A new assessment on mechanical properties of jute fiber mat with egg shell powder/nanoclay-reinforced polyester matrix composites

ABSTRACT

Natural fiber polymer matrix composites occupy the major percentage in applications due to its ecofriendly and low-cost nature. This study investigates the mechanical properties of a polyester matrix nanocomposite reinforced by the NaOH-treated jute fabric mat (NJM) and untreated jute fabric mat (UJM). In addition, the effects of egg shell powder (ESP) and nanoclay (NC) to the above has also been studied. The matrices were prepared with different combinations of presence and absence of the ESP, NC, and both as well as different weight percentage using compression molding process. The mechanical and morphological properties of the composites were determined. The tensile strength, flexural strength, and impact strength of NJM with NC 1.5%wt and ESP 1.5%wt were found to be 29.28 MPa, 39.51 MPa and impact strength 3.03 J, respectively. This composition is superior to the other compositions. Morphological analysis of tensile fractured surface showed interfacial adhesion between UJM and NJM composites. NJM composites contained smaller amount of pullouts and the splits compared with the UJM composites, which hold up the better performance.     

Electrospun zein/PVA fibrous mats as three-dimensional surface for embryonic stem cell culture

This paper reports a new method of producing electrospun zein/polyvinyl alcohol (PVA) mats as three-dimensional (3D) cell culture surface material. The electrospun structure has many advantages and protein-based biomaterials possess unique properties preferred for cell biocompatibility. However, electrospun fiber matrices developed from proteins have poor mechanical properties and morphological stability in the aqueous environments required for cell culture. Efforts have been made to improve the properties of electrospun protein scaffolds, including dry mechanical for handling and surface hydrophilicity, but the current methods have major limitations, such as cytotoxicity and low efficiency. In this research, experimental data showed that the adding different proportion of PVA influenced the properties of the zein mats. Considering the properties of the mats and mouse embryonic stem cells growth behavior on the various electrospun mats, the EM3 (zein/PVA with mass ratios of 3:1) showed better growth status than any other mats. EM3 affixed to cover-glass could be autoclaved for 30?min at 120°C. In addition, embryonic stem cells cultured on chosen electrospun zein/PVA mats in vitro proved that culture products were easily attached onto mat and mat could be used for induction of stem cell differentiation and therefore promising mats for 3D cell culture surface applications.     

细菌纤维素/聚己内酯微米纤维复合膜的制备及性能

为制备模拟细胞外基质结构的微纳尺度复合材料,利用静电纺丝技术制备了聚己内酯(Polycaprolactone,PCL)微米纤维膜,通过与纳米尺度的细菌纤维素(Bacterial Cellulose,BC)原位复合,制备了BC/PCL复合纤维支架。采用扫描电镜、红外光谱分析、X射线衍射分析对材料的形貌、结构进行了表征。通过单轴力学测试对复合材料力学性能进行了研究,并利用成纤维细胞对复合材料的生物相容性进行评价。结果表明:通过静电纺丝法制备的PCL微米纤维的平均直径,随聚合物纺丝液质量分数的增加有增加的趋势,BC与PCL微米纤维复合后,BC纳米纤维渗透入微米纤维膜内部,实现微纳米纤维较好的复合。红外光谱分析和X射线衍射分析进一步证明BC和PCL微米纤维成功复合。PCL微米纤维膜复合BC膜后,相比PCL微米纤维膜增加了其断裂强度,同时复合支架无明显细胞毒性,可应用于生物医学领域。     

Influences of moisture absorption and chemical treatments on the resin flow characteristics of natural fibre nonwoven mats

A major challenge for the use of natural fibres in polymeric composites is their incompatibility with commonly used matrices, causing weak interfaces of the final composites. Many surface treatments to natural fibres have been proposed to eliminate or reduce these problems. In this paper, we evaluate the influences of three commonly used natural fibre chemical treatments on the resin flow characteristics of flax fibre nonwoven mats in a vacuum-assisted resin transfer moulding process. The alkalization treatment significantly increases the in-plane permeability and flow anisotropy of the natural nonwoven mat due to changes in fibre diameter, fibre surface tension and mat structure. The effects of silane and acetylation treatments on resin flow are much smaller. It is well known that in comparison with glass fibre, natural fibres can absorb a large amount of moisture from surrounding air. The absorption of moisture causes a considerable reduction in the in-plane permeability of natural fibre nonwoven mats.     

