Reactive compatibilization of poly(l‐lactic acid)/poly(propylene carbonate) blends: Thermal,thermomechanical, and morphological properties

Poly(l ‐lactic acid) (PLLA) was blended with poly(propylene carbonate) (PPC) with various compositions by a melt‐blending process to evaluate their general properties for a potential flexible packaging field. The mechanical properties, including the tensile strength and modulus, revealed a tendency to decrease with the addition of ductile PPC; this was induced by the poor interfacial adhesion between PLLA and PPC with the cavities and clear edges and was observed through morphological observation. Reactive compatibilization was applied to improve the interfacial adhesion between PLLA and PPC, and the elongation at break was profoundly enhanced because of the improved interfacial adhesion between the two phases. The compatibilized PLLA/PPC blends showed considerable improvements in the storage modulus in the transition region with stable thermal stability; this could be a benefit for thermal processing. The addition of PPC had a great effect on the solidlike behavior and increased the elasticity of the PLLA/PPC blends. Up to 2.0 phr maleic anhydride showed a great efficiency in enhancing the dynamic storage modulus and complex viscosity of the PLLA/PPC blends. We also confirmed that it was feasible to fabricate PLLA/PPC blends with controllable barrier properties with combination of PLLA and PPC under reactive compatibilization while retaining the biodegradability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43388.     

Reactive compatibilization of high‐impact poly(lactic acid)/ethylene copolymer blends catalyzed by N,N‐dimethylstearylamine

The inherent brittleness of poly(lactic acid) (PLA) limits its wide application in many fields. Here, high‐impact PLA/ethylene–methyl acrylate–glycidyl methacrylate random terpolymer (EMA–GMA) blends were prepared with the addition of a small amount of N,N‐dimethylstearylamine (DMSA) catalyst. It was found that the notched impact resistance of various PLA/EMA–GMA blends could be considerably improved by adding DMSA. In particular, the notched Izod impact strength of the blend with 20 wt% EMA–GMA increased from 35.6 to 83.5 kJ m^?2 by adding 0.2 wt% DMSA. Reactive compatibilization between PLA and EMA–GMA with DMSA was studied using Fourier transform infrared spectroscopy. The results indicated that DMSA promoted the reaction between the epoxide group of EMA–GMA and end groups (–OH, –COOH) of PLA. This considerably improved the interfacial adhesion, leading to better wetting of the dispersed phase by the PLA matrix and finer dispersed EMA–GMA particles. Therefore, the significant increase in notched impact strength was attributed to the effective reactive compatibilization promoted by DMSA. © 2013 Society of Chemical Industry     

Synthesis of poly(tetrafluoroethylene)/poly(butadiene) core-shell particles and their graft copolymerization

This article describes how to convert the unreactive surface of poly(tetrafluoroethylene) (PTFE) into poly(styrene-co-acrylonitrile) (SAN). Composite particles with a crosslinked poly(butadiene) (PB) shell covered over a PTFE core were prepared by an emulsifier-free seeded emulsion polymerization of butadiene in the presence of PTFE latex. It was found that the increase in the PB crosslink density resulted in depressing the formation of PB secondary particles. Then, styrene and acrylonitrile were able to graft onto PB shell in high efficiency of 70%. SAN-modified PTFE/PB core-shell particles could eventually be dispersed homogeneously in a SAN matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:185–190, 1998     

Statistical design of sustainable composites from poly(lactic acid) and grape pomace

Biocomposites from poly(lactic acid) (PLA) and grape pomace (GP) were created via injection molding to examine the effects of GP in a PLA matrix. To optimize the mechanical performance the biocomposites were compatibilized with maleic anhydride grafted PLA (MA-g-PLA). The objective of this work was to create a model that could accurately predict the mechanical properties of GP/PLA biocomposites. A region of feasibility for the biocomposites was determined using a statistical design of experiments. Linear regression was used to model the mechanical performance and predicted results with an error of 10% for both tensile and flexural strength and 16% for impact strength. The model was verified with a biocomposite of PLA/GP/MA-g-PLA with a ratio of 62/36/2. This biocomposite had a tensile strength, flexural modulus, and impact strength of 25.8 MPa, 40.0 MPa, and 18.4 J/m, respectively. It was found that a linear model can accurately predict the mechanical properties of PLA/GP/MA-g-PLA biocomposites.     

