Crystallization Of Polylactic Acid Research Articles

Trap-induced hydro-charging polylactic acid nonwovens with high charge storage capability for stable and efficient air filtration

Under the background of carbon neutrality, eco-friendly biodegradable polylactic acid (PLA) melt-blown nonwovens have been developed in air filtration. Nevertheless, the filtration performance of existing PLA melt-blown nonwovens is in an embarrassing situation and fails to meet the requirement of high efficiency air filters. Here, with controllable doping of N, N′-ethylene bis-stearamide (EBS), and barium titanate (BaTiO3) into PLA, through the melt-blown process, the charge-storage capacity of PLA nonwovens enhanced significantly. By utilizing the hydro-charging technology thereafter, we have prepared hydro-charged PLA/EBS/BaTiO3 nonwovens (HCP-EB) with excellent filtration performances. The doped EBS and BaTiO3 could improve the crystallization and charge storage capacity of PLA during the melt-blown process, thus constructing a large number of interfacial traps between crystalline and amorphous regions, leading to more electric charges captured during the hydro-charging process. The HCP-EB exhibited a high filtration efficiency (99.69 %) for PM0.3, a low pressure drop (27.44 Pa), and superior charge storage stability. Furthermore, the HCP-EB, remained at 99.18 % filtration efficiency after 48 h of treatment at 90 % relative humidity. After 3 months of storage, it still possessed an excellent filtration efficiency (99.02 %). Our work will contribute to the practical application of PLA melt-blown nonwovens in air filters and masks, and inspire the research of next-generation biodegradable electret air filtration materials.

Crystallization of poly(lactic acid) nucleated with the sorbitol TBPMN

We report on the crystallization of poly(lactic acid) (PLA) films in the presence of a sorbitol-based nucleating agent; 1,2,3-tridesoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol (TBPMN). Dispersion of the nucleating agent was performed by solution-mixing and melt-blending. Crystallization behavior was studied by differential scanning calorimetry (DSC). The structure and morphology were characterized by wide-angle X-ray scattering (WAXS), optical imaging, and atomic force microscopy (AFM). A significant impact of the nucleating agent was observed at or above a threshold concentration of 2 wt%, which was assigned to the solubility limit of TBPMN. The degree of crystallinity reached up to 39.6 % with 2 wt% TBPMN. An influence of the dispersion method was observed on the peak temperature of crystallization (Tcp). While Tcp decreased slightly for solution-mixed films, a sigmoidal trend was noted for melt-blended samples. Under isothermal conditions at 100 °C, the crystallization half-time was lowered from 6.5 min to 1.0 min. Avrami analysis pointed to the formation of 2-dimensional or 3-dimensional crystalline domains; WAXS data revealed α- and α'-crystals, depending on the dispersing method. AFM imaging showed a nanosized fibrillar network of the nucleator within the PLA matrix, demonstrating that TBPMN acted as a soluble self-assembly nucleator.

Fabrication of novel macromolecular P–S synergistic flame retardants and its applications in biodegradable poly (lactic acid): Combustibility, anti-melt dripping behavior, crystallization, and mechanical properties

As a biodegradable material, polylactic acid (PLA) has very bright application prospects, but its high flammability and poor crystallinity limit its use in electronics, automotive components, and other applications. In this paper, a macromolecular P–S synergistic multifunctional flame retardant (PTP) was obtained by an easy one-pot approach using polyethyleneimine, thiophene-2-formaldehyde and phytic acid. The addition of PTP to PLA improved the combustion resistance, anti-melt dripping and crystallization performance. The PLA compounds attained UL-94 V-0 grade at an ultra-low load (3 wt%) of the PTP, and the limiting oxygen index improved to 28.3 % when added at 9 wt%. The effective heat combustion and the total heat release value of PLA/9PTP composite were reduced from 24.4 and 93.1 to 18.9 MJ/kg and 86.0 MJ/m2, respectively. PLA/PTP composites provided a denser and more stable char layer during combustion than PLA and emitted significantly less-flammable gaseous volatiles. Meanwhile, PTP significantly facilitated the nucleation and crystallization of PLA, and the crystallinity elevated from 2.9 % to 35.5 % while the crystallization half-time reduced to 3.3 min about 10 % of pure PLA at 110 °C when added at 3 wt%. Besides, as PTP was a macromolecular flame retardant, PLA/PTP composites still maintained superior mechanical properties with the addition of PTP. This article gave an easy and effective way to fabricate PLA compounds with excellent flammability resistance, anti-dripping, crystallization and mechanical performance, which may be helpful for extending practical applications of PLA materials.