天然高聚物的静电纺丝技术及应用

天然高聚物具有良好的生物相容性、生物降解性和人体亲和性,用其静电纺得的制品可广泛应用于生物医学、防护服装、内衣和农业等许多领域。文章主要介绍了天然高聚物的静电纺丝工艺以及日前静电纺天然高聚物的应用情况,并对其未来的发展趋势进行了展望。     

Glassy state in relation to the thermal inactivation of the enzyme invertase in amorphous dried matrices of trehalose, maltodextrin and PVP

The stabilization of invertase by its incorporation in aqueous trehalose and polymer solutions, followed by freeze-drying and desiccation to ‘zero’ moisture content, was studied. The dried amorphous preparations of trehalose, maltodextrin (MD; DE = 10.9), and poly(vinyl)pyrrolidone (PVP), molecular weights 360000, 40000 and 10000, greatly protected invertase—as compared with its behavior in liquid solution—from heat inactivation at elevated temperatures. Significant invertase inactivation was observed in heated PVP and MD matrices kept well below their glass-transition temperature. Under glassy conditions the extent of enzyme protection by MD and PVP systems was related to their glass-transition temperature (T_g) since systems of higher T_g afforded better protection. However, the data for trehalose deviated from this behavior since invertase stabilization was higher than expected on the basis of the results obtained with polymer matrices. Present results suggest that invertase inactivation in dried amorphous systems cannot be adequately explained by the glass-transition theory and this is particularly true for trehalose, for which some additional mechanism of enzyme protection is likely to operate.     

Physical characteristics of fish oil encapsulated by β-cyclodextrin using an aggregation method or polycaprolactone using an emulsion–diffusion method

Fish oils have many dietary benefits, but have strong odours and are easily oxidised. For these reasons, β-cyclodextrin (β-CD) a water-soluble polymer and polycaprolactone (PCL) a water-insoluble polymer were used to encapsulate fish oil in this study. In addition, the stabilities of freeze-dried fish oil (FO) in encapsulated complexes were investigated to determine fish oil release rates at different relative humidities and storage temperatures. In order to facilitate the practical applications of the water-soluble and insoluble fish oil complexes produced, release studies of fish oil were performed in de-ionised water, NaCl solution and fish sauce. Based on our studies, fish oil loaded β-CD at a mixing ratio of 10:20 (β-CD:FO (w:w)) was the best composition in terms of encapsulation efficiency (84.1%), fish oil loading (62.7%), fish oil leakage after freeze-drying (11.0%), and eicopentaenoic acid (EPA) encapsulation efficiency (6.5%). In addition, fish oil release rates from β-CD particles were slower in de-ionised water and in 15% and 25% NaCl than in fish sauce at all mixing ratios between β-CD and FO. The storage stabilities of freeze-dried β-CD–FO complexes at 10:20 (w:w) mixing ratio at various relative humidities retained 97% of fish oil within the particles during 3 days. However, the release rate of fish oil from β-CD–FO complexes of 10:20 mixing ratio was accelerated in fish sauce. In terms of the emulsion–diffusion method, PCL more efficiently retarded the release of FO in liquid or powder form, although particles were broken by freeze-drying. It is supposed that PCL better protected FO because of its water insolubility.     

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: laboratory column evaluation

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats (installed in series) to be used as permeable reactive barriers for delivery of oxidants and reductants to induce sequential bioremediation of ammonium-contaminated groundwater (approximately 120mg L(-1) NH4+-N), without bioaugmentation. The strategy was for the first group of polymer mats to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/ nitrate as the groundwater moved past and for the second group of polymer mats to deliver hydrogen or ethanol, to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. Once purging of the first polymer mat commenced, ammonium concentrations decreased downgradient from the polymer mats. Nitrification rates increased and stabilized over the 6-month experiment, with stable nitrification half-lives in the range 0.07-0.25 days. Nitrification most likely occurred in a biologically active zone at the polymer wall/aqueous interface. With hydrogen delivery via the polymer mats, a denitrification half-life (nitrate plus nitrite removal) of 3.5 days was induced. Denitrification rates were significantly enhanced when ethanol was delivered via a polymer mat, with denitrification half-lives in the range of 0.12-0.34 days. Nitrification/ denitrification rates were maintained for groundwater flow rates up to 300 m yr(-1), suggesting oxygen and ethanol delivery rates via the polymer mats were sufficient not to limit nitrification or denitrification. In soil columns, the polymer mat delivery system provided an effective and reliable technique for delivery of oxygen and hydrogen or ethanol for sequential nitrification/denitrification of ammonium-contaminated groundwater. Scale-up of this concept to a field pilot-scale is currently underway.     

