Hasil untuk "Polymers and polymer manufacture"

M. Mehdikhani, L. Gorbatikh, I. Verpoest et al.

Voids, the most studied type of manufacturing defects, form very often in processing of fiber-reinforced composites. Due to their considerable influence on physical and thermomechanical properties of composites, they have been extensively studied, with the focus on three research tracks: void formation, characteristics, and mechanical effects. Investigation of voids in composites started around half a century ago and is still an active research field in composites community. This is because of remaining unknowns and uncertainties about voids as well as difficulties in their suppression in modern manufacturing techniques like out-of-autoclave curing and parts with high complexity, further complicated by increased viscosity of modified resins. Finally, this is because of the increasing interest in realization of more accurate void rejection limits that would tolerate some voidage. The current study reviews the research on formation, characterization, and mechanical effects of voids, which has been conducted over the past five decades. Investigation and control of void formation, using experimental and modeling approaches, in liquid composite molding as well as in prepreg composite processing are surveyed. Techniques for void characterization with their advantages and disadvantages are described. Finally, the effect of voids on a broad range of mechanical properties, including inter-laminar shear, tensile, compressive, and flexural strength as well as fracture toughness and fatigue life, is appraised. Both experimental and simulation approaches and results, concerning voids' effects, are reviewed.

Meltem A Karataş, H. Gökkaya

Abstract Fiber reinforced polymer (FRP) composite materials are heterogeneous and anisotropic materials that do not exhibit plastic deformation. They have been used in a wide range of contemporary applications particularly in space and aviation, automotive, maritime and manufacturing of sports equipment. Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials, among other fiber reinforced materials, have been increasingly replacing conventional materials with their excellent strength and low specific weight properties. Their manufacturability in varying combinations with customized strength properties, also their high fatigue, toughness and high temperature wear and oxidation resistance capabilities render these materials an excellent choice in engineering applications. In the present review study, a literature survey was conducted on the machinability properties and related approaches for CFRP and GFRP composite materials. As in the machining of all anisotropic and heterogeneous materials, failure mechanisms were also reported in the machining of CFRP and GFRP materials with both conventional and modern manufacturing methods and the results of these studies were obtained by use of variance analysis (ANOVA), artificial neural networks (ANN) model, fuzzy inference system (FIS), harmony search (HS) algorithm, genetic algorithm (GA), Taguchi's optimization technique, multi-criteria optimization, analytical modeling, stress analysis, finite elements method (FEM), data analysis, and linear regression technique. Failure mechanisms and surface quality is discussed with the help of optical and scanning electron microscopy, and profilometry. ANOVA, GA, FEM, etc. are used to analyze and generate predictive models.

H. Kargarzadeh, M. Mariano, Jin Huang et al.

Qin Chen, Yang Shen, Shihai Zhang et al.

S. Mangaraj, A. Yadav, Lalit M. Bal et al.

C. Sánchez

Petroleum-based plastic materials as pollutants raise concerns because of their impact on the global ecosystem and on animal and human health. There is an urgent need to remove plastic waste from the environment to overcome the environmental crisis of plastic pollution. This review describes the natural and unique ability of fungi to invade substrates by using enzymes that have the capacity to detoxify pollutants and are able to act on nonspecific substrates, the fungal ability to produce hydrophobins for surface coating to attach hyphae to hydrophobic substrates, and hyphal ability to penetrate three dimensional substrates. Fungal studies on macro- and microplastics biodegradation have shown that fungi are able to use these materials as the sole carbon and energy source. Further research is required on novel isolates from plastisphere ecosystems, on the use of molecular techniques to characterize plastic-degrading fungi and enhance enzymatic activity levels, and on the use of omics-based technologies to accelerate plastic waste biodegradation processes. The addition of pro-oxidants species (photosensitizers) and the reduction of biocides and antioxidant stabilizers used in the plastic manufacturing process should also be considered to promote biodegradation. Interdisciplinary research and innovative fungal strategies for plastic waste biodegradation, as well as ecofriendly manufacturing of petroleum-based plastics, may help to reduce the negative impacts of plastic waste pollution in the biosphere.

Kunpeng Ruan, Xuetao Shi, Yongqiang Guo et al.

Abstract Thermally conductive polymer composites have become a research hotspot and an important branch in the fields of thermal conduction such as 5G communication equipment, electronic packaging and energy transmission due to their light weight, easy processing and low manufacturing cost, etc. However, the thermal conductivity coefficients (λ) of reported thermally conductive polymer composites are far from expected, and one of the most important reasons is the inherent interfaces between phases in the polymer composites and the high interfacial thermal resistance (ITR). This review summarizes the research history and the latest progress of ITR in thermally conductive polymer composites from 4 aspects: mathematical models, computer simulations, measurement techniques and strategies to reduce ITR. Furthermore, the problems of researches on ITR in urgent need for solution as well as corresponding possible solutions are illuminated, hoping to provide some guiding suggestions for the rapid and efficient improvement on λ of thermally conductive polymer composites.

