The effect of triethyl citrate on the dispersibility and water vapor sorption behavior of polylactic acid/zeolite composites

The aim of this study was to investigate the water vapor adsorption behavior and mechanical properties of poly (lactic acid) (PLA)/zeolite (5, 10, or 15 phr) composites prepared with triethyl citrate (TEC; 20 phr) via a melting process. TEC was used to improve the flexibility of the PLA and the dispersibility of the zeolite in TEC-zeolite suspensions that were ultra-sonicated. It was found that zeolite was uniformly dispersed in the PLA matrix, and the interfacial adhesion between the PLA matrix and zeolite was enhanced by TEC. In addition, the tensile strengths and Young's modulus of the composites improved with increasing zeolite content. The PLA/zeolite composites prepared with TEC had increased water vapor permeability and contact angles compared to neat PLA and standard PLA/zeolite due to the presence of TEC. In particular, TEC accelerated the hydrolysis of the PLA surface in a high humidity environment, resulting in an improvement in water vapor sorption capacity. At the same zeolite content of 15 phr, the equilibrium moisture content (EMC) values of PLA/zeolite films prepared with TEC increased by up to 39.25 mg/g whereas those prepared without TEC only increased by up to 24.33 mg/g. The results suggest the possibility of applying PLA/zeolite films prepared with TEC as a flexible active packaging material.     

稻壳炭基固体酸催化剂的制备及其催化酯化反应性能

以热解稻壳炭为原料, 浓硫酸为磺化剂制备了固体酸催化剂. 采用X射线衍射、X射线光电子能谱、元素分析、孔结构分析和热重-质谱联用等手段对其进行了表征. 以油酸和甲醇的酯化为探针反应, 考察了磺化温度和时间对催化剂活性的影响, 探讨了反应条件对油酸转化率的影响, 并对所制催化剂的稳定性进行了研究. 结果表明, 制备该催化剂的适宜磺化温度和时间分别为90℃和0.25 h, 在该条件下制得的催化剂为无定形碳结构, 磺酸基密度为0.7 mmol/g. 该催化剂表现出较高的催化酯化反应活性, 在催化剂用量为5%、甲醇/油酸摩尔比为4、酯化温度和时间分别为110℃和2 h的条件下, 油酸的酯化率可达98.7%. 该催化剂具有较好的稳定性, 经7次连续反应后, 油酸的酯化率仍可达96.0%.     

不同提取方法对所得稻壳基木质素的影响研究

本文以稻壳这种在我国来源十分丰富的农业副产物为原料,采用三种方法(乙二醇法、乙醇法、碱法)提取稻壳中的木质素,考察相应处理条件下的木质素提取率、羟基含量来确定提取适宜条件。乙二醇提取法所得木质素的羟基值和产率可以分别达到275.2mg/g和45.2%;乙醇法在适宜的提取条件下得到稻壳基木质素羟基值和产率分别为269.1mg/g和51.1%;碱溶液提取法可获得羟基值和产率分别为324.7mg/g和64.1%的碱木质素,无论何种木质素都富含活性官能团为后续再利用提供条件。     

钾元素对生物质及其三组分热解的影响

采用机械混合法将KCl加入到纤维素、半纤维素、木质素以及稻壳和稻壳模拟物等生物质中,得到了一系列不同K含量的生物质样品,通过热重(TG)实验考察了K元素对生物质热解特性的影响.结果表明,K元素对生物质三组分热解特性的影响比较复杂,纤维素的最大热解失重速率随着KCl添加量的增加而降低,但KCl对半纤维素和木质素热解特性的影响不显著.无论是否添加KCl,模拟生物质的热解特性均可以认为是三组分热解的简单叠加.但酸预处理稻壳三组分间的稳定结构,导致其DTG曲线在300 ℃左右的热解峰由稻壳模拟物的尖峰变为肩峰,其热解焦炭收率也比稻壳模拟物的略低.此外,实验还采用浸渍法向酸预处理稻壳中添加了KCl.TG实验结果表明,K元素的存在对生物质热解具有一定的催化作用,但KCl的添加方式不同,生物质的热解特性有明显差别,生物质样品经机械混合添加KCl后,其热解焦炭收率呈下降趋势(纤维素除外),浸渍法添加的KCl导致酸预处理稻壳的最大热解失重速率和焦炭收率升高.     

