PP-g-MAH对聚乳酸流变行为和阻隔性能的影响

采用双螺杆熔融共混法制备了聚乳酸/马来酸酐接枝聚丙烯(PLA/PP-g-MAH)共混复合材料,研究了PP-gMAH对PLA流变行为及气体阻隔性的影响。动态流变研究结果表明:随着PP-g-MAH用量的增加,PLA/PP-g-MAH共混体系在线性黏弹区的储能模量逐渐增大,体系的介质损耗(tanδ)峰向低温区移动,表明PP-g-MAH与PLA基体有一定的相容性。共混体系的现行临界应变表现出逐渐减小的趋势,且在第二平台区表现出相同的规律,同时共混体系的损耗模量和储能模量均随着PP-g-MAH用量的增加而增大。此外,PP-gMAH与PLA的界面反应极其微弱,主要以物理缠结为主。共混体系的Cole-Cole曲线表明:高PP-g-MAH用量下,PLA/PP-g-MAH共混体系相分离现象明显,体系的松弛行为显示了一个附加的松弛过程,并向较低的频率延伸。阻隔性能测试结果表明:PLA/PP-g-MAH复合材料的水蒸气及氧气透过系数均随着PP-gMAH含量的增加而减小。在实验范围内,添加20%的PP-g-MAH,可使水蒸气、氧气透过系数均达到最小,分别为4.5×10~(-15) cm~3·cm/(cm~2·s·Pa)和1.3×10~(-10) g/(m·s·Pa)。     

聚碳酸亚丙酯与聚乳酸共混物性能及热分解动力学分析

采用溶液浇铸法制备了聚碳酸亚丙酯(PPC)/聚乳酸(PLA)共混物,通过力学性能测试、衰减全反射红外光谱分析、差示扫描量热分析和热失重分析研究了共混物的性能,并对共混物进行了热分解动力学研究。结果表明,随着PLA含量的增加,共混物的拉伸强度增大,断裂伸长率减小,PPC/PLA共混物的力学性能得到改善;随着PLA的含量从10%(质量分数,下同)增加到90%,共混物热失重10%所对应的温度(T-10%)从255℃逐渐增加到281℃,当PLA的含量分别为10%、50%和90%时,最大速率失重温度比纯PPC分别提高了3.45、15.51和41.58℃;采用Coats-Redfern法得出,PLA的加入能提高PPC的活化能,其中PLA含量为30%和50%时,共混物的活化能比纯PPC分别提高了12.72%和40.68%,说明PLA改善了PPC的热稳定性。     

两种抗冲改性剂增韧聚乳酸体系力学性能研究

研究了两种抗冲改性剂增韧聚乳酸(PLA)体系的力学性能。结果表明:两种抗冲改性剂均能提高PLA的冲击强度和断裂伸长率。抗冲改性剂2在用量为5%时,使PLA体系的冲击强度提高到11.8 kJ/m2,比添加前提高了140.8%;当两种抗冲改性剂的用量为10%时,PLA体系的冲击强度均从4.9 kJ/m2提高到约16.0 kJ/m2,提高了226.5%。两种抗冲改性剂用量为5%时,PLA体系的断裂伸长率从9%分别提高到33%和20%;抗冲改性剂1用量为10%时,体系的断裂伸长率提高到173%。     

PP-g-MAH对PLA性能的影响

采用双螺杆挤出机以熔融共混法制备了聚乳酸(PLA)和马来酸酐接枝聚丙烯(PP-g-MAH)共混物,以傅立叶变换红外光谱(FTIR)、热重(TG)分析、动态热机械分析(DMA)和扫描电子显微镜研究了不同PP-g-MAH含量对PLA力学性能和微观结构的影响。DMA测试发现,随着PP-g-MAH含量的增加,PLA/PP-g-MAH共混物的损耗因子向低温区移动,表明PLA与PP-g-MAH分子链具有良好的相容性。FTIR分析证实了这种良好的相容性归因于PLA分子链羟基和酸酐基团之间的酯化反应。TG分析研究表明,PP-g-MAH的加入限制了PLA分子链的运动,提高了共混物的耐热性,一定程度上抑制了PLA的分解。PP-g-MAH在一定程度上提高了PLA/PP-g-MAH共混物的力学性能,添加质量分数15%的PP-g-MAH时,PLA/PP-g-MAH共混物的Iozd缺口冲击强度和弯曲弹性模量都有所提高,分别由纯PLA的2.83 k J/m2,2 668 MPa提高到5.38 k J/m2,2 970 MPa,分别提高了90.1%和11.3%,但拉伸强度却有一定程度的降低。阻隔性能实验表明,随着PP-g-MAH含量的增加,水蒸气和氧气透过系数降低。添加质量分数20%的PP-g-MAH,氧气和水蒸气的透过系数分别为4.5×10-15(cm3·cm)/(cm2·s·Pa)和1.3×10-10 g/(m·s·Pa),与纯PLA相比,分别下降了74.7%和45.1%。     

