PLA/MMT-HTCC纳米复合材料的绿色合成、表征及热降解动力学分析

以乳酸锌为绿色催化剂,采用丙交酯开环聚合法制备了聚乳酸/壳聚糖季铵盐改性蒙脱土(PLA/MMT-HTCC)纳米复合材料。通过红外光谱、X射线衍射(XRD)、热重分析、扫描电子显微镜和透射电子显微镜进行了表征,采用Kissinger法和Ozawa法进行热降解动力学分析,得到材料的表观活化能。结果表明,PLA/MMT-HTCC为插层型纳米复合材料,PLA/MMT-HTCC的热分解峰值温度(Tp)比PLA最多高35.18℃,通过MMT-HTCC插层的实现,材料的热分解活化能得到了提高,从而提高了其热稳定性。     

聚乳酸/蒙脱土纳米复合材料研究进展

分析了聚乳酸(PLA)/蒙脱土(MMT)纳米复合材料的结构,介绍了溶液插层复合法、原位插层复合法、熔融插层复合法等PLA/MMT纳米复合材料的制备方法,从力学性能、热稳定性能、降解性能、气体阻隔性能等方面阐述了PLA/MMT纳米复合材料的性能,并对PLA/MMT纳米复合材料的发展前景进行了展望。     

溶液插层法制备PLA/HTCC-MMT纳米复合材料及其性能表征

以壳聚糖(CTS)和新疆地产蒙脱土(MMT)为原料制备了壳聚糖季铵盐改性蒙脱土(HTCC-MMT),通过溶液插层法制备了聚乳酸(PLA)/HTCC-MMT纳米复合材料。利用X射线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)、热重分析仪(TG)等对其微观结构、力学性能、热稳定性及降解性进行了表征和分析。结果表明:HTCC-MMT用量达到5%时,PLA/HTCC-MMT纳米复合材料的力学性最佳;HTCC-MMT的加入使PLA/HTCC-MMT纳米复合材料热稳定性得到了提高加,快了PLA的降解。     

熔融插层法制备聚乳酸/有机蒙脱土纳米复合材料及其性能研究

以新疆地产蒙脱土和聚乳酸为原料,通过熔融插层的方法制备了聚乳酸(PLA)/有机蒙脱土（OMMT）纳米复合材料。分别采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、热重分析仪等对复合材料的微观结构、形貌及热稳定性进行了表征和分析。研究表明,PLA大分子链已经插入OMMT片层间,层间距明显增大,形成PLA/OMMT纳米复合材料,体系的相容性良好。PLA/OMMT纳米复合材料的热失重曲线移向高温端,其热分解温度提高。PLA/OMMT纳米复合材料的熔点、维卡软化点、冲击强度、拉伸强度、热稳定性均比PLA基体有明显的提高。PLA/OMMT纳米复合材料的降解性初步研究表明其是一种良好的生物可降解环保塑料。     

叶片挤出机制备PLA/MMT复合材料性能的研究

利用以拉伸形变为主导的叶片挤出机制备了不同质量比的聚乳酸/蒙脱土(PLA/MMT)纳米复合材料,通过透射电子显微镜(TEM)和X射线衍射仪(XRD)表征了该复合材料的微观结构及形貌,并探讨了不同含量的MMT对PLA/MMT复合材料的力学性能以及动态力学性能的影响。结果表明:PLA分子链插入MMT片层之间,形成了具有插层结构的PLA/MMT纳米复合材料;该复合材料的拉伸强度、拉伸模量及冲击强度均随着MMT含量的增加呈先增后减的趋势;当MMT含量为2.5%时,复合材料的综合力学性能达到最佳,其中拉伸模量比纯PLA提高了170%,冲击强度则提高了130%,说明少量MMT的加入对PLA能起到增强增韧的作用。另外,动态力学性能测试结果表明,随着MMT含量的增加,复合材料的玻璃化转变温度有下降的趋势。     

