Browsing by Subject "Youngin moduuli"

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  • Veijanen, Terhi (Helsingin yliopisto, 2020)
    Granulation is used to improve the flowability of pharmaceutical powders, reduce the amount of fines and increase the density of the material. Roller compaction has shown growing interest in recent years and it is used ever more frequently in pharmaceutical industry. Roller compaction has many superior qualities compared to wet granulation such as good control of process and absence of moisture and heat in the process. It is also cost effective compared to traditional granulation methods. New APIs are often sensitive to moisture. Therefore traditional granulation methods cannot be used. In the roller compaction process powder mixture is fed between two counter-rotating rolls where the compaction occurs and ribbon is formed. After compaction the ribbon is crushed into granules of desired size. The aim of this study was to find out how the mixture ratio of plastic and brittle material affects the physical properties of roller compacted ribbons such as the strength and stiffness of the ribbons and the structure of the ribbon surface. The materials used were microcrystalline cellulose and dicalsiumphosphate. Nine powder mixtures of 0 to 40 w-% of dicalsiumphosphate were prepared after which the mixtures were roller compacted with the same compactor parameters. Two methods were developed to study the above mentioned characteristics of the ribbons. For the stiffness and strength studies a 3-point bending method was developed for Lloyd material tester. For the surface structure characteristics of ribbons a measurement set up for FlashSizer 3D image analysis device was designed. Bending tests for the ribbons were performed in two different directions. For each batch of ribbons a slope of the linear area and maximum point of bending curves were defined, which represent the stiffness and strength of the ribbons accordingly. Also Young’s modulus and tensile strength were calculated, which are characteristics of a given material. In addition area under curve, which represents the work done to break the ribbon, was calculated. The strength and stiffness of the ribbons decreased with the increasing amount of dicalsiumphosphate. A clear trend was observed. Also Young’s modulus, tensile strength and AUC decreased accordingly. The increase of dicalciumphosphate led to diminished compactibility of the powder mixtures. The compaction force was probably not high enough to fragment the dicalsiumphosphate particles. The ribbons showed higher strength and stiffness when the bending was done perpendicularly ie. across the ribbon width compared to parallel measurements. Also relative standard deviations were smaller in this measurement set up. The 3-point bending method could not mostly distinguish between adjacent formulations from each other but when the difference in the amount of dicalsiumphosphate increased to 10-20 w-% statistically significant differences were observed in most of the calculated values. The surface structure of the ribbons differed between formulations when evaluated visually. Ribbons with less dicalsiumphosphate had a surface structure that followed the knurled pattern of the compactor rolls better.
  • Palomäki, Emmi (Helsingfors universitet, 2012)
    3D-imaging is based on combining two or more pictures to form one three-dimensional picture. Most of the methods used provide only surface pictures, but tomography acquires also information about the inside-structure of investigated material. Young's modulus is a method, which has been used for long time to determine toughness hard materials, such as steal. In traditional method a beam-shaped piece is bent. When the size of piece, used force and amount of bending are known, Young's modulus of piece can be calculated. Although the method has traditionally been used to research very hard materials, it has been applied without changes with pharmaceutical materials. It is, however, open to the question whether or not the method is appropriate for those materials. There are also methods to determine Young's modulus based on compressing a tablet or using ultrasound. Determining tablet's toughness with ultimate strength test is complicated because it breaks tablet. For that reason it would be good to find compensatory methods to measure strength of tablet. The aim of the study was to validate Flash Sizer 3D appliance, which is used in 3D-imiging. Another goal was to investigate possible correlations between 3D-imiging, Young's modulus and traditional ultimate strength method. Lastly, the feasibility of Young's modulus as a substitute for traditional ultimate strength measurement in self life studies was investigated. Flash Sizer 3D was validated by measuring particle size distribution of pellets, which were made of microcrystalline cellulose (Cellets). Sizes of the investigated pellets were 100 µm, 200 µm and 500 µm. Also binary mixture of 100 µm and 200 µm was investigated. From microcrystalline cellulose was made tablets and 3D-pictures were taken. Ultimate strength test was made for half of the tablets. Young's modulus was measured from half of the tablets in tableting day, day after that and nine days after tableting. Results show that Flash Sizer 3D is suitable for investigating bigger Cellet. With smaller particles distinguishing of tablets wasn't probably good enough. Still it seems to be quite good method to determine surface roughness of tablet. Young's modulus seems to be very promising as compensating method for traditional ultimate strength measurement. In future in self life studies tablets hardness might be able to investigate by measuring Young's modulus and not measuring ultimate strength. If correlation between Young's modulus and solubility meets the case, Young's modulus might also replace also solubility measurements in self life studies.