PLA在受控堆肥条件下的生物降解行为研究

依据ISO 14855的检测方法,研究了聚乳酸(PLA)在受控堆肥条件下的生物降解性能,结果表明:PLA具有良好的生物降解性。在培养土提取液中,以蛋白酶K对PLA膜进行降解,显微镜观察发现,PLA膜表面逐渐被蛋白酶侵蚀;红外光谱研究表明,PLA膜在降解前后的分子结构没有发生很大变化。     

Biodegradation of Poly(butylene succinate) Powder in a Controlled Compost at 58 ��C Evaluated by Naturally-Occurring Carbon 14 Amounts in Evolved CO2 Based on the ISO 14855-2 Method

The biodegradabilities of poly(butylene succinate) (PBS) powders in a controlled compost at 58 °C have been studied using a Microbial Oxidative Degradation Analyzer (MODA) based on the ISO 14855-2 method, entitled “Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions—Method by analysis of evolved carbon dioxide—Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test”. The evolved CO₂ was trapped by an additional aqueous Ba(OH)₂ solution. The trapped BaCO₃ was transformed into graphite via a serial vaporization and reduction reaction using a gas-tight tube and vacuum manifold system. This graphite was analyzed by accelerated mass spectrometry (AMS) to determine the percent modern carbon [pMC (sample)] based on the ¹⁴C radiocarbon concentration. By using the theory that pMC (sample) was the sum of the pMC (compost) (109.87%) and pMC (PBS) (0%) as the respective ratio in the determined period, the CO₂ (respiration) was calculated from only one reaction vessel. It was found that the biodegradabilities determined by the CO₂ amount from PBS in the sample vessel were about 30% lower than those based on the ISO method. These differences between the ISO and AMS methods are caused by the fact that part of the carbons from PBS are changed into metabolites by the microorganisms in the compost, and not changed into CO₂.     

An automated multi‐unit composting facility for biodegradability evaluations

A system has been developed for studying the biodegradation of natural and synthetic polymeric material. The system is based on standard methods developed by the European Committee for Standardisation (CEN TC 261) (ISO/DIS 14855) and the American Society of Testing Materials, ‘ASTM Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials under Controlled Composting Conditions’ (ASTM D 5338‐92). A new low‐cost compost facility has been used which satisfies the requirements of these standards. The system has been automated for data collection and has been run under the conditions specified by the standards. In the system, cellulose, newspaper and two starch‐based polymers were treated with compost in a series of 3 dm³ vessels at 52 °C and under conditions of optimum moisture and pH. The degradation was followed over time by measuring the amount of carbon released as carbon dioxide. © 2001 Society of Chemical Industry     

Biodegradability assessment of aliphatic polyesters‐based blends using standard methods

Important information concerning polymer's final fate in the environment can be achieved in biodegradation studies. In this context, the focus of this study was to evaluate the biodegradability of blends containing aliphatic polyesters using standard methods. Blends of high‐density polyethylene, biodegradable polymer, and polyethylene modified with maleic anhydride (used as compatibilizer) were prepared in a corotating twin‐screw extruder. Biodegradable polymers used were poly(lactic acid) (PLA), poly(ε‐caprolactone) (PCL), and Mater‐Bi (thermoplastic starch with PLA or PCL). Biodegradation tests were carried out using two standard methods: (i) ISO 14851 (1999), biochemical oxygen demand in a closed respirometer and (ii) ASTM G 22‐76, microbial growth of test microorganisms. Both biodegradability tests suggested that the blend containing PCL is more biodegradable than the one containing PLA. Addition of starch increased the biodegradability of the PLA blend. The biodegradability of the blends evaluated in this study by the biochemical oxygen demand method ranged from 22% (PLA 60) to 52% for corn starch/PCL 30/70 (% wt) (SPCL 70). Therefore, the blends may not be considered “readily biodegradable” according to the OECD standard. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of natural fibers on the mechanical properties and biodegradation of poly(lactic acid) and poly(ε‐caprolactone) composites: A review

This article highlights developments in viable poly(lactic acid) (PLA) and poly(ε‐caprolactone) (PCL) ecofriendly products with enhanced mechanical properties and biodegradation based on natural resources for both reinforcements and matrices. In recent times, several techniques have emerged with emphasis on enhancing mechanical, biological, and chemical properties equivalent to or superior to conventional polymers in use. Chemical and physical modifications of the fibers and in some cases polymer matrix or both are used to obtain properties suitable for the intended application. The mechanical properties and biodegradation of PLA and PCL natural fiber composites were enhanced by the treated fibers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Synthesis of biodegradable and flexible,polylactic acid based,thermoplastic polyurethane with high gas barrier properties

