Minerals for filling and reinforcing PVC
Buy all PEX supply such as: Plastic, Polymers, plumbing on best online PEX store PexUniverse.com
Mineral fillers are natural or synthesized particles with a solid surface, not containing metal or carbon black. These fillers have different shapes – from the particles is almost spherical shape to a plate and pin. In describing the form of filler particles is recommended to use the term “aspect ratio”, which describe the relation of one particle size to another. Mineral fillers for PVC historically include calcium carbonate (ground and precipitated), aluminum trihydrate (TGA), barite, talc, mica, kaolin, feldspar, nepheline syenite and wollastonite. The main achievement is the improvement of such properties as mechanical strength, fire resistance and weight. For cables and wires are very important electrical properties.
Typically, mineral fillers described together with their action. Due to the fact that mineral fillers can provide more than just cost reduction, to show their added value in industry use the term “functional filler. For example, the selected filler can perform the function of increasing the tensile strength and elongation. Some fillers can improve the hardness, the other – heat resistance and electrical resistance. Often increase rigidity with functional fillers. Fillers, which are used primarily to reduce the cost of material, often referred to as a diluent. However, such fillers, not even improve the physical properties, is often added to facilitate processing and improve product quality, so reduce the allocation of solid ingredients in the metal surfaces of processing equipment (plate-out), sticking to the rolls, regulate gloss, improve light resistance in the UV -region and extruded, as well as reduce the dry mixture. Therefore, to some extent, all fillers are “functional.”
An important property of compositions based on PVC is rigid, which is often characterized by modulus of elasticity in bending. This property, in contrast to the tensile modulus, are very much dependent on the ratio of the particle size of filler. For example, the introduction of calcium carbonate filler with a low aspect ratio, provides only a slight increase in the rigidity of PVC, and the difference between precipitation (OCC) and hammer (ICC) was very small. To increase by 30% the modulus of elasticity in bending model tracks need to add approximately 60% of the ICC or OCC, that, to some extent, determined by particle size, since the module composition increases with decreasing average particle size. Fillers having a higher ratio of dimensions, such as talc, are more effective for improving the rigidity. Ideally want to get a balance of rigidity and impact strength. It is usually supposed that there is a critical particle size of fillers to obtain the optimum balance of these properties in compositions based on PVC, equal to about 1 micron.
In the construction industry is very important dimension stability, and therefore measure the coefficient of thermal expansion. Its value is greatly influenced by the ratio of particle size of filler. High values increase the internal stresses of the finished product and can lead to distortion or cracking, or warping of products. In normal be introduced on the number of calcium carbonate provides a slight increase in dimensional stability. Filling with a higher ratio of particle sizes, such as talc, leads to improved properties, particularly at elevated temperatures. At the highest regard to size, such as a glass, its introduction to 15% for lower thermal expansion. Developer compositions should bear in mind this possibility and if necessary, to use it.
Plasticized PVC, being essentially amorphous, may contain fillers of different shape and composition. Fillers with a high ratio of particle sizes tend to have a strong negative effect on impact resistance of PVC unplasticised, their sharp edges lead to the germination of cracks and to decrease healing craze (micro-cracks). The above considerations explain the prevalence of calcium carbonate as a filler with a low ratio of particle sizes. Mixtures of calcium carbonate and fillers with a high ratio of particle size often improve impact resistance compared to using only the latter. However, the most effective way is to use to suppress the crack propagation of polymer modifiers improve impact strength. There are now also investigating the modification of the shock strength through a combination of filler and particle impact resistance modifier.
Tags: aluminum trihydrate, calcium carbonate, fillers, plumbing
