| PP possesses excellently comprehensive properties, it has a wide application in injection molding, extrusion, blow molding etc. But its notch impact property is bad limitingits using range. This paper investigates the effect of differentαandβnucleating agent on properties of PP. It focuses on rare earth nucleating agent toughing modification PP. The thesis consists of six parts:1.In chapter 2, using fourαnucleating agents and threeβnucleating agents to modify PP, studies on the influence of each nucleating agent's content on the mechanical properties and crystal.2. Chapter 3 investigates effect of the content of a new rare earth nucleating agent (WBG2) on the mechanical properties and thermal characteristics of PP, also the relationship between mold temperature, cooling time, heat treatment temperature and time with mechanical properties.3. Chapter 4 researchesβ-iPP non-isothermal crystal and dynamics, effect of cooling rate on degree of crystallinity andβcrystal relative content, surveys hot history, drawing, pressure influence onβ-iPP crystal andβ→αphase change.4. Chapter 5 investigates the effect of isothermal, non-isothermal and shearing onβ-iPP supramolecular structure, emphasizing on which temperature and cooling rates affectsβ-iPP supramolecular structure.5. Chapter 6 studies the influence ofβnucleating agent using together withαnucleating agent,,βnucleating agent using together with other cooperative agent on mechanical properties and crystal of iPP.6. Chapter 7 is preliminarily survey of the influence of PPαandβnucleating agent on crystal properties of PA and PET. Following conclusions are made:1. Fourα-nucleating agents were selected, added in iPP, inducingαcrystals and enhancing the speed of crystal. Tensile strength of the sample increased, break elongation and impact strength decreased. The effect of TM-1 was better than IrgaclearD. Reinforcement effect of Aryl-phosphoric acid nucleating agent TMP-5 and NA11 are the best.2. Threeβ-nucleating agents were selected, added in iPP, inducingβ-crystals and enhancing the speed of crystal. Impact strength ofβ-iPP was sensitive to temperature,it enhanced as temperature increased. The impact strength of WBG2-0.1 and TMB5-0.1 in iPP was 7.9 kJ/m~2 and 7.2 kJ/m~2 respectively, raised 146.9 % and 125 % comparing with pure PP. When the addition was in the range of 0.1～0.5%, impact strength of samples decreased gradually, tensile strength enhanced gradually as the concentration ofβ-nucleating agent increased.3. Rare earth nucleating agent WBG2 possessed hot stability, it could diminish oxygenization in processing, and the samples were white. TMB5 and TMB20 in iPP didn't have effect of antioxygenation, and the samples were primrose or snuff color.4. In injection moulding, increasing melt temperature was useful of eliminating thermal history in extrusion, being propitious to generateβ-crystals. When not controlling the mould temperature, impact strength of samples decreased as the cooling time prolonged. Heat treatment at appropriate temperature was in favor of improving heat deflection temperature and impact strength. The temperature of heat treatment was higher,β→αphase change happened more easily, the best heat treatment temperature was 100℃, the best method of heat treatment was water bath.Controlling of mould temperature could improve impact strength of samples with low-content nucleating agent, but it was bad to tensile strength.5. WBG2 could induceβ-crystals efficiently,βendothermic peak of samples were apparent all the same after four heat cycles. It was a kind of steady and efficientβnucleating agents. In injection moulding, from skin near cavity die to center, cooling rate decreased gradually, the total degree of crystallinity and relative content ofβ-crystals increased gradually. High pressure (0.75GPa) improvedβ degree of crystallinity and relative content ofβ-crystals. But time of crystallizing at high pressure was too long, degree of crystallinity and relative content ofβ-crystals decreased. In drawing,β-iPP phase change happened, secondary yield happened in some samples. After drawing,β-crystals change toα-crystals mostly.6. This paper quantitatively investigated the relationship between cooling rate andβ-crystals content, that research appeared few in literature. It proved that low cooling rate was propitious to improve degree of the degree of crystallinity,β-melting point andβ-phase relative crystallinities of the samples. With decrease the cooling rate from 20 to 2.5℃/min, theβ-melting point increased from 149.7 to 156.9℃, and the total degree of crystallinity increase from 61.8 to 69.6 %, the relative content ofβ-phase increase from 63.1 to 91.4%.7. The non-isothermal crystallization kinetics ofβ-PP was not fit to use the method of Ozawa analysis but Mozhishen's method.8. A kind of new supramolecular structure was found firstly, and that supermolecular structure hasn't been report in previous literature. This structure exhibited the center is snow-likeβ-crystals, the surrounding is negative spherulite.Warming up at 10℃/min and 20℃/min, the central snow-likeβcrystals melt first,periphery negativeβspherulites melt after. If warming up at 100℃/min, the melting order was opposite. This provedβ→αphase change happened in slow warming process.9. A new study method was designed:β-iPP and pure PP were concatenated after they were pressed into film, then observed by polarization microscope on line.When the conditions were same, the growth and evolvement ofα-crystals andβ-crystals could be observed at one time, the difference of two crystals was apparent.10. The supermoleculars structure ofβ-iPP was much more influnced by the cooling rate. When W-0.2 cooled at 100℃/min and 20℃/min, small and disordered crystals formed.β-Spherulites surrounding the snow-likeβcrystals formed when cooled at 10℃/min and 5℃/min. Slow cooling rate benefit the growth and perfect ofβ-phase. With lowly shear rate,β-iPP formed fibriform crystals first and at last formed cylindrites. With high shear rate,β-iPP formed dense fibriform crystals and at last formed a lot of small crystals.11. The nucleating cooperative agent A,C,D,F,G were found, which could largely reduce the cost and increase the nucleating effect. WBG2 using together with A,C,D,F,G can increase impact strength largely, the cooperate domino effect of A was the best, it could increase the impact strength of pure PP from 3.2 kJ/m~2 to 15.1 kJ/m~2.WBG2 using together with theαnucleating agent TMP-5, TMP-5 took leading role. The tensile strength was increased in evidence, but the break elongation and impact strength were decreased in evidence.12. The influence of six polypropylene nucleating agents on the crystal properties of PET and PA was observed. NA11 and TMB5 added in PET could avoid the crystal of recrystallization, it benefit the size stability of product. WBG2 could increase the crystallinity of PET. The other fiveαandβnucleating agents except TM1 could increase the crystal rate of PA a little.
|
PDF Full Text Request