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To enrich the properties of polylactic acid (PLA)-based composite films and improve the base degradability, in this study, a certain amount of poly(propylene carbonate) (PPC) was added to PLA-based composite films, and PLA/PPC-based composite films were prepared by melt blending and hot-press molding. The effects of the introduction of PPC on the composite films were analyzed through in-depth studies on mechanical properties, water vapor and oxygen transmission rates, thermal analysis, compost degradability, and bacterial inhibition properties of the composite films. When the introduction ratio coefficient of PPC was 30%, the tensile strength of the composite film increased by 19.68%, the water vapor transmission coefficient decreased by 14.43%, and the oxygen transmission coefficient decreased by 18.31% compared to that of the composite film without PPC, the cold crystallization temperature of the composite film increased gradually from 96.9 °C to 104.8 °C, and PPC improved the crystallization ability of composite film. The degradation rate of the composite film with PPC increased significantly compared to the previous one, and the degradation rate increased with the increase in the PPC content. The degradation rate was 49.85% and 46.22% faster on average than that of the composite film without PPC when the degradation was carried out over 40 and 80 days; the composite film had certain inhibition, and the maximum diameter of the inhibition circle was 2.42 cm. This study provides a strategy for the development of PLA-based biodegradable laminates, which can promote the application of PLA-based laminates in food packaging. [ABSTRACT FROM AUTHOR]

In recent years, under the pressure of resource shortage and white pollution, the development and utilization of biodegradable wood-plastic composites (WPC) has become one of the hot spots for scholars' research. Here, corn straw fiber (CSF) was chosen to reinforce a poly(lactic acid) (PLA) matrix with a mass ratio of 3:7, and the CSF/PLA composites were obtained by melt mixing. The results showed that the mechanical properties of the corn straw fiber core (CSFC) and corn straw fiber skin (CSFS) loaded PLA composites were stronger than those of the CSFS/PLA composites when the particle size of CSF was low. The tensile strength and bending strength of CSFS/CSFC/PLA are 54.08 MPa and 87.24 MPa, respectively, and the elongation at break is 4.60%. After soaking for 8 hours, the water absorption of CSF/PLA composite reached saturation. When the particle size of CSF is above 80 mesh, the saturated water absorption of the material is kept below 7%, and CSF/PLA composite has good hydrophobicity, which is mainly related to the interfacial compatibility between PLA and CSF. By observing the microstructure of the cross section of the CSF/PLA composite, the research found that the smaller the particle size of CSF, the smoother the cross section of the composite and the more unified the dispersion of CSF in PLA. Therefore, exploring the composites formed by different components of CSF and PLA can not only expand the application range of PLA, but also enhance the application value of CSF in the field of composites. [ABSTRACT FROM AUTHOR]

Feedstock recovery plays a crucial role in the further application of polylactic acid (PLA), yet it still lacks efficient ways, resulting from an unclear understanding of PLA pyrolysis. Hence, the co-pyrolysis of PLA and the major components of biomass additives cellulose, hemicellulose and lignin was carried out to enhance the feedstock lactide yield and explore the pyrolysis mechanism. Compared to cellulose/PLA and hemicellulose/PLA, the co-pyrolysis of lignin/PLA had the strongest synergistic effects. Based on in situ FTIR and Py-GC/MS, the promoting mechanism was as follows: 4-ethyl-2-methoxy-phenol produced by the pyrolysis of lignin provided additional free radicals for the free radical reaction of PLA so that the production of lactide increased by 162.8%. The activation energy of co-pyrolysis was 30.6% and 13.8% lower than those of lignin and PLA, respectively, which was also due to the fact that lignin promoted the free radical reaction of PLA. It was indicated that co-pyrolysis required less energy than that of single pyrolysis. In addition, the generated lactide was not well-compatible with other bio-oils and solidified at room temperature, so it could be recycled by simple physical separation. This work provided a new method for the reuse of large amounts of waste PLA and lignin waste such as papermaking black liquor. [ABSTRACT FROM AUTHOR]

