Reactable versus soluble DOPO derivatives in poly(lactic acid)/poly(butylene adipate-co-terephthalate) composites: Flame retardance,mechanical properties and morphology

Flame retardant poly(lactic acid)/poly(butylene adipate-co- terephthalate) (PLA/PBAT) composites containing 9,10-dihydro-9-oxa-10- phosphaphenanthrene-10-oxide (DOPO) derivatives (phosphorus-containing diol compound of DOPO-HQ, and bis DOPO phosphonates of DIDOPO) were systematically and comparatively investigated. Results showed that the different structures of the two derivatives with reactable or soluble characteristics display different effects. DIDOPO endows a higher limiting oxygen index and a better UL-94 rating for PLA/PBAT composites compared with DOPO-HQ. Compared with that of PLA/PBAT, the peak heat release rate of PLA/PBAT/DIDOPO-12.5 is 8.4% lower and that of PLA/PBAT/DOPO-HQ-12.5 is 30.6% lower. The flame retardant mechanism of the main gaseous and minor condensed phases is evident for the flame retardant PLA/PBAT composites. In comparison, DIDOPO displays a greater flame inhibition effect, and DOPO-HQ shows better barrier and protective functions in PLA/PBAT composites. Besides, the elongation at break of the composites with DOPO-HQ is slightly superior to that of PLA/PBAT/DIDOPO. After the introduction of flame retardant, the blends show dispersed particles with size reduction relative to those of PLA/PBAT. This work provides a guidance to design PLA composites with simultaneously improved flame retardancy and toughness.     

Morphological and rheological characterization of multi-walled carbon nanotube/PLA/PBAT blend nanocomposites

Biodegradable poly (lactic acid) (PLA)/poly (butyleneadipate-co-butyleneterephthalate) (PBAT)/multi-walled carbon nanotube (MWNT) polymer blend nanocomposites were prepared by using a laboratory-scale twin-screw extruder. Fractured surface morphology of the polymer blend/MWNT nanocomposites were examined via SEM. Furthermore, cross sectioned samples obtained using an ultramicrotome was observed via TEM. In addition, effects of both MWNT reinforcement and phase affinity of MWNT on thermal and rheological properties of the PLA/PBAT blends were investigated by TGA and rotational rheometer. Immiscible PLA/PBAT blend with MWNT nanocomposites showed two-step thermal degradation. The onset temperature of thermal degradation started in the PLA much earlier than in the PBAT. Nonetheless, based on TGA data, it was found that the MWNT enhanced thermal property of the PLA/PBAT blend/MWNT nanocomposites. Rheological properties revealed that both shear and complex viscosities showed unique shear thinning behavior due to selectively localized MWNT dispersion state.     

PLA/PBAT共混物的降解性能研究

通过双螺杆挤出机和吹膜机组制备不同比例的聚乳酸/聚对苯二甲酸己二酸丁二酯（PLA/PBAT）共混物薄膜,测量共混物的热性能、力学性能,并观察其相形貌,计算共混物在堆肥条件下的生物降解率,研究共混物降解前后的结构、热力学行为和元素的变化。结果表明,PLA与PBAT是不相容体系,加入PBAT后PLA的韧性得到改善;PLA的生物降解率高于PBAT,共混物的生物降解率随着PBAT含量的增加而降低,且在降解初期,PLA的降解产物会促进PBAT的水解;PLA、PBAT及其共混物在堆肥降解前期只是大分子链水解为小分子链的过程,不发生分子链的结构变化;PLA及PBAT的降解会先发生在无定形区,共混物中PLA在无定形区的降解速度受到PBAT的影响而变慢,且共混物中PLA、PBAT的降解行为发生变化,无定形区与结晶区的降解同时发生;共混物在堆肥试验初期的降解以水解为主。     

Mechanical properties and morphological changes of poly(lactic acid)/polycarbonate/poly(butylene adipate‐co‐terephthalate) blend through reactive processing