Tailoring the morphology and properties of poly(lactic acid)/poly(ethylene)‐co‐(vinyl acetate)/starch blends via reactive compatibilization

Poly(lactic acid)/poly(ethylene‐co‐vinyl acetate)/starch (PLA/EVA/starch) ternary blends were prepared by multi‐step melt processing (reactive extrusion) in the presence of maleic anhydride (MA), benzoyl peroxide and glycerol. The effects of MA and glycerol concentration on the morphology and properties of the PLA/EVA/starch blends were studied using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, the Molau experiment, dynamic mechanical thermal analysis and differential scanning calorimetry etc. The plasticization and compatibilization provided a synergistic effect to these blends accompanied by a significant reduction in starch particle size and an increase in interfacial adhesion. Starch was finely dispersed in the ternary blends with a dimension of 0.5 ? 2 µm. Furthermore, EVA‐coated starch or a starch‐in‐EVA type of morphology was observed for the reactively compatibilized PLA/EVA/starch blends. The EVA with starch gradually changed into a co‐continuous phase with increasing MA concentration. Consequently, the toughness of the blends was improved. Since property stability of starch is an issue, the tensile properties of these blends were measured after different storage times and the blends showed good property stability. Copyright © 2012 Society of Chemical Industry     

茶粉/聚乳酸复合材料的增韧改性

为高值化利用茶产业剩余物资源,以茶粉（TD）为生物质填料,聚乳酸（PLA）为基体,以甘油（GL）、聚乙二醇400（PEG400）、环氧大豆油（ESO）和乙酰柠檬酸丁酯（ATBC）为增塑剂,制备了可降解TD/PLA增韧复合材料,并采用红外吸收光谱、热重分析、转矩流变仪、扫描电镜及力学性能测试等考察了增塑剂对TD/PLA复合材料结构与性能的影响。结果表明：4种增塑剂都可改善TD/PLA复合材料的加工流变性,GL的添加不利于复合材料韧性,PEG、ATBC及ESO的添加提高了复合材料韧性,其中ESO增韧效果最佳,其添加制备的复合材料断裂伸长率及缺口冲击强度分别提高了154.23%和65.53%,GL增韧效果最差,ATBC增韧后复合材料力学强度和模量最高。FTIR分析表明,ATBC和ESO可与PLA发生一定相互作用,使C-O键红外吸收峰位增大,其增韧后复合材料吸水率下降。ESO添加提高了TD/PLA复合材料的维卡软化点和热稳定性。SEM图片显示,TD/PLA/ESO复合材料断面粗糙,ESO分散较均匀,与PLA部分相容,而TD/PLA/GL复合材料断面出现严重相分离结构。该研究结果可为进一步探索聚乳酸基茶塑复合材料制备及应用提供试验数据和理论参考。     

Preparation of single poly(lactic acid) composites

An approach for making poly(lactic acid) (PLA) single‐polymer composites (SPCs) on the basis of PLA's slowly crystallizing characteristics was investigated. As a slowly crystallizing polymer, PLA can be processed with standard polymer processing techniques into end‐use products with varied crystallinities, from amorphous films to highly crystalline fibers. In this study, amorphous PLA sheets and crystalline PLA fibers/fabrics were laminated and compression‐molded to form an SPC at a processing temperature substantially lower than PLA's melting temperature. The effects of the major process conditions on the performance of the SPC were studied. The processing temperature played a profound role in affecting the fiber–matrix bonding properties. As the processing temperature increased, a drastic improvement in the interfacial bonding occurred at a temperature of around 135°C, which indicated the lower boundary of the process window. The compression‐molded SPC exhibited enhanced mechanical properties; particularly, the tearing strength of the fabric‐reinforced SPC was almost an order higher than that of the nonreinforced PLA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Compatibilization of the poly(lactic acid)/poly(propylene carbonate) blends through in situ formation of poly(lactic acid)‐b‐poly(propylene carbonate) copolymer

The in situ formation of poly(lactic acid)‐b‐poly(propylene carbonate) (PLA‐b‐PPC) block copolymers were carried out by the reaction between PLA and PPC in the presence of tetrabutyl titanate via transesterification. Molecular weight measurements and ¹³C nuclear magnetic resonance spectroscopy revealed that PLA‐b‐PPC block copolymers with higher molecular weight were obtained by controlling the reactivity point ratio between PLA chains and PPC chains in PLA/PPC reaction system. The sample with a composition of PLA:PPC = 40:60 (wt %) and a catalyst amount of 0.5 wt % had a more proportionable reactivity point ratio between PLA chains and PPC chains compared with other samples, resulting in a most conspicuous transesterification and inconspicuous chain scission reaction. Therefore, its high molecular weight fraction (M_w > 40.0 × 10⁴) increased 80%. The formation of macromolecular PLA‐b‐PPC copolymer could strengthen the entanglement between PLA and PPC molecular chains, which resulted in an increased viscosity of blends at low shear rate. In addition, the elongation at break of sample with a composition of PLA:PPC = 40:60 (wt %) and a catalyst amount of 0.5 wt % was nearly as twice as which without catalyst because of the improving miscibility of PLA domains and PPC matrix by the compatibilization of PLA‐b‐PPC copolymer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46009.     