The difficulty of dispersing cellulose nanocrystals (CNCs) in poly(lactic acid) (PLA) was still a primary obstacle to enhance the properties of PLA nanocomposites. In this work, two different methods were used to modify CNCs that were then added dropwise and mixed with the PLA solution to conveniently obtain the composites. Transmission electron microscopy and Fourier transform infrared spectroscopy were used to characterize CNCs before and after modification. Ultraviolet–visible spectroscopy, tensile tests, differential scanning calorimetry, and thermogravimetric analysis were used to characterize the PLA nanocomposites. The results revealed that the CNCs that were modified with surfactant had better dispersion and thermal stability in the PLA nanocomposites. The Young's modulus and strength of PLA/SCNC nanocomposites were significantly reinforced (up to 66.0% and 29.8%, respectively). Meanwhile, the transmittance remained above 60% in the visible range. The solution precipitation approach was effective and simple, which could be used with other polymers. [ABSTRACT FROM AUTHOR]

Biodegradable poly(lactic acid) (PLA) composites were prepared using an innovative combination of wood fiber (WF) and 1,3,2,4‐bis(3,4‐dimethylobenzylideno)sorbitol (DMDBS). DMDBS acted as an effective nucleating agent, which improved the mechanical properties and slowed down the degradation of the WF/PLA composites. The enzymatic degradation of the composites was examined by immersing in proteinase K or cellulase buffer. The presence of DMDBS resulted in a 26.7% increase of the crystallinity compared to the WF/PLA composites. The increase in crystallinity enhanced the thermal stability and tensile strength of the WF/DMDBS/PLA composites by 8.5%. The durability of the WF/DMDBS/PLA composites after nucleated modification was enhanced after enzymolysis. After nucleated modification, the surface of the WF/PLA composites showed clear cracks due to degradation, while these appeared about 2 weeks later in the case of the WF/DMDBS/PLA composites. The results revealed that the introduction of cellulase degraded WF in the composites, which increased hydrolysis or enzymolysis sites. The combination of nucleated modification and enzyme buffer gave an expanded downstream application of WF/PLA composites in packaging and agricultural materials. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract Polylactic acid (PLA), one of the most likely green and environmentally friendly materials, is an alternative to petroleum-based plastic. It still remains a challenge to increase the degradation rate and decrease the cost of PLA without compromised mechanical properties. Low cost PLA/wood flour (WF) composite was elaborately designed and fabricated with improved interface compatibility through the introducing of polymethyl methacrylate (PMMA). The result indicated that compared with that of neat PLA, the tensile strength and bending strength of PLA/WF/PMMA (8:2) (80 wt% of the PLA, 20 wt% of WF and PMMA (8:2)) were increase by 4.60% and 26.54% respectively. Through the hydrolysis experiments combined with the SEM analysis, the main reason for the improvement of the mechanical properties of composite materials was that PMMA makes continuous three-phase composition, and interface compatibility of PLA and WF with overly different polarity was modified. Meanwhile, the hydrolysis rate of PLA/WF/PMMA was much faster than that of PLA. Finally, there was a more significant discovery that the addition of PMMA changed material degradation mechanism, and it was why to efficiently accelerate the degradation rate of the material. This will provide a new inspiration for PLA degradation research, and a fresh perspective is to be given other materials. Graphical abstract fx1 Highlights • PMMA makes continuous three-phase composition to reinforce interface of PLA-WF. • The enhancement of degradation performance of material to be applied and degraded quickly. • By changing the material degradation mechanism to accelerate the degradation rate. [ABSTRACT FROM AUTHOR]

Soil burial degradation was confirmed to be an efficient waste disposal method for the biodegradable materials with short service life, such as starch/poly (lactic acid) (PLA) composite. The biodegradation behavior about chemical and thermal properties of starch/PLA composite was analyzed by using X-ray photoelectron spectroscopy (XPS), infrared microscopy (IRM), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). XPS and IRM results indicated that the biodegradation of PLA occurred at the ester groups in PLA chains. XPS demonstrated the cleavage of C O linkages between glucose rings in starch. DSC and TGA results showed that the starch/PLA composite degraded faster than the pure PLA. During the soil burial degradation, the glass transition temperature of starch/PLA composite exhibited an obviously decrease while it had a slight variation for PLA. The thermal stability of starch/PLA composite shifted towards to that of PLA when they were subjected to soil burial for the same time. It is established that the starch can accelerate the degradation of PLA-based materials, which will enlarge the markets of biodegradable PLA materials used for short service life products. [ABSTRACT FROM AUTHOR]