PLA/OMMT纳米插层复合材料的合成、表征及降解性研究

以乳酸单体和有机蒙脱土(OMMT)为原料,通过原位插层聚合法合成了聚乳酸(PLA)/OMMT纳米插层复合材料, 分别采用傅立叶变换红外光谱( FT-IR)、X 射线衍射（XRD）、透射电子显微镜（TEM）等对PLA/OMMT复合材料的结构、形貌进行了表征和分析,同时研究了材料的降解性能。FT-IR表明,OMMT在聚合过程中被剥离成很小的粒子并分散在PLA基体中形成PLA/OMMT复合材料。由XRD分析可知MMT的层间距为1.260 nm,OMMT层间距为1.993 nm,PLA/OMMT复合材料中OMMT层间距为2.287 nm,层间距明显增大,表明PLA分子链插入到OMMT片层间,实现了原位插层聚合。透射电镜（TEM）分析表明,制备的PLA/OMMT复合材料形成了插层型结构,与红外光谱与XRD表征结果吻合。降解试验表明,介质对材料降解作用的次序为：NaOH＞HCl＞去离子水。在磷酸盐缓冲溶液中,随着降解时间的延长,材料的特性黏度在降解过程中不断下降。PLA/OMMT复合材料的降解速度要快于PLA,表明由于OMMT纳米粒子的存在,会加速材料的降解。     

聚乳酸/蒙脱土纳米复合材料的制备及其性能研究

采用熔融共混法制备聚乳酸/蒙脱土（PLA/MMT）纳米复合材料。用X射线衍射仪、透射电子显微镜、差示扫描量热仪对材料的力学性能、微观结构和形貌进行表征。结果表明,PLA分子链插入MMT片层间,MMT层间距由1.801 nm增大到3.530 nm并呈纳米级均匀分散在PLA基体中,体系相容性良好;MMT的加入量为3 %（质量分数,下同）时,复合材料的力学性能得到最大改善,拉伸强度由纯PLA的53.1 MPa提高到62.8 MPa,冲击强度由纯PLA的18.00 kJ/m2提高到23.30kJ/m2,加入3 % MMT的复合材料结晶度为42.63 %,试样平均晶粒粒径尺寸为0.285 nm,而纯PLA的结晶度是24.52 %,平均晶粒粒径尺寸0.305 nm,MMT的加入明显提高了PLA的力学性能和结晶度。     

铁基蒙脱土改性及其聚苯乙烯复合材料的阻燃性能

采用十六烷基三甲基溴化铵(CTAB)或双十二烷基二甲基溴化铵(DDAB)对制备的铁基蒙脱土(Fe MMT)进行有机改性,分别得到C-Fe OMT和D-Fe OMT。通过熔融共混法,制备了聚苯乙烯(PS)/Fe MMT、PS/C-Fe OMT、PS/D-Fe OMT纳米复合材料。通过红外光谱、X-射线衍射、热失重、锥形量热及扫描电镜等测试方法对Fe MMT有机插层效果及其PS纳米复合材料的热稳定性、热释放速率、生烟率、燃烧残炭形貌等进行了研究。研究结果表明,Fe MMT层间可插层性较好;有机改性Fe MMT可提高PS纳米复合材料的热稳定性和阻燃性,其中D-Fe OMT对PS的阻燃性能提升相对最好,具有膨胀阻燃效果。     