ADR对PLA/PBAT共混物流变性能的影响

通过转矩流变仪制备ADR/聚乳酸(PLA)/己二酸丁二醇酯-对苯二甲酸丁二醇酯共聚物(PBAT)共混物,利用转矩流变仪和毛细管流变仪研究了ADR含量对PLA/PBAT流变性能的影响。结果表明:ADR的扩链作用抑制了共混过程中PLA的降解,使体系转矩增大。当ADR添加量达到0.3%时,体系的转矩最平稳。通过毛细管流变仪分析发现共混体系遵守幂律方程,熔体呈现剪切变稀现象;随着ADR含量的增多,共混物非牛顿指数n减小,黏流活化能Eη变大。     

凹凸棒石/聚乳酸纳米复合材料的力学性能和流变性能

采用熔融共混法制备凹凸棒石(ATT)质量分数分别为1%、3%和5%的ATT/聚乳酸(PLA)纳米复合材料,研究了ATT/PLA纳米复合材料的力学性能和流变性能。红外光谱分析结果表明:ATT与PLA基体之间存在较强的相互作用,使得二者之间具有较好的相容性。当ATT含量低于5%时,其可均匀分散在PLA基体中,而达到5%时,则会发生部分团聚。添加ATT后,PLA基体从脆性材料变为韧性材料,ATT起到增韧作用,并显著提高了复合材料的力学性能。当ATT含量为3%时,断裂伸长率达到26.36%,比纯PLA增加了297.6%,并且复合材料的冲击强度也比纯PLA增加了19.7%。ATT/PLA纳米复合材料的复数黏度、储能模量和损耗模量随ATT含量的增加呈先增大后减小趋势。由于ATT与PLA之间有良好的结合力,ATT的加入增大了复合材料的弹性和黏性,且低频区的变化明显高于高频区的变化。     

PBAT/PLA复合材料的制备及其微球发泡行为研究

采用熔融共混法制备了聚(己二酸丁二醇酯-对苯二甲酸丁二醇酯)/聚乳酸(PBAT/PLA)共混复合材料,并对PBAT/PLA共混体系的流变性能、结晶性能、力学性能、微观形貌以及发泡行为(热膨胀微球作为发泡剂)进行了表征。结果表明:随着PLA含量的增加,PBAT/PLA共混体系的非牛顿指数先减小后增大,其中当PLA含量为30%时达到最小值;PLA的引入改善了PBAT的结晶性能,且PBAT与PLA对彼此的晶型均无影响;随PLA含量的增加,PBAT/PLA共混体系的拉伸强度增大、断裂伸长率降低,其中当PLA含量为50%时,拉伸强度和断裂伸长率分别达到25.3 MPa和422.2%;PLA与PBAT的相容性差,当PLA含量为30%时,PLA/PBAT共混体系发生相分离;此外,当PLA含量为10%时,PBAT/PLA复合发泡材料的密度达到最小值0.34 g/cm~3。     

转矩流变仪研究羧酸对聚乳酸热稳定性的影响

通过建立模型,计算流动活化能(Ef)和降解速率常数(K),用转矩流变仪研究了癸酸、十二酸和十六酸对聚乳酸(PLA)热稳定性的影响。结果表明:羧酸的加入降低了聚乳酸的热稳定性。随着羧酸主链碳原子数增加,羧酸对聚乳酸的热稳定性影响呈逐渐降低的趋势;羧酸的摩尔分数从0%增至1.00%时,PLA/羧酸体系的熔体黏度从238.4 Pa.s下降至142.1 Pa.s,Ef从70.28 kJ/mol增至159.04 kJ/mol,K从0.72×10-3m in-1增至3.46×10-3m in-1。     