Polylactic acid (PLA) has the beneficial properties of good mechanical strength, biodegradability and biocompatibility, and these properties make it suitable for use as an environmentally friendly packaging material. However, its use has been limited by its brittleness and poor stability. In this work, we successfully developed an efficient synthesis scheme to improve the mechanical properties, flexibility and gas barrier properties of PLA‐based polymers. Four different PLA‐based thermoplastic polyurethane (PLAPU) polymers were synthesized through the reaction of PLA diol with hexamethylene diisocyanate, followed by chain extension with polycaprolactone (PCL) diol. The relative compositions of the hard PLA and the soft PCL diols in the PLAPU polymers were controlled systematically to optimize the physical properties of the polymers. For example, increasing the content of PCL resulted in higher molecular weight PLAPU polymers that had increased tensile strengths and elongations at break, but their moduli were decreased. At the optimized PLA:PCL ratio of 1:3, the PLAPU polymer had an excellent elongation at break of 1053% with a relatively high Young's modulus of 51.8 MPa. In addition, the gas barrier properties of the PLAPUs were significantly enhanced depending on the molecular weight and PCL content of the polymers. To demonstrate the feasibility of using PLAPU polymers for biodegradable packaging materials, hydrolytic degradation tests were performed in phosphate buffer solution, and the PLAPU polymers were degraded gradually at rates that depended on the content of PCL in the polymers. This optimized PLAPU polymer exhibited excellent flexibility and gas barrier property, as well as high elongation, demonstrating its potential utility as packaging materials. © 2013 Society of Chemical Industry     

Polylactic acid blends: The future of green,light and tough

Polylactic acid (PLA) is a biobased product and a compostable aliphatic polyester that has been studied for use in several applications over the last decade. Many properties of PLA, such as strength, stiffness, and gas permeability, have been found to be comparable to those of traditional petrochemical-based polymers. However, PLA-based materials exhibit a number of limitations for specific applications, such as slow biodegradation rate, high cost, and low toughness. The modification of PLA using the polymer blending technique to achieve suitable properties for different applications has been receiving significant attention over the past few years. Hence, the aim of this work is to summarize the current developments regarding the preparation and properties of PLA polymer blends. In this review, the recent advances in PLA preparation are broadly introduced. In addition, the miscibility and compatibilization strategies of PLA polymer blends are discussed. The preparations and characterizations of PLA blends with both biodegradable and non-biodegradable polymers are outlined. Finally, the biodegradation, mechanical properties, and potentiality of PLA blends are presented.     

一种新型口罩在两种堆肥条件下的生物降解性比较

为探索一种新型口罩在需氧和厌氧两种堆肥条件下的生物降解性能差异，采用国际上广泛认可的标准方法分别开展研究，获得了该新型口罩的生物降解率数据。统计分析结果显示，在ISO 14855-1和ISO 15985试验条件下，新型口罩在第90天时的生物降解率分别为66.4%和21.2%，该新型口罩在需氧条件中的生物降解性能远优于厌氧条件。研究表明，该新型口罩废弃后，宜采用需氧工业堆肥装置进行处理。     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.     

Hemocompatibility of polymers for use in vascular endoluminal implants

Implanted polymers for cardiovascular applications may function as structural supports, barriers, or provide a means for local drug delivery. Several thermoplastic biodegradable drug delivery polymers are potential candidates for blood-contacting implant applications. For intravascular applications specifically, a criterion for material selection is the intrinsic hemocompatibility of the baseline polymer. As an initial screening approach for selection of polymers for in vivo use, thin films of polyesters: poly(ɛ-caprolactone) (PCL), poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA); polyanhydrides: poly(fatty acid dimer-co-sebacic acid) (PFAD:SA) and poly(biscarboxyphenoxypropane-co-sebacic acid) (PCPP:SA); and poly(ethylene glycol) (PEG)-ylated polyesters: PLA:PEG, PCL:PEG and PCL:PLA:PEG polymers were spin-cast on glass cover slips and placed in an in vitro flow system exposing them at a controlled shear to overflowing human whole blood. Platelet adherence, aggregate formation, and thrombus formation, as well as leukocyte adherence were assessed following 5 min of flow. At 5 min of flow the rank order of materials, in terms of least to most thrombogenic was: PCL < PFAD:SA < PCPP:SA < PLGA < PLA. All PEGylated materials, in general, had less thrombus formation than baseline unmodified materials.     

