聚乳酸/DMSO增塑淀粉复合材料的制备与表征

采用聚乳酸分别和纯淀粉及二甲基亚砜(DMSO)塑化淀粉进行共混制备了淀粉/聚乳酸复合材料,通过力学性能测试,DSC测试,TG分析及SEM观察发现淀粉含量增加,材料力学性能降低,而经DMSO塑化淀粉共混物虽然其拉伸强度等力学性能降低,但冲击强度和弯曲应变均提高,且复合材料结晶度有较大提高,DMSO质量分数为3%时,复合材料的冷结晶温度降低9.4℃,熔融温度降低2.2℃。纯淀粉和聚乳酸共混复合材料呈现明显的两相结构,加入DMSO之后,界面黏结加强,呈现均相特征。     

An in-depth study on crystallization kinetics of PET/PLA blends

The crystallization behavior and mechanical properties of PET/PLA blends with various amounts of PLA were investigated using a wide angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and tensile analyses. The crystallization rate and relative crystallinity of the PET/PLA blends were studied by theoretical models of Kissinger, Avrami, Ziabicki and Ozawa. The WAXD analysis showed that the PLA phase was wholly amorphous in all blends after cooling from the melt to ambient temperature. Crystallization behavior assessments on PET/PLA blends suggest that PLA acts as a nucleating agent for PET phase leading to an increase in the initial and peak crystallization temperatures. Kissinger’s model showed a rise in activation energy up to 72% for the PET/PLA blends containing 30 wt% PLA. Ziabicki’s model gave a minimum value for kinetic parameter in PET/PLA (70/30 w/w) due to the nucleating action of PLA. On the other hand, PLA acted as a retarder for chain segments of PET tending to diffuse through the surface of growing crystals. Therefore, at an optimal composition of PET/PLA, crystallization occurs appropriately. However, an increase in PET content leads to fall in ductility, tensile strength, modulus, elongation-at-break, and fracture toughness of PET/PLA blends.     

聚乙二醇对聚乳酸/淀粉纳米晶复合材料性能的影响

以聚乳酸（PLA）和淀粉纳米晶（SNC）为主要原料,聚乙二醇（PEG）为增塑剂,采用溶剂蒸发法制备PLA/SNC和PLA/SNC/PEG复合材料,通过差示扫描量热仪（DSC）、热台偏光显微镜（PLM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）等研究了PEG对复合材料结晶行为、力学性能及界面相容性的影响。结果表明,PEG能够与SNC协同促进PLA结晶,使PLA/SNC/PEG复合材料的结晶速率明显提高;PEG的添加未改变PLA/SNC复合材料的结晶结构;随着PEG含量的增加,PLA/4%（质量分数,下同）SNC复合材料的拉伸强度先升高后下降,断裂伸长率不断提高;当PEG含量为2%时,PLA/4%SNC/2%PEG复合材料的力学性能最佳,拉伸强度为47.86 MPa,断裂伸长率为10.20%,PLA与SNC间界面相容性得到改善。     

MDI作为聚乳酸/木薯淀粉共混物交联剂的研究

用木薯淀粉作(Tapioca)为聚乳酸(PLA)的填充剂,以4,4-二苯基甲烷二异氰酸酯(MDI)为界面兼容剂,通过密炼机共混,用DSC测试热力学性质,以及SEM分析断面形态。当MDI含量为0.5%时共混PLA70Tapioca30的抗张强度由38.2MPa提高到61.0MPa。     

Tri‐(butanediol‐monobutyrate) citrate plasticizing poly(lactic acid): Synthesis,crystallization, thermal,and mechanical properties

Tri‐(butanediol‐monobutyrate) citrate (TBBC) as a new plasticizer for poly(lactic acid) (PLA) was synthesized via a two‐step esterification. The chemical structure of TBBC was characterized by ¹H‐nuclear magnetic resonance. The studies on solubility parameters, transparence, and storage stability indicated the good miscibility between PLA and TBBC. The glass transition, crystallization, thermal, and mechanical properties of PLA plasticized by TBBC were evaluated. With an increase in TBBC content, the glass transition temperature (T_g), melting point (T_m), and the cold crystallization temperature (T_cc) of plasticized PLA gradually shifted to a lower temperature. The elongation at break and flexibility were greatly improved by the addition of TBBC. After 30 days of storage, PLA plasticized with up to 20 wt% of TBBC exhibited good storage stability and remained the original transparence and mechanical properties. The flexibility of PLA/TBBC films can be tuned by changing TBBC content. The corresponding crystalline morphology and structure were investigated by Polarizing optical microscope and X‐ray diffraction as well. This study revealed that TBBC was miscible with PLA and may therefore be a promising plasticizer for PLA‐based packaging materials. POLYM. ENG. SCI., 55:205–213, 2015. © 2014 Society of Plastics Engineers     