The development of starch/poly (lactic acid) (starch/PLA) biodegradable composite materials can alleviate the dependence of the plastic industry on the oil resources, and fundamentally solve the problem of white pollution" caused by traditional plastics. The mechanical properties, water resistance and melt processability of starch/PLA composites can be effectively improved by the compatible interface constructed between starch and PLA. This paper summarizes the interface characteristics and construction mechanism of starch/PLA, and reviews the development of compatible interface in starch/PLA composites from the modification of starch, the modification of compatibilizer, the hydrophobic modification of starch and the hydrophilic modification of PLA. In view of the shortcomings of the research on construction methods and construction mechanism of starch/PLA composite materials, some suggestions for further research are put forward. [ABSTRACT FROM AUTHOR]

Composites of poly(lactic acid) with wood flour which was grafted by melt extruding with methyl acrylate in the presence of benzoyl peroxide (BPO) were investigated. The modification of filler (WF-g-PMA) was carried out to enhance the filler-matrix interactions, while the treated component was characterized by infrared spectrum. Properties of binary (PLA/WF, PLA/WF-g-MA) composites were analyzed as a function of the grafting monomer amount by scanning electron microscopy, differential scanning calorimeter, thermogravimetric analysis, water absorption and mechanical tests. Compared with the untreated system (PLA/WF), all treated composites showed higher interfacial compatibility as a result of chemical bonding between WF and grated monomer. All composites showed higher tensile modulus and lower strength and elongation at break as compared to pure PLA; grafting modification with methyl acrylate led to an increased stiffness and decreased water absorption of the composites because of an enhanced filler-matrix interfacial compatibility. [ABSTRACT FROM PUBLISHER]

In this study, composites of thermoplastic poly (lactic acid) filled with wood flour (WF) were prepared via melt extrusion. Before that, alkali treatment was performed on WF to improve the properties of the WF/PLA composite materials. The effect of the solution concentrations of NaOH, namely 0.5, 1.0, 5.0, and 10.0%, on mechanical properties of the composites was evaluated. The results showed that the properties of the composites with treated WF were enhanced greatly compared with that of the untreated composites. The composites had a best improvement in its compatibility and mechanical strength when the concentration of NaOH solution was 5.0%. The brittle fracture of composites showed that the chemical modification of WFs improved the compatibility between the filler and matrix. [ABSTRACT FROM AUTHOR]

ABSTRACT An entirely biosourced blend composed of poly(lactic acid) (PLA), starch, and wood flour (WF) was prepared by a co-extruder with glycerol as a plasticizer. The morphology, rheological properties, and mechanical properties of the WF/starch/PLA blends were comprehensively analyzed. The results showed that with the decrease of the starch/WF ratio, the morphology experienced a large transformation, and the compatibility of the blends was found to be superior to other blends, with a starch/wood flour ratio of 7/3. The dynamic mechanical thermal analysis (DMA) results demonstrated the incompatibility of the components in WF/starch/PLA blends. Following the decrease of the starch/WF ratio, the storage modulus ( G″) and the complex viscosity (η*) of the blends increased. The mechanical strength first increased, and then decreased with the increase of the WF concentration. The water absorption results showed that the water resistance of the blends was reduced with the lower starch/WF ratio. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44743. [ABSTRACT FROM AUTHOR]

ABSTRACT MA modified wood flour/PLA composites were prepared by one-step reactive extrusion, in which wood flour and poly(lactic acid) (PLA) were used as raw material, maleic anhydride (MA) was used as modifier, and dicumyl peroxide (DCP) was used as initiator. The influences of MA concentration on the morphology, thermal stability, rheological, and mechanical properties of the composites were studied. The addition of MA improved the compatibility of the composites significantly. The thermal and rheological results showed that with the increase of the concentration of MA, the thermal stability of the composites decreased, the storage modulus and complex viscosity of the composites also decreased. The MA modified composites had an enhanced mechanical strength compared to the unmodified one. As the concentration of the MA increased, the tensile and flexural strength of the composites first increased and then decreased, and reached a maximum when the concentration of MA was 1 wt %. The MA modified composites showed a better water resistance than the unmodified ones. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43295. [ABSTRACT FROM AUTHOR]

