Industrial Applications of Polymer Composites E-Book
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- Herausgeber: Bentham Science Publishers
- Kategorie: Fachliteratur
- Serie: Frontiers in Polymer Science
- Sprache: Englisch
- Veröffentlichungsjahr: 2000
This volume is a comprehensive guide to the industrial use of polymer composites. Edited contributions demonstrate the application of these materials for different industrial sectors. The book covers the benefits, future potential, and manufacturing techniques of different types of polymers. Contributors also address challenges in using nanopolymers in these industries. Readers will find valuable insights into the current demand and supply of polymer composites and future scope for research and development in this field of polymer science.
The volume presents seven chapters, each exploring a different application of polymer composites. Chapter 1 discusses the use of polymer additives for improving classical concrete and the workability and durability of polymer composite concrete. Chapter 2 explores the use of polymer nanocomposites in packaging, including smart/intelligent packaging, modified atmosphere packaging, and vacuum packaging. Chapter 3 delves into the use of polymer composites in tissue engineering, including manufacturing techniques and various applications. Chapter 4 explores energy storage applications for polymer composites, while Chapter 5 discusses their use in microbial fuel cells. Chapter 6 explores the use of carbon nanotubes in polymer composite gas sensors. Finally, Chapter 7 discusses the use of polymer composites in automotive applications.
This is an ideal reference for researchers, scientists, engineers, and professionals in the fields of materials science, polymer science, engineering, and nanotechnology. The content is also suitable for graduate and postgraduate students studying industrial manufacturing.
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FOREWORD
This is a great pleasure for me to write a foreword for the book “Industrial Applications of Polymer Composites” which would definitely be a great addition to the library of documents concerning Polymer Science and Technology and more precisely the areas of polymer technology dealing with the applications of different polymer composites, the area of material science now under sharp investigation. Considering the growth of polymer technology to cater to the ever-increasing demand of society, polymer composites have appeared to us as God’s blessings. The importance and scope of utilities of polymer composites cannot be overemphasized. The entire world of Material Science has been revolutionized since people could sense the widespread applicability and flexibility of polymer composites which now can be tailor-made. It can possibly be mentioned very concisely that the evolution of material science in the last three decades is the evolution of polymer composites.
The present book is a nice compilation of the scope of utilization of different types of polymer composites. The vision of the editors and the authors who are young and energetic academicians with very good exposure and practical experience in the different fields of construction, packaging, tissue engineering, batteries, microbial fuel cell, sensors and automotive appliances is really praiseworthy. Their tenacious endeavour in presenting the current scenario of the role of polymer composites in fabricating items of the different fields as mentioned above is quite inspiring and interesting. The field of construction has seen a sea change with the advent of polymer composites. The use of multi-layered laminar composites has enabled the civil engineer to substitute a substantial proportion of heavy concrete and thus help to reduce the total weight of the construction, an essential need of time. Many polymeric additives are now available to enhance the flow properties of concrete material. A highly durable, light weight construction is now readily available. The packaging industries have greatly benefitted from the use of polymer composites in a great way. The concept of multi-layered films, each film in its turn being a composite one has enabled the packaging scientists to control permittivity and diffusivity of the various harmful environmental gases and thus prolonging the shelf life of the contents. The synthesis of semi-permeable membrane, the most essential component of microbial fuel cells could not have reached so advanced stage so early without the polymer composites. The different gadgets and accessories meant for the automotive sector would not have been possible to be fabricated without the polymer composites. It is worthwhile mentioning here that the authors having expertise in the respective fields described in the book have tried their best to make the readers acclimatized with the products made up of polymer composites finding applications in different fields for their properties that cannot be challenged by other materials commonly available.
I presume the basic mission of the editors and authors has been successful. The readers would definitely be able to feel and sense the fragrance of the book on reading. I pray to the Almighty for its widespread success.