Effect of Polybutylene Succinate Additive in Polylactic Acid Blend Fibers via a Melt-Blown Process.

This work aimed to study the influence of the polybutylene succinate (PBS) content on the physical, thermal, mechanical, and chemical properties of the obtained polylactic acid (PLA)/PBS composite fibers. PLA/PBS blend fibers were prepared by a simple melt-blown process capable of yielding nanofibers. Morphological analysis revealed that the fiber size was irregular and discontinuous in length. Including PBS affected the fiber size distribution, and the fibers had a smoother surface with increased amounts of added PBS. Differential scanning calorimetry analysis (DSC) revealed that the crystallization temperature of the PLA sheet (105.8 °C) was decreased with increasing PBS addition levels down to 91.7 °C at 10 wt.% PBS. This suggests that the addition of PBS may affect PLA crystallization, which is consistent with the X-ray diffraction analysis that revealed that the crystallinity of PLA (19.2%) was increased with increasing PBS addition up to 28.1% at 10 wt% PBS. Moreover, adding PBS increased the tensile properties while the % elongation at break was significantly decreased.

Enhancing interfacial interaction and crystallization in polylactic acid-based biocomposites via synergistic effect of wood fiber and self-assembly nucleating agent

Incorporation of natural fibers into polylactic acid (PLA) provides a feasible pathway to improve the performance of PLA with a low environmental impact. However, the insufficient interfacial adhesion between fiber and matrix limits the reinforcement efficiency of fiber and final mechanical properties of the biocomposites. Herein we reported an efficient method to simultaneously enhance interfacial interaction, crystallization and mechanical performance of PLA-based biocomposites via combination of wood fiber (WF) and a self-assembly nucleating agent (TMC-300). The interactions between WF and TMC-300 and its influence on PLA, including interfacial crystal morphology, crystallization behavior, and mechanical performance were studied. The results showed that TMC-300 could self-assemble into dendritic-like structure on WF surface driven by hydrogen bonding, inducing the epitaxial crystallization of PLA. This unique interfacial crystallization integrated PLA matrix with WF, resulting in better interfacial adhesion. Under the optimal TMC-300 content (0.5 wt%), the flexural strength and notched impact strength of PLA composites increased by 10 % and 69 % compared with neat PLA, respectively. Additionally, TMC-300 and WF synergistically functioned as effective nucleating agents, which significantly accelerated the crystallization rate and improved the crystallinity of PLA. This work provides a new insight into the enhancement of interfacial bonding in natural fiber/PLA biocomposites.

Composites made of Ginkgo biloba fibers and polylactic acid exhibit non-isothermal crystallization kinetics

Polymer crystallization affects material microstructure and the final product quality, and the crystallization kinetics that govern this process are critical. In this study, alkali-treated Ginkgo biloba fibers (GFs) were melt blended with polylactic acid (PLA) to obtain GF/PLA blends. The non-isothermal crystallization kinetics of the GF/PLA composites were subsequently investigated using the Avrami, Jeziorny, Ozawa, and Liu-Mo methods, and the crystallization activation energies of the systems were calculated by Kissinger and Friedman models. The results showed that the GFs significantly promoted PLA crystallization, accelerated the crystallization rate, and shortened the crystallization time. The Avrami method showed some deviation from the linear relationship due to the effect of secondary crystallization, while the numeric value obtained by the Jeziorny method increased with the cooling rate. The Ozawa method could only be used in a very narrow range of temperatures, while the Liu-Mo method showed a more desirable fit. Crystallization activation energy calculations showed that the GFs promoted an increase in the crystallization capacity of the blend and a decrease in the effective potential barrier. This resulted in more selective biocomposites than pure PLA, offering greater applicability in domains including tissue engineering and 3D printing.

