Fabrication and evaluation of novel sulfur/epoxy resin composites

In recent years, and with the progress of oil and natural gas purification processes, it has been noticed that huge quantities of sulfur are produced with millions of tons as byproducts, which is considered a dangerous substance that may threaten the safety and health of the environment. So, this study aims to maximize elemental sulfur benefits in construction applications, especially in the coating sector. In this study, sulfur has been modified to be used with epoxy as a high-performance coating material. Firstly, sulfur was modified with linseed oil at 160 °C. The modified sulfur was chemically characterized by using FTIR and XRD. After that, epoxy was then partially replaced by polymeric sulfur with different weight percentages starting from 10 to 40%. Then, the hardener was added to form cured sulfur/epoxy composites. Different techniques were used to examine the morphology of the prepared composites such as AFM, polarizing microscope, and SEM. The thermal study was also conducted by TGA. In addition, the mechanical properties were comprehensively studied including Young’s modulus, toughness, tensile strength, hardness, and adhesion. The results approved that Young’s modulus, toughness, tensile strength, hardness, and adhesion of the PC4 composite have been improved by 54%, 87%, 15%, 40%, and 33%, respectively. Moreover, the prepared composites give high thermal stability than virgin epoxy. The overall results approved that the epoxy can be partially replaced by modified sulfur with high weight ratios reached to 40%.

On the mechanical and morphological properties of highly performant composite laminates based on epoxy resin and oxidized ultrahigh-molecular-weight polyethylene fibers

In this study, new high-performance composite laminates were prepared from epoxy resin and surface modified ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. The UHMWPE fibers underwent two types of chemical modifications, namely through chromic acid and potassium permanganate oxidations. The adopted chemical procedure aimed the grafting of polar groups on the outer surface of fibers for an improved chemical and physical compatibility with the polymeric matrix. The efficiency of the grafting methodology was confirmed by vibrational, thermal, and morphological analyses, and the grafting mechanism was thoroughly discussed. Furthermore, composite laminates were prepared to study the effects of chemical treatments on the mechanical and morphological properties of the resulting composites. The grafting techniques allowed consequent improvements in the tensile and bending properties, up to 34% and 23% for the tensile and flexural strengths, respectively. The study of the fractured surfaces confirmed the exceptional compatibility between the fillers and the polymeric matrix and further corroborated the mechanical findings. Finally, the adopted modification techniques can be regarded as cost-effective and highly suitable for the manufacturing of structural composites for advanced applications.

Study of UHMWPE Fiber Surface Modification and the Properties of UHMWPE/epoxy Composite

Abstract: Ultra-high molecular weight polyethylene (UHMWPE)/epoxy composites with excellent adhesive properties were prepared by forming an interface membrane on the UHMWPE fiber surface. The interface membrane of the UHMWPE fiber and epoxy resin was polymerized by an aldol condensation between polyvinyl alcohol (PVA) and glutaraldehyde. Different surface treatment methods of UHMWPE fibers were optimized and the two-step PVA-glutaraldehyde condensation (Corona-PG-2S) method is the best. The interfacial adhesion between UHMWPE fiber and epoxy resin was enhanced, and the adhesive properties of the composite were improved. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrum (EDS) results of the fiber treated by Corona-PG-2S shows that the surface oxygen content was up to 25.0 wt %, with an increase of 17.3 wt % compared with the surface oxygen content of unmodified UHMWPE fiber, which indicated that the surface polarity was greatly enhanced. The adhesive properties were improved by improving the polarity of the surface. The peel strength, ultimate cohesive force, tensile strength and flexural strength of the composite treated by Corona-PG-2S were greatly increased to 262.8 %, 166.9 %, 139.7 %, 200.6 % compared with those of unmodified samples. The composite prepared by Corona-PG-2S had excellent adhesive properties, demonstrating that the Corona-PG-2S method plays a major role in significantly improving the composite adhesive properties.

Development of Oxygen-Plasma-Surface-Treated UHMWPE Fabric Coated with a Mixture of SiC/Polyurethane for Protection against Puncture and Needle Threats

Although considerable research has been directed at developing materials for ballistic protection, considerably less has been conducted to address non-firearm threats. Even fewer studies have examined the incorporation of particle-laden elastomers with textiles for spike, knife, and needle protection. We report on a new composite consisting of ultra-high-molecular-weight polyethylene (UHMWPE) fabric impregnated with nanoparticle-loaded elastomer, specifically designed for spike- and needle-resistant garments. Failure analysis and parametric studies of particle-loading and layer-count were conducted using a mixture of SiC and polyurethane at 0, 30, and 50 wt.%. The maximum penetration resistance force of a single-layer of uncoated fabric increased up to 218–229% due to nanoparticle loading. Multiple-layer stacks of coated fabric show up to 57% and 346% improvement in spike puncture and hypodermic needle resistance, respectively, and yet were more flexible and 21–55% thinner than a multiple-layer stack of neat fabric (of comparable areal density). We show that oxygen-plasma-treatment of UHMWPE is critical to enable effective coating.

Nanoparticle-Infused UHMWPE Layer as Multifunctional Coating for High-Performance PPTA Single Fibers

High-performance fibers made of poly-(p-phenylene terephthalamide) (PPTA) with high stiffness and high strength are widely used in body armor for protection due to their high degree of molecular chain alignment along the fiber direction. However, their poor mechanical properties in the transverse direction and low surface friction are undesirable for applications requiring resistance to ballistic impact. Here we provide a simple yet effective surface engineering strategy to improve both the transverse mechanical properties and the tribological property by coating PPTA fibers with ultra-high molecular weight polyethylene (UHMWPE) embedded with silica nanoparticles. The coated-PPTA fiber shows remarkable enhancement in transverse mechanical properties including ~127% increase of Young’s modulus, which is attributed to both the alignment of UHMWPE chains in the transverse direction and the embeded ceramic nanoparticles. Meanwhile, the surface friction of the coated fiber increases twofold as a result of the ceramic nanoparticles. In addition, the coated fibers exhibit an enhanced chemical resistance to external harsh environment. The improved transverse mechanical properties, surface frictional characteristics, and chemical resistance demonstrate that coating with UHMWPE and ceramic nanoparticles can be used as an effective approach to enhance the performance of PPTA and other high-performance polymer fibers for body armor applications.

Various surface functionalizations of ultra-high-molecular-weight polyethylene based on fluorine-activation behavior

The various high-density surface functionalizations of UHWMPE based on fluorine activation and subsequent derivatization reactions are reported, and offer a simple and convenient pathway to incorporate useful functional groups.

Surface Properties of UHMWPE Fiber after Low Temperature Argon-Plasma Treatment

To improve the adhesion between ultra-high-molecular-weight polyethylene (UHMWPE) fibers and matrix, the UHMWPE fibers were treated by low temperature argon-plasma. The effects of argon-plasma treatment on the properties of UHMWPE have been investigated. The roughness and wetting ability were all found to increase significantly after modifications. The tensile strength of UHMWE fibers were decreased with the plasma treatment time. The optimum plasma treatment is 2min.The increasing of roughness and wetting ability of UHMWPE fiber are beneficial to the improvement the adhesion between UHMWPE fiber and matrix.