Modeling the physical processes relevant during hot pressing of wood-based composites. Part II. Rheology

A rheological model to describe the development of the vertical density profile and of internal stresses within wood-furnish mats during hot pressing is presented in this paper. The rheological model is part of a comprehensive three-dimensional simulation model that accounts for those mechanisms most important during the pressing process, including heat and mass transfer inside the mat and adhesive cure. To model the rheological behavior of the mat, the four-element Burgers model commonly used to describe visco-elastic material behavior has been expanded with the addition of a fifth element that represents plastic and micro-fracture related deformation. The coefficients of the non-linear model are highly dependent on the material conditions. Equations of the coefficients as a function of temperature, moisture content and density, as well as a mathematical formulation of the five-element model is presented in this paper. Furthermore, model predictions for both a batch and a continuous press are given. A comparison with experimental results shows that the expanded Burgers model is suitable to predict typical features of the vertical density profile, such as the development of density maxima near the surfaces, shoulders or side maxima as a consequence of intermediate or final densification steps, and differences in the density profile between the mat center and the edges in the horizontal plane. Such agreement provides the basis for a wide range of industrial and research applications.     

Long term hygroscopic characteristics of polypropylene based hybrid composites with and without organo-modified clay

Recycled PP contains various impurities and has poor and variable mechanical properties compared to virgin PP. This, in general, rules out the use of recycled PP in the original applications and in other high-value applications. Hence, this study investigated the effects of polymer matrix type, weight fraction of wood flour and organoclay on the thickness swelling and water absorption behavior of PP based hybrid composites. WPCs based on polypropylene (virgin and recycled), wood flour, organoclay and maleated polypropylene (MAPP) were made using melt compounding and subsequent injection molding. Composites made from recycled polypropylene (rPP) exhibited better dimensional stability compared to the virgin (vPP) based ones. Besides, wood flour did not completely encapsulate in the polymer matrix at 50 % weight fraction. Incorporation of nanoclay exhibited a beneficial effect on both the water absorption and thickness swelling by creating a tortuous path as a result of its characteristic barrier property. The improvements in hygroscopic characteristics of hybrid composites using rPP and nanoclay were further supported by scanning electron microscopy and X-ray diffraction methods. Conclusively, PP recycled from post-consumer applications can be used in value-added composites without accepting the expense of separating out impurities from the polymer.     

Experimental Investigation of Load Settlement Behavior of Coir Mat and Coir Fiber Reinforced Sand

An experimental study in terms of model footing test were performed to comparatively assess the effect of form of reinforcement, viz., mat and fiber, on the load intensity response of reinforced sand. Coir reinforcement was used in this present investigation to assess comparative performance of coir mat and coir fiber reinforced sand, as it is highly durable among all other natural materials. Model footing test were conducted by placing coir mat and coir fiber at different u/B ratios. Load deformation behavior was compared with the help of peak strain, bearing capacity ratio and settlement reduction factor. The experimental and calculated theoretical values of peak stress of coir mat reinforced sand were compared and found that both the values were in good agreement with predicted values. The results of the present experimental investigation indicated that the form of reinforcement viz., mat/grid and fibers has significant influence on load deformation behavior of reinforced sand. Coir mat when located within the failure zone intercepting the shear zone below the loaded footing is most beneficial in terms of load carrying capacity of reinforced sand, in consistent with earlier investigations. However maximum increase in bearing capacity of coir fiber reinforced sand does indicate an optimum u/B ratio of 1.0. Maximum SRF for coir mat reinforced sand corresponds to u/B = 0.6 where for coir fiber reinforced sand it corresponds to u/B = 1.0.     