PREFACE
A polymer composite is a three-dimensional combination of at least an organic or inorganic filler dispersed in a continuous or co-continuous phase of an individual polymer or a polymeric blend. The presence of polymers as well as fillers in different blends may be wisely utilized in different combinations to overcome the limitations of the individual components toward achieving the required characteristics of industrial products. The ability to achieve a set of desired characteristics such as mechanical, chemical, physical, electrical, electrochemical, biological, etc., suiting the needs, processability, dimensional stability, thermal, cost, and so on has allowed polymeric composites to be used in a wide range of industrial applications such as construction, packaging, tissue engineering, energy storage, sensors, transportation, and so on. The consumption of polymer composites for industrial applications is ever-growing with time. With the advent of upgraded and new technologies related to the preparation of individual components and composites, different combinations of materials have attracted researchers from academia as well as industries. To meet the demand of consumers, new material development as well as finding new applications for the existing materials have become the major focus of industrial research. Several books were published on polymer composites in the last decade with a primary focus on materials, characterization, or any specific area of application. However, it is envisaged that a single book encompassing the knowledge related to polymer composites in different fields of application is unavailable in the market. In this book, the focus is on the recent developments in various major sectors where composite materials are very popular and significantly used. With the rich experience in polymer composites and nanocomposites of the editors, especially in application development, technical services, and new product development, we thought of bringing together authors having expertise in polymer composites in specific industrial domains. The outline of the book encompasses relevant knowledge from an application point of view and represents its diversities in a nutshell. Therefore, we feel the proposed book may attract a broad readership from industry as well as academia.
We thank all the contributors for their generous efforts and cooperation in providing chapters highlighting recent research and findings across the globe. We are thankful to all the authors of the studies cited in the present book. We also like to express our gratitude to the entire team of Bentham Science Publishers for their collaboration, prompt assistance, and patience during the publication of this book.
List of Contributors
Polymer Composites for Construction Applications
Dinesh Rathod1,Madhuri N. Mangulkar2,Bhagwan Ghanshamji Toksha3,*Abstract
Polymer composite concrete (PCC) nowadays plays a major role in the construction industry. PCC is a valuable element in the development of sustainable construction materials. The polymers and classical concrete blends offer newer properties and applications. A polymeric action in the field of admixtures provides insight into the development of highly performing modified mineral concrete and mortars. The influence of various polymers on the properties of concrete is variable due to the polymeric chain reactions. The optimization of properties such as crack resistance, permeability, and durability with the addition of polymer is required. The present work reviews the types, performances, and applications of PCC to improve various properties of concrete in both fresh and hardened states as they have shown a strong potential from technical, economical, and design points of view.
INTRODUCTION
In the history of mankind, the last two centuries have witnessed rapid advances in construction material technology enabling civil engineers to achieve structures with increased safety and functionality at the economy of scale which could have served the common needs of society [1-4]. The elongation of structural life span against environmental deterioration, sustaining natural calamities such as earthquakes, heavy traffic densities, blast impact from terror attacks, debris flow, and highly corrosive environments demands better quality of reinforced concrete for building structures. The activities encompass the upgradation of design codes and strength requirements. This leads to the exploration of reinforced concrete (RC) materials which could provide strengthening in structures to meet the adequate strength requirements and extend the service life [5-9].
The use of polymer additives may be practiced either as a part of a concrete admixture recipe or as external support to already existing structures. The basic composition of concrete is a mixture of fine sand and liquid cement. This formulation is one of the most widely used items in the world after water which is used for construction of all building purposes [10]. The use of concrete is twice as the mixture of aluminium, wood, and plastic as well. As it is widely used globally, it is expected to generate about $600 billion in revenue in the upcoming 5-10 years [11]. Considering the massive use of concrete, there are some disadvantages as they contribute ca. 8% of greenhouse emissions [12-16]. The possible alternatives and related concerns with the usage of supplementary cementitious materials to address the issue of greenhouse gas emissions from the use of concrete were reviewed by Sabbier Miller et al. [17]. Other environmental concerns include large-scale illegal sand mining, as well as some effects on the surrounding environment, such as the changes in river surface leaf flow, the effects of urban heat on islands, and the effects of toxic factors on public health. There is a need for extensive research and development to control further damage to the environment still meeting human needs. One of the promising alternatives is to increase the production of secondary raw materials reducing the volume of conventional concrete with still maintaining the construction standards.
