| The application of high-performance polypropylene has been more and more wide. Studies have shown that introducing the nucleating agent is a simple, effective way to modify polypropylene. At present, the relevant studies about liquid crystal types of nucleators are almost no report. With the expansion of market demand, research about the type of nucleators has great scientific value and produce meaning.In this paper, three liquid crystal monomers were designed and synthesized, which included 4-(undec-10-enoyloxy)biphenyl-4’-pentylbenzoate (M1), cholestery14-(10-undecen-1-yloyloxy)benzoate (M2),4-(4-(2-(acryloyloxy)ethoxy)benzoyloxy) biphenyl-4’-pentylbenzoate (M3). The polymer P1 was prepared by graft polymerization reaction with M1 and PMHS(DP=35), and the polymer P2 was prepared by graft polymerization reaction with M2 and PMHS(DP=35). The polymer P3 was prepared by free radical reaction with M3 under certain conditions. The iPP(T30S) was blended with different content(0.0-1.2wt%) of nucleators (M1, M2, M3, P1, P2, P3) under specific processing conditions.The chemical structures, liquid crystal properties and thermal properties of the synthesis of intermediate, monomer and polymer were investigated with FT-IR,1H-NMR, POM, DSC and TGA. The impact of liquid crystal nucleator on the the crystallization structures and thermal properties of the blend samples were investigated with WAXD, POM, DSC, melt flow rate tester, rheometer.M1 exhibited texture of smectic B(SB) phase, texture of smectic B(SB) phase, texture of smectic B(SA) phase on heating process, schlieren texture of nematic phase, fan-shaped texture of smectic A(SA) phase, broken fan-shaped texture of smectic C(SC) phase, and mosaic texture of smectic B(SC) phase on cooling process. M2 exhibited cholesteric oily streak texture on heating process, focal conic texture of cholesteric on cooling process. M3 exhibited thread-like texture of nematic phase on heating process, the fan-shaped texture and mosaic texture appeared on cooling process. P1 and P3 exhibited texture of nematic phase on heating process and cooling process. P2 exhibited texture of smectic phase. The liquid crystal nucleators were "liquid crystal state" in the range of temperature (90～140℃),which was the main crystallization temperature of iPP. Thus, all of them accorded with the design. And thermal decomposition temperatures for three kinds of polymers were 362.9℃,322.6℃ and 380.5℃, demonstrating that they are thermally stable.WAXD testing showed that the liquid crystal nucleators(M1, M2, M3, P1, P2 and P3) had the ability to induce the β-form of iPP. The nucleator contents were 0.6wt%,0.6wt%,0.6wt%, 0.8wt%,0.2wt% and 0.6wt% respectively. The crystallization temperatures were 120℃, 130℃,125℃ 120℃,120℃ and 120℃ respectively. All of the crystallization times were lh. The best relative contents of the β-form (Kβ) in blend system were 28.7%,34.5%,28.7%, 47.8%,66.3% and 34.0% respectively. The result showed that P1, P2 had more ability of inducing β-form than M1, M2 respectively. However, P3 had the same ability of inducing P-form as M3.The observation of POM showed that the introduction of liquid crystal nucleator could induce β-form. The β-spherulites were bright and colorful, had obscure boundaries, and exhibited sheaf-like structures. The a-spherulites were black and white, had clear boundaries exhibited radial structures. With the temperature rising, the colorful β-form started to be extinction. The a-form with black and white started to be extinction in the higher temperature.DSC testing showed that the characteristic melting peaks of β-form appeared in all the DSC heating curves of iPP blends with nucleators. The crystallization peaks of all the DSC cooling curves of iPP blends with liquid crystal nucleators shifted to high temperatures, the crystallization temperature and the crystallization velocitiy had been increased.MFR testing showed that three kinds of nucleators could change the liquidity of the blends effectively and P2/iPP had the best liquidity. Flow curve testing showed that three kinds of blends rendered shear thinning behaviors with the rise of shear rate. The results were consistent with the analysis of the MFR. The analysis of shear sensitivity showed that P1 and P2 could change the shear sensitivity effectively at 190℃. P1/iPP had the same shear sensitivity as P2/iPP, and they were still more sensitive than iPP. With the increase of temperature, the shear sensitivity of iPP and P1/iPP improved at different degree, but the shear sensitivity of P2/iPP decreased. The analysis of temperature sensitivity showed that the temperature sensitivity of three blends had a declining trend with the rise of shear rate. The nucleators P1 and P2 had the ability to make temperature sensitivity of iPP decreased at lower shear rate. |
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