溶液插层法制备有机磷酸锆/聚乳酸纳米复合材料及其性能表征

采用氟化氢(HF)沉淀法得到高结晶度,晶相单一的磷酸锆(α-ZrP),然后通过甲胺(MA)进行预插层,再利用十八烷基三甲基氯化铵进一步对预插层产物进行有机改性从而制得有机磷酸锆(OZrP)。以OZrP为增强剂通过溶液插层法制备有机磷酸锆/聚乳酸(OZrP/PLA)纳米复合材料。对OZrP/PLA纳米复合材料的力学性能、热稳定性、热老化性能及降解性进行了研究,通过X射线衍射仪(XRD)、傅立叶红外光谱仪(FT-IR)、扫描电子显微镜(SEM)对磷酸锆改性前后的微观结构进行了表征。结果表明:当有机磷酸锆的用量为3份时,复合材料的拉伸强度达到最大值37.85 MPa;OZrP的加入使PLA复合材料的耐热老化性和热稳定性能得到了提高;OZrP的加入加快了PLA的降解;微观结构表征分析表明,磷酸锆经过甲胺预插层及十八烷基三甲基氯化铵插层改性实现了有机改性,层间距从0.76 nm扩大到3.77 nm,片层松散,结构发生明显变化,利于制备插层型结构的OZrP/PLA纳米复合材料。     

溶液插层法制备聚乳酸/SDS改性镁铝水滑石纳米复合材料及其性能表征

通过微波辐照制备镁铝水滑石(Mg-Al-LDHs),并用十二烷基硫酸钠(SDS)改性制备SDS有机改性镁铝水滑石(SDS-Mg-Al-LDHs).以其为助剂,采用溶液插层击制备聚乳酸/SDS改性镁铝水滑石(PLA/SDS-Mg-Al-LDHs)纳米复合材料,并且测定其力学性能、热稳定性、降解性.通过X射线衍射仪(XRD)、傅里叶红外光谱仪( FT-IB)、透射电子显微镜(TEM)、热重分析仪(TG)对材料进行表征和结构分析.结果表明:SDS-Mg-Al-LDHs用量达到3％时,PLA/SDS-Mg-Al-LDHs纳米复合材料的力学性能达到最大.同时加入SDS-Al-LDHs提高了PLA纳米复合材料的热稳定性.降解性研究表明SDS-Mg-Al-LDHs有利于提高PLA的可降解性.     

Morphology and thermal stabilization mechanism of LLDPE/MMT and LLDPE/LDH nanocomposites

The morphology and thermal stabilization mechanism of polymeric nanocomposites prepared by solution intercalation of linear low density polyethylene (LLDPE) with montmorillonite (MMT), MgAl layered double hydroxide (LDH), and ZnAl LDH have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). Both LLDPE/MMT and LLDPE/MgAl LDH nanocomposites exhibit mixed intercalated-exfoliated structures, whereas the LLDPE/ZnAl LDH nanocomposites exhibit completely exfoliated structures because the ZnAl LDH layers can be easily broken during the refluxing process. All nanocomposites show significantly enhanced thermal stability compared with virgin LLDPE due to the increases of the effective activation energy (E_α) during degradation process. However, LDHs nanocomposites show much higher thermal degradation temperatures than MMT nanocomposites with the same filler content because they have much higher E_α than MMT nanocomposites at the early degradation stage. The data of real time FTIR spectroscopy and morphological evolution reveal a catalytic dehydrogenation effect presents in MMT nanocomposites, which may decrease the E_α of degradation and thermal stability of MMT nanocomposites.     

The effect of organic modifier‐12‐aminolauric acid on morphology and thermal properties of polylactide nanocomposites

A novel organically modified montmorillonite (OMMT) based on a bifunctional organic modifier‐12‐aminolauric acid (ALA) was synthesized. Polylactide (PLA) nanocomposites with this new and traditional OMMT were prepared by solution casting method. The effects of the organic modifiers on structure, morphology and thermal properties of PLA nanocomposites have been investigated using Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicate that ALA has distinct effects on the dispersion of MMT platelets into the PLA matrix, where partial exfoliated as well as intercalated structures have been obtained, when compared with ordinary modifier, cetyltrimethyl ammonium bromide (CTAB). TGA data verifies that PLA nanocomposites with ALA‐MMT organoclay display enhanced thermal stability. The optimal clay loading of ALA‐MMT occurs at 3%wt, leading to the best compromise between clay dispersion and thermal properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Effect of organoclay on non-linear rheological properties of poly(lactic acid)/poly(caprolactone) blends