The second type of usage of polymer composite as external support includes repair, rehabilitation, and strengthening of structural elements such as beams/columns. The orthodox approaches to rehabilitation, and strengthening structures include the use of an external layer of metallic plate, textile fibre sheet, wire mesh, post tensioning, concrete or steel jacketing, and injection of epoxy [18-22]. The conditions and criteria for selecting one reinforced concrete over another are largely dependent on the type of structure, the degree of strengthening required, and the associated cost. The extent of strengthening and the cost at which it is achieved is a delicate balance to maintain. There are certain challenges with these conventional methods. The heavy weight of externally bonded steel plates requires mechanical fastening and ongoing maintenance to prevent corrosion [18]. The requirement of installation of steel anchorages, deviators, and protection of the steel strand and anchorages against corrosion are some of the downsides of external post-tensioning [24, 25]. These requirements add to the labour and cost of the solution. The need for section enlargement, erection of temporary formwork, and mechanical interlock achieved by the installation of steel dowel bars are un-desirous in concrete jacketing [21, 22]. Polymers and polymer composites were developed very fast compared to other civil engineering tools [23]. Advanced polymer composites have been used the primarily in the aerospace and marine industries, but have also been used in civil engineering for the last few years as they have some unique properties [24]. The scoring points for a particular reinforced concrete system will be fulfilling all design requirements, having the shortest installation time, and realization at the lowest cost including the initial material supply and installation, as well as future maintenance costs such as ongoing corrosion protection, regular inspection, and monitoring. There is a huge amount of polymeric materials available in the form of waste or recycled materials. The adaptation of circular economics modifying the current conventional economy of the construction industry is depicted in Fig (1). This model of inclusion of polymer materials is crucial for completing the cycle in a cost-effective way and addressing the environmental issues [25]. Polymer-based materials for reinforced concrete systems are one of the most promising solutions. Their characteristics being non-destructive, light weight, having high tensile strength, corrosion-resistance, lack of long-term maintenance requirements and cost-effectiveness increase their usability in reinforced concrete (RC) materials. Traditional approaches began to take shape in the early 20th century. Concrete-polymer composites including polymer-modified (or cement) mortar and concrete, polymer mortar and concrete, and polymer-impregnated mortar and concrete have been developed in the world for over the past 50 years. In 1965, the first sample of polymer-impregnated concrete (PIC) was discovered at Brookhaven National Laboratory [25]. After this, the whole world was drawn to it [26]. The implementation of polymer-based solutions for reinforced concrete needs to address the issues such as fire performance to provide the necessary fire endurance period without collapse [27]. The other limiting concern with the polymer-based solutions is the limits on the degree of strengthening that may be achieved. The use of fibre polymers in reinforced concrete will improve performances, compared to those realised through other existing techniques [28]. The comparison of stress-strain values of various materials used in concrete composites was recorded by Theodoros Rousakis et al. [29].
Polymer concrete is used in specialized construction projects where there is a need to resist several types of corrosion and is supported to have durability i.e., to last longer. It can be used similar to ordinary concrete. Polymer concrete is applied for various construction purposes such as repairing corrosion-damaged concrete [31], pre-stressed concrete [32], nuclear power plants [33], electrical or industrial construction [34, 35], marine works [36], prefabricated structural components like acid tanks, manholes, drains, highway median barriers, waterproofing of structures, sewage works and desalination plants. Contemporary researchers are taking the help of advanced technological tools to explore the field of polymer concrete [37-40]. The use of artificial intelligence has also occupied space in enhancing the field of polymer concrete. The newer models are recently getting evolved for FRP- confined concrete [41]. The comparison between the hybrid models with the existing design relations of the ultimate strain and strain capacities has revealed that the hybrid models have superior abilities in terms of
accuracy. The feasibility and accuracy prediction by AI algorithms are utilized for predicting the bond strength between FRPs and concrete [42].
