Contemporary Polyester and Viscose Staple Fiber Production Line

Polypropylene staple fibers

Introduction:

It is a crack-proof fiber specially used for preventing cracks in the plastic stage of mortar. It can effectively prevent plastic cracks in the initial stage of mortar and plays a role of "secondary reinforcement" in mortar. Polypropylene staple fiber is made by adding modified masterbatch into polypropylene chips by melting, drawing and drawing. It is chemically modified, physically modified, antistatic and ultraviolet resistant by special process. It has the characteristics of small diameter, large specific surface area and uniform dispersion. Three-dimensional random structure is formed inside the mortar, which can lock the moisture in the mortar, prevent and reduce the micro-cracks caused by the tip effect, reduce the early stress of the mortar and prevent the cracks caused by the early evaporation of moisture, thus hindering the formation of large-scale cracks.

Physical parameters:

The effect of fibers in mortar:

(1) Improving crack resistance

(2) Improving the impermeability of mortar

(3) Improving the toughness, fatigue resistance and abrasion resistance of cement mortar

(4) Improving the resistance of cement mortar to freeze-thaw damage

(5) Improving the Durability of Cement Mortar

Main advantages:

(1) Good dispersion, strong grip force; (2) High acid and alkali resistance, high radiation resistance;

(3) anti-freezing and anti-corrosion, strengthening toughness; (4) physical reinforcement, anti-cracking reinforcement;

(5) stable performance, safety and non-toxicity; (6) simple construction, economic and reliable.

The basic principle and theoretical basis of polypropylene fibers used in concrete engineering and painting engineering:

There are two theoretical explanations for the reinforcement mechanism of concrete by uniform and random short fibers in concrete: (Romualoli, USA) put forward the "fiber spacing mechanism" (also known as fiber crack resistance mechanism). According to linear elastic fracture mechanics, the restraint effect of fibers on the occurrence and development of cracks is explained. It is believed that there are original defects in concrete. In order to increase the strength of this material, it is necessary to reduce the degree of defects as much as possible, improve the toughness and reduce the stress concentration factor at the end of the internal crack. Theoretical analysis and experimental results show that when the average center spacing of fibers is less than 7.6MM, the tensile or flexural initial cracking strength of fiber reinforced concrete can be improved. (2) The starting point of the theory of "composite material mechanism" put forward by swamy, mangat et al. in Britain is the mixing principle of composite materials. Fiber reinforced concrete is regarded as a fiber reinforced system. The tensile and flexural strength of fiber reinforced concrete is deduced by the mixing principle. The strength of fiber reinforced concrete and the amount, direction and length of fiber are put forward. The relationship between diameter ratio and bonding force. The above two theories show that the use of fibers in concrete/mortar has a great effect.

Crack resistance and waterproofing mechanism of polypropylene fiber in concrete:

The mechanism of crack resistance and waterproofing of polypropylene fibers is based on the microscopic study of the consolidation and shrinkage of concrete. In the process of hardening and forming strength of concrete, the volume of concrete is smaller than the volume of raw materials because of the crystallization of cement reaction in the initial stage, which results in the shrinkage of concrete volume, thus causing cracks and micro-cracks. Most of the development of slit to fine cracks (70%) is completed within 3-7 days of gelation. At this time, the tensile strength of concrete is less than 1Mpa. When cracks develop into fine cracks, they will inevitably encounter many different fibers. Due to the resistance of fibers, energy consumption will be difficult to further develop and effectively inhibit. The generation and development of early dry shrinkage and segregation cracks of concrete greatly reduce the shrinkage cracks of concrete and effectively restrain the generation of connected cracks. At the same time, a large number of fibers evenly distributed in concrete reduce the water evolution and aggregate settlement on the surface of concrete, thus greatly reducing the pore content of concrete with a diameter of 50-100 nanometers.

Polypropylene fibers have the following properties:

1. High quality fibers are used to form the surface of special effect fibers, and various physical indicators are excellent.

After chemical modification, physical modification and hydrophilicity, the fiber has strong bonding strength, which ensures a certain bonding strength with concrete.

3. Polypropylene is used as raw material to ensure the toughness and durability of the fibers.

4. High melting point. It is non-toxic and has no effect on human body.

5. It has good chemical stability, can not react with concrete, does not affect concrete hydration and hydration products, and can not be eroded by concrete hydration products.

Concrete with polypropylene fibers can improve the following properties:

A To prevent non-structural cracks caused by various plastic shrinkage, segregation and other factors, adding polypropylene fiber can increase the ductility of concrete in the plastic stage, improve the cohesion and water retention of concrete, improve the workability of concrete, thereby reducing segregation, bleeding and sinking, thus effectively preventing the early stage. The generation of shrinkage and subsidence cracks.

B In the hardening stage of concrete:

(a) Polypropylene fiber improves the impact strength and fatigue strength of concrete;

1. Polypropylene fibers can effectively reduce the crack size, increase the continuity of material medium, and reduce the local stress concentration caused by the blocking of shock wave.

2. Polypropylene fibers can absorb impact energy, especially after initial cracking, and can continue to absorb impact energy, at the same time, it can slow the expansion of crack width.

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