A strategy to prepare high‐robust and ultra‐tough polylactic acid/polycaprolactone/talc composites with thermo‐resistance

AbstractBlending with ductile polycaprolactone (PCL) is one of the common toughening methods for polylactic acid (PLA). However, it seems inevitable to experience a trade‐off in mechanical strength and thermal stability of PLA. Therefore, this study aimed to improve the mechanical and thermal properties of PLA/PCL blends by adding different contents of talc (0–10 wt%) and conducting annealing treatments. Interestingly, the maximum tensile strength (52.04 MPa), elongation at break (83.51%), and impact strength (6.05 kJ/m2) were achieved by incorporating 2.5 wt% talc into the blends without annealing. Meanwhile, the addition of just 1 wt% talc shortened the semi‐crystallization time of PLA to one‐third of the neat PLA at 100°C. Particularly, after annealing treatment, the crystallinity of PLA increased to 32.1%, and the Vicat softening temperature reached as high as 133.3°C with 2.5 wt% talc. Importantly, the increase in crystallinity did not compromise the toughness of PLA composites but significantly enhanced the impact strength to 8.91 kJ/m2. This study provides an updated understanding of the relationship between toughness and crystallinity in PLA composites.Highlights Thermo‐resistance of polylactic acid (PLA) composite increases to 133.3°C. Talc aids nucleation and promotes PLA crystallization. Increased crystallinity and high toughness are simultaneously realized. Adding 1 wt% talc reduced PLA semi‐crystallization time by one‐third. Crystal transformation and sea‐islands structure are vital for reinforcements.

Taguchi design and optimization of the PLA/PCL composite filament with plasticizer and compatibilizer additives for optimal 3D printing

Abstract3D printing (3DP) has brought endless possibilities to the manufacturing industry. Biodegradable high‐polymer materials such as polylactic acid (PLA) and polycaprolactone (PCL) have attracted widespread attention. However, to optimize printing performance, this study prepared six PLA/PCL composite materials with ratios of 4:6, 5:5, and 6:4, by adding Polyethylene Glycol 4000 (PEG 4000) as a plasticizer and nano silica as a reinforcing agent. Parameters that can affect printing quality, including formulation, printing temperature (150, 170, and 190°C), filling density (305, 40%, and 50%), and printing speed (20, 30, and 40 mm/s), were examined and optimized. The optimal factor level combination determined by Taguchi fractional factorial design were silica addition 0.6 g, PLA content 60 wt%, printing temperature 190°C, infill density 50%, and printing speed 20 mm/s. The obtained minimum error value was 0.338 mm. Analysis of variance revealed the statistical significance of PLA content and printing temperature. A general linear model was established for result prediction, showing a difference of 9.25% from the actual error values. SEM results indicated poor compatibility between PLA and PCL in the melt‐blended mixture, while the addition of SiO2 nanoparticles facilitated PCL and PLA crystallization. DSC analysis demonstrated that the incorporation of PLC and SiO2 led to an increase in crystallinity, with 5PLA/5PCL/SiO2 exhibiting the highest crystallinity at 51.4%. Tensile testing results showed that the addition of 50 wt% PCL to PLA significantly improved the fracture elongation of the PLA/PCL material with a 5:5 formulation, averaging about 4 times higher than that of pure PLA, while the tensile strength decreased by 1.5 times. This study not only expands the research on PLA/PCL blends but also provides process guidance for 3D printing of the materials.

The effects of cellulose nanocrystal and dicumyl peroxide on the crystallization kinetics of polylactic acid

AbstractCellulose nanocrystals (CNCs) have been blended into polylactic acid (PLA) to improve the polymer's properties. The dispersion of CNC in the matrix has a strong influence on the properties of the nanocomposites. In this study, PLA and CNC were compounded by a reactive extrusion process using dicarbonyl peroxide (DCP) as the free radical initiator. Isothermal and non‐isothermal crystallization kinetics of the resulting nanocomposites were investigated to understand the effect of PLA‐D‐CNC on the crystallization of the materials. Nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses confirmed the grafting of PLA onto CNC via reactive extrusion. The Avrami and Tobin model studies showed that the reactive extrusion product PLA‐D‐CNC exhibited much higher crystallization rates compared to neat PLA, PLA/CNC (without DCP), and PLA/DCP. The maximum crystallization rate temperature of PLA, PLA/CNC, and PLA/DCP was increased from ~100 to ~110°C for PLA‐D‐CNC. The results showed that CNC promoted PLA nucleation and crystallization at high temperatures under the action of DCP. Specifically, the maximum crystallization rate of PLA‐D‐CNC was 46 times higher than that of neat PLA. PLA‐D‐CNC showed a two‐stage crystallization process, while the other three samples exhibited mostly single‐stage processes. The much‐enhanced crystallization of PLA‐D‐CNC was ascribed to the improved interaction between PLA and PLA‐D‐CNC and the homogeneous dispersion of CNC.Highlights PLA chains were grafted onto CNC with the assistance of DCP free radicals. PLA‐grafted CNC facilitated heterogeneous nucleation of PLA. Crystallization studies confirmed improved PLA crystallization in the presence of PLA‐D‐CNC.

