Study of physical and mechanical properties of polypropylene nanocomposites for food packaging application: Nano-clay modified with iron nanoparticles

Polypropylene (PP) nanocomposites were prepared via melt interaction of clay in a twin screw extruder. The evaluation of PP nanocomposites containing montmorillonite (OMMT) with or without iron nanoparticles modification was studied for food packaging applications. The nanocomposites were investigated by thermal, mechanical, morphological and gas barrier analyses. The X-ray diffraction patterns of all nanocomposites revealed an increment in d-spacing of the OMMT layers and proved the compatibility of neat PP and clay, along with the intercalation and partial exfoliation of the layers. Addition of nanoparticles had reverse effect on the intercalation and exfoliation of the clay to some extent. Transmitting optical and scanning electron microscopy revealed certain homogeneity with uniform distribution of OMMT and nano-particles in the PP matrix. According to the acquired thermal properties, a tendency for the melting temperatures increased with the clay concentration. Also, crystallization temperature and crystallinity decreased with the clay concentration; however, nanoparticles compensated the effect of clay. Despite of no significant change in the ultimate tensile strength and elongation properties were observed in nanocomposites, the yield strength presented a substantial enhancement and the rigidity as well. Melt flow index (MFI) examination revealed decreasing melt viscosity of nanocomposite through increasing OMMT and iron nanoparticles. Besides, OMMT showed a high capacity to improve oxygen and water vapor barrier properties of PP. The use of clay increased the mobility distance of the gas molecules, led to oxygen permeability of neat PP being reduced whereas nanoparticle acted as an active oxygen scavenger and was capable of intercepting and scavenging oxygen by undergoing a chemical reaction with. Migration test also showed no restrictions in the use of nanocomposite films in food packaging.     

Effect of montmorillonite clay and biopolymer concentration on the physical and mechanical properties of alginate nanocomposite films

Alginate-based nanocomposites at different montmorillonite clay (MMT) loadings were produced by solvent casting method. The combined effect of biopolymer and MMT content on the mechanical and physical properties of the obtained nanocomposites was investigated. The MMT weight percent relative to alginate was varied from 1% to 5% and polymer concentration was 1 and 1.5% w/v. Films containing 5% (wt/wt) of MMT show, with respect to neat alginate, reduced water permeability of about 19% and 22% and an increased water solubility of about 36% and 40%, for 1% and 1.5% alginate films, respectively. The tensile strength of neat alginate films increased significantly with increasing alginate concentration (about 36%) but slightly increased with increasing clay content up to 3%. The values of elongation decreased with increasing the both of clay content and polymer concentration. Results on X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed well developed exfoliated nanocomposite films especially at low level of nanoclay addition.     

Preparation and characterization of polypropylene/wood flour/nanoclay composites

In this study, the effects of coupling agent and nanoclay loading on the mechanical properties and water absorption of composites are investigated. Composites based on polypropylene (PP), wood flour, nanoclay, and maleated polypropylene (MAPP) were made by melt compounding and then injection molding. The mechanical analysis showed that the biggest improvement of the tensile and flexural strengths can be achieved for the nanoclay loading at 3%. However, further increasing of the loading of nanoclay resulted in a decrease of all the mechanical properties. The maximum tensile and flexural strengths (increase of ??46%, compared to the pure PP) were achieved in the composites when 7.5% MAPP was used as coupling agent in the manufacture of the composites. Finally, it was found that addition of nanoclay or MAPP reduced the water absorption property of the composites. However, the extent of improvement in the water absorption is more prominent with MAPP.     

