Study Of High Performance Coacervation Structure Polyolefin Pipes Extruded By Shearing-Drawing Two-Dimensional Stress Field Die

Around the world, many scholars have been dedicated themselves to study the reinforcement of plastic pipe for many years. Some resorted to reinforcing materials, such as glass fiber. Others resorted to oriented crystallization methods. But there were many defects in these studies. Firstly, pipe has not been reinforced on axial and circular properties at the same time. One of the properties descended sometimes even when the other had been reinforced. Secondly, the quantity of reinforcing materials was always more than 20% and the cost of production was very high. Thirdly, although some studies had reinforced the axial and circular properties at the same time, yet the productivity was very low. Furthermore, studies of axial and circular properties of plastic pipes reinforced simultaneously by shearing-drawing two-dimensional stress field pipe-extrusion die have not been reported. So two equipments of shearing-drawing two-dimensional stress field pipe-extrusion die were designed and made by us. By simple methods of pipe molding and industrial productivity, polyolefin pipes whose axial and circular properties reinforced by SGF or themselves simultaneously had been manufactured successfully. The mechanical properties,crystalline morphology and coacervation structure,oriented crystallization theory,shearing-inducing crystallization theory,molecular microstructure and reinforcing mechanism of pipe had been studied in this thesis synthetically. It was found that: 1. Put forward by us, new idea of reinforcement on the circular and axial properties of plastic pipe extruded by shearing-drawing two-dimensional stress field die simultaneously was tested and terrified by the study. It made up the defect of not reinforcing the axial and circular properties of plastic pipe of the past studies simultaneously and efficiently. 2. Plastic pipe was extruded at low temperature closing to its melting point efficiently and continuously in the study. It not only solved the problem of bad results of self-reinforcement of conventional high temperature extrusion whose disorientation is acute but also avoided the low efficiency of solid-state or semi-solid-state extrusion. 3. Idea of short glass fiber inducing crystallization of polymer pipe was tested and verified by the study. In the reinforced pipes of SGF/HDPE/PP, not only SGF oriented on two-dimensional but also the polymer molecular chains oriented and crystallized twice. Interlocking shish-kebab structure oriented and crystallized twice had been achieved at the same time. So two-dimensional self-reinforcement polyolefin pipe had been obtained. 4. New idea of inducing crystallization of relatively low molecular weight system by adding a little of relatively high molecular weight ingredient was tested and verified by the study. The effect of shearing-inducing crystallization was more obvious when a little of HDPE 1158 whose molecular weight is relatively high had been added to HDPE 6100M system whose molecular weight is relatively low. It developed the shearing-inducing crystallization theory. 5. Idea of inducing crystallization by adding β-nucleator was tested and verified by the study. Obvious interpenetrating polymer network structure andβ-crystals had been achieved in the reinforced pipes of PP T30S(40) : HDPE 6100M(60%) with 0.3%β-nucleator. The continuous phase network had been composed of PP T30S molecular chains between the crystals of HDPE 6100M. The crystals of HDPE 6100M acted as reinforcing phase which was well-destributed in the PP T30S continuous phase network and reinforced pipe. 6. Put forward by us, idea of twice-oriented-crystallization appeared during the process of obtaining polyolefin pipe in shearing-drawing two-dimensional stress field die was tested and verified by the study. Molecular microstructure of reinforced pipes was composed of much microfibril which was arranged regularly and oriented finely. It had become twice-oriented-crystallization interlocking shish-kebab structure obviously. At the same time, axially and circularly oriented molecular and shish-kebab structures had been achieved too. So the two-dimensional properties of these pipes had been improved further. 7. Though there was not any study report of improving the axial and circular properties of plastic pipe by shearing-drawing two-dimensional stress field all over the world, equipment of shearing-drawing two-dimensional stress field pipe extrusion die was designed and manufactured by us. It could improve the two-dimensional properties of polyolefin pipe on condition that of industrial productivity. 8. By the results of mechanical properties test, it was found that both of axial and circular strength and modulus of these pipes extruded at high productivity had been improved. The results as follows: (1),the highest strength of HDPE 1158 pipes had been increased more than 54% to 33.5MPa. Its highest modulus had been increased more than 1.4 times to 529.8MPa. (2),The axial highest modulus of HDPE 1158(40%) : HDPE 6100M(60%) pipes had been increased 37.68% to 235.3MPa. Its axial highest strength had been increased 29.08% to 24.9MPa. Its circular highest modulus had been increased 78.19% to 335MPa. Its circular highest strength had been increased about 25% to 27.78MPa.(3),Both of the axial and circular properties of shearing-inducing crystallization pipes of HDPE 1158 : HDPE 6100M had been improved obviously, especially the improvement of HDPE 1158(4%) : HDPE 6100M(96%) pipes extruded on that condition of 145℃was good on all aspects. Its axial highest modulus had been increased 55% to 243.7MPa. Its axial highest strength had been increased 54.73% to 35.85MPa. Its circular highest modulus had been increased 62.85% to 312MPa. Its circular highest strength had been increased 44.17% to 31.53MPa. (4),The highest strength of HDPE/PP pipes reinforced by 3% SGF had been increased more than 40% to 35.5MPa. (5),The axial highest modulus of HDPE 6100M pipes had been increased 26.5% to 199MPa. Its circular highest modulus had been increased 40% to 286.8MPa. Its axial highest strength had been increased 15.8% to 21.43MPa. Its circular highest strength had been increased 17.6% to 24.37MPa. (6),The axial highest strength of HDPE 6098 pipes had been increased 14.8% to 25.82MPa. Its circular highest strength had been increased 13% to 24.52MPa. (7),The axial highest strength of PP C180 pipes had been increased about 10% to 25.85MPa. Its circular highest strength had been increased about 17% to 26.54MPa. (8),The axial highest modulus of the pipes of PP T30S(40%) : HDPE 6100M(60%) with 0.3% β-nucleator had been increased 16.58% to 251MPa. Its circular highest modulus had been increased 19.17% to 271.7MPa. Its axial highest strength had been increased 23.63% to 27.32MPa. Its circular highest strength had been increased 17.07% to 25.86MPa. (9),The axial highest modulus of PPR pipes had been increased 21% to 159.6MPa. Its circular highest modulus had been increased 76.07% to 247.9MPa. Its axial highest strength had been increased 16.77% to 25.48MPa. Its circular highest strength had been increased 11.85% to 25.39MPa. It was found that the circular effects of improvements of strength and modulus were better than the axial effects and the effects of modulus were better than the strength's too. After reinforced, the weld mark of pipe had been eliminatedcompletely and the circular properties of pipe were better than or close to the axial properties. So the properties of polyolefin material had been distributed more reasonably and satisfied the real needs of internal pressure pipes. At the same time, the improvements of axial and circular properties of relatively high molecular weight ingredient inducing-crystallization system, glass fiber inducing-crystallization system and β-nucleator inducing-crystallization system were more obvious by contrast. 9. The degree of axial and circular orientations of reinforced pipes was better than that of the conventional pipes. Its lamellar thickness was thicker. Its crystallinity was higher and its heat resistance of reinforced pipes was better than that of the conventional pipes too. 10. Results of the study had good industrial prospect and economic results. The productivity of these pipes was high. The cost of equipments,raw material and production were very low and the properties of pipe were well. It could satisfy the need of industrial production.