Abstract Going up further on the basis of excellent mechanical properties and solving the long-standing shortcoming of the slow degradation rate were developed in parallel for polylactic acid (PLA). The polylactic acid/wood flour/polymethylmethacrylate (PLA/WF/PMMA) composites were prepared by melt blending used PLA as matrix, WF of diverse particle size with PMMA at 8:2 mass ratio totally filled with 20 wt%. The PLA/WF/PMMA composites were studied by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), melting index test, and universal mechanical properties test. The result shows that WF of 150 μm < particle size < 180 μm executed the optimal improvement to mechanical properties of PLA/WF/PMMA. Tensile strength, flexural modulus and Young's modulus of PLA/WF/PMMA (150–180 μm) were enhanced 10.02%, 37.21% and 32.80% in relation to neat PLA, respectively. Hydrophilic contact angle test, water absorption measurement and hydrolysis assessment were performed to the hydrolysis degradation performance of materials. Furthermore, PMMA and WF cooperatively assisted in enormously accelerating hydrolysis of PLA, eventually having a good performance. Improving mechanical properties and accelerating degradation at the same time are of great significance for expanding the application of PLA. Graphical abstract Unlabelled Image Highlights • The key to mechanical properties of PLA/WF/PMMA lies in the size of WF. • PMMA skillfully locks WF during hydrolysis to accelerate the degradation of composite. • Accelerating hydrolysis and mechanical modification are achieved simultaneously. [ABSTRACT FROM AUTHOR]

The key to achieving high-performance plant fiber/polylactic acid (PLA) composites lies in solving the interfacial compatibility issue between the two components. However, current mainstream methods for interfacial modulation often come with energy consumption and environmental concerns. To address this, our study proposed the development of fully bio-based bamboo fiber (BF)/PLA composites based on the principles of non-toxicity, low carbon footprint, and environmental friendliness. In this study, we aimed to construct a molecular-scale multiphase crosslinking network structure in BF/PLA composites. To achieve this, we utilized cyclodextrins (CD) to induce a regularized alignment of PLA molecular chains and employed epoxidized soybean oil (ESO) ring opening reaction to form bonds connecting BF, CD, and PLA molecules. This approach ensured that the composite is fully bio-based while still exhibiting remarkable mechanical properties. The resulting BF/PLA@CD-ESO composites demonstrated impressive bending strength, reaching 108.65 MPa, which was 23.11 % higher than that of the BF/PLA composites. Moreover, the tensile strength reached 67.48 MPa, which was 39.06 % higher than that of BF/PLA composites. This study provides a convenient, green and sustainable method for preparing PLA-based composites. The resulting composites are expected to be used in disposable tableware, food packaging and environmentally friendly furniture. [Display omitted] • Raw materials are all bio-based, composites are green and environmentally friendly. • Molecular-scale interfacial engineering of multiphase crosslinking structure was constructed. • The composites have excellent mechanical properties and are at the leading edge of the study field. [ABSTRACT FROM AUTHOR]

The high density and poor thermal insulation of traditional wood-plastic composites limited the application in the field of building materials. In this paper, wood fiber (WF) and PLA were used as raw materials and azodicarbonamide was used as the foaming agent. Lightweight WF/PLA composites were prepared by the hot-pressing foaming method, aiming to obtain renewable, low-density material with high strength-to-weight ratio and thermal insulation performance. The results showed that after adding 20 % WF into PLA, the cell morphology was excellent and the cell size was uniform. The magnification reached the minimum value of 0.36 g/cm3 and the foaming magnification was 3.42 times. The impact strength and compressive strength were 3.16 kJ/m3 and 4.12 MPa, its comprehensive mechanical properties were outstanding. The thermal conductivity of foamed materials was 0.110–0.148 (W/m·K), which was significantly lower than that of unfoamed materials and common wood. Its excellent mechanical properties and thermal insulation can be suitable for application in the construction field to replace traditional wood. [Display omitted] • Preparation of renewable and lightweight wood fiber/poly(lactic acid) composites • The composites have high mechanism strength and thermal insulation performance. • Wood flour content can affect the lightweight material properties. [ABSTRACT FROM AUTHOR]