A novel active bionanocomposite film incorporating rosemary essential oil and nanoclay into chitosan

Montmorillonite (MMT) nanoclay and rosemary essential oil (REO) were incorporated into chitosan film to improve its physical and mechanical properties as well as antimicrobial and antioxidant behavior. The MMT weight percent relative to chitosan was varied from 1 to 5 and was activated by three REO levels (0.5%, 1%, and 1.5% v/v), and their impact on physical, mechanical, and barrier properties of the chitosan films was investigated. Total phenolic and antimicrobial activity were also evaluated. Microstructure of chitosan/MMT–REO nanocomposites was characterized through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that incorporating MMT and REO into chitosan improves water gain, water vapor permeability, and solubility of the chitosan film by more than 50%. It was also shown that the combined effect of clay and REO improves significantly the tensile strength and elongation of chitosan (p < 0.05). The XRD and FTIR results confirmed that the improvements are related to the MMT exfoliation and good interaction between chitosan and MMT in the presence of REO. Antimicrobial properties of the films also improved by REO incorporation in 1.5% v/v.     

淀粉-聚乙烯醇-大豆蛋白改性蒙脱土复合薄膜的结构与性能研究

通过大豆蛋白对天然蒙脱土进行改性,制备淀粉-聚乙烯醇-大豆蛋白改性蒙脱土复合薄膜。利用X射线衍射(XRD),透射电子显微镜(TEM)分析其结构,并且对复合薄膜的机械性能和水蒸气阻隔性能进行了研究。结果表明,当蒙脱土经大豆蛋白改性,黏土层之间的分子间力降低;淀粉、聚乙烯醇、黏土层间的相容性增加,这导致黏土片层在聚合物基质中更好的分散,形成了剥离程度较高的纳米结构。纳米结构的形成,使淀粉/聚乙烯醇薄膜水蒸气透过性显著下降,拉伸强度增加,断裂伸长率下降。     

Use of starch granules melting to control the properties of bio‐flour filled polypropylene and poly(butylene succinate) composites: Mechanical properties

The feasibility and industrial potential of using bio‐flours from tropical crop residues, in particular starch containing bio‐flours, for the manufacture of bio‐composites was investigated. Polypropylene (PP) and poly(butylene succinate) (PBS) were compounded with bio‐flours from pineapple skin (P) and from non‐destarched (CS) and destarched (C) cassava root by twin‐screw extrusion. In CS composites, two levels of starch granules melting were achieved by adjusting the extrusion temperature, enabling control of morphological and mechanical properties. The use of bio‐flours reduced tensile strength by 26–48% and impact strength by 14–40% when the proportion of bio‐flour was increased to 40% w/w, while flexural strength initially increased upon addition of bio‐flours, before decreasing at higher loads. The use of compatibilizers, in particular maleic anhydride‐polypropylene (MAPP) in PP composites with 30% bio‐flour resulted in tensile strength similar to non‐compatibilized composites with 10% bio‐flour (34–35 MPa). MAPP also increased flexural strength to higher levels than pure PP, resulting in a stronger, but less flexible material.     

Preliminary study of the stiffness enhancement of wood–plastic composites using carbon nanofibers

Vapor-grown carbon nanofibers (CNFs) were compounded into polypropylene (PP) with southern pine wood flour (WF) by high shear melt blending to investigate the reinforcement effects of CNFs on the stiffness of conventional wood flour/plastic composites. CNF loadings of 1, 2 and 5 parts by weight per 100 parts of PP were employed with three WF levels (20, 40 and 60 parts). Maleated polypropylene (MAPP) was used as a coupling agent to improve WF to PP compatibility. The incorporation of CNFs significantly increased the modulus of elasticity of these nanocomposites with MAPP addition. The presence of 0.61 wt?% of CNF within a 36.6%WF/1.83%MAPP/61%PP composite exhibited a modulus (7590 MPa) that was 59% greater than its counterpart without CNF (36.8%WF/1.84%MAPP/61.4%PP) (4783 MPa) and 90% greater than pure PP. The origin of this enhancement is not yet understood.     