聚乳酸/聚乙醇酸共混合金界面改性研究

用熔融共混挤出法制备了不同配比的聚乳酸(PLA)/聚乙醇酸(PGA)共混合金,并分别加入环氧型扩链剂ADR 4370F进行对比分析,通过拉伸性能测试、弯曲性能测试、缺口冲击强度测试、扫描电子显微镜(SEM)和差示扫描量热(DSC)仪研究了共混合金力学性能、相容性和结晶性能。结果表明:与纯PLA和纯PGA相比,PLA/PGA共混合金的相容性差,导致力学性能降低,纯PLA、纯PGA和70%PLA/30%PGA合金的拉伸强度、弯曲强度、断裂伸长率和缺口冲击强度分别为58.6 MPa,123.5 MPa,8.52%,9.0 J/m;91.9 MPa,157.6 MPa,7.9%,5.2 J/m;41.2 MPa,91.2 MPa,3.8%,2.0 J/m。PLA和PGA可以互相加快结晶速度,加入环氧型扩链剂可以改善合金的相容性,上述四个力学性能可相应提高到49.2 MPa,96.0 MPa,4.5%,4.3 J/m,而且降低了PLA和PGA的结晶度。另外,向PLA中加入1%PGA时,PGA可以充当PLA的成核剂,使PLA的冷结晶温度降低10℃左右,结晶度提高1.3%。     

原位反应法制备聚乳酸/聚氨酯共混物及性能

以聚乳酸（PLA）、聚四氢呋喃醚二醇（PTMG）和液化4,4′-二苯基甲烷二异氰酸酯（L-MDI）为原料,通过原位反应法制备了PLA/聚氨酯（PU）共混物,研究了PLA/PU共混物的反应原理、力学性能、断面形貌、动态流变性能以及结晶性能。结果表明,在原位反应中有微交联结构PU生成,且伴随着PLA的扩链和枝化反应;PLA/PU共混物的韧性得到显著提高,当PU含量为30 %（质量分数,下同）时,共混物的断裂伸长率、断裂韧性和缺口冲击强度分别达到230 %、134.13 MJ/m3和34.19 kJ/m2,较纯PLA分别增加了16.6、8.1和11.1倍,此时拉伸强度仍保持在较高水平（49.7 MPa）;纯PLA和PLA/PU共混物熔体均为假塑性流体,共混物具有更高的储能模量和复数黏度;PLA/PU共混物比纯PLA的结晶速率高,晶体完善程度高。     

不同填料对聚乳酸复合材料导热及结晶行为的影响

通过熔融挤出法制备了分别由铁粉（Fe）、铜粉(Cu)、铝粉(Al)和氧化铝(Al2O3)粉4种导热填料填充的聚乳酸（PLA）复合材料,研究了填料种类、用量对复合材料的热导率、固化以及结晶行为的影响。结果表明,其中添加10 % (质量分数,下同)Fe可使复合材料的热导率提高90 %,10 % Al2O3的加入使冲击强度提高55 %,填料种类和用量对肖氏硬度(A)没有显著影响;随着填料用量的增加,复合材料的结晶速率明显提高,添加5 %填料可使复合材料结晶速率平均提高83 %,而添加10 %的填料时结晶速率仅提高79 %。     

Poly (vinyl alcohol)/polylactic acid blend film with enhanced processability,compatibility, and mechanical property fabricated via melt processing

Poly (vinyl alcohol)/polylactic acid (PVA/PLA) blend film, which is environment friendly and has potential applications in food and electronic packaging fields, was fabricated by melt extrusion casting. Fourier transform infrared spectroscopy analysis confirmed the formation of the hydrogen bonding between PLA and PVA, which improved the compatibility of PLA with PVA, making PLA uniformly dispersed in PVA matrix as small spheres, even when PLA content increase to 15 wt%. In this way, the original hydrogen bond network among PVA was disturbed and the chain mobility of PVA was activated, endowing PVA/PLA blends with lower melt viscosity than bot modified PVA and PLA, and the blend films with the increased crystallinity, mechanical property, and water resistance. Compared with PVA film, the crystallinity, tensile strength and Young's modulus of the blend film with 15 wt% PLA, respectively, increased by 15.1%, 9 and 51 MPa, and the water contact angle enlarged from 23° to 60°.     