Bamboo fiber (BF) is favored by people for its renewability, low cost, fast growth, low density, high hardness, pollution-free, and easy harvesting. However, when preparing composites by blending and extruding BF and degradable plastic PLA, the significant difference in polarity between the two leads to a significant decrease in mechanical properties, which limits the application of BF in bamboo plastic composites. In order to improve the compatibility between PLA and BF, this study used polymerized carbodiimide (PCD) as a compatibilizer to prepare modified BF/PLA composites and investigate the effect of BF content on the composites. The results showed that the addition of PCD increased the flexural strength, flexural modulus, impact strength, tensile modulus and tensile strength of PCD-BF/PLA compared to BF/PLA composites, with the impact strength increasing the most significantly by 20.91 %. Meanwhile, the tensile strength improved by 15.06 % from 55.1 MPa to 63.4 MPa, and the flexural strength improved by 14.82 % from 80.3 MPa to 92.2 MPa. The experimental investigation of BF content revealed that when the ratio of BF to PLA was 4:6, the impact and flexural strength of the BF composites did not significantly decrease, but the flexural modulus and tensile strength increased, with the flexural modulus increasing the most significantly by 90.53 % compared to PLA, while the cost has been reduced by 13.80 %. The porosity experiment also showed that as the BF content increased, when the ratio of BF to PLA was 4:6, the porosity of the composite material was only 3.98 %, which was not further significantly increased compared to 3.62 %. The prepared high proportion biomass can be used in tableware, and other fields. [Display omitted] • High proportion of biomass material bamboo fiber was added. • Cost of PCD-BF/PLA reduced by 13.8 %, offering potential for food tableware use. • The flexural modulus of PCD-BF/PLA increased by 90.53 % compared to PLA. • PCD-BF/PLA has high mechanical strength and is environmentally friendly. [ABSTRACT FROM AUTHOR]

Biodegradable poly (lactide) (PLA) and poly (butylene adipate- co -terephthalate) (PBAT) composite films were made by a co-precipitation and hot-pressing method. The property of composite films like the chemical interaction, phase morphology, mechanical properties, and thermal properties were studied. The Fourier transform infrared spectroscopy (FTIR) test manifested that there was a small amount of the transesterifications between the PBAT and PLA during hot pressing, which could improve the compatibility of the two phases. The tensile strength of the film only reduced by 7.4%, while the elongation at break was increased by 119.1% compared with PLA after adding 4%wt PBAT. The composite films showed a high Ultraviolet-visible (UV) light barrier property. The UV blocking rate of the composite after adding 4%wt PBAT was 6.95 times higher than that of pure PLA at 380 nm. The PLA/PBAT composite films with excellent thermal stability, satisfactory mechanical properties and UV-light barrier have high a possibility for an UV screening packaging application. [Display omitted] • The PLA/PBAT composite films made by a co-precipitation method • The transesterification between the PBAT and PLA has existed. • The PBAT at low addition levels blended with PLA can realize the compatibility. [ABSTRACT FROM AUTHOR]

The rapid growth of polylactic acid (PLA) production and the slow hydrolysis rate make PLA a potential environmental pollutant. In order to make better reuse of the waste PLA in energy fields and solve the potential pollutant, PLA/wood flour (WF) compounds in all different proportions were co-pyrolyzed to study the co-pyrolysis behavior in terms of energy and products. The apparent activation energy of the 50%wtWF50%wtPLA compounds during co-pyrolysis decreased by 28% than PLA and 29.4% than WF. In addition, the pyrolysis of PLA provided additional energy for the co-pyrolysis of compounds which reduced the external input energy. The chemical reactions between WF and PLA during co-pyrolysis could be called synergistic interactions which promoted the free radical reaction of PLA and lead to the increase of lactide production. The yield of the harmful acetaldehyde reduced by 85.9% in the co-pyrolysis of 25%wtWF75%wtPLA compounds. In addition, the production of small molecular benzene ring substances was increased. For example, the phenol yield increased by 31.3% in the co-pyrolysis of 25%wtWF75%wtPLA compounds. The carbon number distribution of the main products was mainly concentrated on C5–C7 which was better for the reuse of bio-fuels during co-pyrolysis. [Display omitted] • Co-pyrolysis greatly reduced the production of the harmful gas products. • Pyrolysis of polylactic acid provided additional energy for the pyrolysis of wood flour. • The carbon number distribution of products concentrated on C5–C7. [ABSTRACT FROM AUTHOR]