V. Shanmugam, Deepak Joel Johnson, K. Babu et al.

Abstract The development of fibre composites in recent years has been remarkably strong, owing to their high performance and durability. Various advancements in fibre composites are emerging because of their increased use in a myriad of applications. One of the popular processing methods is additive manufacturing (AM), however, polymer-fibre composites manufactured through AM have a significantly lower strength compared to the conventional manufacturing processes, for instance, injection moulding. This article is a comprehensive review of the mechanical testing and performance analysis of polymer-fibre composites fabricated through AM, in particular fused deposition modelling (FDM). In particular, the review highlights the effect of the various processing parameters, involved in the FDM of polymer-fibre composites, on the observed mechanical properties. In addition, the thermal properties of FDM based fibre composites are also briefly reviewed. Overall, the review article has been structured to provide an impetus for researchers in the concerned engineering domain to gain an insight into the mechanical properties of fibre-reinforced polymeric composites manufactured through AM.

A. Mora, P. Verma, Shanmugam Kumar

Abstract We present electrical conductivity measurements and modeling aspects of carbon nanotube (CNT)/polymer composites enabled via fused filament fabrication (FFF) additive manufacturing (AM). CNT/polylactic acid (PLA) and CNT/high density polyethylene (HDPE) filament feedstocks were synthesized through melt blending with controlled CNT loading to realize 3D printed polymer nanocomposites. Electrical conductivity of 3D printed CNT/PLA and CNT/HDPE composites was measured for various CNT loadings. Low percolation thresholds were obtained from measured data as 0.23 vol. % and 0.18 vol. % of CNTs for CNT/PLA and CNT/HDPE nanocomposites, respectively. Moreover, a micromechanics-based two-parameter agglomeration model was developed to predict the electrical conductivity of CNT/polymer composites. We further show that the two agglomeration parameters can also be used to describe segregated structures, wherein nanofillers are constrained to certain locations within the matrix. To the best of our knowledge, this is the first ever electrical conductivity model to account for segregation of CNTs in the matrix. A good agreement between measured conductivity and predictions demonstrates the adequacy of the proposed model. We further evince the robustness of the model by accurately capturing the conductivity measurements reported in the literature for both elastomeric and thermoplastic nanocomposites. The findings of the study would provide guidelines for the design of electro-conductive polymer nanocomposites.

Jing Jie, Yulong Liu, Lina Cong et al.

Abstract Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based gel polymer electrolytes are widely studied owing to their electrochemical stability and high dielectric constant. However, most gel polymer electrolytes show unsatisfied safety and interface compatibility due to excessive absorption of volatile and flammable liquid solvents. Herein, by using a safe solvent (N-methyl-2-pyrrolidone) with higher boiling (203 °C) and flash points (95 °C), we initiatively fabricate a flexible PVDF-HFP based gel polymer electrolyte. The obtained gel polymer electrolyte demonstrates a high ionic conductivity of 7.24 × 10−4 S cm−1, an electrochemical window of 5.2 V, and a high lithium transference number of 0.57. As a result, the synthesized polymer electrolyte exhibits a capacity retention of 70% after 500 cycles at 0.5 C, and a discharge capacity of 86 mAh g−1 even at a high current rate of 10 C for LiFePO4 based Li metal batteries. Moreover, a stable Li plating/stripping for more than 500 h is achieved under 0.1 mAh at both room temperature and 70 °C. Our results indicate that the PVDF-HFP polymer electrolyte is promising for manufacturing safe and high-performance Li metal polymer batteries.

Yuhan Li, Milo S. P. Shaffer

Microscopy is routinely applied to characterize nanomaterials and nanocomposites. Optical microscopy (OM) and scanning electron microscopy (SEM) are frequently adopted for their simple sample preparation and efficient image acquisition. The majority of literature analyses rely on 2D surface imaging or cross-sectional imaging, often at a single magnification, although they may not be representative, due to the multiscale nature of the structures, as well as preparation and projection artifacts. This paper presents a comprehensive 3D imaging workflow combining serial sectioning OM and SEM to obtain realistic volumetric nanocomposite structures. The relationship between SEM acceleration voltage, electron penetration depth, and image contrast is investigated to enhance sub-surface imaging. Correlative OM and SEM characterization is achieved through multimodal imaging and landmark-based registration. Multiscale reconstruction is demonstrated on three representative ‘graphene’ nanocomposite systems, providing rich datasets on dispersion, distribution, orientation, and morphology. The methodology presented is broadly applicable to other nanocomposites and hierarchical systems.