Mechanical,thermal, and dielectric properties of poly(lactic acid)/chitosan nanocomposites

Poly(lactic acid) (PLA) loaded with various levels of chitosan nanoparticles (CsNP) (0–5.0%) were prepared by twin‐screw extrusion. The nanocomposites were investigated based on their morphology, thermal, mechanical and dielectric properties. The SEM morphology showed that CsNP was dispersed uniformly in the PLA matrix. Thermal analysis through DSC revealed that the cold crystallization temperature of PLA in the case of nanocomposites slightly decreased with increasing content of CsNP; indicating a limit nucleating effect of CsNP. TGA analysis revealed that the incorporation CsNP slightly decreased the thermal stability of the PLA matrix. The mechanical analysis indicated that the incorporation of the CsNP in the PLA matrix improved the elongation and the impact strength, but decreased the tensile strength. The dielectric properties of these materials have been investigated for the α‐relaxation process as a function of the temperature and frequency. The α‐relaxation process was analyzed with Vogel–Fulcher–Tamman and Havriliak–Negami models and fitting parameters and their evolution were obtained. POLYM. ENG. SCI. 56:987–994, 2016. © 2016 Society of Plastics Engineers     

聚乳酸/芦苇纤维复合材料降解性能研究

采用熔融共混法制备了不同比例的聚乳酸/芦苇纤维（PLA/RF）共混物,并通过吹塑制备了相对应的薄膜。研究了在蛋白酶K的作用下不同RF含量的PLA/RF薄膜的生物降解性能,同时用差示扫描量热法（DSC）和扫描电子显微镜（SEM）测定了样品降解过程中的结晶行为以及表面形貌变化。结果表明,RF对PLA的酶解降解有促进作用,随着RF含量的增加PLA/RF复合材料的酶解速率提升,其中含有30 %（质量分数,下同）芦苇纤维的PLA/RF薄膜的降解速率最大,16天内可降解81.11 %。研究还表明,加入芦苇纤维可以降低PLA的结晶度,从而影响降解速度。     

Development and properties evaluation of bio‐based PLA/PLGA blend films reinforced with microcrystalline cellulose and organophilic silica

The preparation and properties of hybrid materials based on poly(lactic acid)/poly(lactic acid‐co‐glycolic acid) (PLA/PLGA) blends using microcrystalline cellulose (MCC) and organophilic silica (R972) as fillers have been investigated. Hybrid materials were manufactured by solution casting using chloroform as solvent to prepare films. R972 was incorporated in a ratio of 3 wt%, and MCC was added in ratios of 3, 5, or 7 wt% with respect to the weight of the polymeric matrix. Films were prepared with only MCC addition or with MCC and R972 combined. Properties of the films were evaluated by X‐ray diffraction (XRD), nuclear magnetic resonance, differential scanning calorimetry (DSC) and mechanical property measurements. The results show that each filler, when added individually or in combination, affects the structure and final properties of the films differently. MCC acts as a nucleating agent for the crystallization of the polymeric matrix. An increase in the MCC content increased the crystallinity of the films. This effect became more pronounced with silica addition. The domain distribution curves showed PLA/PLGA blends to be homogeneous, which was further confirmed by DSC. An improvement in the mechanical performance was observed with MCC addition, especially when silica was added together with cellulose. POLYM. ENG. SCI., 57:464–472, 2017. © 2016 Society of Plastics Engineers.     