In order to overcome the consumption of non renewable resources and serious environmental pollution caused by traditional petroleum based polymers, blending and modifying renewable PLA and wood fibers to replace traditional petroleum based plastics has become a current research hotspot. However, due to the large polarity difference between PLA and wood fibers, the performance of the composite material prepared is not ideal. To improve the performance of polylactic acid/poplar fiber (PLA/PF) composites and simplify the process, this study used cellulase and 2,2 '- (1,3-phenylene) - dioxazoline (PBO) co modification, a safe, environmentally friendly and simple process, to prepare the composites. The results show that the crystallization properties of cellulase and PBO-modified composites will be appropriately reduced, the microstructure shows that the interface of PLA/CF -5.5 /PBO is more tightly bonded, and the mechanical test results show that the modified material has excellent mechanical properties. Compared to the unmodified PLA/PF, PLA/CF -5.5 /PBO has a 28.85% increase in tensile strength, reaching 63.65 MPa. while its flexural strength reaches 116.07 MPa, representing a 21.45% increase. Surprisingly, the tensile and strength of PLA/CF -5.5 /PBO exceeds that of pure PLA, with the flexural modulus showing a significant increase of 43.96% compared to PLA. The above analysis shows that the effect of the two synergistic modification methods is significant, and the research results provide an environmental protection idea for the development of PLA matrix composites with high compatibility, good mechanical properties and good environmental adaptability, and broaden the application scope and value of the composites. [Display omitted] • Cellulase-treated wood fibers are eco-friendly, energy-saving, simple process. • New method: synergistic enhancement of PLA with wood fiber treated by cellulase and PBO. • The mechanical properties of PLA/CF -5.5 /PBO are at a high level in the research field. • PLA/CF -5.5 /PBO has higher tensile, flexural strength and modulus than pure PLA, adding 20% wood fibers reduces cost. [ABSTRACT FROM AUTHOR]

Abstract This study aims to access the durability of sustainable poly (lactic acid) (PLA) composites with the presence of starch and wood flour by using artificial weathering method. Chain scissions such as photolysis and hydrolysis resulted in significant decrease in molecular weight. After artificial weathering, thermal stability decreased for all materials, but very slightly for WF/PLA composite. Both the changes of molecular weight and thermal stability revealed that the weathering rate followed the order: PLA > starch/PLA > WF/PLA, indicating that starch and wood flour improved the durability of PLA. Tensile test suggested that the PLA composites introduced in starch and WF had a better environmental survivability. At last, mathematical models were established to evaluate the decrease in tensile strength with weathering. The obtained results offer an opportunity to estimate the material's durability, and provide an idea to design sustainable PLA-based materials with enhanced durability for outdoor application. Graphical abstract Image Highlights • Influence of starch and wood flour on weathering performance of PLA were compared. • Enhanced durability of the sustainable PLA-based composites was demonstrated. • Wood flour was more efficient to resistant the UV weathering of PLA. • Mathematical models were established to estimate the decrease in tensile strength. [ABSTRACT FROM AUTHOR]

Biodegradation behavior of biodegradable starch/wood power/polylactic acid (PLA) composites from the natural northeast Chinese soil environment was investigated in this study. The microstructural changes of the materials for 105 days was comprehensively characterized by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). XRD results showed that the crystallinity of the composites increased at the initial soil burial period, followed by a decrease during the degradation period. DSC of the surface and interior of the composites at different degradation times further characterized the changes in composite microstructures. After degradation, short molecular chains were formed, which slowly gained various extents of chain mobility. FTIR analysis indicated that the random fracture sites of PLA and starch were C=O and C-O groups, respectively. The absorb intensity of C=O and C-O groups decreased with the prolonged degradation time. The P-S5W5 showed a higher degradation rate than others, likely due to the synergetic effect between starch and wood power. [ABSTRACT FROM AUTHOR]