Ans Al Rashid, S. Khan, Sami G. Al‐Ghamdi et al.

Abstract Polymer nanocomposites have attracted increasing interest in research and development with several current and potential industrial applications due to their wide margin of superiority over conventional materials. Polymer composites provide a higher strength-to-weight ratio, easily customizable product properties, flexible manufacturing processes, high resistance to corrosion or erosion, and lower cost. The recent progress in additive manufacturing (AM) methods has paved the way for even a broader range of flexibilities in design and materials in several industrial sectors, including aerospace, biomedical, construction, electronics, telecommunication, mechanical, and defense. However, some hindrances remain in the synthesis of polymer composites and their fabrication through AM technologies. A comparative review of AM processes for polymer composites and their applications is presented in this study. This study aims to provide engineers and scientists with an updated understanding of the underlying issues, barriers, limitations, and opportunities. It will also help the reader to systematically reveal the research problems and future directions related to materials synthesis and AM processes.

Priyadarsini Morampudi, K. Namala, Yeshwanth Kumar Gajjela et al.

Abstract Glass fiber reinforced polymer composites were prepared by different manufacturing technology and are extensively used for various applications. In recent times more research is carried out on glass fiber reinforced composites owing to their excellent mechanical properties. This study deals with the analysis of glass fiber reinforced polymer composites manufactured by different types of glasses, Matrix materials prepared using different production technologies. Glass fibers possesses good properties such as high strength, flexibility, stiffness, durability etc. With an increase in the content of glass fiber volume the properties of GFRP composites were improved. The mechanical & thermal attributes of various polymer composites reinforced by glass fiber when subjected to mechanical loading have been studied and reported.

Shubham Utekar, Suriya V K, N. More et al.

Abstract The thermosetting polymer composites are considered to be a revolutionary material due to their superior properties and versatility in application. The growth extent in the manufacturing and rigorous usage of polymer composites raised the environmental concerns due to the disposal constraints. This article discusses the various methods used for recycling the thermosetting polymer composites. The term “recycling” has been stressed in most of the engineering applications since civilization. This article explains the potential methods by which the materials or the energy can be recovered through the recycling process. The authors have also tried to comprehend the need for recycling and the early approaches made. This review has been developed with few suggestions on advanced methods and their scope in the recycling of thermoset composites.

Pooneh Abachi, Reza Khoshbin, Ramin Karimzadeh

Silica gel is a solid adsorbent known for its unique property of changing color as it adsorbs moisture. The main component in the production of silica gel is sodium silicate, which can be derived from natural raw materials such as sugarcane bagasse ash, rice husk ash and coconut shell. In this study, sodium silicate was extracted from rice husk ash (RHA), followed by the synthesis of silica gel using the sol-gel method. The resulting silica gel was then colored orange using iron (ⅠⅠⅠ) chloride salt. FE-SEM image showed a homogeneous distribution of particle size and color on the surface of the silica gel. The BET surface area of orange silica gels synthesized from commercial sodium silicate and RHA (Aging time = 24 hours) was found to be 248.6 and 179.86 m2/gr, respectively but the high Smeso/Smicro in silica gel from rice husk ash contributes to its suitable moisture adsorption capacity compared to silica gel from industrial sodium silicate.

Wang Linyu, Mao Lei, Wei Wei et al.

Stretchable conductive yarns have received crucial attention in the direction of wearable electronics. Integration of ordinary yarns with conductive phase endows additional functions such as strain sensing. Herein, highly responsive, stretchable, conductive wrapped yarns with different wrapping densities were prepared, using elastane filament as core, co-wrapped with silver-plated nylon filament (SPNF) and polyester filament. It was found that a wrapping density of 750 T·m−1 was an optimal alternative, taking into account tensile and elastic-related properties, keeping the elastane draw ratio constant. By virtue of the helical-interlaced structure and spiral configuration of wrapping components, the optimized yarn can bear up to nearly 200% strain and exhibit larger-strain cyclic robustness. By incorporating SPNF into the wrapped yarn, it can serve as a stretchable conductor, and it is also able to precisely detect body motion (e.g. finger bending) with high responsiveness (shorter response time). Such functional yarns hold tremendous prospects for wearable electronics.