Bio‐polyester–date seed powder composites: Morphology and component migration

Biodegradable polyesters poly‐l ‐lactide (PLA) and poly(butylene adipate‐co‐terephthalate) (PBAT) were reinforced with varying amount of date seed powder (DSP) with an aim to utilize the date seed waste as well as to achieve composites with improved properties. The PLA composites exhibited increase in the elastic response over the viscous response as a function of filler fraction, whereas the PBAT composites retained the viscous dominance irrespective of DSP content. The tensile modulus of the PBAT composites had enhancement of more than 300% in the composite with 40% filler content. The PLA composites also enhanced the modulus marginally till 20% filler content, however, it was still significant because of the very high modulus of PLA as compared to PBAT. Thermal analysis also indicated the stability of the composite, thus, confirming the usefulness of DSP as filler for the polymers. The TEM and light microscopy characterization revealed presence of voids in the composites which were present around the filler particles as well as dispersed in the polymer matrix. Such features were confirmed through TGA‐MS to be resulting from the escape of water vapor bound in DSP. The composites with 10% DSP content had lower extent of such voids and the morphology remained relatively unchanged with time. In the composites with 30% DSP content, in the seasoned sample, a soft and sticky phase resulting from the surface migration of date seed oil was also observed. The generation of the soft phase was also a slow process as 24 h were not enough to generate this phase. The migration of the oil to the surface was also confirmed by the IR and X‐ray diffraction studies. After embedding in compost soil, the PLA composite with 40% filler content had nine times more biodegradation after 120 days as compared to pure polymer, whereas it was 11 times for PBAT composite with same filler content. It confirmed that the addition of DSP did not lead to any thermal and mechanical degradation of the bio‐polyesters and resulted in enhanced mechanical and biodegradation behavior along with oil migration. The controlled component migration can lead to potential generation of commercially important self‐lubricating composite materials. POLYM. ENG. SCI., 55:877–888, 2015. © 2014 Society of Plastics Engineers     

Rheological and mechanical characterization of poly(lactic acid)/polypropylene polymer blends

Poly(lactic acid) (PLA) was melt blended with polypropylene (PP) with the aim of replacing commodity polymers in future applications. Since cost of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. This paper reports the preparation of poly(lactic acid)/polypropylene polymer blends (PLA/PP) using a laboratory scale single screw extruder. Rheological and mechanical properties of the prepared blends were determined. The rheological experiments were carried out on a capillary rheometer, the effect of shear rate, temperature and PLA content on the flow activation energy and true viscosity of the blends were described. Mechanical properties of the blends were investigated on dog bone-shaped samples obtained by injection molding; tensile tests were performed using Testometric M350-10KN. The effect of PLA content on Young’s modulus, strain at break and stress at break of the blends were described. The rheological results showed that the true viscosity of the blends is between that of the pure polymers, whereas the flow activation energy of the blends is less than that of the pure polymers. The mechanical results showed incompatibility between PLA and PP in the blend.     

Mechanical properties of poly(ε‐caprolactone) and poly(lactic acid) blends

The aim of this work was to better understand the performance of binary blends of biodegradable aliphatic polyesters to overcome some limitations of the pure polymers (e.g., brittleness, low stiffness, and low toughness). Binary blends of poly(ε‐caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by melt blending (in a twin‐screw extruder) followed by injection molding. The compositions ranged from pure biodegradable polymers to 25 wt % increments. Morphological characterization was performed with scanning electron microscopy and differential scanning calorimetry. The initial modulus, stress and strain at yield, strain at break, and impact toughness of the biodegradable polymer blends were investigated. The properties were described by models assuming different interfacial behaviors (e.g., good adhesion and no adhesion between the dissimilar materials). The results indicated that PCL behaved as a polymeric plasticizer to PLA and improved the flexibility and ductility of the blends, giving the blends higher impact toughness. The strain at break was effectively improved by the addition of PCL to PLA, and this was followed by a decrease in the stress at break. The two biodegradable polymers were proved to be immiscible but nevertheless showed some degree of adhesion between the two phases. This was also quantified by the mechanical property prediction models, which, in conjunction with material property characterization, allowed unambiguous detection of the interfacial behavior of the polymer blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(lactide)-based supramolecular polymers driven by self-complementary quadruple hydrogen bonds: construction,crystallization and mechanical properties