Effect of incorporation of graphene oxide and graphene nanoplatelets on mechanical and gas permeability properties of poly(lactic acid) films

Nanocomposite thin films of poly(lactic acid) (PLA) were produced incorporating small amounts (0.2 to 1 wt%) of graphene oxide (GO) and graphene nanoplatelets (GNP). The films were prepared by solvent‐casting. Mechanical properties were evaluated for plasticized (by residual solvent) and unplasticized films. Plasticized nanocomposite films presented yield strength and Young's modulus about 100% higher than those of pristine PLA. For unplasticized films improvements in tensile strength and Young's modulus were about 15 and 85%, respectively. For both film types, a maximum in mechanical performance was identified for about 0.4 wt% loadings of the two filler materials tested. Permeabilities towards oxygen and nitrogen decreased, respectively, three‐ and fourfold in films loaded with both GO or GNP. The glass transition temperature showed maximum increases, in relation to unloaded PLA films, of 5 °C for 0.4 wt% GO and 7 °C for 0.4 wt% GNP, coinciding with the observed maxima in mechanical properties. Copyright © 2012 Society of Chemical Industry     

Properties and weldability of plasticized polylactic acid films

The objectives of the presented work were to investigate films based on polylactic acid (PLA) and polyethylene glycol (PEG) in order to improve ductility and weldability of PLA films. The effect of plasticizer amount on the thermal, rheological, and mechanical properties of PLA plasticized films was investigated. The PEG content does affect the glass transition and the cold crystallization temperature of PLA in blends, while the melting temperature was not affected by the addition of PEG. The complex viscosity of the neat PLA granules and of plasticized films showed strong temperature and angular velocity dependence. The Young's modulus and tensile strength of plasticized films were improved with increasing plasticizer concentration, while the elongation at break stays rather constant. Plasticized PLA films were furthermore heat welded. These investigations showed that plasticized PLA films can be welded by heat welding. The obtained weld strength is strongly depending on the PEG amount as well as on selected welding parameters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40394.     

Miscibility and thermal and mechanical properties of melt‐mixed poly(lactic acid)/poly(trimethylene terephthalate)/(methyl methacrylate)‐butadiene‐styrene copolymer blends

This study examined the miscibility and mechanical properties of melt‐mixed poly(lactic acid) (PLA), poly (trimethylene terephthalate) (PTT), and PLA/PTT blend with 5–10 phr of methyl methacrylate‐butadiene‐styrene copolymer (MBS). The isothermal crystallization kinetics of the PTT blends were analyzed by using the Avrami equation. The Differential Scanning Calorimetry (DSC) and scanning electron microscope results indicated that the miscibility of the PLA/PTT blends was improved by adding 5–10 phr of MBS. Although PLA, with the addition of 10 phr of MBS, had lower tensile strength at yield and higher breaking elongation and impact strength than pure PLA, no improvement in these mechanical properties could be observed in PLA/PTT blends. This result is explained by assuming that the crystallization of PTT at the interface favors the disentanglement of MBS from the PTT domain. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Interactions between PLA,organo-montmorillonite and plasticizer: Synergistic effect on the barrier and mechanical properties of PLA nanocomposites blown films

In this study, the impact of incorporating a plasticizer on the compatibility between organo-montmorillonite (OMMt) and polylactic acid (PLA) is investigated, and the resulting barrier and mechanical properties are reported. Four polymers were chosen as plasticizers to prepare the PLA nanocomposite blown films: poly(ethylene glycol), poly(ethylene oxide), polycaprolactone (PCL), and random ethylene-methyl acrylate-glycidyl methacrylate terpolymer. Firstly, 5 wt% of each plasticizer and 3 wt% of OMMt (Dellite® D43B) were mixed simultaneously with PLA in a twin-screw extruder and then introduced into the hopper of a single screw extruder to produce D43B-PLA/plasticizer nanocomposite films. The compatibilization effect was examined based on microstructure observations and thermodynamic predictions. Crystallinity was evaluated using DSC and XRD measurements. The results obtained for permeability and mechanical testing showed that the improvement of barrier and mechanical properties depends directly on the degree of compatibility between plasticizer, OMMt, and PLA. Indeed, the interfacial properties, XRD diffraction, and TEM images showed that a synergistic effect can result from high interfacial interactions between different compounds.     

Physico-chemical,thermal, and mechanical properties of PLA-nHA nanocomposites: Effect of glass fiber reinforcement

