Study On Reinforcement Modification Of LDPE Based On Twin-channel-screw Strengthened Vibration Extrusion

Low density polyethylene(LDPE) had been widely used in the field of agricultural and construction packaging films for its own strengths, such as softness、high elongation、electrical insulation、transparency, etc. Modification on reinforcement had been a major research direction of low density polyethylene. By adding vibration force field into the extrusion process, the processing of forming could be optimized to a large extent. The aggregation structure of polymer could be largely influenced by the extrusion process, thus giving the product desired performances so as to meet the needs of wider range of applications. The mechanically stimulated dynamic extruder was used in this paper, which could apply the vibration force field into the whole polymer extrusion process. Moreover, the unique twin-channel-screw could also strengthen the vibration force field.LDPE products were produced from vibration extrusion and steady extrusion in this paper. By comparing the structure and properties of LDPE products from two kinds of extrusion process, the influences of vibration force field on aggregation structure and mechanical properties of LDPE products were revealed. Studies showed that, under the vibration force field, the crystallinity of LDPE was improved, crystal area was more compact, lamellar thickness was increased, part of the crystals was oriented under the force field. Compared to steady extrusion, the improvement on tensile strength and modulus was achieved, in addition, the surface hardness of LDPE was also increased. Finally, we’ve found when the vibration frequency is nearly 5 Hz ~7 Hz, the amplitude is about 0.6mm, best reinforcements on LDPE samples were achieved.In addition, LDPE/PLA blends on a fixed ratio was adopted in this paper. The effects of vibration parameters on aggregation structure, interfacial structure and mechanical properties of LDPE/PLA blends were studied. Results showed that, compared to steady extrusion, vibration extruded LDPE/PLA blends exhibited an increase on crystallinity on each parts. Lamellar thickness increased and crystal orientation effects of LDPE part were reflected. In addition, the vibration force field also induced the dispersed PLA parts to form fibers in LDPE matrix. The formation of the fiber structure weakened the decline effects on mechanical properties of the blends, which were caused by the poor interfacial strength between LDPE and PLA. In this way, the tensile strength and modulus of the blends could be eventually enhanced. Finally, the experiment data revealed that, when the vibration frequency was nearly 3 Hz ~5 Hz, the amplitude is about 0.55 mm ~0.6 mm, LDPE/PLA blends showed best improvements on crystallization properties. What’s more, under these vibration parameters, the induced orientation effects were more obvious, PLA exhibited best fiber-forming structure, the best improvements on mechanical properties and surface hardness could be achieved.