Fig. (1)) Inclusion of polymers in construction industry circular economics [30].POLYMER ADDITIVE FOR ALTERING CLASSICAL CONCRETE
Classically, cement and its mixtures react with other elements to form a hard matrix making the material like durable stone which has many applications [43]. The currently practiced alternatives as a solution to mitigate the pollution of other industries are capturing wastes such as coal fly ash or bauxite tailings and residue with concrete being the main material for a structure that is resilient to weather disasters [44]. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical quality of that wet mixer. Concrete is often poured with the reinforcing material which provides higher tensile strength; it is termed reinforced concrete. Many other types of non-cementation concrete are also used, such as asphalt concretes are used for road works, and polymer concretes that are polymer mixtures, are used for building materials and for many new types of works as well [45]. The materials that are used in composite formation encompass carbon, glass, aramid, and basalt fibres that are bonded together by the matrix of a polymer such as epoxy, vinyl ester, or polyester to form various reinforced polymers. The polymer composite concrete for construction is the composite phase made by fully/partially replacing the cement hydrate binders of conventional cement concrete with polymer binders or liquid resins [46]. The hardening of polymer concrete is done via liquid resins such as thermosetting resins, methacrylic resins, and tar-modified resins by polymerization at ambient temperature. The binder phase of polymer composite concretes consists of polymers, and does not contain any cement hydrate. The binding of aggregates is done via the use of polymeric binders. As compared to the basic ordinary cement concrete, the properties of polymer composite concrete such as strength, adhesion, water-tightness, chemical resistance, freeze-thaw durability, and abrasion resistance are being improved to an extent such that it is considered as a replacement.
The liquid form of polymers (latex) usually is referred to as resin. There are numerous polymeric resins commonly used such as methacrylate, polyester resin, epoxy resin, vinyl ester resin, and furan resins. The use of unsaturated polyester resins is prevalent in resin systems for polymer concrete because of their low cost, easy availability, and good mechanical properties [47]. The downsides of their use are higher flammability and disagreeable odour. However, it has received some attention because of its good workability and low temperature curability [48]. The selection of the particular type of resin depends upon various factors namely the cost, chemical or weather resistance, desired properties, etc. For polymer concrete, unsaturated polyester resins are the most versatile polymers used owing to their cost efficiency, good mechanical properties of concrete, and easy availability. The curing effect in case of polymer composite concrete with resins is rapid at ambient temperature. The curing time is reportedly reduced to a greater extent as compared to conventional concrete with polymer concrete developing 80% strength after one day of curing at room temperature while the conventional concrete could gain 20% strength of its 28-day strength in one day [49]. The adhesive nature of polymers brings ease in binding the organic substrate to each other. The selection of a specific resin depends upon factors like cost, desired properties, and chemical/weather resistance required. The choice between epoxy resins and polyester is made by mechanical properties as well as better durability when subjected to harsh environmental factors. The higher cost in case of epoxy resins limits their widespread acceptance. The comparison of epoxy and polymer concrete revealed that traditionally epoxy concrete demonstrated better properties as compared to polyester concrete. The study also concluded that the properties of polyester concrete could be elevated by adding micro fillers and silane coupling agents [50]. The polymer concrete formulations with resin dosage reported in the literature were as high as 20% by weight. The compressive strength of polymer concrete varied as a function of the resin content [51]. Both the compressive strength and flexural strength depend on polymer content. The peak attained would lead to either decreased or unaltered with a further increase in the resin content. The flexural and compressive strength reaching the maximum values between 14 and 16% resin content by weight were reported in the literature. Variation in compressive strength of polymer concrete for various types of resins and their dosage has been reported in the literature [52]. It was observed that the highest strength was obtained in all types of resins at a resin dosage of 12%. For two types of epoxy resins, the strength decreased by increasing the resin content to 15%, whereas, for polyester resin, it almost remained constant. The nature of aggregate used in the polymer concrete formulations was also decisive in deciding optimum resin content. The resin dosage can be set to higher values while using fine aggregate owing to the large surface area of these materials [53, 54].