The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate‐co‐terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin‐screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05–1 μm for RP, whereas it was approximately 10 μm without RP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The Potential Use of Epoxy-POSS as a Reactive Hybrid Compatibilizers for PLA/PBAT Blends: “Effect of PBAT Molecular Weight and POSS Type”

This article focuses on the effect of molecular weight of poly(butylene adipate-co-terephthalate) (PBAT) on the immiscible poly(lactic acid) (PLA)/PBAT blends compatibilized with epoxidized polyhedral oligomeric silsesquioxanes (Epoxy-POSSs) having different numbers of epoxy groups per molecule. Mechanical, thermomechanical, thermal, rheological, and morphological properties of the blends were investigated as a function of PBAT molecular weight and epoxy-POSS type. Mechanical tests revealed that all epoxy-POSS types significantly improved the performance of the blends containing low-molecular-weight PBAT. On the other hand, epoxy-POSS with three epoxy functional groups (TriEpPOSS) and Epoxy-POSS with multiple-epoxy functional groups (MuEpPOSS) only slightly improved the performance of blends with high-molecular-weight PBAT. Thermomechanical and thermal test results supported that the compatibilization effects of the epoxy-POSSs were more prominent in the PLA/PBAT blends with low-molecular-weight PBAT due to the observation of the shifts in the glass transition temperatures of the PLA phase. According to the rheological results, the addition of epoxy-POSSs increased the interactions between the PLA and PBAT phases much more effectively in the PLA/PBAT with low-molecular-weight PBAT. The dispersed phase size of the PBAT further decreased in the low-molecular-weight PLA/PBAT blend system due to the enhanced compatibility much better. POLYM. ENG. SCI., 60: 398–413, 2019. © 2019 Society of Plastics Engineers     

Binary and ternary blends of polylactide, polycaprolactone and thermoplastic starch

In this study binary and ternary blends of polylactide (PLA), polycaprolactone (PCL) and thermoplastic starch (TPS) are prepared using a one-step extrusion process and the morphology, rheology and physical properties are examined. The morphology and quantitative image analysis of the 50/50 PLA/TPS blend transverse phase size demonstrate a bimodal distribution and the addition of PCL to form a ternary blend results in a substantial number of fine dispersed particles present in the system. Focused ion beam irradiation, followed by atomic force microscopy (AFM) shows that dispersed PCL forms particles with a size of 370 nm in PLA. The TPS phase in the ternary blends shows some low level coalescence after a subsequent shaping operation. Dynamic mechanical analysis indicates that the temperature of the tan δ peak for the PLA is independent of TPS blend composition and that the addition of PCL in the ternary blend has little influence on the blend transitions. Both the α and β transitions for the thermoplastic starch are highly sensitive to glycerol content. When TPS of high glycerol content is blended with PLA, an increase in the ductility of the samples is achieved and this effect increases with increasing volume fraction of TPS. The ternary blend results in an even greater ductility with an elongation at break of 55% as compared to 5% for the pure PLA. A substantial increase in the notched Izod impact energy is also observed with some blends demonstrating three times the impact energy of pure PLA. The mechanical properties for the ternary blend clearly indicate a synergistic effect that exceeds the results obtained for any of the binary pairs. Overall, the ternary blend approach with PLA/TPS/PCL is an interesting technique to expand the property range of PLA materials.     