Development of PEO nanofibers having novel morphologies via distance positioning apparatus

In this study, PEO nanofibers with novel architectures were developed via newly designed distance positioning apparatus in order to feed polymer solution in a different way. The surface morphology and alignment of nanofibers were observed using a scanning electron microscope (SEM). SEM micrographs revealed that different morphologies could be obtained by changing feeding position. For the first time in the nanofibers literature; nanofibers were simultaneously collected on three different positions (collector plate, X-axis, and Y-axis) and surface morphology of these nanofibers was found to be different which is promising in terms of their potential regarding utilization of same nanofibrous mat for functional applications.     

聚己内酯/聚乙二醇大孔径纳米纤维膜的制备及其在组织工程支架中的应用

为使细胞在静电纺纳米纤维支架上得到更佳的生长与黏附,采用改进的静电纺丝装置制备具有良好生物相容性的聚己内酯(PLC)/聚乙二醇(PEG)大孔径复合纳米纤维膜,探究纺丝溶液中溶质质量配比与溶液质量分数对纳米纤维膜形貌及性能的影响,确定最佳工艺参数;将最佳工艺条件下制备的纳米纤维膜初步应用于组织工程,并与传统静电纺丝装置制备的纤维膜进行细胞相容性对比分析。结果表明:当PLC和PEG的混纺质量比为80∶20,纺丝溶液质量分数为25%时,获得的PCL/PEG大孔径纳米纤维膜质量最好;与传统静电纺PCL/PEG纳米纤维膜相比,PCL/PEG大孔径纳米纤维膜更利于细胞的生长和增殖,更适合作为组织工程支架材料。     

Role of initial apparent viscosity and moisture content on post irradiation rheological properties of guar gum

Guar gum is a polygalactomannan used in various industries. Previous studies on radiation processing of guar gum showed a decrease in its viscosity during irradiation. Present work reports rheological properties and magnitude of depolymerization as affected by initial apparent viscosity (AV) and moisture contents of guar gum during irradiation processing. Rate of degradation was found to be dependent on the initial moisture content of guar gum during irradiation. D₅₀ values for oven dried gum was 490 Gy and it increased to 1250, 2600 and 2420 Gy in samples having 10%, 25% and 30% initial moisture respectively. EPR spectroscopy showed disappearance of anisotropic signals with increasing moisture content indicating crosslinking of polymer. FTIR spectroscopy results suggested that there were no major chemical functional group transformations during irradiation.     

Effect of Alkali and Silane Treatments on Mechanical and Interfacial Bonding Strength of Sugar Palm Fibers with Thermoplastic Polyurethane

Sugar palm fibers (SPF) are one of valuable natural fibers which are abundantly available in Malaysia as agricultural biomass. The aim of this study to investigate on the effects of alkali, silane, and combination between alkali (6%) and silane (2%) on physical and mechanical properties of SPF to improve interfacial bonding of SPF with thermoplastic polyurethane (TPU) matrices. Scanning electron microscopy and Fourier transform infrared spectroscopy was used to observe the effectiveness of the alkali and saline treatments in the removal of impurities. Silane treated SPF exhibits better tensile strength than those of alkali, alkali-silane treated and untreated SPF. Droplet test indicates that the interfacial stress strength (IFSS) of alkali and silane treated SPF are enhanced whereas silane treated fibers exhibit highest IFSS. It is assumed that fiber treatments will help to develop high performance SPF reinforced polymer composites for industrial applications.     

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: field evaluation

A pilot-scale field trial was undertaken to evaluate the potential of in situ polymer mats (installed in series) as permeable reactive barriers within a treatment wall remediation system to induce sequential bioremediation of ammonium-contaminated groundwater. The treatment wall consisted of 10 m wide impermeable wings on either side of a 0.75 m wide permeable reactive zone flow-through box. Two polymer mats were positioned in the flow-through box. The upgradient polymer mat within the flow-through box was used to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/nitrate as the groundwater moved past. The downgradient polymer mat delivered ethanol to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. The field trial was carried out at a near-shore location. Initially the flow-through box was left open; however, this resulted in substantial groundwater mixing, which inhibited sequential remediation. Once the flow-through box was in-filled with gravel, groundwater mixing was reduced, achieving a greater than 90% reduction in total N. Estimated first-order half-lives for nitrification and denitrification rates were 1.2 and 0.4 d, respectively. Field nitrification half-lives were approximately an order of magnitude greater than rates determined in large-scale columns using soil and groundwater from the site, while denitrification half-lives were similar. The results of this pilot-scale field trial indicate that sequential bioremediation of ammonium-contaminated groundwater at field scale is feasible using in situ polymer mats as permeable reactive barriers, although hydraulic conditions can be complex in such barrier systems.     

