix as droplets, when higher than 8.4 wt% it forms a co-continuous phase and when above 42wt% it’s PLA that dissolves in PBS. PLA/PBS compositions are both used in binary or ternary state (with a third component as compatibilizers, nucleating agents, epoxy or isocyanate chain-extenders or free radical initiators [4]. The effect of a third component may not always be beneficial. Homklin et al.[5] studied a 50:50 PLA/PBS blends with nano-sized precipitated calcium carbonate (NPCC) and sodium benzoate (SB). It was found out that the fillers acted like stress concentrators reducing tensile strength, elongation at break and energy at the break. Ou-Yang and co-authors [6] produced a filament for FDM 3D printing from various ratios of PBS to PLA in blends and all of these were characterized by excellent processing properties and exhibited typical ductile behavior (elongation up to 300%). PLA/PBS blends can be successfully used as a replacement for regular, commodity synthetic polymers, e.g., in the packaging industry. Bhatia et al. [7] stated that for different contents of PBS in PLA the tensile strength and Young’s modulus decrease together with a rising amount of PBS, according to the mixing rule. Nevertheless, the positive effect on elongation at break was not observed up to the PBS content of 80–90%, which may indicate some processing problems, e.g., limited miscibility or interfacial adhesion.

PBAT is one of the most attractive additives to PLA, because it improves its flexibility and processability. PLA/PBAT compositions can be used in the automotive, agricultural, pharmaceutical and packaging industries [8]. As PBAT is a costly material, its blending is often required to limit the price [9]. Wang et al. [1] studied the PLA/PBAT blends prepared by in situ compatibilization reaction using ADR (multifunctional epoxy oligomer) as compatibilizer. Various ratios were tested, but in each case, the elongation at break was significantly (up to 579.9%) improved in comparison to the neat PLA. Ding and co-authors [10] fabricated tri-block copolymers of PLA-PBAT-PLA characterized by superior interfacial interaction, enhanced interpenetration and miscibility between PLA and PBAT resulting in higher elongation at break. Lyu et al. [11] dotted the PLA/PBAT blend for 3D printing with 10% of PLA-g-GMA (PLA grafted with glycidyl methacrylate) and measured the tensile strength and elongation at break for PLA70PBAT30 to equal, respectively, 42.6 MPa and over 200%. Sritham and co-authors [12] tested PLA/PBAT with different ratios of both polymers (from 10 to 40% of PLA) in terms of their tensile properties. Although the tensile strength remained similar for all blends, the elastic modulus slightly increased with the growing content of PLA. Simultaneously, the elongation dropped together with the higher content of PLA.

TPS blends with PLA were reviewed by Zaaba and Ismail [13]. Thermoplastic starch is known to be another common material that can help to mitigate the brittle behavior of PLA. Nevertheless, the crucial limitation of this solution comes from the poor adhesion between the hydrophilic starch granules and hydrophobic polylactide. If needed, a similar approach may be undertaken as for PBAT—modification with compatibilizers, crosslinking agents etc. Moreover, the number of recycling (NOR) for PLA/TPS blends is limited as they are very sensitive to repeated processing, which ends up in deterioration of their mechanical properties [14]. There are also reported works on the manufacturing PLA/TPS-based composite materials, e.g., by joining them with cassava pulp (CP) [15]. CP-reinforced PLA/TPS composites can be readily subjected to injection molding. The most beneficial CP content was revealed to be 22.1% resulting in increased tensile strength (up to 354%) and Young’s modulus (up to 722%). Li and Huneault [16] proved that the addition of chain-extenders to PLA/TPS blends does not affect the tensile strength and Young’s modulus, nor the elongation. PLA/TPS mixture, due to its exceptional biodegradability, was chosen by Labus et al. [17] as a preferred material to be applied in the fabrication of long-term drug delivery systems (carriers). They can also be used in food packaging applications [18]. Przybytek et al. [19] found out that the joining of PLA with TPS and epoxidized soybean oil (ESO) enhances the elongation without comprising the biodegradability and compostability. There are also some attempts [20] at the creation of terpolymers, e.g., TPS/PBSA (butyl glycol ester copolymer)/PLA, where PLA is added to increase the compatibility of TPS/PBSA blends, maintaining them to be biodegradable.