Preparation and Characterization of Bio-Based PLA/PEG/g-C3N4 Low-Temperature Composite Phase Change Energy Storage Materials.

As energy and environmental issues become more prominent, people must find sustainable, green development paths. Bio-based polymeric phase change energy storage materials provide solutions to cope with these problems. Therefore, in this paper, a fully degradable polyethylene glycol (PEG20000)/polylactic acid (PLA)/g-C3N4 composite phase change energy storage material (CPCM) was obtained by confinement. The CPCM was characterized by FTIR and SEM for compatibility, XRD and nanoindentation for mechanical properties and DSC, LFA, and TG for thermal properties. The results showed that the CPCM was physical co-mingling; when PLA: PEG: g-C3N4 was 6:3:1, the consistency was good. PEG destroys the crystallization of PLA and causes the hardness to decrease. When PLA: PEG: g-C3N4 was 6: 3: 1, it had a maximum hardness of 0.137 GPa. The CPCM had a high latent enthalpy, and endothermic and exothermic enthalpies of 106.1 kJ/kg and 80.05 kJ/kg for the PLA: PEG: g-C3N4 of 3: 6: 1. The CPCM showed an increased thermal conductivity compared to PLA, reaching 0.30 W/(m·K),0.32 W/(m·K) when PLA: PEG: g-C3N4 was 6: 3: 1 and when PLA: PEG: g-C3N4 was 3: 6: 1, respectively. Additionally, the CPCM was stable within 250 °C, indicating a wide appliable temperature range. The CPCM can be applied to solar thermal power generation, transportation, and building construction.

Morphology and Properties of Polylactic Acid Composites with Butenediol Vinyl Alcohol Copolymer Formed by Melt Blending.

Due to its poor toughness and hydrophilicity, the application of polylactic acid (PLA) in the field of absorbent sanitary materials is restricted. A butenediol vinyl alcohol copolymer (BVOH) was used to improve PLA via melt blending. The morphology, molecular structure, crystallization, thermal stability, tensile property, and hydrophilicity of PLA/BVOH composites with different mass ratios were investigated. The results show that the PLA/BVOH composites possessed a two-phase structure with good interfacial adhesion. The BVOH could effectively blend into PLA without a chemical reaction. The addition of the BVOH promoted the crystallization of PLA, improved the perfection of the crystalline region, and increased the glass transition temperature and melting temperature of PLA in the heating process. Moreover, the thermal stability of PLA was markedly improved by adding the BVOH. The addition of the BVOH also had a significant effect on the tensile property of the PLA/BVOH composites. When the content of the BVOH was 5 wt.%, the elongation at the break of the PLA/BVOH composites could reach 9.06% (increased by 76.3%). In addition, the hydrophilicity of PLA was also significantly improved, and the water contact angles decreased with the increase in the BVOH content and time. When the content of the BVOH was 10 wt.%, the water contact angle could reach 37.3° at 60 s, suggesting good hydrophilicity.

Effect of crystallinity on the migration of plastic additives from polylactic acid-based food contact plastics

The dependence of swelling and migration on polymer crystallinity was investigated in the case of polylactic acid (PLA)-based plastics. Migration and swelling kinetic experiments were performed at two different temperatures, using plasticized/non-plasticized and annealed/unannealed PLA test specimens. Both swelling and migration proved to be inhibited by the presence of polymer crystals. Crystallization induced clear differences in migration at 40 °C contact temperature, which got more pronounced with the increasing molecular weight (Mw) of additives. At 60 °C the differences diminished, except for Irgafos 168, possibly because of the formation of an inclusion complex type structure. Consequently, to lessen migration, the application of crystallized PLA and high Mw additives in food packaging industry is advantageous. The solvent-induced crystallization of PLA in ethanol 95 v/v% was also confirmed, therefore this alternative food simulant should be used with restrictions in the migration testing of PLA-based plastics.

Evaluation of the Effect of Castor Oil-Based Experimental Additives on Pla/Starch Foils

Biodegradable packaging materials are attracting more and more interest nowadays, the primary driving force of which is the generation of enormous amounts of plastic packaging waste. The aim of this study was to investigate the effect of two castor oil-based experimental additives on the properties of foils made from incompatible biodegradable polylactic acid (PLA) and native starch (10-50 wt%). Differential Scanning Calorimetry (DSC) measurements and tensile tests were used. It was found that increasing the starch content affected the crystallization of PLA in the blends. Furthermore, since the additives did not significantly change the glass transition temperatures, the additives did not affect the mobility of PLA chains. Regarding the tensile tests, the tensile strength of the 60:40 PLA:starch longitudinal sample could be increased by approximately 10 and 6 MPa at 25 and -25 °C, respectively, when additives were introduced.

