Papers by Keyword: Polymer Fibers

Abstract: Cement-based penetrating waterproof compounds compact the concrete structure due to penetration into the microcracks, pores and capillaries of slightly soluble crystalline hydrates. The coatings made from them do have some drawbacks such as low tensile strength and shrinkage, which may lead to cracks and reduce impermeability. Dispersed fiber reinforcement allows improving these parameters. The surface electric properties of glass fibers and polyester fiber were studied; their ability to be a substrate for the growth of crystalline hydrates was studied; X-ray phase and thermal analysis of cement hydration products with a complex chemical additive providing penetrating action were carried out; electron microscopic studies of the contact zone between fibers and crystalline hydrates were carried out; experimental studies of the dependence of the composition physical and mechanical and hydrophysical properties on the additive and fiber content were carried out. It was found that a dense liner of crystalline hydrates and hydrosilicate gel is formed around the glass fiber and polyester fiber with a silicone dressing size. Between the crystalline hydrates and the fiber surface, strong electro-heterogeneous contacts are formed, which provide the high physical and mechanical properties of the composite. The amount of the complex chemical additive and polyester fiber that provides the maximum strength and minimum water absorption of the composition is determined experimentally.

Abstract: Microfibrillar reinforced composites (MFC) are self-reinforced polymer-polymer composites, consisting of a cold drawn (fibrillized) phase in an isotropic matrix. They are manufactured via melt blending of two immiscible polymers with different melting temperatures, followed by a subsequent cold drawing and thermal annealing step. The present study examines the manufacturing of composite material out of melt-spun microfibrillar reinforced filaments. Polypropylene (PP) and Polyethylene terephthalate (PET) were chosen as the low-melting matrix and the high-melting reinforcement phase, respectively.The filaments were woven to flat textile structures and processed to composites via hot pressing. They represent a bidirectional reinforced composite, comparable to other fiber reinforced polymers. To ensure optimized processing the influence of relevant parameters has been investigated with respect to mechanical properties of the MFC‑filaments and the derived composites. In addition, the morphology was visualized by SEM imaging after all manufacturing steps. An important observation was that the reinforcing fibrils are still intact after thermal processing, leading to a significant increase in mechanical properties of the resulting composites. Quasistatic tensile tests show more than 100 % higher modulus and more than 50 % higher strength of the only 20 wt-% reinforced PET‑PP composites compared to neat PP. The influence of the amount of PET reinforcement, the variation in processing conditions and composite layup were investigated. Additionally, an outlook on the melt-spinning of blends with Polyamide (PA) is given. In future work it is meant to show that a broad spectrum of tailored properties can easily be achieved by such polymer blends and composites outperforming existing homopolymers as well as thermoplastic composites like short glass‑fiber‑reinforced Polypropylene.The material cost reduction thanks to adding cheaper mass‑production polymers and the transfer onto conventional manufacturing lines is meant to ensure the feasibility of industrial production. The low density and excellent recycling options of these composites underline their potential for automotive and aircraft applications.

Abstract: The property of some materials to change their color in response to temperature changes is called thermochromism. A polymer fiber manufactured in such way that a thermochromic pigment is embedded in the polymeric matrix material develops accordingly thermochromic functionality and can be used as a temperature change indicator. The characterization of a polymer thermochromic fiber with respect to its color change in response to temperature change is presented in this paper. A specially developed characterization apparatus was developed for this purpose. The temperature span of the involved experiment was from 23.5°C (room temperature) to 60°C, while the tested fiber was found to be responsive regarding its chromatic variance mainly within the temperature range 30.5oC - 50oC. During the involved digital image processing, the chromatic shift of the sample was characterized according to the HSV (hue-saturation-value) color model. Fiber’s original color was found to change with temperature by presenting a monotonic reduction of saturation and value with temperature increase.

Abstract: This paper presents an experimental investigation on fire resistance of densified normal strength concrete (DNSC), at water/binder (W/B) ratios of 0.45, 0.36, and 0.32, of which compressive strength of 28-days ranged from 42.5 MPa to 56.3 MPa. The results of the spalling test reveal that DNSC encountered explosive under high temperature. Polymer fiber can be used to improve fire resistance of DNSC. DNSC subjected to high temperature lost its mechanical properties in a similar manner to that of high-strength concrete.

Abstract: Reinforced concrete structures are often conceived for a certain time span of serviceability. Due to the superposition of different kinds of loads and particularly due to the presence of aggressive substances the resistance of construction materials is insufficient in numerous cases. Hence, many structures have to be repaired before the end of their designed life span. In case of reinforced concrete structures these repair measures are not only very expensive but they also consume high amounts of energy and materials which causes strong environmental impacts. The main challenge in developing reliable concrete technologies is the capability to enhance the life span of new and already repaired structures to a reasonable maximum. When aiming this objective not only durability related material properties have to be accomplished but their environmental impact has to be minimized simultaneously. This paper evaluates different concrete technologies and materials from diverse perspectives: Durability (simulating expected life span using numerical analyses), ecology (product life cycle and environmental impact assessments) and economy (estimating life cycle costs by investment appraisals). This kind of combined analysis facilitates the efficient design of structural elements and repair measures and provides the possibility to significantly increase the life span of new and repaired concrete structures.