A series of poly(lactide) (PLA)-based supramolecular polymers based on linear PLLA-b-PCL-b-PLLA triblock copolymers (PLLA, poly(l -lactide); PCL, poly(ε-caprolactone)) or/and three-arm star (PCL-b-PDLA)₃ block copolymers (PDLA, poly(d -lactide)) were synthesized. The effects of the structure and composition on crystal structure, crystallization behavior, spherulite morphology and mechanical properties of the synthesized supramolecular polymers were investigated. The results of DSC and polarized optical microscopy indicated that the supramolecular polymer exhibited poor crystallization ability with respect to PCL/PLA block copolymer, and the crystallinity of the supramolecular polymer with alternating PCL/PLA multiblock structure was stronger than that with similar crosslinked network structure. The presence of molten PCL blocks disturbed the orientation of lamellae, forming spherulites with feather-like dendrites, and ring-banded spherulites were observed as the molecular weight of the PLA blocks increased. The results of tensile tests demonstrated that supramolecular polymers with larger molecular weight of PLA blocks showed the pronounced ductile fracture. On this basis, stereocomplexed supramolecular polymers were also synthesized, and it was found that the stereocomplex crystals had a significant impact on the crystallization and mechanical properties of the supramolecular polymers. Therefore, in this work a novel technique for manufacturing toughened PLA-based material and tuning its performances is proposed, which may promote the application of PLA-based materials in more fields. © 2022 Society of Industrial Chemistry.     

Interfacially compatibilized poly(lactic acid) and poly(lactic acid)/polycaprolactone/organoclay nanocomposites with improved biodegradability and barrier properties: Effects of the compatibilizer structural parameters and feeding route

Nanocomposites with enhanced biodegradability and reduced oxygen permeability were fabricated via melt hybridization of organomodified clay and poly (lactic acid) (PLA) as well as a PLA/polycaprolactone (PCL) blend. The nanocomposite microstructure was engineered via interfacial compatibilization with maleated polypropylene (PP‐g‐MA). Effects of the compatibilizer structural parameters and feeding route on the dispersion state of the nanolayers and their partitioning between the PLA and PCL phases were evaluated with X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. Although highly functionalized PP‐g‐MA with a low molecular weight was shown to be much more effective in the intercalation of PLA and the PLA/PCL blend into the clay gallery spaces, composite samples compatibilized by high‐molecular‐weight PP‐g‐MA with a lower degree of maleation exhibited lower oxygen permeability as well as a higher rate of biodegradation, which indicated the accelerating role of the dispersed nanolayers and their interfaces in the enzymatic degradation of PLA and PLA/PCL matrices. This evidenced a correlation between the nanocomposite structure and rate of biodegradation. The size of the PCL droplets in the PLA matrix was reduced by nanoclay incorporation, and this revealed that the nanolayers were preferentially wetted by PCL in the blend. However, PCL appeared as fine and elongated particles in the microstructure of the PLA/PCL/organoclay hybrids compatibilized by higher molecular weight and less functionalized PP‐g‐MA. All the PLA/organoclay and PLA/PCL/organoclay hybrids compatibilized with high‐molecular‐weight PP‐g‐MA displayed a higher dynamic melt viscosity with more pseudo solid‐like melt rheological responses, and this indicated the formation of a strong network structure by the dispersed clay layers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

“True” biocomposites with biopolyesters and date seed powder: Mechanical,thermal, and degradation properties

Biopolymers have gained research focus due to enhanced property profiles as well as need to replace the fossil fuel based polymeric materials. The generation of biocomposites with functional biofillers can lead to further enhancement of their potential. In this study, composites of date seed powder with biopolyesters poly(butylene adipate‐co‐terephthalate) (PBAT) and poly‐l ‐lactide (PLA) have been demonstrated. The composites exhibited individual degradation peaks for the components in the thermogravimetric analysis (TGA), but still had suitable thermal performance confirmed by the dynamic TGA. The filler also modified the crystalline morphology of the polymers differently. The tensile modulus of the PBAT‐based composites had enhancement of more than 300% in the composite with 40% filler content. The PLA composites also enhanced the modulus marginally till 20% filler content, however, it was still significant due to the very high modulus of PLA as compared to PBAT. The rheological properties indicated the polymer still had viscous behavior even when high amount of filler was added. The storage and loss modulus of the composites enhanced with filler fraction, the PLA composites with 30 and 40% content, however, exhibited very high values probably due to filler aggregates and low filler‐polymer interfacial interactions. The filler particles were observed to be uniformly distributed in the polymer matrices, though some filler aggregates were also observed in the composites with higher filler fractions. After embedding in compost soil, the composites had significantly enhanced extent of biodegradation as compared to pure polymers, thus, confirming the “true” biocomposite nature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40816.     