علی اکبر یوسفی, امیرحسین برنج چی

در حین فرایندهای ریسندگی الیاف، تولید نخ، بافندگی پارچه یا رنگرزی آن، عملیات تکمیلی مختلف انجام می‌گیرد تا ارزش افزوده محصول نهایی ارتقا پیدا یابد یا فرایندهای تولید آن با مشکلی مواجه نشود. انجام عملیات تکمیلی باعث می‌شود تا افزون بر ایجاد تغییرات در ساختار فیزیکی و شیمیایی نخ و پارچه، ویژگی­ های نوینی در آن­ها ایجاد شده و در نتیجه دامنه کاربرد این محصولات برای رفع نیاز مشتری گسترده‌تر شود. فرایند پلیمرشدن امولسیونی به­ دلیل مزیت‌هایی چون سادگی فرایند تولید، امکان تولید پلیمرهایی با وزن مولکولی زیاد و مصرف کم انرژی دارای کاربردهای فراوانی در حوزه‌های مختلف، به­ویژه صنایع نساجی است. فرایند پلیمرشدن ادمیسلی نیز ایجاد انواع پوشش‌های پلیمری با ضخامت اندک بر روی انواع سطوح را امکان­ پذیر می ­سازد. بنابراین، به ­دلیل آسانی انجام فرایند پوشش‌دهی، قابلیت زیادی در اصلاح خواص سطحی منسوجات دارد. از فرایندهای پلیمرشدن امولسیونی و ادمیسلی به­ طور گسترده در صنعت نساجی برای انجام عملیات تکمیلی الیاف، نخ و پارچه برای بهبود خواص منسوجات و ایجاد ویژگی ­های جدید در آن­ها استفاده می‌شود. در این مقاله، ابتدا فرایندهای پلیمرشدن امولسیونی و ادمیسلی معرفی می­ شوند. سپس، کاربرد آن­ها در صنعت نساجی شامل عملیات تکمیل منسوجات مانند دافع آب کردن، ضدآتش کردن، رسانای الکتریکی کردن، ضدمیکروب­ سازی، پرتوافکنی فرابنفش، معطرسازی و نیز تولید چسب­ های محلول در آب برای کاربرد در فرایندهای رنگرزی و چاپ پارچه مرور می ­شود.

Aravind Raj, Pachipala Rithik, Prathipati Sai Sudheer et al.

In this study, polypropylene (PP) was blended with polylactic acid (PLA) to enhance PP's mechanical properties, such as tensile strength and modulus, and to encourage the adoption of eco-friendly, renewable resource based material in polymer production. Even though PLA's biodegradability cannot be fully utilized in PP/PLA blends, but PLA can still improve PP's mechanical properties and provide an alternative resource for biobased raw materials. To meet the requirement, PP and PLA were blended in a 70:30 ratios with a compatibilizer and nanosilica at different loading levels by melt-blending. Blends of PP and PLA materials were processed without any problems, since both materials have melting points in the range of 170°C. Despite this, the properties of polymer blends are limited by the immiscibility between these neat polymers. To solve this problem, compatibilizers like polypropylene-grafted-maleic anhydride (PP-g-MA) were added to blends to improve their compatibility. Nanosilica was also added to this compatibilizer to study the system's compatibility and modify the hydrophobicity of PLA. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), tensile strength, and field emission scanning electron microscopy (FESEM) were used to analyze the polymer blend. Results indicate that compatibilizers play a significant role in improving tensile properties, thermal stability, and blend dispersion in the system, mainly in 5 parts compatibilizer-based systems. Composition with 5 parts compatibilizer increases tensile strength of 70/30 blend from 19.7 to 27 MPa, while elongation increases from 2.2 to 3.6 %. Additionally, a composition with 0.7 parts of nanosilica increases the modulus from 1488 to 1732 MPa when compared to the 70/30 blend.

Wenbo Gao, Xiarui Fan, Xinwei Zhou et al.

The impact of UV radiation on the high-temperature behavior of polyphenylene sulfide (PPS) fiber was investigated in this study. The ultimate strength, failure strain elasticity modulus and toughness were employed to evaluate the degradation caused by the coupling effects of UV radiation and high temperature. The degradation characteristics of PPS fiber were observed and evaluated based on the scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that both UV exposure and high temperature can effectively reduce the mechanical performance of PPS fiber. The ultimate strength, failure strain and toughness were reduced to the minimum value after UV exposure 150h at room temperature. Both the initial and second elastic modulus of PPS fiber exhibited obvious decreasing trends with the UV exposure time and temperature increasing. The micro defects and molecular structure changes were detected as the degradation characteristics of PPS fiber caused by the coupling effects of UV radiation and high temperature. The Weibull model was applied to quantitatively analyze the dispersion of strength of PPS fiber under extreme conditions.

R. Brighenti, M. P. Cosma, L. Marșavina et al.

Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves.