In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most promising materials for numerous applications. However, alginate potential for various applications is relatively limited due to brittleness, poor mechanical properties, scaling-up difficulties, and high water vapor permeability (WVP). Choosing an appropriate plasticizer can alleviate the situation by providing higher flexibility, workability, processability, and in some cases, higher hydrophobicity. This review paper discusses the main results and developments regarding the effects of various plasticizers on the properties of alginate-based films during the last decades. The plasticizers used for plasticizing alginate were classified into different categories, and their behavior under different concentrations and conditions was studied. Moreover, the drawback effects of plasticizers on the mechanical properties and WVP of the films are discussed. Finally, the role of plasticizers in the improved processing of alginate and the lack of knowledge on some aspects of plasticized alginate films is clarified, and accordingly, some recommendations for more classical studies of the plasticized alginate films in the future are offered.

Current standards do not consider the diameter of glass fiber-reinforced polymer (GFRP) bars used as internal reinforcement in concrete structures to be a factor influencing bar durability. This paper investigates the effects of bar diameter on the physical and mechanical properties as well as the durability of GFRP reinforcing bars conditioned for three months at 60°C in an alkaline solution simulating a concrete environment. Five diameters (nominal diameters of 9.5, 12.7, 15.9, 19.1, and 25.4 mm) were considered; bar properties were assessed before and after conditioning. Microstructural analyses and measurement of physicochemical properties were also carried out. The results show that bar size had no significant effect on bar physical properties, except for water absorption. The smaller diameter bars had higher water absorption than the larger ones because of their higher surface area-to-volume ratios. In the case of the unconditioned bars, the tensile strength and modulus were not significantly affected by bar diameter, but there was a size effect for interlaminar shear strength and flexural strength. Conversely, the conditioning in the alkaline solution had a greater negative effect on the tensile strength of the larger bars than on the smaller ones. Scanning electron microscope (SEM) observations and Fourier transform infrared spectroscopy (FTIR) analysis revealed that the degradation remained at the surface of all the conditioned specimens. Nevertheless, there were only small variations between the physical and mechanical properties of the GFRP bars of different diameters. This indicates that the current provisions in standards that do not relate strength retention limit to bar size are acceptable.

Fiber-reinforced polymer (FRP) composites are increasingly being used in civil engineering applications due to their numerous advantages. Moreover, some environmental conditions can potentially enhance their long-term durability. Therefore, the study of their long-term behavior is crucial to ensure their durability. To perform durability study in a reasonable time limit, accelerating factor, such as high temperature, is generally used. However, the use of very high temperature of conditioning could amplify the reduction of the properties leading to conservative prediction of long-term properties. The present paper attempts to clarify the effects of high temperatures on the mechanical and barrier properties (moisture absorption) of GFRP’s internal reinforcement, by presenting some experimental results and conclusions of laboratory accelerated studies.

One of the most important fields of research dealing with the use of carbon-, basalt-, and glass-fiber composites in the civil construction industry is their behavior under various chemical exposure conditions. Fiber-reinforced-polymer composites used as internal and external reinforcement in various structural applications can be subjected to widely differing pH situations. This study investigated the chemical durability of various carbon, basalt and glass fibers. The fibers were immersed in four types of solutions with acid, saline, alkaline, and deionized-water conditioning schemes. The fiber mass loss and surface damage along with changes due to chemical reactions were observed through weight-loss measurements and scanning electron microscopy. A criterion was developed to characterize the performance of fibers as very good, good, fair, and poor. This methodology can also be used by manufacturers as a quick quality-control tool for evaluating the chemical resistance of different fibers prior to large-volume production. The results reveal that the carbon fibers exhibited higher chemical resistance than the basalt and glass fibers based on weight loss and evidence of chemical reactions. Moreover, the determination of the fiber chemical composition before and after conditioning in acid and alkaline solutions clearly shows that the E-glass fibers, which are known to contain boron, were very sensitive to chemical corrosion. The ECR-glass fibers showed excellent chemical durability, even better than the basalt fibers.

Natural fibers have been approved as an excellent alternative for traditional reinforcements in polymer composites. However, the main disadvantage of natural fibers as reinforcements is their poor interaction with polymeric matrices due to their hydrophilic nature. In order to improve their compatibility as composite reinforcement, surface treatments are required. Silane treatment has been widely used to modify hygroscopic properties of natural fibers. In this study, a new method of silane treatment has been developed without the prehydrolysis and curing/dehydration of silanol groups. To do so, flax fibers were modified through 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation followed by direct application of the amino-silane. The fiber/matrix interfacial adhesion was examined by measuring interlaminar shear strength. Thermogravimetric analysis and dynamic mechanical analysis were performed to study the thermal resistance and thermomechanical properties of the composites. The results revealed that fiber/matrix adhesion was improved in the oxidized silanized fiber composite. In addition, water absorption was significantly reduced (20%) in the oxidized silanized fiber reinforced composite compared with the as-received one.