Effect of accelerated weathering time and glycerol on the photodegradation behavior of starch/wood flour/PLA composites was studied. The decreased intensity of diffraction peaks characterized by XRD indicated that the crystal structure was damaged. The chemical structure changes characterized by FTIR showed the formation of carboxylic acid. The decreased extent of the C O absorbance intensity of the composite with 15% glycerol proved that glycerol had a stabilize effect on the UV durability of the composites. After weathering, the maximum decomposition temperature decreased prominently due to the chain cleavage. With the prolonged weathering time, the tensile and flexural strengths decreased gradually. [ABSTRACT FROM AUTHOR]

Using polylactic acid (PLA) as the green wall insulation materials have the advantages of environmental protection and renewable, but they are not widely used due to poor performance. To solve this problem, azodicarbonamide (AC) used as the foaming agent and PLA/rice straw (RS) bio-composite foams were processed using the moulded foaming method. And degradable polycaprolactone (PCL) was added to improve the performance of foams. After the addition of 40 wt% PCL, the impact strength, compression strength and water resistance of the foams were improved by 357.7 %, 277.1 % and 803.9 %, respectively. All foams exhibited excellent insulation performance of 0.038–0.040w/(m·k). Thus, this study provides an effective way to resource utilization of crop waste and prepare high-performance wall insulation foam materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • PLA can be burned as a fuel because the incineration is regard as carbon neutral. • Pyrolysis of PLA with MgO and its co-pyrolysis with biomass is very promising. • Alcoholysis of PLA is considered to be the most suitable method for chemical recovery of PLA. • The hydrolysis of PLA can upcycle lactic acid with low energy consumption compared to that from starch fermentation. • The products have higher added value and wider usages during ammonolysis of PLA. Polylactic acid (PLA) is currently the highest production of all bio-based plastics globally. Its production will increase year by year to replace part of petroleum-based plastics to reduce environmental pollution and curb carbon emissions. However, the raw materials for synthesizing PLA mainly come from sugary foods, and mass production will pose a threat to food security. In addition, the degradation rate of PLA is slow, and a large amount of waste PLA accumulation still causes pollution. As a high-quality carbon source, compared with direct degradation, recycling PLA is a more green and environmentally friendly method. Because PLA can not only be depolymerized into raw materials for synthesizing PLA but also can be upcycled to chemicals required by various industries, which helps to reduce the use of petroleum resources. In addition, the recycling of PLA helps to reduce CO 2 emissions, because the source of PLA does not consume petroleum resources, but rather fixes CO 2 in the air. This review summarizes the works of upcycling waste PLA as an alternative carbon source for energy and other chemicals from the perspectives of tertiary and quaternary recycling, which provides a reference for the proper treatment of a large amount of waste PLA. [ABSTRACT FROM AUTHOR]

A comparative study of the thermal behavior of PLA/starch blends annealed at different temperatures has been conducted. Annealing was found to be beneficial to weaken and even eliminate the enthalpy relaxation near T g . The degree of crystallinity was evaluated by means of DSC, and the results showed that the crystallinity of the samples increased as the annealing temperatures were increased. It was observed that, during the annealing process, the disorder α (α′) crystal modification tended to transform into the order α crystal modification. All of the PLA/starch blends showed a double melting behavior. With the increase of annealing temperatures, the lower T m1 increased, while the T m2 showed no evident change. The XRD patterns also showed that annealing was beneficial to the samples to form higher crystallinity. The TGA results indicated that the annealed samples did not show any higher thermal stability than the virgin samples. The activation energy calculated by the Flynn–Wall–Ozawa method at lower conversion degrees confirmed that the annealing slightly slowed the degradation. The activation energy did not show any dependence on the conversion degree, which indicated that there existed a complex degradation process of the PLA/starch blends. The average activation energy did not show obvious differences, indicating that the annealing treatment had little influence on the degradation activation energy. [ABSTRACT FROM AUTHOR]

Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C O, C O and C H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C O, C O and C H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T 0 , T i and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA. [ABSTRACT FROM AUTHOR]