Polymer composite materials are formed by incorporation of aggregates into polymers [55]. In general, fiber reinforced polymer materials contain high-strength fibres [56]. This material is generally developed using fibers such as natural fibers (jute, kenaf, cellulose), synthetic (glass, carbon, aramid), hybrid fiber (jute/glass, sisal/glass) [57]. Such class of materials is commonly referred to as fiber-reinforced polymer or fiber-reinforced plastic (FRP) composites. Composite materials are applied almost everywhere, because of their unique properties such as binding with another particle, long time workability, durability, crack resistance, etc. The sources of composite materials used can be waste materials in some other process. In construction, polymeric composite materials are being used extensively, in which many industrial waste materials can be used as aggregates. One of the most commonly used aggregates for polymeric concrete is glass [58], which can be used in a variety of ways such as, glass fiber, glass dust, and coarse inorganic waste. Also polyester resin and polymer concrete have various aesthetic and structural advantages [59]. Glass fiber reinforced polymeric [60] waste material, incorporated in the polymer matrix, has been used in many construction materials. Additional constituents of the particulates in the polymeric matrix can be in the form of silica, sand, calcium carbonate, mica, white cement, gypsum, perlite, or others. The use of these materials can be cost-effective [61]. The fibers in such compositions have good load-carrying capacity, as well as they are rigid and strong. Moreover, this material has corrosion resistance, good appearance, high temperature resistance, environmental stability, as well as heat, and electrically resistance [62]. There are three types of fiber which are used in the construction industry i.e. E-, S- and Z-type glass fiber [63]. Reportedly, carbon fiber is successfully utilized in strengthening and rehabilitation of columns, freeway piers, and chimneys. Consequently, the use of natural fibers can be a great alternative to the sustainable development of the construction sector. However, natural fibers have some drawbacks, such as low durability and low strength. As an alternative to this problem, hybrids of two or more different types of fiber reinforced polymers can be used. e.g., sisal/GFRP, Abaca/jute GFRP, sisal/jute GFRP, and jute GFRP [64]. The types of polymeric materials used in building construction along with their applications, advantages, and disadvantages are presented in Table 1.
Synthetic polymer/polymer concrete is one of the alternative options for the Portland cement or construction purpose used to bond a mixture of aggregates together with epoxy resin binders [82]. Polymer concrete is created by different resins and monomers such as epoxy resin [83], polyester [84], and acrylic [85]. The polymer composite concrete thus achieved good resistance against water [86] and it has good durability [87], and good mechanical properties [88]. The adhesive properties of polymer concrete allow the repair of a new kind of cement-based concrete [89]. Epoxy polymer concrete is a type of composite material which is conglutinated aggregate with epoxy resin.
POLYMER COMPOSITE CONCRETE CONCOCTION AND WORKABILITY
The literature reveals different polymer concoctions and their workability in making polymer composite concretes. The research in the direction of usability of polymer concretes aim at elevating their thermal properties such as thermal conductivity, thermo-mechanical properties, and thermo-gravimetric properties. The polymer matrix phases have poor thermal and fire resistance; and along with temperature dependence of mechanical properties that is the hurdle yet to be fully overcome. The experimental parameters such as the glass transition temperature of the polymer matrix phases need to be considered from the viewpoint of thermal properties. The polymer materials have a characteristic behavior by which they generally retain their practical properties at temperatures below the glass transition point and beyond the transition temperatures beginning to decompose thermally. The operational temperature range of the thermoplastic resins may be improved by the addition of suitable cross-linking agents having higher glass transition points. The specific structural requirement with high-voltage electrical insulation is reported by Bowen Xu et al. [90]. The liquid styrene and acrylic (SA) monomers, wollastonite, and muscovite mixed in Portland cement led to the polymer composite material. The improvement in dielectric strength as high as 16.5 kV/mm and a reduction in dielectric loss factor by 0.12 along with thermal stability and thermal conductivity were reported.