In the following paper, PLA base material was combined with plasticizing secondary polymeric compound: PBS or PBAT or TPS. Manufactured blends were characterized in terms of their tensile properties (tensile strength, elongation at break, yield strength and Young’s modulus). Selected processing parameters such as melt flow ratio (MFR) and melt volume ratio (MVR) were investigated in order to evaluate the possibility of utilization of the studied biodegradable compositions in common technologies, e.g., extrusion, injection molding or 3D-printing. The work was complemented with DSC test results identifying softening, glass transition, cold crystallization and crystallization temperatures of mixtures. Moreover, heat deflection temperatures for 1.8 MPa and 8 MPa (HDT A and HDT C) together with Vicat softening temperatures for two loadings of 10 N and 50 N (VST A and VST B) were tested. In order to facilitate the fabrication process no additional compatibilizers have been used. The paper gathers novel data concerning the influence of temperature on tensile properties, describing the materials’ stability under variable conditions.

Material and methods

The following base materials were used for the preparation of the blends: PLA (PLI 005, NaturePlast), PBS (PBI 003, NaturePlast), PBAT (Ecoflex F Blend C1200, BASF), TPS (a starch-based biopolymer, MaterBi EF03A0, Novamont). The composition of the mixtures was based on PLA, which is characterized by the high strength (60–70 MPa) and, at the same time, the low plasticity (A = 7–8%). The second, additional material came from the group of plastic materials (PBS, PBAT, TPS). The mixtures of biodegradable plastics were prepared by the melt blending method (mixture compositions 70:30, 50:50, 30:70 by mass) using a twin-screw extruder (Haake PolyLab QC, Thermo Scientific). After extrusion, the materials were cooled and granulated. The granules were used successively to produce test specimens by injection molding. The test samples were made using a 50t Demag Ergotech Compact 50–120 injection molding machine. Paddle-like specimens were injected into a cold-channel two-cavity mold. Nozzle temperatures were adjusted experimentally to ensure the proper flow of the blend and complete filling of the mold (see Table 1). For each of the previous zones, the set temperature was 5–10 °C lower.

Table 1 Injection molding parameters—nozzle temperatures
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Static tensile tests were carried out with the use of a TINIUS OLSEN H25KT testing machine in accordance with the standard PN-EN ISO 527-1:2020-01. The aim of the research was to determine the materials parameters: yield strength Re, tensile strength limit Rm, elongation at break A, longitudinal elasticity modulus E depending on the deformation temperature ( − 20, 0, 20 and 40 °C) under quasi-static conditions (deformation rates 0.01 and 0.1 s−1 corresponding to the respective tensile test speeds: 50 and 500 mm/min). Tests were performed in a conditioned chamber equipped with heaters for the elevated temperatures and liquid nitrogen inflow for the lowered ones. Each of the tested series consisted of at least three specimens.

Attempts to determine MFR and MVR were carried out in accordance with the PN EN ISO 1133-1: 2011 standard using the Melt Flow Junior (Ceast) apparatus. The DSC Differential Scanning Calorimetry tests were performed with the use of the TA Instruments DSC Q20 apparatus. DSC measurements were carried out according to ASTM D 3418 standard. The samples were tested in pursuance of the following procedure: heating in the temperature range from − 40 to 200 °C (heating speed 10 °C/min), cooling in the temperature range from 200 to − 40 °C (cooling speed 5 °C/min) and second heating under the same conditions as the first one. HDT and VST were tested in accordance with the standard PN-EN ISO 306:2014-02 with the use of the Vicat/HDT (Service Zone 3D) at the heating rate of 50C/h for two different loading conditions each (HDT A—1.8 MPa, HDT C—8 MPa, VST A—10 N, VST B—50 N).

Results and discussion

Mechanical properties: tensile strength tests

The mechanical properties determined during static strength tests carried out at ambient temperature (see Fig. 1 and Table 2) at strain rates of 0.01 and 0.1 s−1 allowed to confirm that the PLA material is the most durable material among the considered biodegradable base materials (Rm up to 75 MPa) with very low deformability (7–8%). PBS material is characterized by medium tensile strength (over 37 MPa) and high deformability (150%). TPS and PBAT materials show low tensile strength (below 16 MPa) and very high elongation (up to 500%—although no breakage was stated, it was maximum, because of the chamber’s limited height). All of the above can indicate that the mixture of high strength material (PLA) with plastic materials (PBS, PBAT or TPS) will allow one to obtain a mixture of relatively high strength combined with high susceptibility to deformation. Young’s modulus of PLA equals 3.3–3.5 GPa, while for the rest of the tested materials it is 0.7 GPa for PBS, 0.1 GPa for PBAT and 0.1–0.2 GPa for TPS. Yield strength for PLA and PBS are nearing their tensile strengths, but for PBAT and TPS they are slightly lower.