PLA/PPC/OMMT纳米复合材料的结构与性能研究

采用双螺杆挤出机制备了聚乳酸（PLA）/聚碳酸亚丙酯（PPC）共混物和PLA/PPC/有机改性蒙脱土（OMMT）纳米复合材料,采用偏光显微镜、差示扫描量热仪和力学性能试验机等对共混物和纳米复合材料的相态结构、熔融与结晶行为和力学性能等进行了研究。结果表明,在PPC含量低于30 %时,随着PPC含量的增加,PLA/PPC和PLA/PPC/OMMT体系中PLA的玻璃化转变温度（Tg）均降低,在PPC含量为50 %时出现了明显的相分离;随着PPC含量的增加,PLA/PPC的冲击强度增大;OMMT的含量小于1.5 %时,PLA/PPC/OMMT体系的结晶度、拉伸强度、断裂伸长率和冲击强度均随OMMT含量的增加而增大。     

PLA-b-PMMA嵌段结构对PC/PLA共混形态和性能的影响

制备了具有不同嵌段长度的聚乳酸b聚甲基丙烯酸甲酯（PLA-b-PMMA),并将其作为大分子相容剂用于聚碳酸酯/聚乳酸（PC/PLA）共混体系,研究嵌段结构对PC/PLA共混体系形态与性能的影响。用傅里叶红外光谱仪和核磁共振氢谱表征嵌段共聚物的结构,用差示扫描量热仪、扫描电子显微镜和力学性能测试表征共混体系的结构及性能。结果表明,PLA-b-PMMA的加入改善了PC与PLA之间的相容性,其增容效果取决于PLA-b-PMMA的添加量及两嵌段的长度;当PLA-b-PMMA添加量为6 %时,PC与PLA之间的相容性较好;在PMMA嵌段长度一定时,随着PLA链段长度从3390提高到9780,共混体系中两相的相容性不断改善,共混物的力学性能增强;在PLA嵌段长度一定时,随着PMMA链段长度从20680提高到99680,增容效果逐渐下降。     

The effects of plasticizers on the dynamic mechanical and thermal properties of poly(lactic acid)

Poly(lactic acid) (PLA) was blended with five plasticizers in a batchwise mixer and pressed into films. The films were analyzed by means of dynamic mechanical analysis and differential scanning calorimetry to investigate the properties of the blends. Triacetine and tributyl citrate proved to be effective as plasticizers when blended with PLA. The glass transition temperature of PLA decreased linearly as the plasticizer content was increased. Both plasticizers were miscible with PLA to an extent of ～ 25 wt %. At this point, the PLA seemed to be saturated with plasticizer and the blends tended to phase separate when more plasticizer was added. There were also signs of phase separation occurring in samples heated at 35, 50, and 80°C, most likely because of the material undergoing crystallization. The presence of the plasticizers induced an increased crystallinity by enhancing the molecular mobility. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1227–1234, 2002     

Tributyl citrate oligomers as plasticizers for poly (lactic acid): thermo-mechanical film properties and aging

Poly (lactic acid), PLA, is a biodegradable thermoplastic that can be produced from renewable resources. The polymer is of interest for production of films for packaging applications. However, plasticization of PLA is required in order to obtain films with sufficient flexibility. PLA was blended with tributyl citrate (TbC) and two oligomers of TbC that were synthesized by transesterification of tributyl citrate (TbC) and diethylene glycol (DEG). Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were used to investigate the dynamic mechanical and thermal properties of the blends. All the plasticizers investigated decreased the glass transition temperature of PLA, and the reduction was the largest with the plasticizer having the lowest molecular weight. The PLA matrix became saturated with plasticizer at a certain concentration and phase separation occurred; the higher the molecular weight of the plasticizer, the lower the saturation concentration. Aging of the blends at room temperature for several months induced partial phase separation in the material. It was observed that the morphological stability of the blends was enhanced when the plasticizer concentration was reasonably low, i.e. 10-15 wt%.     