In this study, tri-layered composites were prepared by reinforcing poly-lactic acid (PLA) nano-hydroxyapatite (n-HA) (1 and 5 wt%) and 20 mol% continuous phosphate glass fibers (PGF). Initially, the effect of addition of 1 and 5% n-HA on the structural, thermal, mechanical, and thermo-mechanical properties of 100% PLA was investigated. With 5 wt% n-HA addition the tensile modulus (TM), flexural modulus (FM), tensile strength (TS), and flexural strength (FS) of 100% PLA was improve by 14.9, 47.4, 6, and 32.9%, respectively. Whereas, the un-notched impact strength of the nanocomposites suffer 2% deterioration. However, T _g decreased by 0.3°C and T _c increased by 10°C as 5 wt% n-HA was added to 100% PLA. Afterwards, the 5% n-HA/PLA composite were reinforced with 20 mol% continuous PGF and the TM, FM, TS, and FS of the tri-layered composites were 162.6, 412.5, 28.4, and 157.4% higher as compared to 100%PLA. Furthermore, the storage modulus of the 1% n-HA-filled composites was 500 MPa lower than 100%PLA, while 5 wt% n-HA-filled composites showed similar storage modulus as 100% PLA. 5 wt% n-HA-filled composite showed the highest peak of loss modulus which may be attribute to the chain segment of PLA matrix after the incorporation of HA. Thus, n-HA and PGF reinforcement resulted in improved mechanical properties of the composites and have great potential as biodegradable bone fixation device with enhanced load-bearing ability.     

纳米纤维素协同聚氨酯增强增韧聚乳酸的研究

以聚乳酸（PLA）为基体、聚氨酯（PU）为增韧相、纳米纤维素（NCF）为增强相,通过溶液法与熔融共混制得PLA/PU/NCF复合材料,研究了PU和NCF的含量对PLA力学性能与热稳定性的影响。采用傅里叶变换红外光谱仪、热失重分析仪、扫描电子显微镜和力学性能测试手段对PLA/PU/NCF复合材料的结构和性能进行了表征和分析。结果表明,柔顺的PU分子限制了PLA的结晶,提升了PLA基体的韧性;刚性的NCF通过氢键作用提升了PLA基体的强度;当NCF含量为3 %、PU含量为17 %时,PLA/PU/NCF复合材料的拉伸强度和断裂伸长率比纯PLA提升了12.10 %和694.91 %;高温热稳定性有了显著改善,复合材料的600 ℃残炭率为19.36 %。     

扩链剂TMP-6000对聚乳酸/聚（3-羟基丁酸-co-3 -羟基戊酸酯）共混物性能的影响

以扩链剂TMP-6000为增容剂,采用熔融共混制备了聚乳酸（PLA）和聚（3羟基丁酸co3羟基戊酸酯）（PHBV）复合材料,研究了TMP-6000对PLA/PHBV复合材料的结晶行为、微观结构、力学性能的影响。结果表明,无定形PLA的加入抑制了PHBV的结晶,TMP-6000的加入使得PLA/PHBV复合材料的结晶能力变弱,提高了PLA的冷结晶温度,且当TMP-6000含量为0.5 %（质量分数,下同）时,PLA的冷结晶峰开始消失,且适量的TMP-6000使得PHBV的玻璃化转变温度（Tg）升高;TMP-6000的加入使得PHBV均匀分散于PLA基体中,且当TMP-6000含量为0.7 %时,PLA与PHBV的相容性最好;TMP-6000的加入显著提高了PLA/PHBV复合材料的分子量;TMP-6000提高了PLA与PHBV之间的结合力,提高了复合材料的拉伸强度,但断裂伸长率有稍微地降低。     

Talc reinforcement of polylactide and biodegradable polyester blends via injection-molding and pilot-scale film extrusion

As a renewable and biodegradable polymer, polylactide (PLA) has taken a foothold in the packaging industry. However, the thermomechanical and barrier properties of PLA-based films need to be improved to facilitate a wider adoption. To address this challenge, we examined the effect of talc reinforcement in composites based on PLA and a biodegradable polyester. Masterbatches of the polymers and talc were produced by melt compounding and processed by either injection-molding or film extrusion in a pilot-scale unit operating at 60–80 m/min. The effect of talc was investigated in relation to the morphological, thermal, mechanical, and barrier properties of the composites. Based on SEM-imaging, talc was found to increase the miscibility of PLA and the polyester while acting as a nucleating agent that improved PLA crystallinity. While this effect did not track with an increased mechanical strength, the composites with 3–4 wt% talc displayed a significantly higher barrier to water vapor. Compared to the neat polymer films, a reduction of water vapor transmission rate, by ~34–37%, was observed at 23°C/50% RH. Meanwhile, the systems loaded with 1 wt% talc showed a reduction in oxygen transmission rates, by up to 34%. Our results highlight the challenges and prospects of commercial PLA-based blends filled with talc from films extruded in pilot-scale units.