High-Temperature Response Polylactic Acid Composites by Tuning Double-Percolated Structures.

Due to the properties of a positive temperature coefficient (PTC) effect and a negative temperature coefficient (NTC) effect, electrically conductive polymer composites (CPCs) have been widely used in polymer thermistors. A dual percolated conductive microstructure was prepared by introducing the polybutylene adipate terephthalate phase (PBAT) into graphene nanoplatelets (GNPs)-filled polylactic acid (PLA) composites, intending to develop a favorable and stable PTC material. To achieve this strategy, GNPs were selectively distributed in the PBAT phase by injection molding. In this study, we investigated the crystallization behavior, electrical conductivity, and temperature response of GNP-filled PLA/PBAT composites. The introduction of GNPs into PLA significantly increased PLA crystallization capacity, where the crystallization onset temperature (To) is raised from 116.7 °C to 134.7 °C, and the crystallization half-time (t1/2) decreases from 35.8 min to 27.3 min. The addition of 5 wt% PBAT increases the electrical conductivity of PLA/PBAT/GNPs composites by almost two orders of magnitude when compared to PLA/GNPs counterparts. The temperature of the heat treatment is also found to play a role in affecting the electrical conductivity of PLA-based composites. Increasing crystallinity is favorable for increasing electrical conductivity. PLA/PBAT/GNPs composites also show a significant positive temperature coefficient, which is reflected in the temperature-electrical resistance cycling tests.

Fully biodegradable PLA composite with improved mechanical properties via 3D printing

Poly (ε-caprolactone) (PCL) is often used as a toughening agent for polylactic acid (PLA) due to its good toughness and biodegradability, but they are immiscible polymer blends. Employing nanocellulose (TOBC) as the stabilizers, we prepare fully biodegradable PLA/PCL/TOBC ternary composites via Pickering emulsion approach here, which is further used for 3D printing. The printed composites are characterized by SEM, XRD, DSC and fluidity analysis. It is found that TOBC exhibits good dispersion in the composites and promotes PLA crystallization via heterogeneous nucleating, while PCL improves the fluidity of PLA chains and increases the toughness of the composites. The effect of PCL content on the mechanical property of the composites is further investigated and the optimal content of PCL is obtained. When PCL content is 10%, the tensile strength and elongation at break of the composites are increased by 17.4% and 208% in comparison with that of neat PLA, respectively.

Preparation of modified polylactic acid melt coated urea material and its green coating technique

The low utilization efficiency, residue of coating materials of slow-release fertilizers (SRFs) and use of organic solvents in the coating process a serious negative effect on the environment. In this study, a degradable polymer-coated fertilizer with good slow-release performance was prepared using a two-step melting process. First, Polylactic acid (PLA) was modified with isopropyl tris(dodecylbenzenesulfonyl) titanate (TDBSP), polycaprolactone (PCL) and acetyl tributyl citrate (ATBC) to prepare a slow-release coating material by melt blending. Second, a modified PLA slow-release fertilizer was prepared using the molten coating method. A small amount of TDBSP as a transesterification accelerator improved the low-temperature fluidity of PLA. The effect of TDBSP on the crystallization and branching behavior of PLA was explored by DSC, XRD, POM, and Rheology. SEM indicated that the coating on the surface of the urea pellets prepared by using 18 parts (phr) of the coating material per hundred parts of urea was intact. The soil column leaching experiment indicated that the controlled-release effect of the fertilizer melting coating was significant compared with that of pure urea. Furthermore, the SRF with 21 phr coating exhibited the best slow-release effect, with a nutrient release rate of 13.43 % after a day and a cumulative release rate of 81.08 % after 28 days. The melting method was used to coat urea, avoiding the solvent recovery of the currently used solution method for coating polymer films. Therefore, this is an environmentally friendly method for the preparation of slow-release urea. This study provides a novel concept for the preparation of biodegradable organic coating materials and method for solvent-free melt-coated fertilizers.

