Studies On The Structure And Properties Of LDPE Film Resin

With the rapid development of domestic packaging industry, the demand of the low density polyethylene(LDPE) films resin is growing, meanwhile the terminal customers put forward higher requirements for LDPE films resin. However, domestic LDPE resin’s quality still has a certain gap with developed countries at the same time. So we need to take a series of technology research, development and production of high performance LDPE film grade resin to meet the needs of the market. This issue characterized the LDPE film resin’s brand-2320D’s structure and properties which is newly developed by Lanzhou petrochemical company, and conducted comparison researches with the domestic LDPE resin 2426H、1810D、2420D and LD26 D, provided theoretical guidance for raising the quality of the resin and processing applications.The 2320 D and other four brand of LDPE resin first were tested by high temperature gel chromatography, the results show that the 2320D’s number average molecular weight is slightly bigger than other LDPE, but heavy molecular weight and Z molecular weight are smaller, molecular weight distribution relatively narrow. Tive kinds of LDPE resin’s molecular chain branching were tested by FTIR, researches indicate that the 2320 D branching is lower, the molecular chain arrangement is relatively structured. Five kinds of LDPE resin’s crystallinity were tested by WAXD, the results show that the crystallinity of the 2320 D is lower.The five kinds of LDPE resin melt’s viscoelastic was tested, in the process of shear rheological, with the increase of shear rate, 2320 D melt flow possess shear thinned behavior, in accordance with power law equation; The melt viscosity showed a trend of decrease with the increase of shear rate and the rising of temperature, showed the melt viscosity has a strong sensitivity to shear rate and temperature, but the viscous flow activation energy is lower than other LDPE; the shear stress, shear viscosity, and swell ratio are higher than other LDPE, the melt liquidity is relatively poor than other LDPE resin. In the process of tensile rheological, with the increase of drawing speed, the 2320 D melt tensile force and melt strength increases, are higher than other LDPE, elongational viscosity first balanced, then increased, last declined with the increase of stretching rate, stretching melt flow rate is good, easy to processing. In the test of the stress relaxation, 2320 D to the stress relaxation balance time is longer, the melt elasticity restoring force is poorer.The films were tested by light transmittance and haze, tensile strength, elongation at break, right-angled tearing strength and thermal shrinkage performance, to further study of the properties of the films after processing. Study results show that the 2320 D film pervious to good light quality and glossiness, vertical mechanics performance is better, but transverse mechanical properties, impact resistance and thermal shrinkage performance is worse than other LDPE resin films.The results of the study show that: because of the polymerization process, there is a big difference between the material structure of several LDPE resin products, the performance of its results can affect the rheological behavior of material and film products. So we can optimize and adjust the appropriate process parameters, improve the processing performance of LDPE resin, resin to get higher quality, in order to better meet market and user requirements.