Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice 
husk and acetyl tributyl citrate

doi:10.21203/rs.3.rs-4688218/v1

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Research Article

Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice
husk and acetyl tributyl citrate

https://doi.org/10.21203/rs.3.rs-4688218/v1

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Developing a stiffness-toughness balance, low-cost, and biodegradable PLA composite is an effective strategy for improving product market competitiveness, reducing dependence on petroleum-based resources and protecting the environment. Rice husk (RH) is extensively used as a filler in polymers, but the addition of too much rice husk into PLA has damaged the toughness of the composite. In this work, fully biodegradable composites with a stiffness-toughness balance and low cost are successfully fabricated through melt blending of PLA, RH and acetyl tributyl citrate (ATBC). The results show that bio-based plasticizer ATBC can improve the flowability of PLA composites, further enhancing their processability, which promotes the dispersion of RH in PLA. The impact strength and elongation at break of PLAC20 reach the value of 100 J/m and 148%, achieving an increase of 4.3 and 60.1 times compared with PLAC0, respectively. The torque rheological test shows that the maximum torque and equilibrium torque arrive 25.3 N/m and 2.3 N/m, and are about 67.4% and 63.5% lower than those for PLAC0 after incorporation of 18 phr ATBC, respectively, indicating a significant improvement in processing performance. As the ATBC amount increases, the water absorption rate of the composite progressively rises, while the contact angle steadily diminishes, resulting in the improvement for hydrophilicity, thereby broadening its potential applications.

Poly (lactic acid) (PLA)

rice husk (RH)

acetyl tributyl citrate (ATBC)

stiffness

toughness

As a consequence of the rapid advancement of technology and the growth of the universal standard of living, public attention to environmental issues is on the rise ^[1–3]. Recent studies have demonstrated the presence of microplastics from the depths of the ocean (10,890 m) to the top of Mount Everest (8,840 m above sea level), which further exacerbates the prevailing concern regarding the environmental contamination of the planet ^[4–6]. In the contemporary era, the utilization of biodegradable plastics, including Poly (lactic acid) (PLA) ^[7–10], Poly butylene succinate (PBS) ^{[11, 12]}, Poly (butylene adipate-co-terephthalate) (PBAT) ^[13], Polypropylene carbonate (PPC) ^{[14, 15]}, and so forth, has emerged as a pivotal strategy to curb the reliance on petroleum-derived plastics and mitigate the detrimental effects of white pollution. Wherein, PLA is undoubtedly one of the most commercially valuable materials in the field of bioplastics, accounting for 18.9% of the market share of bioplastics ^[16], and has been applied in fields such as medical, packaging, agricultural and textile due to its excellent advantages in biocompatibility, biodegradability, and high transparency, but the inherent defects of PLA such as poor toughness, low thermostability, and high cost are significant factors limiting its broader use in industrial and commercial sectors ^{[9, 17, 18]}. By blending PLA with modifier, fillers or other biodegradable materials, products with desired properties can be obtained, which is a simple, effective, and highly cost competitive method ^{[10, 19]}. At present, for the purpose of realizing high-value utilization of waste and ensuring sustainable economic development, the use of waste resources as fillers in developing PLA-based composites has been widely studied ^[20–26]. Song et al. ^[22] used stannous octanoate as a catalyst to graft bamboo flour (BF) onto lactide (LA) in the molten state to form BF-g-LA, and then PLA is blended with BF (PLA/BF, 85/15 wt%) to prepare PLA/BF/BF-g-LA composites using BF-g-LA as a compatibilizer. It is found that the addition of BF-g-LA improved the interfacial compatibility between PLA and BF. When the amount of BF-g-LA is 2 phr, the tensile and impact strengths of PLA/BF/BF-g-LB composites are 55.3 MPa and 9.56 kJ/m, respectively, which are 30% and 27% higher than the corresponding values of PLA/BF composites.

Rice husk is a byproduct of the rice production process that is often disposed of through open burning, the practice that presents a significant challenge to the ecosystem, particularly in developing countries ^[27–29]. Green PLA composites manufactured using rice husk as a reinforcing material offer a novel technology that not only promotes environmental stewardship by reducing waste and carbon footprint, but also enhances prosperity by providing innovative economic opportunities for rice cultivation ^{[30, 31]}. However, PLA is a brittle material that is not easily processed, and the incorporation of rice husks has not resulted in a significant toughening effect ^[32]. In order to enhance the toughness of PLA/RH composites, it is necessary to add the ternary component, such as elastomers or small molecule plasticizers.