Preparation,characterization and application of maleic anhydride-modified polylactic acid macromonomer based on direct melt polymerization

A one-pot two-step method based on direct melt polymerization (DMP) for the synthesis of polylactic acid (PLA) macromonomer and its further functionalized application has been developed. The first stage of the reaction is a copolycondensation of lactic acid (LA) and maleic anhydride (MAH) to obtain the macromolecule poly(lactic acid-co-maleic anhydride) (PLAM) with reactive double bonds, and the second stage is a radical copolymerization of different acrylates with PLAM to afford the modified PLA functional materials. The influences of the acrylates have been investigated. The results show that the species with substituted methyl groups in acrylate can polymerize relatively stable. On the other hand, the more carbon atoms in the ester segment of acrylate, the higher intrinsic viscosity [η] and terminal decomposition temperature for the acrylate-modified PLAMs. Among six kinds of acrylates used as the third monomer, such as acrylic acid (AA), methyl acrylate (MA), butyl acrylate (BA), methacrylic acid (MAA), methyl methacrylate (MMA), and butyl methacrylate (BMA), the BMA-modified PLAM has the biggest [η] (0.7566 dL/g) and the terminal decomposition temperature (418 °C) for there are more carbon atoms in BMA. Due to excellent reactivity of the intermediate PLAM, the final modified product can have the anticipated properties for the PLA material by the controllable regulating as different purposes. Thus, this strategy as a green and simple method provides well application prospect for PLA materials in industrial plastics, biomedicine etc.     

The effect of dynamic crosslinking on morphology,thermal and mechanical properties of polylactic acid and bioelastomer blend

The objective of this work is to enhance the toughness of In the current study, inherently brittle polylactic acid (PLA) has been toughened using a biobased polyester without compromising the biocompatibility, renewability, strength and thermal properties of PLA. For this purpose, biodegradable Renewable resources resource based flexible aliphatic polyester (BBPE) has been synthesized and the same has been confirmed by FTIR and ¹H NMR. Melt blending of BBPE elastomer with PLA in presence of free radical initiator dicumyl peroxide (DCP) leads to the development of crosslinked PLA/BBPE (PBE) blends of tunable properties. Additionally, the mechanical, morphological, thermal, crosslink density and water absorption behaviour of PBE blends were explored. It was observed that the synthesized biobased BBPE elastomers contribute to toughening of the PLA matrix consequently, improving the its impact strength and elongation at break. of the blend     

A Study on the thermal destruction of rice husk in air and nitrogen atmosphere

The methods of X-ray analysis, infrared spectroscopy, differential thermal analysis and scanning electron microscopy were used in this study. The objects of the experiments were rice husk obtained during processing of rice, variety Krasnodarski 424. The rice husk was burnt in air and in non-oxygen medium at several burning temperatures. The color of the oxidized product was stipulated by the burning temperature. The X-ray analysis showed that the amorphous SiO₂ present in the rice husk begins to crystallize in the form of α-cristobalite at 850°C. Using differential thermal analysis, the thermal destruction of rice husk was studied in air and nitrogen media and the initial and final temperatures of the process were determined. The silica distribution was examined by scanning electron microscopy and infrared spectroscopic techniques.     

The role of Carica papaya latex bio-catalyst and thermal shock in water on synthesizing rice husk

A bio-catalyst made of natural resources, such as Carica papaya latex, is very challenging for nanoparticle separation. In addition, differences in thermal conditions between nanoparticles affect the movement of substances in the separation process. The study experimentally investigated the role of Carica papaya latex bio-catalyst and thermal shock in water on synthesizing rice husk (RH). The synthesis retained the Mg and C elements attached to SiO₂, which were generally neglected during the process. The study's objective was to evaluate the effectiveness of biocatalysts and thermal effects on the separation of Mg-SiO₂-C from rice husk carbon nanoparticles (CNPs-RH). The research involved various treatment processes, such as RH pyrolysis in obtaining charcoal, High energy milling (HEM) to have carbon particles, and washing to get nano-sized carbon particles. The bonding of elemental compounds to rice husk carbon particles (CPs-RH) was released using NaOH and coagulation using a bio-catalyst. Coagulated CPs-RH was injected into water at a temperature of 60–70 °C to have a thermal shock effect for H₂O clusters in Na⁺ and Mg²⁺ ions attached to the surface of the nanoparticles. Several tests were carried out, such as the SEM-EDX, TEM, XRD, and FTIR tests, to investigate the two nanoparticle clusters formed up to the nanometer scale. The results indicated that CNPs-RH nanoparticles consist of spherical particles with a diameter of 1.2 nm, while Mg-SiO₂-C nanoparticles have a diameter of 0.6 nm. Both are classified as amorphous. Based on the FTIR test, CNPs-RH is hydrophilic, while Mg-SiO₂-C is hydrophobic. Thermal shock in water strengthens the ion's mobility, increasing the interfacial dipole forces between nanoparticles and accelerating the separation process.     

Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6–RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6–RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V⁻¹) was proportional to the Sb(III) concentration in the range of 1.42 × 10⁻⁸ to 6.89 × 10⁻¹¹ M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 × 10⁻¹¹ M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6–RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.     

Surface treatment of lignocellulose biofiller for fabrication of sustainable polylactic acid biocomposite with high crystallinity and improved burning antidripping performance

In this work, we incorporated surface-treated coffee husks (CHs) into a polylactic acid matrix to fabricate environmentally friendly composites, with high crystallinity and satisfactory antidripping performance for flame retardancy. CHs are lignocelluloses that contain cellulose, hemicellulose, and lignin that are present as interlinked complex macromolecular structure. CH spectroscopic characterization confirmed that the phytic acid/amine silane agent was successfully attached and bonded with the cellulose portion of CHs. Morphological analysis of the composites revealed that the surface-treated CHs helped to improve the interfacial interaction between the filler and the matrix. Furthermore, the differential scanning calorimetry analysis showed that the crystallinity of the composites increased with CH loading. Flammability and combustion tests confirmed that the combined effect of P/Si/N on surface treatment improved the flame retardance behavior of the composites. The tensile strength and modulus of the composites exhibited a 28.7% and 34.4% increase compared with the corresponding composite with raw CHs.     

Structural and catalytic investigation of vanadia supported on ceria promoted with high surface area rice husk silica

Rice husk silica was utilized as the promoter of ceria for preparing supported vanadia catalysts. Effect of vanadium content was investigated with 2–10 wt.% V₂O₅ loading over the support. Structural characterization of the catalysts was done by various techniques like energy dispersive X-ray (EDX), X-ray diffraction (XRD), BET surface area, thermal analysis (TGA/DTA), FT-infrared spectroscopy (FT-IR), UV–vis diffused reflectance spectroscopy (DR UV–vis), electron paramagnetic spectroscopy (EPR) and solid state magnetic resonance spectroscopies (²⁹Si and ⁵¹V MASNMR). Catalytic activity was studied towards liquid-phase oxidation of benzene. Surface area of ceria enhanced upon rice husk silica promotion, thus makes dispersion of the active sites of vanadia easier. Highly dispersed vanadia was found for low V₂O₅ loading and formation of cerium orthovanadate (CeVO₄) occurs as the loading increases. Spectroscopic investigation clearly confirms the formation of CeVO₄ phase at higher loadings of V₂O₅. The oxidation activity increases with vanadia loading up to 8 wt.% V₂O₅, and further increase reduces the conversion rate. Selective formation of phenol can be attributed to the presence of highly dispersed active sites of vanadia over the support.     

Effects of polylactic acid and rPET minor components on phase evolution,tensile and thermal properties of polyethylene‐based composite fibers

High mechanical performance and partially biodegradable PE‐composite fibers modified with polylactic acid (PLA) and recycled polyethylene terephthalate (rPET) minor components were prepared using melt extrusion and hot drawing process. Rheological properties, morphology, tensile, and thermal properties were investigated. All blends exhibited shear thinning behavior except for starting PLA and rPET. PLA and rPET dispersed phases appeared as droplets in as‐extruded strand, and PLA droplets were mostly larger than those of rPET. The fibrillation of both PLA and rPET domains was achieved after further hot drawing as the fiber. The morphology and tensile properties of the fibers mainly depended on the types and contents of dispersed phases including draw ratios. The ultimate strength of the polymer fibers at draw ratio of 20 was more than 600 times higher than that of the as‐spun sample of the same composition. Remarkable improvement in secant modulus and ultimate strength was found for PE‐30PLA, but the drawing process of this composition encountered some difficulties and rough surface of the fiber was observed. The stiffness and tensile stress for PE‐10PLA‐10rPET fiber were clearly improved when compared with PE and PE‐10PLA. A decrease in thermal stability of PE/PLA composites was observed with increasing PLA content whereas additional presence of rPET significantly increased the stability of the composites both in nitrogen and in air. PE/PLA/rPET fiber possessing high stiffness with good thermal stability prepared in this work has high potential for being utilized as structural parts for load‐bearing applications.     

