Chromatography Column With Ultra-high Molecular Weight Polyethylene Microporous Sieve Sintering Mechanism And Preparation Process

High performance ultra high molecular weigh polyethylene (UHMWPE) porous sheet is one of the most important tools to realize the function of affinity chromatography column. It's usually prepared through the direct compression molding (DCM) process. But there are many problems in the fabricated products, such as the inaccurate size of pores, the low porosity and permeability, the poor surface texture, and the shedding of granules. The sinter mechanism of UHMWPE porous material and its evaluation criterion are studied. The relationships between the processing parameters and the performance of products are summarized. According to the specific requirements of the chromatography column, the UHMWPE porous sheet is fabricated.The sinter mechanism of UHMWPE porous material was analyzed through the powder sinter theories. Differential scanning calorimetry (DSC) and scanning electron microscope(SEM) were used to acquire the characteristic temperatures and the particle morphology of UHMWPE. A polarizing hot stage microscope was used to capture the sinter rate. The results show that the UHMWPE with different particle sizes have close characteristic temperatures and complex surface topography, and that the surplus surface energy at the complex surface is the major contributor to the discrepancy of sintering rate between theoretical and experimental results. The prediction fuction for sintering rate is fitted based on the results.According to the specific requirements of UHMWPE porous sheet, the three indicators, i.e max pore size, porosity and permeability, were selected to characterize the samples. A test device for porous materials capable of characterizing pore size, pore size distribution and permeability was developed, which served as an effective testing plateform for porous material research and development as well as process improvement.In process research, the sintering temperature window for porous UHMWPE was determined to be 146℃-150℃, by DSC and tensile test; single experiment method was used to investigate the effect of partical size, forming pressure, sintering temperature and sintering time on permeability, porosity and max pore size of the obtained porous sample, providing a basis for process set-up and improvement.Orthogonal experiment design was adopted to develop the UHMWPE porous sheet which meets the specific requirements for chromatography column applications. The optimum processing parameter combination was determined, which was 83～58μm for particle size, 2.5MPa for forming pressure,149℃for sintering temperature and 45min for sintering time. Microstructure and tensile cross-section were studied by SEM. Results show that numerous spatial microchannels exist in the porous sheet; neighboring particles are connected through necks, which have a strong tensile strength.