The epoxy binder is made from resin and amine hardener (BS5462), wherein the epoxy equivalent weight and density were 200 g/equiv. and 1.1 g/cm3, respectively. Also, the equivalent weight and density of the hydrogen amine and hardener were 100 g/equiv and 0.985 g/cm3. The granite aggregate was 45 wt. % fine aggregate with a size of less than 4.75 mm, and 55 wt.% coarse aggregates with a size falling between 4.75 mm and 9.5 mm. The weight ratio of 2:1 of epoxy resin was mixed with a hardener and aggregates were incorporated into a mixture. The mixture was finally molded and cured at 25 °C for 72 h [65]. The study reports the use of an epoxy binder with room temperature (RT) viscosity of 5000 and 12000 m.Pa and density in the range 1.42 to 1.48 g/cm3. The resin/hardener ratio was maintained at 100:60 by weight. The inorganic aggregates used in this are commercially silico-calcaire aggregates, 0/4 sand and 4/10 gravels with actual densities of 2470 and 2530 kg/m3. The experimental conditions maintained were such that the mixture was dried at 105 degrees for 24 hours before it was ready to use [91]. A control mixer of polymer concrete with two variations of mixtures was set in experimental research. The control mixture of polymer concrete was prepared in a dosage of 12.4% epoxy resin, and a mixture of fly ash and natural river aggregate in a dosage of 12.8%, was prepared in two forms. Sort 1 (0-4 mm) and Sort 2 (4-8 mm) both were in equal proportions. The two waste mixtures were made from epoxy resin, fly ash and 4-8mm sort, and were replaced with only 0-4mm sort dust and chopped PET bottles. The first and second mixtures replaced the dust and PET bottles in 0-4mm sort but kept their proportions at 25%, 50%, 75%, and 100%. To prepare the concrete, fly ash, waste, and PET bottles were mixed and the concrete was prepared by mixing in epoxy resin hardener [92]. The sample was prepared and tested according to the European standardization method [93]. The workability of concrete was reported to increase with increasing PET bottle dosage and decreasing with the increase of waste dosage. It was reported that for resin, diglycidyl ether of bisphenol A (DGEBA) possessing low viscosity was used, and as curing agent polyamine hardener was used. Also, basalt aggregates with a size up to 5 mm were used to study different chemical combinations.
Samples of unfilled and basalt-filled epoxy concrete were prepared using a curing agent DGEBA according to various wt.% of basalt aggregation. The mixture was then poured into a silicone mold and placed in the oven until air bubbles appeared on its surface and then kept at room temperature for a few days. The specimens thus realized were subjected to various tests to test their workability. The workability of this, when the increasing resin into basalt aggregate reaches 25 wt.%, it increased the mechanical properties [94]. Opthophalic polyester resin containing 33wt% styrene as binder, methyl ethyl ketone peroxide (MEKP) as an initiator, and cobalt naphthenate containing 6 wt.% cobalt as a promoter were used in this literature. The particle size of the aggregate was less than 10 mm. Polymer concrete was prepared by mixing crushed gravel, sand, calcium carbonate, and different concentrations of unsaturated polyester resin such as 60, 14, 14 and 12 wt.%. The fresh mixture was poured into the metal mold and allowed to stand for 24 hours at room temperature [95]. The polymers were included in concrete admixtures for improving adhesion to the old surface, flexural strength, tensile strength, and freeze/thaw durability. The mixtures were also useful in reducing permeability, the intrusion of chlorides, salts, and carbon dioxide along with improved abrasion resistance. The polymers replacing natural fine aggregates were reported to reduce chloride ion migration into the concrete samples. The observation is an indication that polymers have inhibited the free chlorides inside concrete [96]. The major concern with the use of a polymer material is the unavailability of all desired functionalities in one material or recipe. Each material brings its own strengths and weaknesses on its inclusion in concrete. Moreover, the effect of polymer addition is not uniform and weak in most of the cases [97]. The polymers are better at ultraviolet light (UV) blocking, and efficient at transmitting water vapor, but are weak at re-emulsification on re-wetting. The condition of meeting the requirement raises the economic point of view. A cost-effective polymer emulsion is required for preparing high-performance concrete [98]. The recycled polymer admixtures have an uneven effect on the concrete, while affecting durability there was no significant effect on mechanical properties [99].