Molecular structure regulation of functional polylactic acid based on chain expansion reaction and its improved hydrolysis resistance

In this work, the functional polylactic acid (PLA) was synthesized using epoxy chain extender (ADR) as a chain extender agent through melt blending method. The effects of ADR content on the molecular structure, thermal properties, and tensile properties of the functional PLA were investigated. Meanwhile, the hydrolytic behavior of the PLA/ADR materials at different hydrolysis temperatures was explored. It was found that ADR effectively regulated the molecular structure of PLA in the molten state and significantly increased the relative molecular weight, storage modulus, and complex viscosity of PLA. In addition, the Cole-Cole diagram results suggested the branched structure of PLA chain expansion systems. Based on mechanical property tests, it was noted that the addition of ADR made the molecular chain form a micro-crosslinked structure. Additionally, the mass loss rate of PLA/1.6ADR (the dosage of ADR was 1.6 wt%) was 14.75% after 14 weeks of hydrolysis under hydrolysis conditions at 58°C, while that of pure PLA was 25.89%. Moreover, the functional PLA/ADR materials exhibited significantly slower decrease rates in molecular weight, melting temperature, and tensile strength, and still maintained intact morphology after 14 weeks of hydrolysis compared to pure PLA. Therefore, the molecular structure of PLA is effectively regulated by ADR, which greatly enhances the hydrolysis resistance and further promotes the range of application of PLA.     

Oscillatory shear‐induced alignment of ketjen black conductive particles in polylactic acid and its effect on the electrical anisotropy

This study aligned Ketjen black (KB) particles along one preferred direction in a polylactic acid (PLA) matrix using an oscillatory shear flow and investigated the effect of aligned KB on the electrical anisotropy. Under the oscillatory shear, the KB particles are aligned along the flow direction in the PLA matrix, resulting in an oriented conductive network. When the concentration of KB is in the range of 0.88–1.56 vol %, the electrical volume resistivity along the flow direction (ρ_∥) decreases to ～3 × 10⁴ Ω m and that perpendicular to the flow direction (ρ_⊥) remains at ～1 × 10¹⁰ Ω m, showing an extremely large electrical anisotropy, and the ρ_⊥/ρ_∥ value is 3–4 orders of magnitude higher than that of previously reported carbon‐nanotube‐based electrical anisotropic composites. This strong anisotropy is attributed to the preferential alignment of KB particles with lower percolation threshold for conductive path along the flow direction. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 369–373     

Design,synthesis and characterization of novel poly(urethane-urea) based on a macrodiol from poly(lactic acid) and poly(p-dioxanone)

A series of novel poly(urethane-urea)(PUU) was synthesized from poly(lactide-co-p-dioxanone) macrodiol(HO-P(LA-co-PDO)-OH), hexamethylene diisocyanate(HDI) and butanediamine(BDA).The obtained PUU,which is recorded as P(LA-co-PDO)-PUU here,may demonstrate enhanced phase separation and thus improved shape memory property.FTIR was employed to characterize the copolymers,and the effects of NCO/OH molar ratios on T_g of PUU was investigated by means of differential scanning calorimetry (DSC).The results revealed the successful synthesis of P(LA-co-PDO)-PUU.In addition,the T_g of P(LA-co-PDO)-PUU increased from 37.9℃to 44.2℃with the increase NCO/OH ratios from 1.1 to 1.2.The P(LA-co-PDO)-PUU with T_g close to body temperature will have potential applications as shape memory polymers in biomedical fields,especially in minimally invasive surgery.     

Preparation of styrene/methacrylic acid copolymer microspheres and their composites with metal particles

 Poly(styrene-co-methacrylic acid) [P(St-co-MAA)] microspheres were prepared by emulsifier-free emulsion copolymerization of St with MAA. Fourier transform IR spectroscopy and elemental analysis were used to study the change in the content of MAA in the microspheres. The results of X-ray photoelectron spectroscopy measurements indicated the presence of carboxylic functionality on the surface of the microspheres. The P(St-co-MAA) metal composite particles were prepared by chemical metal deposition. Transmission electron microscopy observation and X-ray diffraction measurement were used to study the distribution and structure of the metal particles deposited. Received: 15 September 1999 Accepted: 24 December 1999     

Influences of acid and heat treatments on the structure and water vapor adsorption property of natural zeolite

Natural zeolite was first acid treated and then heat treated. The influences of acid and heat treatments on the structure and water vapor adsorption property of natural zeolite were investigated. X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), thermogravimetric analysis (TG), and Brunauer‐Emmett‐Teller (BET) surface areas were employed to investigate the structure changes of the zeolite samples. Water vapor adsorption property of the samples was investigated in order to determine wettability of the samples. The results showed that nitric acid treatment could remove Al from the structure, decrease relative crystallinity, and significantly increase specific surface area of the zeolite samples. Heat treatment could change or even destroy the structure, effectively remove water molecules from the surface/structure, and decrease the specific surface area of the zeolite samples. Water vapor adsorptions on the acid‐treated zeolite samples were significantly lower than that for the zeolite sample, and the adsorptions further reduced for the heat‐treated zeolite samples. The increase of Si/Al ratio, decreases of silanol groups, and specific surface area of the samples were major reasons related to the reductions of water vapor adsorptions on the zeolite samples.     

Highly stable,active and recyclable solid acid catalyst based on polymer-coated magnetic composite particles

A facile approach has been adopted for coating cross-linked polystyrene(PS) shells on the surface of Fe304 magnetic clusters using reflux-precipitation polymerization(RPP).Treating the PS shell with chlorosulfonic acid yields magnetic composite particles with acid functionality.By adjusting the amount and proportion of monomers(styrene and divinylbenzene),the obtained magnetic composite particle solid acid(MPM-5 S) exhibits a saturation magnetization value of 18 emu/g,a specific surface area of 243 m~2/g and an acid density of 2.113 mmol/g.The MPM-5 S magnetic solid acid catalyst was evaluated for esterification of oleic acid with methanol to prepare biodiesel.Under mild conditions,the conversion of oleic acid reached 91%,which was much higher than the catalytic activity of Amberlyst-15 and close to the catalytic activity of concentrated H_2 SO_4.The solid acid catalyst can be recovered by magnetic separation and reused three times maintaining over 95% of its initial catalytic activity.Additionally,the solid acid can be used to catalyze the dehydration of fructose to 5-hydroxymethylfurfural.     

Highly stable,active and recyclable solid acid catalyst based on polymer-coated magnetic composite particles

Sulfonic acid-functionalized polymer-coated magnetic composite particles were prepared and applied as highly stable, active and recyclable magnetic solid acid catalyst for biodiesel preparation and biomass transformation.     

疏水双功能介孔固体酸的合成及其在乙酸乙酯酯化反应中的应用

通过水热合成法一步合成了具有不同疏水基团－CH₃ 、－(CH₃)₂ 和－(CH₃)₃的双功能介孔固体酸SBA-15-SO₃H－(CH₃)_x催化剂。通过X射线粉末衍射(XRD)、N₂吸脱附、元素分析等方法对催化剂进行了表征,并在乙酸乙酯酯化反应中进行催化性能评价。结果表明,随着疏水前驱体中甲基数的增加,样品的疏水性增强。SBA-15-SO₃H-(CH₃)_x催化剂的催化活性随着疏水性的增强而提高,而具有较强疏水性的材料SBA-15-SO₃H-(CH₃)₃在反应中具有较高的催化性能。以SBA-15-SO₃H-(CH₃)₃为催化剂,酯化反应的最优条件为：温度为120℃,乙酸与乙醇摩尔比为4∶1,催化剂质量分数为1 %,反应时间为1h。在此条件下,乙醇的转化率和乙酸乙酯的选择性分别为93%和100%。