Impact of Pre‐Processing of Montmorillonite on the Properties of Melt‐Extruded Thermoplastic Starch/ Montmorillonite Nanocomposites

A simple and environmentally‐friendly processing method was used to prepare thermoplastic starch (TPS)/ montmorillonite (MMT) nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that glycerol could enlarge the d‐spacing and destruct the layered structure of MMT effectively during the pre‐processing of MMT. So the enlarged d‐spacing and fragmentized platelets of glycerol activated‐MMT were a precondition to form intercalated or exfoliated TPS‐based nanocomposites during the melt extrusion processing. These highly dispersive and compatible TPS/activated‐MMT nanocomposites had increased thermal stability and tensile properties as compared with non‐activated composites. Especially, the tensile strength of nanocomposites could be enhanced to 8.6 MPa, the improvement was about two times the initial tensile strength of TPS.     

Characterization and antimicrobial activity studies of polypropylene films with carvacrol and thymol for active packaging

Antimicrobial active films based on polypropylene (PP) were prepared by incorporating thymol and carvacrol at three different concentrations: 4, 6 and 8 wt.% of both additives as well as an equimolar mixture of them. A complete thermal, structural, mechanical and functional characterization of all formulations was carried out. SEM micrographs showed certain porosity for films with high additives concentrations. A decrease in elastic modulus was obtained for the active formulations compared with neat PP. The presence of additives did not affect the thermal stability of PP samples, but decreased PP crystallinity and oxygen barrier properties. The presence of thymol and carvacrol also increased stabilization against thermo-oxidative degradation, with higher oxidation induction parameters. Finally, thymol showed higher inhibition against bacterial strain present in food compared with carvacrol, leading to higher antimicrobial activity. The obtained results proved the permanence of certain amounts of the studied additives in the polymer matrix after processing making them able to be used as active additives in PP formulations.     

纤维素纳米纤维/纳米蒙脱土复合气凝胶制备及其结构与性能

针对纤维素纳米纤维(CNF)气凝胶易燃、强力低等问题,利用纳米蒙脱土(MMT)共混改性纤维素纳米纤维,基于冷冻干燥的方法制备阻燃隔热的CNF/MMT复合气凝胶。研究了MMT质量分数对CNF/MMT复合气凝胶形貌结构、压缩性能、热稳定性、热导率和阻燃性能的影响。结果表明:MMT的引入使气凝胶具有更加紧密的片层结构,气凝胶力学性能、热稳定性和阻燃性能得到改善;在MMT质量分数为50%时,CNF/MMT复合气凝胶的表观密度最大且仅为0.016 8 g/cm³,应变为10%的应力最大为12.45 kPa,应变为70%的应力最大为77.93 kPa,导热系数最大为 0.04 W/(m·K); 气凝胶中MMT质量分数不低于42.9%时,复合基气凝胶的极限氧指数得到明显提升。     

Preparing dyeable PP fiber nanocomposites using the special cubic mixture experimental design

Polypropylene (PP) fibers loaded with two different amounts of nanoclay (3 and 5%) were prepared by melt mixing technique. Mixture design was used to find these two optimum percentages for preparing the fiber. The PP nanocomposite fibers obtained were uniformly dyed with three distinct disperse dyes at 100 and 130°C. The enhanced dyeability of PP nanocomposite fiber was characterized by spectrophotometric measurements and polarized optical microscope. Good wash fastnesses were obtained after subjection of dyeing to a reduction clear process. It was found that increasing the nanoclay content had a significant effect on dye uptake. Tensile strength tests showed improvements in mechanical properties. Differential scanning calorimeter analysis shows that degrees of crystallinity of the nanocomposites were decreased by increasing the clay content. The dispersion of the nanoclay, a particle in PP, was studied by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analytical techniques.     