Super‐toughened poly(l‐lactic acid) fabricated via reactive blending and interfacial compatibilization

Super‐toughened poly(l ‐lactic acid) (PLLA) was prepared by reactive blending of PLLA with poly(?‐caprolactone) (PCL), glycerol and 4,4′‐methylenediphenyl diisocyanate. The reactive interfacial compatibility between PLLA and the formed crosslinked polyurethane (CPU) in the PLLA matrix was studied in detail. The morphology and the toughness of the blends can be tuned by changing the CPU content. The results indicate that the impact strength of PLLA shows a tendency to higher values with the increasing PCL content up to 20 wt%. The notched impact strength of the blend with 20 wt% PCL increases to 55.01 kJ m^?2, which is 24.9 times higher than that of neat PLLA. The elongation at break is also increased from 5% to 139.4%, indicating the brittle ? ductile transition. The increased interfacial binding strength through the reactive interfacial compatibility and the formation of a CPU network in the PLLA matrix account for the improved toughness of PLLA/CPU blends. Dynamic mechanical analysis results indicate that the compatibility between PLLA and CPU is improved with increasing CPU content resulting in the formation of more interfacial phase. In addition, rheological property measurements indicate that the improvement in storage modulus and complex viscosity is ascribed to the formation of a CPU network in the PLLA matrix. © 2016 Society of Chemical Industry     

聚乳酸/聚乙烯醇纳米纤维的制备及结构

以二甲基亚砜为溶剂,制备不同配比的聚乳酸(PLLA)和聚乙烯醇(PVA)的混合溶液,静电纺丝制得PLLA/PVA纳米纤维。采用红外光谱仪、原子力显微镜等对PLLA/PVA纳米纤维结构与性能进行了表征。结果表明:PLLA/PVA纳米纤维中PVA上的羟基与PLLA上的羰基形成了氢键,PLLA与PVA之间存在一定的相互作用,但PLLA/PVA纳米纤维存在相分离现象;混合溶液的PLLA质量分数为11%,PVA质量分数为8%时可以得到较好的PLLA/PVA纳米纤维,但PVA质量分数为6%时出现液滴及珠丝,PVA质量分数为4%时,不能制得纳米纤维。     

Effect of different compatibilizers on environmentally friendly composites from poly(lactic acid) and diatomaceous earth

Environmentally friendly composites from poly(lactic acid) (PLA) and diatomaceous earth (DE) were successfully manufactured by extrusion, followed by injection moulding. DE was used as a filler; several compatibilizer/coupling agents, namely (3‐glycidyloxypropyl)trimethoxysilane, epoxy styrene acrylic oligomer and maleinized linseed oil, were used to improve polymer–filler interactions. Mechanical characterization was carried out by standard tensile, impact and hardness tests while morphological characterization of the fractured surfaces was conducted by field emission scanning electron microscopy. The effect of DE was evaluated by differential scanning calorimetry and dynamic mechanical thermal behaviour. The results show that the addition of DE provides an improved tensile modulus and induces more brittle composites due to stress concentration phenomena. The addition of compatibilizers in PLA‐DE positively contributes to improve ductile properties, thus leading to high environmental efficiency materials with balanced mechanical properties. Specifically, the compatibility improvement between the PLA and DE was good with maleinized linseed oil and contributed to improving the impact strength, which is a key factor in PLA‐based composites due to the intrinsic brittleness of neat PLA. © 2019 Society of Chemical Industry     

Super-tough poly(lactic acid) using a fully bio-based polyester containing malic acid via in-situ interfacial compatibilization