The nonlinear viscoelastic properties of PLA/PCL blends with and without clay (montmorillonite, MMT) under large amplitude oscillatory shear (LAOS) flow were investigated. The G′ and G″ as a function of strain amplitude, Lissajous plots and FT-rheology methods were used to interpret nonlinear behavior of PLA/PCL blends with and without MMT. Additionally, scanning electron microscopy (SEM) images of PLA/PCL with MMT blends were taken to investigate the effects of clay on the internal structure of the PLA/PCL blends. A relationship between morphological changes and linear and nonlinear rheological properties was observed. SEM image analysis revealed that clay acted as a compatibilizer and then reduced the size of droplets in the PCL domain of the PLA matrix. As a result, nonlinear properties sensitively reflect morphological changes with increasing MMT amount. The nonlinear rheological properties of PLA/PCL/MMT/metallocene-LLDPE (mLLDPE) were also investigated when mLLDPE was used as an impact modifier to improve mechanical properties, and the nonlinear rheological properties of PLA/PCL/MMT and PLA/PCL/MMT/mLLDPE were also compared.     

An investigation of melt rheology and thermal stability of poly(lactic acid)/ poly(butylene succinate) nanocomposites

A systematic investigation of the rheological and thermal properties of nanocomposites prepared with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and organically modified layered silicate was carried out. PLA/PBS/Cloisite 30BX (organically modified MMT) clay nanocomposites were prepared by using simple melt extrusion process. Composition of PLA and PBS polymers were fixed at a ratio of 80 to 20 by wt % for all the nanocomposites. Rheological investigations showed that high clay (> 3 wt %) contents strongly improved the viscoelastic behavior of the nanocomposites. Percolation threshold region was attained between 3 and 5 wt % of clay loadings. With the addition of clay content for these nanocomposites, liquid‐like behavior of PLA/PBS blend gradually changed to solid‐like behavior as shown by dynamic rheology. Steady shear showed that shear viscosity for the nanocomposites decreased with increasing shear rates, exhibiting shear‐thinning non‐Newtonian behavior. At higher clay concentrations, pseudo‐plastic behavior was dominant, whereas pure blend showed almost Newtonian behavior. Thermogravimetric analysis revealed that both initial degradation temperature (at a 2% weight loss) and activation energy of thermal decomposition nanocomposite containing 3 wt % of C30BX were superior to those of other nanocomposites as well as to those of PLA/PBS blend. Nanocomposite having 1 wt % of C30BX did not achieve expected level of thermal stability due to the thermal instability of the surfactant present in the organoclay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of polyvinyl acetate/montmorillonite nanocomposite by in situ emulsion polymerization technique

Exfoliated polyvinyl acetate/montmorillonite nanocomposite (PVAc/MMT) was prepared via in situ emulsion polymerization. The resulting PVAc with various organophilic MMT contents was investigated. In the nanocomposite latex preparation, sodium lauryl sulfate (SLS), ammonium persulfate (APS), and poly (vinyl alcohol) (PVA) are used as anionic emulsifier, conventional anionic initiator, and stabilizer, respectively. The samples were characterized using elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM). The XRD and AFM results demonstrate that the MMT well dispersed at molecular level in the PVAc matrix. Thermal properties of the nanocomposite were studied by using differential scanning calorimetric analysis (DSC). The exfoliated PVAc/MMT nanocomposite showed a higher glass transition temperature and a better thermal stability compared to the pure PVAc.     

亚磷酸三苯酯/蒙脱土协效阻燃聚乳酸

通过溶液浇铸法制备聚乳酸/蒙脱土/亚磷酸三苯酯(PLA/MMT/TPPi)复合膜.对其阻燃性能进行研究.结果表明:蒙脱土与亚磷酸三苯酯的协同阻燃效果明显,总添加量为1.5%时极限氧指数达到33.2%.力学测试、熟分析、缓冲溶液降解等分析结果表明:蒙脱土与亚磷酸三苯酯的加入对材料的力学性能、热性能和降解性能的影响较小.     