Effect of TiO2 nanoparticles on basalt/polysiloxane composites: mechanical and thermal characterization

In the present investigation, a novel technique has been developed to fabricate composite materials containing TiO₂ nanoparticles, polysiloxane resin, and basalt fabric. A high-intensity ultrasonic probe was used to obtain a homogenous molecular mixture of TiO₂ nanoparticles and polysiloxane resin, thus the nanoparticles were infused into the resin through sonic cavitation. The loading effect of TiO₂ nanoparticles on the thermal and mechanical properties of basalt fabric reinforced polysiloxane composite materials has been investigated. Composite samples were prepared, each using two layers of basalt fabric with TiO₂ nanoparticles loading from 0.5, 1, 1.5, 2, 2.5, and 3% by weight. Size distribution of nanoparticles was observed by particle size analyzer and the prepared fabric nanocomposites were characterized by scanning electron microscopy, dynamic mechanical analysis (DMA), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC). Tensile testing was performed as per American standard for testing of materials (ASTM) standards. The dependence of dynamic mechanical parameters E′, E′′, tan (delta), T _g, and heat distortion temperature (HDT) are associated with the filler content and can be controlled by the curing conditions. Tensile results show that 1.5 wt.% loading of TiO₂ nanoparticles in the nanocomposites resulted in highest improvement in tensile modulus compared to the neat system. DMA studies also revealed that 1.5 wt.% doped system exhibits highest storage modulus as compared to the neat and other loading percentages. DSC and TGA studies show that T _g and HDT of the composite increases with the increase in wt.% of nanofillers in the composite. Based on these results, it is clear that miscibility of nanoparticles in the resin is of prime importance with regard to performance.     

Polypropylene fibers modified by polyvinyl alcohol and montmorillonite

This paper describes the preparation of modified polypropylene (PP) fibers. The modified PP composite was prepared by compounding PP in the presence of polyvinyl alcohol (PVA), PP grafted with maleic anhydrate (PPMAH), and montmorillonite (MMT). The resultant PP/PVA/PPMAH/MMT nanocomposite was easily spinnable and the obtained fibers were able to undergo orientation, using the drawing process at which the PP matrix is oriented in the direction of the fiber axis. The thermal properties, degradation, and dyeability of the fibers were studied. The presence of PVA in the fibers supports both the formation of β-modification of PP crystallinity and facilitates the dyeability of the modified PP fibers.     

Alkali Extracted Steam-Exploded Acacia mangium Wood Fiber as Reinforcing Material for Polypropylene-Based Composites

Abstract

Composites of polypropylene (PP) and alkali extracted steam-exploded Acacia mangium wood fiber (AEF) were prepared. The fiber was grafted with maleated polypropylene (MAPP), either Epolene E-43 or Epolene G-3003. Their performance as a compatibilizing agent was compared. Treated fibers were characterized with SEM, ESCA, and FTIR. SEM and ESCA showed the presence of both MAPPs at the fiber surfaces. FTIR spectroscopy was unable to detect ester links between MAPP and AEF. All mechanical properties were improved with the incorporation of the treated fibers due to improved fiber dispersion and fiber/matrix adhesion as revealed by optical and scanning electron micrographs. As a compatibilizer, Epolene E43 performed better than E polene G-3003.     

石墨烯及石墨烯基复合材料研究进展

石墨烯作为一种新型二维平面纳米材料,其特殊的单原子层结构赋予了它许多新奇的物理性质,如优异的力学性能、良好的导电和导热性能、极佳的气体阻隔性能等,在各种领域均表现出良好的应用前景。目前石墨烯及石墨烯基复合材料的制备及应用已成为材料界研究的重点和热点。本文在简要介绍石墨烯的结构和性质的基础上,总结了近年来石墨烯及石墨烯基复合材料的研究概况,介绍了四种石墨烯制备方法;概述了石墨烯基复合材料的制备工艺;并着重分析了石墨烯对其复合材料力学性能、导电性能、导热和耐热性能以及气体阻隔性能的影响规律,展望了石墨烯及石墨烯基复合材料的发展前景及研究方向。     

High resolution electron microscopy structural studies of organo-clay nanocomposites