Figure 1
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Tensile strength and elongation at break for base materials and blends tested at 20 °C—RT

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Table 2 Young modulus and yield strength for base materials and blends tested at 20 °C – RT
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Table 3 Young modulus and yield strength for base materials and blends tested at − 20 °C
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Table 4 Young modulus and yield strength for base materials and blends tested at 0 °C
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Table 5 Young modulus and yield strength for base materials and blends tested at 40 °C
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Figure 2 presents the dependence of engineering stress vs strain for the PLA blends with: a) PBS, b) PBAT, c) TPS. As can be noticed the higher the addition of the ductile polymer is, the higher elongation was achieved, simultaneously reducing the strength of the material. Strain rate does not influence the tensile behavior as the curves for both of the deformation rates applied (0.01 and 0.1 s−1) are overlapping.

Figure 2
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Dependence of engineering stress vs strain for the PLA blends with: a PBS, b PBAT, c TPS at 20 °C—RT

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Figure 3
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Tensile strength and elongation at break for base materials and blends tested at − 20 °C

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Figure 4
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Tensile strength and elongation at break for base materials and blends tested at 0 °C

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Figure 5
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Tensile strength and elongation at break for base materials and blends tested at 40 °C

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Among PLA/PBS blends, for the one in which PLA predominates (PLA70PBS30), the strength and deformability of the mixture is close to the values of pure PLA (Rm = approx. 60 MPa and A = max. 10%). For PLA30PBS70, the strength decreases to approx. 35%, and the deformability increases to 30% (with the neck present in the sample). Obtained results are more beneficial than the ones described in [10] for PLA50PBS50 composition, where the tensile strength value observed was approx. 40 MPa with elongation at break of 3%. On the other hand, it is not as high as was reported in [4], where the elongation has risen up to 20–520%. Young’s modulus, yield point and tensile strength exhibit similar decreasing tendency and values levels with the growing content of PBS as in [6] and [7]. In spite of the conclusion, that PBS, in contrary to PBAT and TPS, did not enhance the elongation of PLA as significantly, only two ratios were hereby considered (30 and 70 wt% of PBS), while for other systems, all of the tests were repeated for three options (30, 50 and 70 wt% of PBAT or TPS). Less visible influence on the elongation may be connected with the fact that PLA and PBS are thermodynamically incompatible [4].

For mixtures composed of PLA and PBAT, the higher the PBAT content, the lower the tensile strength was. A similar tendency was described in [1] for several ratios of PLA to PBAT. The deformation starts to increase even at the minimum content of PBAT (from 20% to a value of 400%). Likewise, in [1] the elongation of PLA-based blends with 10–40% of PBAT reached 350–480%. Results obtained for PLA30PBAT70 are significantly more beneficial than in [12], where elongation was below 100%, the tensile strength of 10 MPa and E of 0.1 GPa. PBAT is expected to be the best candidate to plasticize PLA [1]. Nevertheless, these materials usually exhibit poor compatibility resulting from the highly differing molecular structures of chain segments. From the obtained results, it can be concluded that the tensile strength of the blend remains high at first, but it is reduced when the amount of additive rises. On the other hand, the elongation at break, although improving, is still far from the one offered by pure PBAT. This issue may be tackled by reactive blending, in-situ compatibilization, addition of cross-linking agents or chain extenders [1].

In the case of a mixture of PLA with TPS, the tensile strength drops abruptly with an increase in the content of TPS: PLA70TPS30—40 MPa (slightly higher than in [14]), PLA50TPS50—30 MPa (as also published in [20]), PLA30TPS70—marginally below 20 MPa. The last value is higher than obtained by other authors for PLA40TPS60 composition, where it was reported as ~ 5 MPa [15]. The deformability of the mixture begins to increase to the value of 20% (for the TPS30 content), then to 40–50% (for the TPS50) and to values above 140% for the TPS70.

For both of the groups described above (PLA with PBAT or TPS) Re and E drops linearly with the growing content of the plasticizing additives.

Figures 3, 4, 5 depict the tensile strength and elongation at break results, while Tables 3, 4, 5 gather the measured yield strengths and Young modulus values for tests carried out at lowered and elevated temperatures.

Considering PLA behavior in various temperatures, a slight decrease in tensile strength (by a few MPa) was observed with increasing deformation temperature from the lowest point of − 20 °C to + 40 °C. The exceptions are the tensile curves at 0 and 20 °C (for 0.01 s−1), because the difference in strength for these curves is as high as 20 MPa. No significant influence of the strain rate on the strength was observed for PLA. The exceptions are the tensile strengths for the temperature of − 20 °C, which decreased from 100 to 80 MPa with the increase in speed from 0.01 to 0.1 s−1, the ones for 20 °C, which increased from 60 to 75 MPa with a speed increase from 0.01 to 0.1 s−1. No correlation between the strain rate on the PLA strain value was stated.

Discussing PBS, it was observed that the tensile strength decreases at elevated temperatures—from the value of approx. 60 MPa at − 20 °C through 47 MPa (at 0 °C) and 37 MPa (20 °C) to the value of 33–35 MPa (in 40 °C). It was also observed that the material’s strength is more temperature-dependent at elevated temperatures (the difference between − 20 and 0 °C was several MPa, and between 20 and 40 °C it was approx. 20 MPa). On the basis of the results, no influence of the strain rate on the strength and deformability of the bioplastic material was observed. The lowered temperature conditions caused the material to be noticeably more brittle as the elongation was reduced from approx. 200% to 25–33%.

The PBAT and TPS materials will be discussed simultaneously, because they have a very similar course of the tensile curves at all tested temperatures. For both materials, the influence of the tensile temperature on the value of plasticizing stress was observed—with increasing temperature, the stress value decreased (from about 20 MPa for − 20 °C through 12–14 MPa (0 °C) and 8–9 MPa (20 °C) to 6–7 MPa (40 °C)). As the deformation temperature increased, the stress drop was smaller: first by 6–8 MPa, then 4–6 MPa, and finally by 2–3 MPa. The materials are strain rate insensitive (the stress–strain curves for \(\dot{\varepsilon }\) = 0.01 s−1 and for \(\dot{\varepsilon }\) = 0.1 s−1 were similar). Moreover, E and Re values are also not responding severely to changes in the test speed. The maximum elongation was reduced from a level of 500% to 200% for both elevated and lowered temperatures.

Stress–strain curves determined during static strength tests allowed to state that PLA material is the most durable material among the base materials (75 MPa) with very low deformability (7–8%). Such a low deformability proves that PLA is not susceptible to processing, hence the need to add a plasticizer. PBS material is characterized by medium strength (35 MPa) and very high deformability (150%). TPS and PBAT materials show low strength (up to 16 MPa) and very high deformability (minimum 500%). The preparation of the PLA mixture with PBS/PBAT/TPS (plasticizer) made it possible to reach a compromise between sufficiently high strength and deformability allowing the mixtures to be used in plastics processing.

For all mixtures and both deformation rates, the expected tendency was observed—with the increase in the content of PBS/PBAT/TPS (high deformability plasticizer) in the mixture, its strength decreases (from 60-75 MPa as shown by pure PLA) to 50–60 MPa for PLA70PBS300 and up to 30–40 MPa for PLA70PBAT30 and PLA70TPS30. At the 50:50 ratio, the strength decreases to 25–35 MPa and then below 20 MPa in the case of PLA30PBS70 and PLA30PBAT70, but it does not come close to the low strength of pure PBAT and TPS (10 MPa). The strength for PLA30PBS70 is the same as for pure PBS—40 MPa. Deformability shows the opposite tendency to strength—as predicted, the more plasticizer in the mixture, the greater the deformability. As the PBS content increases, the deformability of the mixture increases (from 10% for pure PLA and PLA70PBS30) to 250% for PLA50PBS50 and to the value of 35% (until the neck appears) and 400% (with the neck present in the sample) for PLA30PBS70. In the case of mixtures of PLA with PBAT the deformation is 20–40% for the proportions 70:30 and 50:50, only for PLA30PBAT70 it increases to a value above 100%. The deformability of the PLA and TPS mixture begins to increase to the value of 20% (for the PLA70TPS30 ratio), then to 50% (for the 50:50 ratio) and to a value above 100% (for the PLA30TPS70).