The nucleation effect of modified carbon black on crystallization of poly(lactic acid)

The nonisothermal crystallization of poly(lactic acid) (PLA), PLA/carbon black (CB), and PLA/modified carbon black (MCB) composites were investigated using differential scanning calorimetry (DSC) analysis. The rate of crystallization and the spherulitic morphologies of the PLA and PLA/MCB composites during isothermal crystallization were investigated using DSC and observed by means of polarizing optical microscopy (POM), respectively. The results show that either CB or MCB acts as an efficient nucleating agent for PLA. The nucleation activities of CB and MCB were quantitatively determined. It is shown that MCB has higher nucleating activity than CB in PLA. An isoconversional method correlates the temperature dependence of the effective activation energy and was used to evaluate the effective activation energy of PLA and PLA/MCB composites. It is confirmed that MCB advances the nuclei density and promotes the crystallization rate of the PLA matrix significantly. In addition, an interesting phenomenon of the periodic cracks of PLA spherulites observed by using POM is reported. The unbalanced surface stresses arising from growth features and thermal shrinkage may be the two main factors accounting for the formation of target pattern cracks. POLYM. ENG. SCI., 50:1658–1666, 2010. © 2010 Society of Plastics Engineers     

The role of nanofillers on the degradation behavior of polylactic acid

This study examines the effect of type and content of various nanofillers on the aging behavior of polylactic acid (PLA)/nanocomposites compared with that of pristine PLA, under specific environmental conditions, namely 80% relative humidity, 40°C temperature, and exposure time up to 6 months. Two different types of nanosized fillers (silica and montmorillonite, MMT) at three different weight fractions as well their mixtures were used for this purpose. The role of the various nanofillers on the aging of pristine PLA and its nanocomposites was investigated in terms of several experimental techniques including Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and tensile testing. All studied samples, except those of PLA/MMT/Si nanocomposites, exhibited the same trend in properties during aging. In particular, no significant changes are noted after 1 month of aging. The materials after 3 months of aging experienced a dramatic lowering of the stress–strain curve, whereas at 6 months a reverse effect was observed. Comparing the effect of nanofiller types on the degradation, one could conclude that PLA/MMT nanocomposites exhibit a more homogeneous degradation effect, having a higher impact on yield stress in comparison with silica. In contrast, silica has a greater effect in Young's modulus and strain at break, compared with MMT. The peculiar behavior of the PLA/MMT/Si nanocomposites during aging is explained by the hindering action of the mixture of the two nanofillers on the molecular reordering of the PLA chains in the amorphous region. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Flame retardant epoxy complex produced by addition of montmorillonite and carbon nanotube

Flame retardant additives of montmorillonite (MMT) and multi-walled carbon nanotube (MWCNT) were embedded in epoxy resin to improve the resin's resistance to oxidation. The MWCNTs reduced the degradation rate of the epoxy complex and increased the char yield, and also increased the limiting oxygen index in a first order relationship with char yield. MMT acted as an energy storage medium to hinder thermal transfer within the epoxy complex. The thermal activation energy increased upon addition of MMT/MWCNT. Addition of MMT and MWCNT significantly improved the flame retardant and anti-oxidation properties of the epoxy complex.     

The mechanical/thermal properties of microcellular injection‐molded poly‐lactic‐acid nanocomposites

This study investigated the influence of montmorillonite (MMT) content on the mechanical/thermal properties of microcellular injection‐molded polylactide (PLA)/clay nanocomposites. Carbon dioxide was the blowing agent. The PLA/MMT nanocomposites were prepared by twin screw extrusion. The results showed that as MMT content is increased, tensile strength, impact strength, and cell density decrease. This is caused by the speed degradation of PLA due to the addition of MMT. MMT decreases the crystallization temperature but increases the decomposition temperature of the nanocomposites. The XRD results showed that the layer spacing of the clay increases as MMT content increases. TEM pictures showed that the MMT is well dispersed within the PLA matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.