Engineering of clay nanocomposite materials by modification of their surfaces can enable the control of retention, transport, and persistence of toxic chemicals in the geosystem. The properties and interactions of clay nanocomposites have been widely studied, but little information exists on their microstructure at a range of scale extending down to atomic dimensions. The pairing of Na-montmorillonite clay with organic cations as well as with the herbicide fluridone, chosen as a model for an organic pollutant, was studied. Three organic cations were selected: hexadecyltrimethylammonium, benzyltrimethylammonium, and benzyltriethylammonium at 0%, 60%, and 100% of cation exchange capacity (CEC) loadings. A detailed microstructural analysis of the organo-clay nanocomposites and of the fluridone nanocomposites was undertaken by high-resolution transmission electron microscopy (HRTEM) and X-ray energy-dispersive spectroscopy (EDS). Morphological observations and chemical analyses were performed simultaneously on the same sample. The combined HRTEM and EDS measurements strongly suggest (a) heterogeneous local intercalation of the organic cations manifested by a range in the measured d001 spacing, implying random expansion of the clay layered structure with increased loading of the organic cations; (b) intercalation within the external layers, which is thoroughly influenced by local defect microstructure and/or edge availability of the montmorillonite nanoparticles as well as by the molecular structure of the intercalating organic cation. Additional intercalation of fluridone molecules did not affect the structure (d001 spacing) of the organo-clay nanocomposites.     

Effect of Type and Content of Modified Montmorillonite on the Structure and Properties of Bio-Nanocomposite Films Based on Soy Protein Isolate and Montmorillonite

Abstract: The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na⁺). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.     

Preparation and characterization of bio-nanocomposite films based on soy protein isolate and montmorillonite using melt extrusion

The non-biodegradable and non-renewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and montmorillonite (MMT) were prepared using melt extrusion. Effects of the pH of film forming solution, MMT content, and extrusion processing parameters (screw speed and barrel temperature distribution) on the structure and properties of SPI–MMT bio-nanocomposite films were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used for structural characterization of the films. Properties of the films were determined by tensile testing, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and water vapor barrier measurement. The arrangement of MMT in the soy protein matrix ranged from exfoliated at lower MMT content (5%) to intercalated at higher MMT content (15%). There was a significant improvement in mechanical (tensile strength and percent elongation at break) and dynamic mechanical properties (glass transition temperature and storage modulus), thermal stability, and water vapor permeability of the films with the addition of MMT. The results presented in this study show the feasibility of using bio-nanocomposite technology to improve the properties of biopolymer films based on SPI.     

熔融纺聚乳酸/聚丙烯纤维的制备及其性能

为提高聚乳酸(PLA)纤维的力学性能,采用聚丙烯(PP)与聚乳酸(PLA)通过熔融纺丝制备PLA/PP纤维,并借助差示扫描热量仪、热重分析仪、万能材料测试仪、纤维双折射仪对其热学性能、热稳定性、拉伸性能和纤维取向度进行表征。结果表明:PP的引入对PLA的玻璃化转变温度和熔融温度没有显著影响,但促进了PLA的结晶,结晶度提高了585.9%;随着PP质量分数的增加,PLA的热稳定性降低(特别是在初始分解阶段),但其残炭率提高,同时PLA/PP共混纤维的取向度提高,力学性能得到改善;当PP质量分数为20%时,PLA/PP共混纤维的取向度、断裂强度和断裂伸长率分别提高了55.6%,98.2%和44.4%。     

乙二醇二缩水甘油醚/蒙脱土协同增强大豆蛋白膜的性能研究

为了提高大豆分离蛋白(SPI)材料的耐水性能与力学性能,扩大其在食品工业领域的应用。本研究以SPI和蒙脱土(MMT)为原料,乙二醇二缩水甘油醚(EGDE)为交联剂,制备SPI/MMT复合膜,并对其物理力学性能及水阻隔性能进行探究。结果表明:MMT和EGDE的加入均能够有效提高复合膜的物理力学性能,当SPI复合膜中同时添加MMT和EGDE(20%)时,各项性能最佳,复合膜拉伸强度为14.95 MPa,比纯SPI膜增加了239.77%、弹性模量增加88.98%、含水率降低16.12%、吸湿性降低31.07%、总溶解物降低39.68%、水蒸气透过率降低35.85%。EGDE与MMT的协同增强作用,提高了SPI复合膜的物理力学性能与水阻隔性。