Process study,development and degradation behavior of different size scale electrospun poly(caprolactone) and poly(lactic acid) fibers

This study describes the preparation of electrospun poly(caprolactone) (PCL) and poly(lactic acid) (PLA) fibrous scaffolds with and without nano-hydroxyapatite (nHAp) having nanoscale, microscale and combined micro/nano (multiscale) architecture. Processing parameters such as polymer concentration, voltage, flow rate and solvent compositions were varied in wide range to display the effect of each one in determining the diameter and morphology of fibers. The effect of each regulating parameter on fiber morphology and diameter was evaluated and characterized using scanning electron microscope (SEM). Degradability of the selected fibrous scaffolds was verified by phosphate buffered saline immersion and its morphology was analyzed through SEM, after 5 and 12 months. Quantitative measurement in degradation was further evaluated through pH analysis of the medium. Both studies revealed that PLA had faster degradation compared to PCL irrespective of the size scale nature of fibers. Structural stability evaluation of the degraded fibers in comparison with pristine fibers by thermogravimetric analysis further confirmed faster degradability of PLA compared to PCL fibers. The results indicate that PLA showed faster degradation than PCL irrespective of the size-scale nature of fibrous scaffolds, and therefore, could be applied in a variety of biomedical applications including tissue engineering.     

含氧配体螯合铝络合物催化环酯聚合研究进展

聚己内酯及聚交酯是可供生物降解的高分子材料,具有良好的生物相容性和优异的力学性能,广泛应用在生物医学领域,可应用于骨骼固定材料、手术缝合线、药物载体和组织修复材料等。本文综述了不同类型含氧配体螯合金属铝络合物以配位-插入机理引发环酯开环聚合近年来的研究成果。     

MnSt2–kaolin–polyethylene film: An eco‐friendly polyethylene composite film and its thermo‐ and biodegradable research

A novel thermo‐ and biodegradable MnSt₂–kaolin–polyethylene (signed as MKPE) composite film was prepared through a melt blending technique. Manganese stearate and common kaolin were employed as thermo‐degradable additives and biodegradable promoter to improve the degradable efficiency of the waste PE. Thermo‐oxidative testing was carried out in an air oven maintained at 70°C simulating a compost temperature. The biodegradation of the aging films was also investigated by analysis of evolved carbon dioxide of films in aquatic test systems according to the International Standards ISO 14852 (1999). The composite film was characterized by electronic universal testing machine, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, attenuated total reflection‐flourier transformed infrared spectroscopy and thermo gravimetric analysis. These results showed that the MKPE film exhibited a high degree of susceptibility to thermo‐oxidation and biodegradation. After thermal aging for 30 days, the mechanical properties of MKPE films reduced quickly and oxygen groups were introduced into the polymer chains. The kaolin particles wrapped in polymers were exposed gradually because of the rupture of polymer chains by thermal aging. The biodegradation degree reached 24.26% after incubation in an aqueous medium for 60 days. A possible mechanism for thermal oxidative degradation and biodegradation was also discussed. POLYM. COMPOS., 36:939–945, 2015. © 2014 Society of Plastics Engineers     

Poly(lactic acid)/carbon nanotube nanocomposites with integrated degradation sensing

For the first time, an in-situ degradation monitoring system for biodegradable polymers is reported in present work. The proposed concept is based on a conductive biodegradable polymer composite, where carbon nanotubes (CNTs) are incorporated in poly(lactic acid) (PLA) in order to develop an intelligent biocomposite system that can sense biodegradation. Changes in electrical resistivity of the PLA/CNT nanocomposites were successfully correlated with degradation levels of the biopolymer. PLA/CNT nanocomposites demonstrated excellent degradation sensing abilities at CNT concentrations around the percolation threshold, with resistivity changes of about four orders of magnitude with biodegradation. In contrast to many other stimuli, biodegradation resulted in a reduction in resistivity due to an increased CNT network density after partial removal of the amorphous phase of the polymer matrix.