Facile dispersion strategy to prepare polylactic acid/reed straw nanofiber composites with enhanced mechanical and thermal properties

The challenge of dispersing nanocellulose in hydrophobic polymers such as polylactic acid (PLA) still obstacles the further application of cellulose nanocomposites. An environment-friendly and facile wet-shearing pretreatment strategy without using any organic solvent was developed in this work. Silane modified lignocellulose nanofiber (SLCNF) was pre-dispersed into PLA by wet-shearing pretreatment, followed by extrusion process and the SLCNF could be dispersed extremely well in PLA matrices. SLCNF formed a crosslinked network and had an improved compatibility, which improved the mechanical and thermal properties of PLA composites. The tensile strength, elongation at break and thermal deformation temperature of the composites were increased by 12.6 %, 32.4 % and 9.1 °C, respectively. Moreover, SLCNF promoted the crystallization of PLA as a heterogeneous nucleating agent and the crystallinity was increased by about 40 %. This study provides an effective way to disperse nanocellulose in polymer matrix with high efficiency to enhance polymer-based composites.

A Sustainable and Antimicrobial Food Packaging Film for Potential Application in Fresh Produce Packaging.

N-halamines are a group of compounds containing one or more nitrogen-halogen covalent bond(s). This high-energy halide bond provides a strong oxidative state so that it is able to inactivate microorganisms effectively. In this study, a sustainable film was developed based on polylactic acid (PLA) with incorporated N-halamine compound 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC), as a promising antimicrobial food packaging material. Results showed that the incorporation of MC prevented the crystallization of PLA and improved the physical properties of the films. In addition, both the moisture barrier and the oxygen permeability were improved with the presence of MC. Importantly, the antimicrobial film was able to inactivate inoculated microorganisms by a factor of seven log cycles in as little as 5 min of contact. Films that contained higher levels of MC further enhanced the antimicrobial efficacy. Fresh strawberries packed with the fabricated films maintained the quality for up to 5 days. Due to the ease of fabrication and the effective biocidal property, these films have a wide range of potential applications in the field of food packaging to extend the shelf life of fresh produce.

Thermal and mechanical properties of PLA-based multiscale cellulosic biocomposites

In this work polylactic acid (PLA) based multiscale cellulosic biocomposites were prepared with the aim to evaluate the effect of the incorporation of cellulose nanocrystals (CNCs) on the PLA biocomposites reinforced with cellulose microfibers (MFCs). For this, PLA composite materials reinforced with both MFCs and with a combination of MFCs and CNCs were prepared, while keeping the content of cellulosic reinforcements constant. The thermal and mechanical properties of these multiscale PLA biocomposites were characterized by thermogravimetry (TGA), differential scanning calorimetry (DSC), flexural mechanical and, dynamic mechanical (DMA) tests. Likewise, they were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the replacement of MFCs by CNCs in the 1–5% range appreciably modifies the thermal and mechanical properties of multiscale compounds. For example, they increase the thermal stability of the materials, modify the PLA crystallization process and play the role of adhesion promoters since the mechanical properties in flexure increase in the order of 40% and the storage modulus increases in the order of 35% at room temperature. Also, the addition of CNCs increases the relaxation temperature of the material from 50 to 60 °C, thereby expanding the temperature range for its use.

Preparation and characterization of compatibilized and toughened polylactic acid/cellulose acetate films by long‐chain hyperbranched polymers

AbstractA type of long‐chain hyperbranched polymers (LCHBPs) was prepared by grafting hydroxyl‐terminated flexible long chain onto hyperbranched polymers (HBPs). The structure of LCHBPs was confirmed by Fourier transform infrared (FT‐IR) and nuclear magnetic resonance (1H‐NMR) analysis. It was then used as the modifier for toughening and compatibilizing the polylactic acid (PLA)/cellulose acetate (CA) blends. Upon the addition of LCHBPs, the compatibility between PLA and CA was improved, the dispersion of CA particles in PLA matrix was more uniform, and the brittle‐ductile tear transition of the PLA/CA blends was occurred. The crystallization of PLA was promoted by the addition of LCHBPs. By adding LCHBPs, glass transition temperature and cold crystallization temperature were reduced, the crystallizability was enhanced, and the crystallization temperature range was expanded. The thermal decomposition temperature of the PLA/CA was found increased with the addition of LCHBPs. When the content of LCHBPs was 1 phr, the elongation at break and the tear strength of the PLA/CA blends were increased by 484% and 38.24%, respectively. Meanwhile, the thermal stability and hydrophilic properties of the blend films were improved by adding LCHBPs.