Blending of poly(lactic acid) and starches containing varying amylose content

Four dry corn starches with different amylose content were blended at 185°C with poly(lactic acid) (PLA) at various starch:PLA ratios using a lab‐scale twin‐screw extruder. Starch with 30% moisture content also was blended with PLA at a 1:1 ratio. Each extrudate was ground and dried. The powder was mixed with about 7.5% plasticizer, and injection molded (175°C) into test tensile bars. These were characterized for morphology, mechanical properties, and water absorption. Starch performed as a filler in the PLA continuous matrix phase, but the PLA phase became discontinuous as starch content increased beyond 60%. Tensile strength and elongation of the blends decreased as starch content increased, but no significant difference was observed among the four starches at the same ratio of starch:PLA. The rate and extent of water absorption of starch/PLA blends increased with increasing starch. Blends made with high‐amylose starches had lower water absorption than the blends with normal and waxy corn starches. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3639–3646, 2003     

聚乳酸/环氧大豆油共混物的性能

聚乳酸（PLA）与环氧大豆油（ESO）经熔融共混制得具有高韧性的PLA/ESO共混物,并研究了ESO含量对PLA微观形态、力学和流变性能的影响规律。结果表明：ESO可显著降低PLA的熔体黏度,提高PLA的韧性;PLA/ESO共混物在低ESO含量（10%）时为部分相容,而在高ESO含量（20%和30%）时发生了相分离,从而使共混物的断裂伸长率和冲击强度随ESO含量增加先增大后减小,且分别在ESO含量为20%和15%时达到最大值,约为PLA的17倍和2.9倍,而拉伸强度则随之减小。     

Thermomechanical film properties and aging of blends of poly(lactic acid) and malonate oligomers

Malonate oligomers were synthesized as plasticizers for poly(lactic acid) (PLA). Esterification reactions were performed between diethyl bishydroxymethyl malonate (DBM) and either adipoyl dichloride or succinyl dichloride. Two molar masses were obtained within each series. Blending was carried out with PLA and the four oligomers as well as the monomeric unit from the syntheses (DBM). Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the viscoelastic mechanical and thermal film properties of the blends. All the investigated plasticizers reduced the glass‐transition temperature of PLA, and the plasticization effect was better for the plasticizers of low molar mass. However, the amorphous domains of PLA became saturated with plasticizer at a certain concentration, and phase separation occurred. A higher molar mass of the plasticizer caused this saturation to occur at lower plasticizer concentrations. Subsequently, the aging of the blends at the ambient temperature for 4 months induced phase separation in the blends containing DBM, whereas those with an oligomeric plasticizer were stable and remained compatible with PLA within the aging period. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2140–2149, 2004     

聚乳酸／醋酸淀粉共混物性能形态研究

采用双螺杆挤出机制备聚乳酸（PLA）／醋酸淀粉（AS）复合材料,研究不同螺杆结构和加工次数对复合材料流变-性能-形态的影响。测试结果表明：通过螺杆Ⅱ、二次挤出后的复合材料的力学性能最优,As含量为60％的复合材料拉伸强度达到27．91MPa。动态流变和SEM的结果表明采用螺杆Ⅱ可以提高PLA与As的共混效果。本文也考察了AS含量对复合材料的力学性能和动态流变性能的影响,结果表明当AS质量含量从45％提高到70％时,复合材料的拉伸强度从36．7MPa降低到16．4MPa;其复数黏度和储能模量则随着AS含量的增加而增加。     

Effects of moisture content and heat treatment on the physical properties of starch and poly(lactic acid) blends

Starch, a hydrophilic renewable polymer, has been used as a filler for environmentally friendly plastics for about 2 decades. Starch granules become swollen and gelatinized when water is added or when they are heated, and water is often used as a plasticizer to obtain desirable product properties. The objective of this research was to characterize blends from starch and poly(lactic acid) (PLA) in the presence of various water contents. The effects of processing procedures on the properties of the blends were also studied. Blends were prepared with a lab‐scale twin‐screw extruder, and tensile bars for mechanical testing were prepared with both compression and injection molding. Thermal and mechanical properties of the blends were analyzed, and the morphology and water absorption of the blends were evaluated. The initial moisture content (MC) of the starch had no significant effects on its mechanical properties but had a significant effect on the water absorption of the blends. The thermal and crystallization properties of PLA in the blend were not affected by MC. The blends prepared by compression molding had higher crystallinities than those prepared by injection molding. However, the blends prepared by injection molding had higher tensile strengths and elongations and lower water absorption values than those made by compression molding. The crystallinities of the blends increased greatly with annealing treatment at the PLA second crystallization temperature (155°C). The decomposition of PLA indicated that PLA was slightly degraded in the presence of water under the processing temperatures used. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3069–3082, 2001     