改性凹凸棒土对PBAT阻燃性能的影响

用费托蜡（FTW）对凹凸棒土（ATP）进行表面改性制备了阻燃剂F-ATP，并对其形貌、结构及其热稳定性进行了表征。将阻燃剂F-ATP加入到聚己二酸/对苯二甲酸丁二醇酯（PBAT）基体中制备了PBAT/F-ATP复合材料。采用极限氧指数测定仪（LOI）、垂直燃烧测试（UL-94）、锥形量热仪（CCT）、TG-IR、拉曼光谱仪和SEM对复合材料的阻燃性能进行了分析。结果表明，改性后的ATP团聚现象消失且热稳定性明显提高。阻燃剂F-ATP质量分数为10%的PBAT/F-ATP复合材料（PBAT-3）阻燃效果最佳，其LOI值达到23.5%,UL-94等级达到V-1级，熔滴现象得到明显改善。与ATP质量分数为10%的PBAT/ATP复合材料相比，PBAT-3复合材料的峰值热释放速率值（PHRR）、总热释放量（THR）分别降低了4.99%和26.11%。PBAT-3复合材料气态产物的释放量在整个燃烧过程中均降低，起到了很好的气相阻燃效果，这主要归因于阻燃剂F-ATP的加入使PBAT/F-ATP复合材料形成致密且连续性好的炭层结构，有效地隔绝了复合材料内部与外界的热量/质量传递。     

Thermal degradation behavior and gas phase flame‐retardant mechanism of polylactide/PCPP blends

The thermal degradation behavior of the blend based on polylactide (PLA) and poly(1,2‐propanediol 2‐carboxyethyl phenyl phosphinate) (PCPP) was investigated by the thermogravimetric analysis (TGA). Thermal degradation activation energies (E_a) of neat PLA and PLA/15% PCPP blend were calculated via the Flynn–Wall–Ozawa method. The E_a of the blends increased with the addition of PCPP increasing when the conversion was higher than 10%. In addition, the appropriate conversion models for the thermal degradation process of PLA and PLA/15% PCPP were studied via the Criado method. At the same time, the main gaseous decomposition products of PLA and its blend were identified by TGA/infrared spectrometry (TGA–FTIR) analysis. And it revealed that the PCPP improved the flame‐retardant property of PLA via altering the release of the flammable gas and nonflammable gas. Moreover, the PCPP improved the flame‐retardant property of PLA by inhibiting exothermic oxidation reactions in the combustion, which was further proved by pyrolysis–gas chromatography–mass spectrometry analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40480.     

The Mechanical,Thermal, Rheological and Morphological Properties of PLA/PBAT Blown Films by Using Bis(tert‐butyl dioxy isopropyl) Benzene as Crosslinking Agent

Blown films of poly(lactic acid) (PLA)/poly(butylene adipate‐co‐terephthalate) (PBAT) blends were prepared, bis(tert‐butyl dioxy isopropyl) benzene (BIBP) as crosslinking agent. From wide‐angle X‐ray diffraction results, PLA/PBAT/BIBP involved all the diffraction peaks were consistent with PLA and PBAT. For the DSC curves of PLA/PBAT/BIBP films, there were two glass transition temperature and two melt temperature, there existed two step decomposition in the thermogravimetric curves. Both Han plots and Cole–Cole plots indicated high homogeneity of the 40/60/0.1 PLA/PBAT/BIBP blend. SEM micrographs of the films revealed more ductile deformation with increasing PBAT content and 40/60/0.1 sample had better miscible compared with others. For the PLA/PBAT/BIBP films, tensile tests indicated that the elongation at break were increased with increasing PBAT content and the values of the tensile strength in the machine direction were higher than those in the transverse direction. The addition of PBAT, enhanced the toughness of the PLA/PBAT/BIBP films. From tear test and heat sealing test, the 40/60/0.1 PLA/PBAT/BIBP film exhibited the highest tear strength and the highest sealing strength among all the samples. POLYM. ENG. SCI., 59:E227–E236, 2019. © 2018 Society of Plastics Engineers     

Rheological and mechanical behavior of non-spherical poly(lactic acid) particles embedded poly(butylene adipate-co-terephthalate) blend

