The Aging Study Of Extrusion Processed FLAX/HDPE Composites

This dissertation mainly studies the composites of flax combings and high density polyethylene (named as Flax/HDPE). The composites are made through combination of single and twin screw extruder. The single factor experiment was carried on in order to find the optimum process parameter and formulation. Then the accelerated aging properties of the composites were tested by SUNTEST XXL xenon lamp aging chamber. The aging performance was evaluated by separately testing the following indexes before and after aging experiment. These indexes were flexural strength, impact strength, tensile strength, density, contact angle, thickness swelling and the color of surface. Although the analysis of scan electron microscope and Fourier transform infrared spectroscopy reflected the microstructure and morphology of composites before and after the aging test. The micro-analyses assisted to testify the macro-results of above, furthermore were advantageous to perfect the extrusion process. The Flax/HDPE composites as the substrate of laminated flooring were extruded by BHMS WPC one step extrusion method. These composites were exposed to the outdoor in order to investigate the mechanical properties of the composites before and after the natural aging test. The compare of natural aging and accelerated aging showed the inside relations. The main study works are in the following.1. The single factor experiment of flax combings’weight percent shows that mechanical properties of the composites rise up at first and then declines. When the weight percent of flax combings is60%, the comprehensive performance of the composites arrive the best. Now the optimum process parameters and formula are decided.2. Flax/HDPE composites having the addition of aging materials UV531and iron red pigment are made through two step extrusion method. Ultraviolet absorbent UV531is a kind of efficient anti aging additives. It can protect the composites and benefits to decrease the color changing, simultaneously retards the loss of mechanical performance. The mechanical properties of the composites behave optimum when the content percent of flax combings is60%and the additive is UV531. The color of composites becomes white and light with the increase of aging time, and the mechanical performance decreases too. The addition of ultraviolet absorbent UV531and iron red do have anti aging effect.3. On the basis of formula experiment and former analyses, the content of further work is improving the process parameters and formulations. Another kind of the composites which has hollow circle hole on cross surface is made by one step method. Then they are exposed out door for natural aging experiment. Many conclusions are getting after analyzing the results of12months. After the aging experiment the flexural strength of the composites concluding70% flax combings and UV531as additives is33MPa. The descend range is0.75%which is the minimum. This situation proves that the resistance capacity to bending is best. The growth of diameter of the composites concluding65%flax combings and uv531as additives is the minimum in the falling ball impact test. This means the shocking resistance is the best too.4. The study contrasts the mechanical properties of two kinds composites made by same formula with different cross section. After12months natural aging and1000hours accelerated aging, the color changing of them is similar. But the natural aging may be influenced by seasons, weather and some other indefinite factors, so the control is difficult. In the natural aging test, the flexural properties of composites concluding60%flax residues and UV531is best with2.4%increase. In the accelerated test, the flexural properties of composites concluding60%flax combings and UV531is best with19.9%decrease. These two numbers are significant different. So the effect of1000hours accelerated aging test is more effective than the six months natural aging test. The diameter of falling ball has changed7.4%in12months natural aging, and54.9%in1000hours accelerated aging. In a word, the effect of1000hours accelerated aging on the composites is much more obviously than12months natural aging.5. SEM photograph of the observed60%linen crumbs composite filler after aging anti-aging agent, did not add surface aging obvious cracks and defects, add UV531and iron-red surface is relatively flat, cracks and severity of defects much lighter, small and plain, the UV531and iron red have a good anti-aging effect.Observed after aging filler composite internal morphology, were added UV531and red iron composite material compatibility is better than not added, some HDPE filled flax fiber pores, the combination of its mechanical properties obtained significantimproved.6. IR spectra of absorption peak at1740cm-1at a carbonyl-C=O absorption peaks, add UV531and iron red C=O absorption peak enhanced, indicating that the increase in the surface of the material C=O structure; characterized in the1057cm-1at thethe peak for the OH absorption peak, indicating that there are a large number of hydroxyl groups in the surface layer of wood-plastic composite material, a hydroxyl group is a strongly polar group, the contrast bands after aging, it can be seen in the OH absorption peak intensity decreased to some extent, OH key breaks the surface of the material after processing instructions, active free radical generating material surface. Olefin=CH in the outer surface due to the bending vibration absorption peak near990cm-1, less obvious before aging after aging peak intensity, the the new compound R1HC=CHR2generated.