Kunshan Xuanyeda Machinery Sharing: Kunshan PVC resin related technical indicators
Bulk density and powder dry flow
Bulk density refers to the apparent density under certain compression conditions, usually 10% to 30% larger than the apparent density, and is an index used to balance the properties of the powder.
The dry material flowability of the resin can predict the feeding performance of the resin in the hopper, and the spherical large particles and the uniform particle size have good dry flow, so that the suspension method and the bulk resin have good dry flow properties.
These two indicators have a great impact on the design and operation of large mixing systems, but currently there are no such two items in conventional resin testing.
The molecular weight distribution
The molecular weight distribution of the PVC resin is closely related to the molding process and the quality of the product, and it is usually a narrow distribution or a bimodal distribution. Since the double bond structure and the like are mostly concentrated in the low molecular weight portion. However, due to the high cost of the test equipment, the general manufacturer does not have such detection capability.
In general, the molding process of the polymer is preferably carried out with a narrow molecular weight distribution because the processability and the properties of the article are relatively uniform. A too broad distribution of the fractions indicates that there is a certain amount of low or high molecular weight fraction in the polymer. The presence of the former will significantly reduce its thermal stability, heat distortion temperature, electrical insulation, mechanical strength and aging resistance; the latter tends to make it difficult to plasticize even under normal processing conditions, and also cause products The intrinsic quality, especially the deterioration of the appearance quality, will result in fishy-eye unplasticized particles on the surface of the product in severe cases.
The average particle size
The average particle size and the residue of the sieve represent the same physical properties of the PVC resin, but are expressed and measured differently. The average particle diameter can be obtained by a laser particle size analyzer method, and the particle diameter information is obtained by diffraction of the particles with respect to the laser light, and the average particle diameter is obtained through analysis and calculation.
Original whiteness
The original whiteness and aging whiteness are completely different indicators. The aging whiteness indicates the thermal stability of the resin, while the original whiteness indicates the color of the resin itself, and has little to do with thermal stability. This index does not process PVC resin. Too much guiding significance. The original whiteness has a certain relationship with the formulation of the resin and the variety and purity of the raw materials.
In addition, the bulk method PVC resin will also detect and analyze the color difference and particle concentration rate. These indicators are extensions based on the relevant indicators in the national standard.
In fact, the core of the PVC resin's processing and product performance and quality is the molecular structure, particle morphology and residual impurities of PVC resin. Because these items are difficult to test under normal conditions, they should not be applied. Therefore, only through various conventional indicators, the different properties of the resin can be seen, which is convenient for detection and utilization in actual production and processing.