One of the uses of recycled polymer materials could be in asphalt pavements as an alternative to develop sustainable road pavements with increased performance. The use of polymeric waste into asphalt mixture phase prepared by wet and dry processes was reviewed by Duarte and Faxina [100]. The promising use of polymeric waste to improve asphalt pavement performance was echoed in this review with poor storage stability as a concern to overcome. The inclusion of polymer results in an improvement in the durability of asphalt pavement, joint damage, and cracks of cement concrete pavement. The compressive, flexural, tensile strength and impact resistance, flexural fatigue resistance, permeability, frost resistance, shrinkage characteristics and wear resistance of polymer modified cement concrete improved these properties, and the improvement effect was proportional to the polymer content [101].
DURABILITY
Generally, the aspects of durability of a polymer concrete need consideration of humidity, temperature, age of curing, etc. The developed polymer concrete material must show higher durability properties for the commercial viability of the product. The basic concrete erodes quickly when exposed to an acidic medium such as sulphuric acid, nitric acid, etc. However, the polymer concrete may withstand to such harsh ambient conditions like coming in contact with acidic or alkali medium owing to its high durability [102].The effect of moisture is a critical factor when incorporating the polymer and polyester phases are included in concrete [103]. The curing gets affected substantially via water-polyester interaction. The mechanical properties deteriorate with the increase in thermal expansion coefficient as moisture content is increased. The environmental exposure of construction materials is inevitable. The fiber-reinforced polymer is looked as a promising and affordable solution to the corrosion problems of steel reinforcement in structural concrete. The mechanical properties and durability properties of such products are most critical in the applications replacing steel reinforcement. The effect of severe environmental and load conditions for long-time exposures is challenging the polymer replacements. The high pH of the pore water solution, formed during the hydration of the concrete, attacks the chemical behavior of fibres. The use of resin could be involved in the use of glass fibre-reinforced plastic materials. The properties of resin strongly influence the durability of reinforcement reducing the damage caused by environmental cycles [104]. The lignin content in a natural fibre enables better thermal performance whereas the adverse effects of moisture were more aggravated. The ratio of fibre to matrix ratio is limited to the extent of moisture content. There is a significant improvement in the natural fibre resistance towards moisture by the chemical treatments. Thus, there could be possibilities of various blend ratios of chemical additives that need to be employed to achieve a balance between strength and durability requirements for natural fibre composites [105]. The harsh environmental conditions deteriorate the physical and mechanical properties of polymeric composite materials such as strength and flexure modulus [106]. The undesirable degradation was also reported to occur for the adhesive joint in carbon fiber reinforced polymer material. There were enough evidences that clearly depicted weakening of the adhesion between the fibres and matrix over the time interval of 0 to 2000 hrs due to humidity [107].
CONCLUDING REMARKS
The use of polymeric waste materials could solve both the issues of environmental concerns and occupying volumes with increased performance. Among the polymers, the recipes involving acrylic polymers and styrene acrylics demonstrated the best water vapor transmission rates i.e., breathability above all the polymers with styrene acrylics having better water resistance and less UV stability. The requirements of pre-packaged products either in wet or dry conditions could be met by using vinyl acetate ethylene. The styrene-butadiene copolymer resin is very cost-effective with very high adhesive properties. Besides this, the products involving this polymer have better water and abrasion resistance. Though polyvinyl acetate is very cost-effective, hydrolysis of the most re-wettable material in wet alkaline environments leads to an undesirable breakdown of the polymer. There are many different formulations of monomers and each manufacturer combines them to create polymers with specific characteristics. The effects of mixing polymeric materials have uneven effects. Still, there are evidence that the applications of polymer composites could significantly contribute to the construction industry.
ACKNOWLEDGEMENT
Declared none.