Acetyl tributyl citrate (ATBC) is a green and non-toxic citrate plasticizer, which has been approved as a plastic plasticizer for food packaging and medical devices ^{[10, 33, 34, 35]}. In this study we prepared a series of PLA/RH composites with ATBC by melt blending and hot compression with a rice husk amount controlled at 30%, exploring the effect of different amount of ATBC on composites characterized by Fourier transform infrared (FTIR) spectrometry, Mechanical properties, Thermogravimetric analysis (TGA), HAAKE torque rheometer, water absorption, contact angle, Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM), which is able to give more excellent comprehensive performance composites.

2.1 Materials

PLA is received from Xinda Co., Ltd (Heilongjiang, China). The Acetyl tri-n-butyl citrate (ATBC) is provided by Yousuo Chemical Technology Co., Ltd (Shandong, China). Rice husks is supplied from market.

2.2 Preparation of composite

Screen out the required size of rice husks (RH) crushed by a crusher using a 150 µm standard sieve, and then dry them in a vacuum drying oven at 100 ℃ for 12 h. At the same time, dry the PLA in an 80 ℃ air drying oven for 8 h. Mix the dried PLA, RH, and ATBC in a mass ratio of 70/30/x (x = 0, 3, 6, 9, 12, 15, 18, 20, respectively), and stir until ATBC has completely soaked the material. Seal with cling film and let stand for a period of time to ensure that the material completely absorbs ATBC, then melt the mixed material for 8 minutes using a HAAKE torque rheometer. The naming and composition of PLA/RH/ATBC composites are shown in Table 1. As shown in Fig. 1 is the schematic diagram of the processing flow of PLA/RH/ATBC composite.

Table 1

The composition of PLA/RH/ATBC composites
Sample	PLA/wt%	RH/wt%	ATBC/phr
PLAC0	70	30	0
PLAC3	70	30	3
PLAC6	70	30	6
PLAC9	70	30	9
PLAC12	70	30	12
PLAC15	70	30	15
PLAC18	70	30	18
PLAC20	70	30	20

2.3 Performance testing and characterization

2.3.1 FTIR Test

The chemical structures of samples are evaluated by FTIR coupled with an attenuated total reflection (ATR-FTIR) (Nicolet IS50, USA). The relevant conditions in the test are 4000 cm^− 1~400 cm^− 1 scanning range, 2 cm^− 1 resolution and each spectrum had been scanned 64 times.

2.3.2 Mechanical properties

According to GB/T1843-2008, the impact strength of the sample is carried out on an electronic cantilever beam impact tester (XJUD-5.5 type, Chengde Jinjian Testing Instruments Co., Ltd.) with an impact speed of 3.5 m/s, and each component sample is tested no less more five times. The tensile strength test of the sample is measured on an Instron tensile tester system (Instron-1121, USA) with a crosshead speed of 50 mm/min in accordance with GB/T1040.1–2018. The samples are made into dumbbell-shaped form and each group sample is repeated at least 5 times. After preparation, all samples are kept at a constant temperature for 24 h to eliminate thermal stress.

2.3.3 Thermogravimetric analysis (TGA)

Weigh 5 ~ 10 mg samples for testing on a thermogravimetric analyzer (TG DTA7200), with a testing temperature range of 30 ℃~600 ℃ and a heating rate of 20 ℃/min.

2.3.4 Rheological property

Rheological measurements are conducted in the HAAKE torque rheometer at a temperature of 180 ℃, a speed of 40 r/min, and a blending time of 8 min.

2.3.5 Water absorption testing

All samples are absorbed in deionized water for 48 h, they are weighed, and the water absorption is calculated, as follows:

$$\:{W}_{A}=\frac{{W}_{0}-W}{{W}_{0}}\times\:100\%$$

In Eq. (1), W_A represents the water absorption, W is the early weight of the samples, and W₀ is the weight of the sample after soaking. The water absorption value of each sample is measured for three times, and the average value is finally taken.

2.3.6 Contact angle test

A contact angle machine is applied to test the value of contact angles (KRUSS-DSA30, Germany). First, all samples are dried in an oven at 60°C for 12 h, then they are put on a platform, onto which 2 µL of DI water is dropped from a syringe. The values of contact angles data are recorded by a computer software.

2.3.7 Dynamic mechanical analysis (DMA)

The dynamic mechanical properties of PLA composites are conducted by a dynamic mechanical analyzer (Diamond PE, Perkin-Elmer, USA) from 20 ℃ to 100°C at a heating rate of 3 ℃/min and a frequency of 1 Hz. The dimension of test strip is set in 30 mm×10 mm×1 mm.

2.3.8 Differential scanning calorimetry (DSC)

The tests are performed on a differential scanning calorimeter under N₂ flow. Samples of 5 ~ 10 mg are first melted to 190 ℃ (1st run) at the rate of 10°C/min, held for 5 min to erase the thermal history and then cooled to 30°C at the rate of 10°C/min, held for 5 min, and re-heated to 190°C (2nd run) at the rate of 10°C/min. The crystallinity (X_C) of PLA/RH composites can be calculated using the following formula:

$$\:\text{Xc}\text{=}\frac{\varDelta\:{H}_{m}-\varDelta\:{H}_{CC}}{{W}_{f}\text{×∆}{H}_{m}^{0}}\text{×}\text{100%}$$

In Eq. (2), X_C is the degree of crystallinity of PLA/RH in the sample, %; ∆H_m and ∆H_CC are the melting enthalpy and cold crystallization enthalpy at secondary heating of the sample, respectively, J/g; $\:{W}_{f}$ is the mass fraction of PLA in the test sample, %; ΔH^θ_m is the enthalpy of crystallization of the pure polymer in the ideal state when fully crystallized (ΔH^θ_m for PLA is 93.7 J/g).

2.3.9 Scanning electron microscope (SEM)

The morphology of the impact cross-section of PLA/RH composites is observed using a scanning electron microscope (JSM5600 type, JEOL Electronics Co., Ltd, Japan). All the samples with impact cross-section are coated with a thin layer of gold on the fractured surface.

3.1 FTIR spectra

As illustrated in Fig. 2 the functional group structures of PLA and its composites are characterized using FTIR. The absorption peaks observed in the range of 3500 ~ 3300 cm^− 1 for the three samples is due to the stretching vibration of hydroxyl group. The absorption peaks observed in the 3000 ~ 2900 cm^− 1 and 1480 ~ 1430 cm^− 1 ranges correspond to the antisymmetric stretching and bending vibrations of a saturated alkyl group (-CH). The stretching vibration peak of aliphatic ester groups occurs between 1740 cm^− 1 and 1760 cm^− 1[36]. The absorption peaks that occur within the range of 1100 ~ 1000 cm^− 1 are caused by the stretching vibration of C-O ^[37]. Figure 2 shows that, following the incorporation of RH, the absorption peak of -OH in PLAC0 broadens, likely due to the association of -OH in RH. The most notable observation is that when plasticizers are introduced into the composites, the C-O stretching peak shifts from 1079 cm^− 1 to 1090 cm^− 1. Similarly, the C = O stretching peak shifts from 1746 cm^− 1 to 1751 cm^− 1. This change is attributed to the formation of hydrogen bonds between the polar carbonyl group on the ATBC molecular chain and the hydroxyl and carboxyl groups at the end of the PLA ^[38]. Through this interaction, on the one hand, ATBC can reduce the polarity connection between the PLA molecular chains, and on the other hand, the non-polar groups in ATBC can be inserted into the PLA molecular chains, playing a role in isolating the PLA molecular chains, reducing or even shielding the van der Waals force formed between the PLA molecular chains, facilitating the movement between the PLA molecular chains, and thus achieving the goal of plasticize PLA. The molecular interaction between PLA and ATBC is shown in Fig. 3.

3.2 Mechanical properties analysis

Figure 4 and Table 2 illustrate the impact of the plasticizer ATBC amount on the mechanical properties of PLA/RH composites. The elongation at break and impact strength of composites are directly proportional to the ATBC amount, while the tensile strength and elastic modulus decrease with the increase of ATBC amount. However, the tensile strength and elastic modulus of the composite slightly increase and the impact strength decreases, when the ATBC amount reaches 3 phr, an "anti-plasticizing" phenomenon occurs ^[39]. The fracture elongation and impact strength slightly increased, but no yield point was observed during the tensile process when the ATBC amount reaches 12 phr. This indicates that the sample exhibited typical characteristics of a rigid sample, such as high strength and obvious brittleness. The reason is that PLA/RH composites retain the inherent brittleness of PLA, and therefore ATBC cannot play a significant plasticizing role when the amount of plasticizer is low. When the ATBC amount reaches 15phr, the elongation at break suddenly skyrockets from 3.33% at ATBC12 to 75%, a significant increase of 22 times, and the mechanical properties of the composite underwent significant changes. This experimental phenomenon shows a high degree of consistency with other related research results ^{[37, 40]}. ATBC mainly achieves the brittle ductile transition by reducing the interaction force between PLA molecular chains, making the movement between PLA molecular chains easier to occur. The elongation at break and impact strength of PLAC20 reach 148% and 100 J/m, marking an increase of 60.1 times and 4.3 times respectively compared to PLAC0. Conversely, both the tensile strength and elastic modulus decreased by 70.1% and 87% respectively from their values prior to plasticization. This is due to the increase in ATBC amount, which continuously transforms the brittleness and rigidity of the composite material into toughness and plasticity. At this time, under the action of external forces, the plastic yield deformation of the PLA matrix occurs, thereby achieving the transformation from brittle fracture to ductile fracture.

Table 2

Mechanical properties of PLA/RH/ATBC composites
Sample	Tensile strength(Mpa)	Elastic modulus(Mpa)	Elongation at break (%)	Impact strength (J/m)
PLAC0	53.0 ± 1.6	2803 ± 84	2.42 ± 0.2	23 ± 1
PLAC3	54.3 ± 1.6	2821 ± 85	2.81 ± 0.2	21 ± 1
PLAC6	48.2 ± 1.4	2579 ± 77	2.86 ± 0.2	29 ± 1
PLAC9	39.5 ± 1.2	2458 ± 73	3.17 ± 0.2	31 ± 1
PLAC12	27.9 ± 0.8	1646 ± 49	3.33 ± 0.2	33 ± 1
PLAC15	16.8 ± 0.5	1100 ± 33	75.0 ± 2	41 ± 1
PLAC18	16.4 ± 0.5	594 ± 18	124 ± 4	66 ± 2
PLAC20	15.8 ± 0.5	364 ± 11	148 ± 4	100 ± 3

3.3 TGA

Thermal stability of PLA/RH/ATBC composites are shown in Fig. 5, and the specific values are listed in Table 3. It can be observed that the T_oneset of PLAC18 decreased by 67.9 ℃ compared to PLAC0 in Fig. 5a, due to the composites are subjected to high temperature conditions, where violent movement occurs PLA molecular chains and the hydrogen bonding between ATBC becomes unstable, leading to the precipitation of ATBC from the composites. Therefore, as the ATBC amount increases, the phenomenon of thermal weight loss in composites become more pronounced. Upon the introduction of a slight amount of ATBC, the value for the peak decomposition temperature (T_max, Step1) experiences a modest elevation. Owing to the incorporation of a substantial amount of ATBC as a plasticizer, the hydrogen bonding between ATBC and PLA is markedly diminished, resulting in considerable migration of PLA molecular chains. Consequently, the T_max of PLAC18 decreases by 21.8°C when compared to PLAC0. The small peak in the front section of the PLA composites curves in Fig. 5b are also caused by the migration of PLA molecular chains ^[41].

Table 3

Thermogravimetric data of PLA/RH/ATBC composites
Sample	T_onset (℃)	T_50% (℃)	T_final (℃)	T_max (℃)
Sample	T_onset (℃)	T_50% (℃)	T_final (℃)	Step1	Step2
PLAC0	294.3	337.3	443.1	338.4	—
PLAC6	264.8	335.8	442.2	342.9	—
PLAC12	241.6	335.6	441.5	342.7	—
PLAC18	226.4	311.2	437.2	316.6	356.1

3.4 Processability

The rheological properties of composites during processing are often reflected by the magnitude of the maximum mixing torque and the equilibrium mixing torque ^[42]. It can be observed that the more ATBC is added, the maximum mixing torque and equilibrium torque of the composites continuously decrease. As illustrated in Fig. 6, when the ATBC amount is 18 phr, the maximum and equilibrium torque values are 25.3 N·m and 2.3 N·m, respectively. These values represent a decrease of 67.4% and 63.5% compared to PLAC0. According to lubrication theory ^[43], ATBC serves as a lubricant within PLA molecular chains, reducing friction between them and thereby increasing the fluidity of the blend system. However, according to the gel theory, this occurs because the small molecules of ATBC plasticizer insert into the PLA molecular chain, forming a hydrogen bond ^[44], thereby increasing the distance between the molecular chains and reducing the degree of entanglement of the molecular chains. The macroscopic performance is represented by the viscosity decreasing and the fluidity increasing, which decreases the mechanical shear force required during processing. Thereby, the addition of ATBC has improved the processing rheological properties of the blend system to a certain extent.

3.5 Water absorption

Figure 7 shows the water absorption rate of PLA composite in 48 hours. As shown in Fig. 7, it can be observed that as the ATBC amount increases, the water absorption rate of the composite gradually increases, because ATBC can plasticize polymers, making polymer chains easier to move and stretch, thus improving the dispersion of RH in the matrix. Therefore, in soaking aqueous solution, water molecules are easier to enter the interior of PLA structure and are better absorbed by hydrophilic RH ^[45].

3.6 Water contact angle

The water absorption is mainly to analyze the internal situations of the sample, and the contact angle is for the surface properties of the sample. From the analysis results of contact angle in Fig. 8, we know that as the ATBC content increases, the water contact angle of the composite gradually decreases, especially for PLAC20, where the water contact angle decreases from 74.9° to 64.3° compared with PLAC0, and the hydrophilicity gradually improves, and this is consistent with the water absorption test results. PLA/RH composites added ATBC could increase water absorption and improved hydrophilicity of the matrices which increased surface wettability.

3.7 DMA

DMA testing of composites can further understand the effect of ATBC plasticizer on the glass transition temperature (Tg) of composites. Figure 9 illustrates that as the increasing of ATBC amount, the Tg of the composite gradually decreases, resulting in enhancing processing performance of the composite. The Tg of the composite decreased by 30.8 ℃ compared with the initial value (59.9 ℃) at an ATBC amount of 18 phr, which decrease is attributed to the decrease in van der Waals forces between PLA molecular chains and the increase in free volume between molecular chains. Therefore, when subjected to external forces, molecular chains are more likely to slide, causing plastic deformation and dissipating internal stress, which results in an increase in toughness at the macroscopic level.

3.8 Crystallization and melting behavior

Figure 10 shows the DSC secondary heating curve of PLA/RH/ATBC composites. The corresponding specific data of heat and crystallization processes are summarized in Table 5. As shown in Fig. 10, it can be observed that all composites exhibit cold crystallization phenomenon, when the amount of ATBC increases, the peak temperature of cold crystallization (T_cc) gradually shifts towards the low temperature direction, indicating that ATBC accelerates the cold crystallization rate of PLA and making it more difficult to generate a complete crystal form of PLA, resulting in a descending crystallinity. The PLAC18 exhibits a 36.38 ℃ decrease in T_cc compared to the PLAC0 due to the addition of ATBC plasticizer, which to extent weakens the mutual binding effect between PLA molecules, enhances the activity of PLA chain segments, and significantly reduces the energy threshold required for PLA chain segments to move ^{[38, 46]}. In addition, the enthalpy of cold crystallization(ΔH_cc) continuous decrease of H_cc further indicates that ATBC improves the cold crystallization ability of composites. The melting temperature (T_m) value and XC of PLAC18 decrease by 4.07 ℃ and 0.44% compared to PLAC0, respectively, which indicated that the T_m and X_C of PLA/RH/ATBC composites generally shows a slight decrease with the addition of ATBC. The observation of shoulder peaks on the melting peak of PLA/RH/ATBC composites, which is attributed to the unstable defect crystals induced by ATBC in PLA, which experience dual melting during the melting and recrystallization processes ^{[38, 47]}.

Table 5

Crystallization and melting properties of PLA/RH/ATBC composites
Sample		T_m (℃)	$\:\varDelta\:{H}_{CC}$ (J/g)	$\:\varDelta\:{H}_{m}$ (J/g)	X_c $\:\text{(\%)}$
PLAC0	117.23	150.98	19.34	21.23	2.88
PLAC6	102.94	152.25	17.53	19.19	2.53
PLAC12	90.27	149.15	14.71	16.36	2.52
PLAC18	80.85	146.91	12.51	14.11	2.44

3.9 Morphology analysis

The influence of ATBC amount on the morphology in the impact cross-section of PLA composites is given in Fig. 11. A large proportion of smooth surface can be obviously observed (Fig. 11a), indicating very evident brittle fracture characteristics in non-plasticizer composite ^[48]. As the ATBC content increases, plasticized bodies begin to emerge in the PLA composite. When the ATBC amount reaches the value of 18 phr, numerous plasticized bodies can be observed, leading to a significant improvement in toughness. The occurrence of the above phenomenon can be explained from the following two aspects. On the one hand, the plasticized bodies absorb the energy when the composite is subjected to impact ^[49]; on the other hand, the plasticizer can reduce the polymer viscosity and improve the processability, which contributes to the dispersion of RH and reduces the occurrence of RH agglomeration in PLA matrix ^[37].

PLA biodegradable composites are prepared by melt blending and hot compression molding processes, and the effects of varying ATBC additions on the properties of these composites are studied. The addition of ATBC effectively improved the toughness and processability of the composites while also enhancing the dispersibility of RH in PLA matrix.

The incorporation of ATBC makes the toughness of the composites undergo a significant increase, that is the Izod impact strength increases by 434% at the amount of 20 phr ATBC, indicating that ATBC is selected to be added to achieve the purpose of toughening.

In the rheological property tests, it can be seen that as the amount of ATBC added increases, the processing torque curve of composites significantly decreases, leading to easy processability.

Thermal property tests show that ATBC causes unstable defect crystals in PLA, which exhibit dual melting behavior during the process of melting and recrystallization and the amount of ATBC increases, the cold crystallization rate of PLA accelerates, resulting in a decrease in T_c, T_g and crystallinity.

The water absorption rate and water contact angle tests show that the composite gradually becomes hydrophilic with the addition of ATBC, thereby broadening its potential applications.

The SEM results demonstrate that plasticized bodies absorb energy and ATBC increase flowability of PLA, which in turn enhances the toughness of the composite.

The authors declare no competing financial interest.

Acknowledgement

This work is financially supported by the Project of Jilin Provincial Department of Science and Technology (20240301030GX).

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You are reading this latest preprint version

Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice
husk and acetyl tributyl citrate

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials and method

2.1 Materials

2.2 Preparation of composite

2.3 Performance testing and characterization

2.3.1 FTIR Test

2.3.2 Mechanical properties

2.3.3 Thermogravimetric analysis (TGA)

2.3.4 Rheological property

2.3.5 Water absorption testing

2.3.6 Contact angle test

2.3.7 Dynamic mechanical analysis (DMA)

2.3.8 Differential scanning calorimetry (DSC)

2.3.9 Scanning electron microscope (SEM)

3. Results and discussion

3.1 FTIR spectra

3.2 Mechanical properties analysis

3.3 TGA

3.4 Processability

3.5 Water absorption

3.6 Water contact angle

3.7 DMA

3.8 Crystallization and melting behavior

3.9 Morphology analysis

4. Conclusions

Declarations

References

Status:

Version 1

Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice husk and acetyl tributyl citrate

Status:

Version 1

Abstract

Figures

1. Introduction

2. Materials and method

2.1 Materials

2.2 Preparation of composite

2.3 Performance testing and characterization

2.3.1 FTIR Test

2.3.2 Mechanical properties

2.3.3 Thermogravimetric analysis (TGA)

2.3.4 Rheological property

2.3.5 Water absorption testing

2.3.6 Contact angle test

2.3.7 Dynamic mechanical analysis (DMA)

2.3.8 Differential scanning calorimetry (DSC)

2.3.9 Scanning electron microscope (SEM)

3. Results and discussion

3.1 FTIR spectra

3.2 Mechanical properties analysis

3.3 TGA

3.4 Processability

3.5 Water absorption

3.6 Water contact angle

3.7 DMA

3.8 Crystallization and melting behavior

3.9 Morphology analysis

4. Conclusions

Declarations

References

Status:

Version 1

Simultaneously improving toughness and strength for biodegradable Poly (lactic acid) modified by rice
husk and acetyl tributyl citrate