Reactive interfacial compatibilization is the most efficient way to prepare super-tough poly (lactic acid) (PLA) materials. Introducing a post-reactive group into a toughening agent that can react with PLA is the key issue. Herein, we reported a series of fully bio-based polyesters (PBSePM) synthesized with sebacic acid, diethyl malate, 1,3-propanediol, and 1,4-butanediol via transesterification in one pot. Super-tough PLA materials can be obtained by reactively blending with PBSePM in the presence of hexamethylene diisocyanate (HDI). In the processing, the side hydroxyl group of the PBSePM reacted with HDI and formed polyurethane elastomer to improve the toughness of PLA. Moreover, the in-situ formed PLA-g-PBSePM grafted copolymer enhanced the interfacial adhesion. With increasing diethyl malate moiety in PBSePM, the PBSePM phase morphology transformed from co-continuous phase structure to semi-continuous and “sea-island” phase structure. When adding 20 wt% PBSePM, all PLA/PBSePM blends have a notched impact strength higher than 53 kJ m⁻², suggested a super toughness effect. Maximum impact strength of 83 kJ m⁻² was realized while the PBSePM containing 20% diethyl malate moiety. In addition, super-tough PLA materials can be achieved by only adding 15 wt% PBSePM20, exhibited a highly efficient toughening effect.     

The synthesis of poly (lactic acid)-fulvic acid graft polymer and its effect on the crystallization and performance of poly (lactic acid)

ABSTRACT

The poly (lactic acid)-fulvic acid graft polymer (PLA-FA) was synthesized with lactic acid and fulvic acid (FA). The optimum parameters were determined by orthogonal experiment. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy exhibited that FA was successfully grafted onto PLA. Then, PLA/PLA-FA composites were prepared with PLA-FA as fillers by melt blending. The structure characterization and performance tests demonstrated that PLA-FA effectively enhanced the comprehensive performance of PLA composites. The rheological analysis demonstrated that PLA-FA had plasticization effect. The non-isothermal crystallization kinetics demonstrated that PLA-FA promoted the crystallization rate of PLA composites, improving toughness of PLA composites.     

Viscoelastic,thermo-mechanical and environmental properties of composites based on polypropylene/poly(lactic acid) blend and copper modified nanoclay

Poly(lactic acid) (PLA)/polypropylene (PP) blends composites were prepared by incorporating 3 wt.% of copper modified montmorillonite (MMT-Cu²⁺), obtained using cation exchange in a CuSO₄ solution, and 10 wt.% of polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer then varying the PLA content until 50 wt.%. These materials were subjected to several investigations such as X-rays diffraction, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile and environmental tests. The DMTA analysis showed that the glassy PLA high stiffness and the PP crystalline phase compensate the decrease in the storage modulus occurring during the PP and PLA glass transitions, respectively. The variations of tan δ revealed no changes on the PP and PLA phases glass transitions temperatures which indicate the immiscibility of the two polymers, as supported by DSC analysis. Blends composites SEM micrographs stated the immiscibility of the system resulting in the poor adhesion of the PLA droplets to the PP matrix. Also, the blends composites exhibited intermediate tensile properties between those of PP and PLA. The incorporation of MMT-Cu²⁺ to the (50/50) PP/PLA blend accentuated its aptitude to water absorption and ensured an efficient antimicrobial activity over a satisfactorily long period of around six months.     

Properties of mineral filled poly(lactic acid)/poly(methyl methacrylate) blend

This study examines the influence of three different minerals, that is, clay, calcium carbonate, and quartz on the physical, thermal, and mechanical properties of poly(lactic acid) (PLA)/poly(methyl methacrylate) blend. Rheological behavior and phase structure were initially studied by small-amplitude oscillatory shear rheology. Clay- and quartz-filled materials presented an increase in viscosity at low frequency associated with the presence of a yield stress. However, this behavior was not observed for calcium carbonate filled materials due to a matrix degradation effect. To elucidate this aspect, thermal stability and thermal properties were examined by thermogravimetric analysis and differential scanning calorimetry, showing that calcium carbonate promotes degradation of the PLA phase. No nucleating effect was observed in the presence of the minerals. Dynamical mechanical analysis and mechanical characterization revealed an increase of the overall softening temperature and, a reinforcing effect for clay- and quartz-based composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46927.     

Utilization of linseed cake as a postagricultural functional filler for poly(lactic acid) green composites

Linseed cake (LC), a byproduct of linseed oil extraction, is used as a functional filler for production of biodegradable composites. To determine the influence of residual linseed crude oil contained in lignocellulosic filler on the properties of the poly(lactic acid) (PLA)-based composites with 5–30% filler content, two types of LC were analyzed: a defatted and an unmodified one. Complex analysis of the composites' properties change was conducted in relation to their structure modification caused by the addition of a waste filler. It was found that the addition of LC resulted in simultaneous plasticization and improved crystallization of PLA. Lignocellulosic particles and crude linseed oil contained in the LC powder provided a modifying effect, influencing the level of crystallinity and mechanical and thermomechanical properties. Using LC may thus overcome one of the main drawbacks of PLA, which is brittleness and low crystallinity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47152.     