In this study, the poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate)(PBAT) blend is investigated to improve rheological and mechanical performances of PBAT based on rheological, mechanical, and thermal behavior analyses. The multi-step mixing method is developed to fabricate the blend with non-spherical morphology. In the multi-step mixing method, blends with a wide composition range (25/75–75/25) are mixed with additional PBAT at a mixing temperature between the melting temperatures of PBAT and PLA to produce the PBAT blend embedded with non-spherical PLA particles (10 wt%). The embedding of non-spherical PLA particles in PBAT increases the resistance against deformation, resulting in strain hardening behavior and an increase in the yield strength as well as the tear resistance of the PBAT. The presence of stiff PLA particles enhances the crystallization behavior of PBAT, meaning that polymer chains may interpenetrate. The findings of this study suggest that the multi-step mixing method is beneficial for embedding non-spherical PLA particles into a PBAT matrix, which in turn facilitates the maintenance of good interfacial adhesion to increase the melt strength, yield strength, and tear resistance.     

聚乳酸/聚己二酸对苯二甲酸丁二酯合共混体系发泡行为研究

采用多环氧基团增容剂制备了聚乳酸/聚己二酸对苯二甲酸丁二酯(PLA/PBAT)共混物,研究了增容剂含量对于PLA/PBAT共混体系的结晶和流变性能的影响。并采用高压釜发泡的方法进行PLA/PBAT共混物的间歇发泡,研究增容剂对发泡材料泡体结构的影响。结果表明,增容剂加入后会降低其绝对结晶度,以及显著改善PLA/PBAT共混体系的熔体弹性,提高其可发性;增容剂可以有效地改善共混体系的泡体结构,降低共混物发泡密度,提高其发泡倍率。     

High performance materials based on a self‐assembled multiple‐percolated ternary blend

In this study, it will be shown that morphologically tailored tricontinuous ternary blends, comprising polybutylene succinate (PBS), polylactic acid (PLA), and poly (butylene adipate‐co‐terephthalate)(PBAT), can generate new materials with excellent properties. Detailed morphological analysis is used to establish that all three phases in the ternary 33%PBS/33%PLA/33%PBAT blend morphology are highly continuous with a phase structure dominated by complete wetting dynamics. PBS is shown to situate itself between PLA and PBAT. This melt processed, self‐assembled, multiple percolated, blend possesses a high elongation at break (567%), high Young's modulus (1130 MPa), high impact strength (271 J/m), and a storage modulus about 50% higher than pure PBS at room temperature. None of the neat materials demonstrate this combination of high properties and the synergy derives from the tricontinuous structure of the system. The ternary nature of the blend allows for a modulation of the crystallinity behavior as examined by differential scanning calorimeter and X‐ray Diffraction. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3005–3012, 2014     

扩链剂增容PLA/PBAT共混物流变性能

通过熔融共混法制备了Joncryl ADR 4370F扩链剂增容聚乳酸/聚对苯二甲酸/己二酸丁二酯(PLA/PBAT)共混物,采用旋转流变仪分别研究了扩链剂和PBAT含量对PLA/PBAT共混物动态流变行为的影响.通过动态应变扫描确定了PLA/PBAT共混物的线性黏弹区,应变选取1％;PLA/PBAT共混物的储能模量和...     

β-cyclodextrin as a Partial Replacement of Phosphorus Flame Retardant for Poly(Lactic Acid)/Poly(Methyl Methacrylate): A More Environmental Friendly Flame-Retarded Blends

β-Cyclodextrin was used together with isopropylated triaryl phosphate ester flame retardant to improve the flame resistance of poly(lactic acid)/poly(methyl methacrylate). Poly(lactic acid)/poly(methyl methacrylate)/flame-retardant blend (with and without β-cyclodextrin) was evaluated using limiting oxygen index, Underwriters Laboratories-94 vertical burning test, scanning electron microscopy, and thermogravimetric analysis (in O₂ and N₂). The addition of β-cyclodextrin was able to reduce the amount of flame retardant required for poly(lactic acid)/poly(methyl methacrylate) blends to achieve self-extinguishing properties. The poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends achieved Underwriters Laboratories-94, V-0, and limiting oxygen index value of 29.3%. A compact and wide coverage of char layer was formed on the burning surface of poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends.     