离散系统最优极点配置问题的研究

提出了一种以极点移动为基础的离散系统最优极点配置的新方法，得到了加权矩阵和最优闭环系统在频域内的关系；讨论了指定闭环极点的选择问题，并举例说明了该方法的有效性和简便性。这种方法的主要优点是保证了加权矩阵的正定性以及不需要求解复杂的矩阵代数Ｒｉｃｃａｔｉ方程也可确定满足指定闭环极点配置要求的状态反馈增益矩阵。     

A Review on Natural Fibre-Based Composites—Part II

Abstract

Natural abundance, much higher strength per unit weight than most inorganic fillers, lower density and their biodegradable nature make natural fillers attractive as reinforcements of engineering polymer systems. However, certain drawbacks such as incompatibility with the hydrophobic polymer matrix, the tendency to form aggregates during processing and poor resistance to moisture greatly reduce the potential of natural fibres to be used as reinforcements in polymers. In this review, the main results presented in literature are summarized, focusing on the processing behaviour and final properties of natural fibres with polymeric matrices (thermoplastics, thermosets and biodegradables) and paying attention to the use of physical and chemical treatments for the improvement of fibre-matrix interaction and composite mechanicaln properties. This work mainly focuses on the use of natural fibres for automotive applications.     

Effects of short-term repeated exposure to different flooring surfaces on the behavior and physiology of dairy cattle

Dairy cattle managed in some pasture-based systems such as in New Zealand are predominantly kept outdoors all year around, but are often taken off pasture for periods of time in wet weather to avoid soil damage. It is common to keep cattle on concrete surfaces during such “stand-off” practices and we investigated whether the addition of rubber matting onto concrete areas improves the welfare of dairy cattle. Sixteen groups of 5 cows (4 groups/treatment, 5 cows/group) were allocated to 1 of 4 treatments (concrete, 12-mm-thick rubber mat, 24-mm-thick rubber mat, or deep-bedded wood chips) and kept on these surfaces for 18 h/24 h for 4 consecutive days (6 h on pasture/24 h). Each 4-d stand-off period was repeated 4 times (with 7 d of recovery between periods) to study the accumulated effects of repeated stand-off. Lying behavior was recorded continuously during the experiment. Gait score, stride length, hygiene score, live weight, and blood samples for cortisol analysis were recorded immediately before and after each stand-off period. Cows on wood chips spent the most time lying, and cows on concrete spent the least time lying compared with those on other surfaces [wood chips: 10.8 h, 24-mm rubber mat: 7.3 h, 12-mm rubber mat: 6.0 h, and concrete: 2.8 h/18 h, standard error of the difference (SED): 0.71 h]. Cows on concrete spent more time lying during the 6 h on pasture, likely compensating for the reduced lying during the stand-off period. Similarly, cows on concrete spent more time lying on pasture between stand-off periods (concrete: 12.1 h, 12-mm rubber mat: 11.1 h, 24-mm rubber mat: 11.2 h, and wood chips: 10.7 h/24 h, SED: 0.28 h). Cows on concrete had higher gait score and shorter stride length after the 4-d stand-off period compared with cows on the other surface types, suggesting a change in gait pattern caused by discomfort. Cows on rubber mats were almost 3 times dirtier than cows on concrete or wood chips. Cortisol and live weight decreased for all treatment groups during the stand-off period. We observed no major effect of the repeated stand-off exposure. In summary, adding rubber matting onto concrete surfaces for stand-off purposes is beneficial for animal welfare. A well-managed wood chip surface offered the best welfare for dairy cows removed from pasture, and the findings of this study confirm that a concrete surface decreases the welfare of cows removed from pasture.