Highlights: [•] Esterified method was a simple process, low cost, and limited amounts of waste water and gas. [•] Maleic anhydride esterified starch was blended with PLA to increase the interface bond strength. [•] The mechanical properties and water resistance of the composite material improved. [•] Contact angle and water absorption test results verify that hydrophobicity increased obviously. [ABSTRACT FROM AUTHOR]

[Display omitted] • Time-dependent hydrolysis behavior of PLA and starch/PLA composites were studied. • Starch slightly slowed down the hydrolysis of PLA, but did not reduce the final hydrolytic degree. • The autocatalysis effect was more prominent at a higher temperature. Structural modification of starch/PLA composites caused by hydrolysis was evaluated at different temperatures. Water uptake of starch/PLA composites showed a time-dependent behavior which did not follow the Fickian behavior well. Molecular weight also showed a time dependence, especially at 50 °C. Combining water uptake and molecular weight change together, the entrapment of acidic products in the bulk could increase the hydrophilicity of materials and catalyze the hydrolysis. The chain scission occurred at the C = O in the PLA chains according to the FTIR results. The presence of starch may induce the hydrolysis to take place at the interface between starch and PLA matrix. In addition, starch may slow down the hydrolysis rate slightly without influencing the hydrolysis degree. This research should provide valuable information for designing green materials to be applied in water-present conditions. [ABSTRACT FROM AUTHOR]

• Synergistic effects of WF-PLA blends in different proportions were studied. • The FWO, DAEM and Starink methods were used to analyze the kinetics analysis. • Synergistic effects effectively reduced the activation energy during co-pyrolysis. • Synergistic effects positively promoted the free radical reaction of PLA. • The addition of WF increased the proportion of C C/H bonds. In this study, WF (wood fiber)/PLA (polylactic acid) composites were pyrolyzed to study the synergistic effects during co-pyrolysis of WF-PLA blends. The co-pyrolysis kinetics, mechanism of synergistic effects and products distribution were studied by TG-FTIR-MS and Py-GC/MS. Through the analysis of co-pyrolysis kinetics, it was found that the activation energy of WF-PLA blends was lower than that of sole WF or PLA. The pyrolysis activation energy of 30%wt WF/PLA composites decreased by 70 KJ/mol compared to sole PLA. TG-FTIR-MS and Py-GC/MS analysis showed the production of lactide increased significantly accompanied by a decrease in acetaldehyde and CO during co-pyrolysis. The interactions between WF and PLA promoted the positive synergistic effects. The synergistic effects essentially promoted the free radical reaction of the PLA during co-pyrolysis, thereby reducing the activation energy of the co-pyrolysis and obtaining more recoverable lactide. This work provided a reference for the reuse of waste PLA and WF in energy field, and provided a solution to the potential PLA pollution. [ABSTRACT FROM AUTHOR]

On the road of wide popularization and application of polylactic acid (PLA), its degradation performance frequently fetters the advancing feet. The work attempted to develop a (PLA & Coating-layer) @Filler [(PLA&C)@F ] model composite with high-effective degradation property in order to clear the obstacles for the promotion of PLA-based-materials products and alleviate the environmental burden. Firstly, PLA/wood flour/polymethyl methacrylate composite was fabricated by melt blending PLA, wood flour and polymethyl methacrylate, and (PLA & polymethyl methacrylate) @wood flour as a demonstration model was established. Then, the degradation rate of PLA/wood flour/polymethyl methacrylate and neat PLA was evaluated by hydrolysis test. The composite of (PLA & polymethyl methacrylate) @wood flour demonstration model achieved satisfying result, its hydrolysis rate was 8.56 times faster than that of neat PLA under the same conditions. The reasons were attained through various testing methods. Lastly, the characterization of Fourier Transform Infrared Spectroscopy (FTIR), the test of differential scanning calorimetry (DSC), and the observation of scanning electron microscope (SEM) to the materials in predetermined stages were applied to determine significant pieces of real-time information. By combining various information to provide right characterization for studying super-fast hydrolysis mechanism of PLA/wood flour/polymethyl methacrylate. The development of (PLA & Coating-layer) @Filler [ PLA&C)@F ] model is a significant work both accelerating research and even controllable exploration of PLA-based composite degradation. [ABSTRACT FROM AUTHOR]