In the case of mixtures, a general conclusion can be drawn—the more PLA material was in the composition of the mixture, the lower was the mixture's sensitivity to the deformation temperature, its strength and Young's modulus increased, and the plasticity decreased. In most cases, as the deformation temperature increases, the stress value decreases and the deformability of the material increases, especially at positive temperatures (20 and 40 °C). The deformation rate affects the stress value in the case of mixtures of PLA with PBAT and TPS (as the speed increases, the stress increases by a few MPa) and does not affect the material deformability. The mixture of PLA and PBS does not show sensitivity to strain rate. On the basis of Tables 2, 3, 4, 5, it can be observed that with the increase in temperature and strain rate, the value of Young's modulus in all tested materials decreases. PLA, PBAT together with their blends were also tested in lowered ( − 18 °C) temperatures by Sritham et al. [12] and the outcomes as well suggest that decreased temperature reinforces the tested material slightly in terms of E and Rm.

Processing parameters: MFR/MVR

MFR and MVR test results are presented in Fig. 6. Melt parameters of base materials stay in agreement with the data delivered by manufacturers. Blends with PBS behave in a comparable way as PLA and PBS base materials. Compositions with PBAT and TPS appear to have a resultant melt flow/volume ratios of its constituents and both decrease with the increasing content of the additional material to PLA. It stays in contrary to the work of Jullanun et al. [15] that tested the MFR of PLA40TPS60 composition and found out it was ~ 36 g/10 min and was superior to the one of sole PLA. Although the blends were prepared without any compatibilizers, the processing parameters were found to be adequate both for extrusion and further injection molding. Most of the considered materials, with the MFR exceeding 10 g/10 min, should also be appropriate to be processed by 3D printing for the purpose of prototyping [21].

Figure 6
figure 6

MFR and MVR for base materials and blends

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Processing parameters: DSC results

All of the considered materials were subjected to DSC in order to identify Tg (glass transition), Tcc (cold crystallization), Tm (softening) and Tc (crystallization) temperatures. For all base materials, the glass transition temperature was recorded. It was the lowest for TPS ( − 31.2 °C), higher for PBAT ( − 27.4 °C) and the highest for PLA (61.6 °C). However, the Tg was not recorded for the PBS matrix, that should be in the theoretical range from − 30 to − 20 °C. Table 6 gathers the detailed temperatures for blends’ compounds, while Fig. 7 presents the obtained DSC curves for all of the analyzed specimens. The PBS-based mixtures also lack the PBS glass transition visible. During heating, the exothermic peak was observed, which corresponds to the softening point. It was observed for PBS (114.6 °C), TPS (118.5 °C), PBAT (121.5 °C) and for PLA (174 °C). PLA/PBAT and PLA/TPS mixtures are characterized by two glass transition temperatures, except for those where the PLA content is 70%, where it is not visible. From the literature it can be expected that Tg for PBAT and PLA should equal, respectively, − 20.53 °C and 61.66 °C [1]. For PLA30PBAT70 the measured temperatures are similar to the ones reported by other authors (Tg1 –  − 36.3 °C, Tg2—55.6 °C, Tm1—128.3 °C, Tm2—147.5 °C—[12]; Tg1— − 26.8 °C, Tg2—61.5 °C, Tm1—122.5 °C, Tm2—173.7 °C—this work). The same situation occurs for the PLA70TPS30 mixture, where no TPS softening peak was noted, it may be due to a small amount of polymer addition in the test sample and was not captured during the measurement. The remaining mixtures are characterized by two Tm peaks from two components. All of the mixtures exhibit two temperatures of cold crystallization, depending on both constituents, and nearly all of them possess two crystallization temperatures (apart from PLA70PBAT30 and PLA70TPS30, where it was not visible). The results are confirmable with, e.g., [12], where two softening and glass transition temperatures for both polymers in PLA/PBAT blends were also clearly distinguished.