Design and preparation of poly(aryl ether ketone)/phosphotungstic acid hybrid films with low dielectric constant

A material with low dielectric constant was produced using nanoparticle phosphotungstic acid (PWA) modified by the silane coupling agent γ‐aminopropyltriethoxysilane (KH‐550) dispersed in a poly(aryl ether ketone) containing (3‐trifluoromethyl) phenyl side groups (FPEEK) matrix synthesized with (3‐trifluoromethyl) phenyl hydroquinone (3FHQ) and 4,4′‐difluorobenzophenone. The material was fabricated using solution‐blending. Moreover, the dielectric, thermal, and mechanical properties of this material were characterized using a precision impedance analyzer, thermal gravimetric analyzer, and universal tester, respectively. The results indicate that modified PWA (m‐PWA)/FPEEK composites show obvious improvement in the dielectric properties compared to unmodified PWA (p‐PWA)/FPEEK composites. This should be attributed to the good dispersion and compatibility of m‐PWA in FPEEK, as proven by scanning electron microscope and wide‐angle X‐ray diffraction. Besides, m‐PWA/FPEEK composites also exhibited the relatively good thermal and mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Online monitoring of reactive compatiblization of poly(lactic acid)/polyamide 6 blend with different compatibilizers

Improvement of poly(lactic acid)/polyamide 6 (PLA/PA6) miscibility is approached by reactive compatibilization with using different reactive agents. Specifically, compatibilizing efficiency of commercially available Joncryl ADR-4368 (Joncryl) and free-radical initiator 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (L101) is compared to that of laboratory synthesized compatibilizers (poly(lactic acid) grafted with itaconic anhydride (PLA-g-IAH) and poly(itaconic anhydride) (PIAH) by online rheology monitoring in internal mixer and oscillatory rheometer. The change of morphology and particle-size distribution is evaluated by scanning electron microscopy (SEM), the extent of PLA-PA6 miscibility is determined by differential scanning calorimetry (DSC), and newly formed polymer phases are identified by high-resolution thermogravimetric analysis (HR-TGA) and solvent extraction in formic acid. Although Joncryl exhibits the most promising results in PLA-PA6 compatibility, other compatibilizers also exhibit specific benefits for PLA/PA6 blend or individual polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48005.     

Morphology and thermal properties of poly(L‐lactic acid)/organoclay nanocomposites

A modified clay was used to prepare poly(L ‐lactic acid)/clay nanocomposite dispersions. X‐ray diffraction and transmission electron microscopy experiments revealed that poly(L ‐lactic acid) was able to intercalate the clay galleries. IR spectra of the poly(L ‐lactic acid)/clay nanocomposites showed the presence of interactions between the exfoliated clay platelets and the poly(L ‐lactic acid). Thermogravimetric analysis and differential scanning calorimetry were performed to study the thermal behavior of the prepared composites. The properties of the poly(L ‐lactic acid)/clay nanocomposites were also examined as functions of the organoclay content. The exfoliated organoclay layers acted as nucleating agents, and as the organoclay content increased, the crystallization temperature increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Study on flax fiber toughened poly (lactic acid) composites

Poly (lactic acid) (PLA) is a renewable and biodegradable polymer with high modulus, high strength but low toughness. Blending PLA with plant fiber has been believed an available strategy to improve the toughness of PLA. PLA/Flax composites were fabricated by extrusion and injection molding processes. The flax fiber surfaces were modified before blending to improve the compatibility, and the chemical structures of both untreated and treated fiber were characterized by Fourier transform infrared spectroscopy. Results of mechanical test showed that the impact strength and elongation at break of PLA/Flax composites were remarkably higher than PLA. The impact fractures of PLA/Flax composites were also observed by scanning electron microscope. The results showed uniform dispersion of fibers in PLA matrix and good compatibility between treated fibers and PLA matrix. Moreover, it can be observed that crazing propagation was hindered by fibers and transcrystalline developed along fibers by polarized optical microscope. Differential scanning calorimetry analysis was carried out to study the crystallinity of PLA and it was found that incorporation of fiber improved the crystallinity of PLA. The toughening mechanism of PLA/Flax composites was discussed according to the results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42573.