Novel ternary blends of natural rubber/linear low-density polyethylene/thermoplastic starch: influence of epoxide level of epoxidized natural rubber on blend properties

Novel degradable materials based on ternary blends of natural rubber (NR)/linear low-density polyethylene (LLDPE)/thermoplastic starch (TPS) were prepared via simple blending technique using three different types of natural rubber (i.e., unmodified natural rubber (RSS#3) and ENR with 25 and 50 mol% epoxide). The evolution of co-continuous phase morphology was first clarified for 50/50: NR/LLDPE blend. Then, 10 wt% of TPS was added to form 50/40/10: NR/LLDPE/TPS ternary blend, where TPS was the particulate dispersed phase in the NR/LLDPE matrix. The smallest TPS particles were observed in the ENR-50/LLDPE blend. This might be attributed to the chemical interactions of polar functional groups in ENR and TPS that enhanced their interfacial adhesion. We found that ternary blend of ENR-50/LLDPE/TPS exhibited higher 100 % modulus, tensile strength, hardness, storage modulus, complex viscosity and thermal properties compared with those of ENR-25/LLDPE/TPS and RSS#3/LLDPE/TPS ternary blends. Furthermore, lower melting temperature (T _m) and heat of crystallization of LLDPE (?H) were observed in ternary blend of ENR-50/LLDPE/TPS compared to the other ternary blends. Also, neat TPS exhibited the fastest biodegradation by weight loss during burial in soil for 2 or 6 months, while the ternary blends of NR/LLDPE/TPS exhibited higher weight loss compared to the neat NR and LLDPE. The lower weight loss of the ternary blends with ENR was likely due to the stronger chemical interfacial interactions. This proved that the blend with ENR had lower biodegradability than the blend with unmodified NR.     

PBAT/PLA薄膜的制备及性能研究

将聚乳酸（PLA）和聚对苯二甲酸-己二酸-丁二醇酯（PBAT）共混制备成共混材料,探讨了不同PLA含量对材料性能的影响。结果表明,PBAT/PLA共混材料中,随着PLA含量的增加,拉伸强度先降低后升高,当PLA含量为90 %时,拉伸强度达到60.12 MPa,而其断裂伸长率从703 %降低至8 %,由韧性材料逐渐转变为脆性材料;PLA含量为30 %时,性能变化出现拐点;PLA含量为50 %时出现明显相分离,且PLA的加入可以加速PBAT材料的结晶,使结晶温度由38 ℃提高至82 ℃;PBAT/PLA共混材料在PLA含量低于70 %时,都可以实现较好的吹膜过程,且薄膜材料的拉伸强度为39.59 MPa,断裂伸长率不低于137 %。     

Compatibility improvement of poly(lactic acid)/thermoplastic starch blown films using acetylated starch

The present research aims to improve the compatibility between relatively hydrophobic poly(lactic acid) (PLA) and hydrophilic thermoplastic starch (TPS) and the properties of the PLA/TPS blends by replacing TPS from native cassava starch (TPSN) with TPS from acetylated starch (TPSA). The effects of the degree of acetylation (DA) of acetylated starch, that is, 0.021, 0.031, and 0.074, on the morphological characteristics and properties of PLA/TPS blend are investigated. The melt blends of PLA and TPS with a weight proportion of PLA:TPS of 50:50 are fabricated and then blown into films. Scanning electron microscopy confirms the dispersion of TPS phase in the PLA matrix. Better dispersion and smaller size of the TPS phase are observed for the PLA/TPSA blend films with low DA of acetylated starch, resulting in improved tensile and barrier properties and increased storage modulus, thermal stability, and T_g, T_cc, and T_m of PLA. Elongation at break of the PLA/TPSA blend increases up to 57%, whereas its water vapor permeability and oxygen permeability decrease about 15%. The obtained PLA/TPSA blend films have the potential to be applied as biodegradable flexible packaging.     