Table 6 DSC results for PLA/PBS, PLA/PBAT and PLA/TPS blends
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Figure 7
figure 7

DSC curves for: a PLA, PBS and their blends, b PLA, PBAT and their blends, c PLA, TPS and their blends

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Processing parameters: VST and HDT

VST and HDT test results are gathered in Table 7. All of the values were obtained as an average of three measurements. Vicat softening temperatures of base materials significantly decrease the higher the load is—for all of the tested materials. For PLA/PBS compositions, the increase in PBS content leads to severe growth of the VST. A similar tendency is observed for VST A for PLA/TPS blends, but not for VST B (also in the case of PLA/PBAT ones)—it is assumed that if the load is too high these materials start to behave in a more ductile way. VST A outcomes obtained for PLA/PBAT can be interpreted analogously, while neglecting the value for PLA70PBAT30 as the one with exceptionally high standard deviation—resulting from difficult mixing between these compounds. Heat resistance is commonly attributed to one of the materials that makes up the majority of the particular blend [22]. On the other hand, if the interfacial adhesion is not sufficient between the composition’s constituents, the VST may be reduced [23]. HDT A outcomes are usually, for most of the studied materials, slightly higher than HDT C, because they correspond to the lower load. The only exception is PBAT, where an increase of the heat deflection temperature was observed. All of the blends were found to perform more similarly to the constituent of higher HDT as a base material. Generally, the higher the heat deflection temperature is, the more suitable the polymer is for injection molding, so it can be concluded that the blends can be processed as well as the base materials. On the other hand, an addition of plasticizing compound usually decreases HDT making it more ductile, what may be, to some point, beneficial for the processing. Among the blends, the highest decrease in HDT was stated for PLA-PBAT ones, what can be combined with their limited miscibility.

Table 7 VST and HDT results for PLA/PBS, PLA/PBAT and PLA/TPS blends
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Conclusions

Summing up, a general conclusion can be drawn about the bioplastics and their mixtures (PLA, PBS, PBAT, TPS):

  • Developed blended materials ensure a beneficial compromise between the mechanical properties characterizing the commonly used biodegradable polymers—strong but brittle PLA and PBS, PBAT and TPS that exhibit lower strength, but significantly higher ductility. Hereby proposed biopolymers can find their use in energy absorption applications, especially for manufacturing thin-walled, honeycomb inserts used in sports helmets as energy absorbers instead of the currently used foamed materials. The advantage of their use is the ability to absorb more impact energy during an accident (there is no spring-back of the material).

  • Deep analysis of mechanical behavior conducted for various temperatures and strain rates and supported by testing of processing parameters can be used to predict the materials’ performance enabling for their tailored usage.

  • The more PLA material was in the mixture’s composition, the lower was its sensitivity to the deformation temperature, but even for these blends their tensile strength decreased at the elevated temperature in comparison to the ambient temperature. On the other hand, the lowered temperature levels caused contrary degradation in terms of mechanical properties—blends exhibited slightly enhanced strength, but they were also highly brittle.

  • Ductile additives, even without the presence of additional modifiers, can be used to plasticize PLA, in order to create more deformable biodegradable compositions. Higher content of PBS, PBAT or TPS causes the material to be more deformable, reducing its tensile strength, yield point and Young’s modulus at the same time.

  • Strain rate, at least in the applied range, does not significantly affect the tensile properties.

  • Although PBS enhances the deformability of PLA to some extent (up to 30%), it is not as beneficial as PBAT and TPS, that allow to obtain the elongation in PLA30PBAT (or TPS)70 blend at RT at the level of 400% and 150%, respectively.

  • Increasing the test temperature caused most of the materials to be more ductile. On the other hand, lowered temperatures ( − 20 °C and 0 °C) led to the toughening of the polymers increasing slightly their Rm, E and Re.

  • The manufacturing trials performed so far, supported by MFR and MFR outcomes, indicate that the fabricated blends are suitable to be processed by common technologies, i.e., extrusion, injection or even 3D-printing. Components tend to be joinable, but not miscible, as DSC analysis results with two peaks for each of the characteristic temperatures, corresponding to both phases. VST and HDT results indicate that the injection molding process for the blends should be appropriate, as well as it is for the base materials, but they also reveal that PLA and PBAT compounds are the most challenging to be joined.