Dynamic mechanical and thermal properties of plasticized poly(lactic acid)

The blends of low molecular weight triacetin (TAC) and oligomeric poly(1,3‐butylene glycol adipate) (PBGA) were used as multiple plasticizers to lubricate poly(lactic acid) (PLA) in this study. The thermal and mechanical properties of plasticized polymers were investigated by means of dynamic mechanical analysis and differential scanning calorimetry. Atomic force microscopy (AFM) was used to analyze the morphologies of the blends. Multiple plasticizers were effective in lowering the glass transition temperature (T_g) and the melting temperature (T_m) of PLA. Moreover, crystallinity of PLA increased with increasing the content of multiple plasticizers. Tensile strength of the blends decreased following the increasing of the plasticizers, but increased in elongation at break. AFM topographic images showed that the multiple plasticizers dispersed between interfibrillar regions. Moreover, the fibrillar crystallite formed the quasicrosslinkings, which is another cause for the increase in elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1583–1590, 2006     

Plasticizing effect of coconut oil on morphological,mechanical, thermal,rheological, barrier,and optical properties of poly(lactic acid): A promising candidate for food packaging

This study explores the plasticizing effect of coconut oil (CO) on PLA for evaluating its suitability for flexible packaging. Changes in morphological, mechanical, thermal, rheological, barrier and optical properties of melt compounded Poly(lactic acid)–Coconut oil (PLA–CO) blend were investigated by varying the mixing ratio. Water vapor permeability of blends decreased by 58% at 7 wt % plasticizer content. The tensile strength showed a decreasing trend with increasing plasticizer percentage while the % elongation showed an increasing trend. At 7 wt % plasticizer content tensile strength decreased from 60 to 41 MPa and % elongation increased from 12% to 54%. Molecular weight (M_n) and onset of degradation (T_onset), upon 1 wt % plasticizer addition showed a reduction of 6% and 0.6%, respectively, which were well within permissible limits required for polymer processing. The melt flow properties of the blends were slightly improved (～16%) upon 5 wt % addition of CO. Transparency of the PLA films was improved by addition of plasticizer. FTIR spectra of PLA‐CO sample confirmed the interaction between PLA and coconut oil via hydrogen bonding. At higher loading, coconut oil shows very limited compatibility with PLA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45390.     

Evaluating effects of biobased 2,5‐furandicarboxylate esters as plasticizers on the thermal and mechanical properties of poly (vinyl chloride)

We synthesized 2,5‐furandicarboxylate esters [i.e., dibutylfuran‐2,5‐dicarboxylate, diisoamylfuran‐2,5‐dicarboxylate, and di(2‐ethylhexyl)furan‐2,5‐dicarboxylate] and investigated their potential application as plasticizers of commercial poly(vinyl chloride) (PVC) products. Fourier transform infrared analysis, mechanical tests, scanning electron microscopy investigation, differential scanning calorimetry analysis, dynamic mechanical thermal analysis, thermogravimetric analysis (TGA), melt flow rate (MFR) measurement, and plasticizer migration measurements were used to the evaluate the comprehensive properties of the blended products. The results of the tensile tests demonstrate that the blends exhibited antiplasticization and flexible plastic characteristics at 10 and 50 phr in PVC, respectively. Moreover, flexural and impact test data indicate that the three types of blends exhibited a similar tendency: the hardness decreased continuously as the amount of plasticizer increased. Their morphology indicated that all of the plasticizers had good compatibility with PVC. The resulting glass‐transition temperature of the investigated plasticizers was lower than that of pure PVC, and reduction was largest for the plasticizer with the highest molecular weight. TGA revealed that the thermal degradation of blended polymers occurred in three stages and that all of the blends were stable up to 180°C. Finally, the MFRs of all of the specimens indicated that the addition of a higher concentration of lower molecular weight biobased esters resulted in improved fluidity, but these compounds migrated more easily from the blends. Hence, 2,5‐furandicarboxylic acid derived from biomass has potential as a plasticizer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40938.