Continuous Blown Film Preparation of High Starch Content Composite Films with High Ultraviolet Aging Resistance and Excellent Mechanical Properties

Starch/PBAT blown films with high ultraviolet aging resistance and excellent mechanical properties were prepared by introducing lignin with polyurethane prepolymer (PUP) as a starch modifier and physical compatibilizer and 4,4′–methylene diphenyl diisocyanate (MDI) as a crosslinker. Starch was modified by reacting the NCO groups of the PUP with the OH groups of the starch to form a carbamate bond. The mechanical properties, hydrophobic properties, ultraviolet barrier, ultraviolet aging properties and microscopic morphology of starch/PBAT films with different contents of lignin were investigated. The results showed that the starch/PBAT films were blown continuously. The addition of lignin did not decrease the mechanical properties. On the contrary, the film with 1% lignin possessed the excellent mechanical properties with longitudinal tensile strength of 15.87 MPa and the elongation at a break of 602.21%. In addition, the higher the lignin content, the better the UV blocking effect. The introduction of lignin did not affect the crystalline properties but improved the hydrophilic properties and sealing strength of the high starch content composite films.

Ultraviolet Aging Mechanism of Asphalt Molecular Based on Microscopic Simulation

In order to reveal the nature of the Ultraviolet aging(UV-aging) behavior of asphalt molecules, simulation by Materials Studio software. The effect of UV aging on the transformation, aggregation and motion state of asphalt microstructure is analyzed by the changes in energy, density of dispersive phase, glass transition temperature and viscosity of the asphalt molecular system. The results show that UV aging enhances the bonding degree of asphalt molecules by increasing the heavy components in the asphalt molecules and increasing the distribution width between the asphalt molecule components, which improves the high-temperature resistance of asphalt. At the meantime, the UV aging causes the asphalt molecular movement state to solidify at low temperature so that the rheological behavior is difficult to occur by reducing the lightweight component and free volume of the asphalt molecule and increasing the glass transition temperature, which reduces the low-temperature resistance of asphalt. In addition, among the factors affecting the viscosity of asphalt molecular, the degree of influence of the molecular structure and molecular weight is significantly greater than the molecular activity. The addition of short branched chain hydrocarbon molecules to the UV-aged asphalt molecules could effectively reduce the viscosity of the asphalt molecules and improve the flowability of the asphalt molecules. The results of the study contribute to the understanding of the characteristics of changes in the microstructural pattern and dynamic behavior of asphalt molecules during UV aging, and achieve interpretation and prediction of changes in asphalt properties at the microscopic level.

Effect of Ultraviolet Aging on Composition, Structure and Properties of Asphalt

Asphalt aging is a pivotal factor affecting the service performance of asphalt pavement. Previous studies often ignored the influence of ultraviolet radiation on asphalt aging. Coincidentally, there is no standard test method of photooxidation aging that can be applied to guide engineering practice. In this paper, the influence of ultraviolet aging on the composition, structure and properties of asphalt was studied by adopting Bert four-component method, Fourier transform infrared spectroscopy aned dynamic shear rheometer. Bert four-component method elaborates that the content of asphaltene increases and the content of aromatic component decreases after UV aging. Fourier transform infrared spectroscopy indicates that there are obvious peaks of carbonyl and sulfoxide groups after aging, the penetration of asphalt decreases while the softening point and viscosity increase. Moreover, the composite modulus of asphalt increases obviously at low temperature, but has little effect on the composite modulus at high temperature.