A novel bio-based charcoal-forming agent based on chitosan and phytate@Mg to improve the flame retardancy of poly(lactic acid)

A novel bio-based carbon forming agent (Mg@PA-CS) containing P and N elements was were synthesized using the complexation characteristics of chitosan (CS) and phytate (PA). The flame retardant behavior of poly(lactic acid) (PLA)/Mg@PA-CS/APP composites (addition of 20 wt% of different ratios of Mg@PA-CS and APP to polylactic acid composites) were investigated by the limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetry test (CCT), and thermogravimetric analysis (TGA). Due to the biphasic flame retardant and synergistic effect, since the 20 wt% flame retardant system (Mg@PA-CS:APP = 1:2), PLA composites passed the UL-94 test V-0 rating, reached 34% LOI value. The peak heat release rate (PHRR) and total heat release rate (THR) were reduced to 1/2 of the pure PLA, char residue could be as high as 11.49% at 800°C. Moreover, the flame-retardant mechanism of PLA composites during thermal decomposition was analyzed using a scanning electron microscope (SEM) and the coupling techniques of TGA linked with FT-IR (TG-FTIR).     

Three in one: β‐cyclodextrin,nanohydroxyapatite, and a nitrogen‐rich polymer integrated into a new flame retardant for poly (lactic acid)

A new halogen‐free flame retardant was developed by integrating β‐cyclodextrin, triazin ring, and nanohydroxyapatite (BSDH) into a hybrid system. A β‐cyclodextrin was grafted to a commercially available SABO®STAB UV94 via an aromatic deanhydrate. The BSDH was prepared in situ in the presence of β‐cyclodextrin‐grafted nitrogen‐rich precursor. The resulting hybrid was applied as a flame retardant for poly(lactic acid) (PLA) and compared for performance with ammonium polyphosphate (APP). PLA composites containing BSDH and APP, individually or simultaneously, were examined for thermal degradation and flammability by TGA, cone calorimeter, and pyrolysis‐combustion flow calorimetry. TGA results confirmed enhancement of thermal stability of PLA with assistance of BSDH compared to APP. The gases evolved during thermal degradation were assessed by a thermogravimetric analysis and Fourier infrared spectroscopy device. APP revealed catalytic effect to initiate PLA degradation, while BSDH continued to release some gases at elevated temperatures. The flame retardancy of PLA/APP/BSDH blend containing only 10 wt.% of additives was significantly improved. In cone calorimetric tests, a significant fall in peak of heat release rate was observed for this sample, 49% more than that of neat PLA, which was indicative of more gas and condensed phase reflected in more char residue. The corresponding PLA/APP sample, however, showed 17% improvement, as compared to neat PLA. Also, total heat release rate of PLA/APP/BSDH was 45 MJ.m^?2, whereas those of PLA and PLA/APP were 89 and 65 MJ.m^?2, respectively. BSDH and APP showed a synergistic effect on improving the flame retardancy of PLA composites.     

磷化瓜尔胶与APP协同阻燃PLA的性能研究

采用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物（DOPO）和1,2,3,6-四氢邻苯二甲酸酐（THPA）对瓜尔胶（GG）进行改性得到磷化瓜尔胶（DTGG）,并通过核磁共振和傅里叶变换红外光谱对其结构进行表征。以DTGG为碳源,聚磷酸铵（APP）为酸源和气源对聚乳酸（PLA）进行阻燃改性。通过垂直燃烧（UL 94）、极限氧指数（LOI）和锥形量热仪（CONE）对PLA共混物的阻燃性能进行测试。采用热失重分析（TG）和场发射扫描电子显微镜（FESEM）对其热性能和形貌进行表征。结果表明,当DTGG/APP的质量比为9/11时,LOI值为33.4%,达到UL 94 V-0等级。同时,样品的总热释放（THR）值最低,与纯PLA相比降低了33.8%。从FESEM观察到阻燃剂在PLA基质中分布均匀。DTGG和APP的协同作用有效地增强了PLA共混物的阻燃性能。最后讨论了DTGG和APP对PLA共混物的协同阻燃作用机制。