β成核剂改性聚丙烯树脂的微观结构、结晶行为及力学性能研究

采用熔融共混法制备了取代芳酰胺类β晶成核剂TMB-4改性聚丙烯(PP),并利用XRD、DSC、POM及SEM对改性PP的力学性能、结晶行为及微观结构进行了研究。结果表明:添加TMB-4成核剂后,PP树脂的α晶型被诱导转变为β晶型,结晶峰温度提高了16.2℃,晶粒细化;改性PP的冲击强度提高了152%,从脆性断裂转变为韧性断裂。     

增韧剂及成核剂对PP–R复合材料性能的影响

采用注射成型法制备无规共聚聚丙烯(PP–R)复合材料,结合差示扫描量热仪、扫描电子显微镜、X射线衍射仪及偏光显微镜等技术,分析了乙烯–辛烯共聚物+高密度聚乙烯增韧剂及WBGⅡ型β成核剂对PP–R复合材料力学性能和结晶行为的影响。结果表明,增韧剂与成核剂对复合材料的综合性能有明显的影响,β成核剂和增韧剂同时加入到PP–R材料中,协效提高了复合材料的冲击强度,为78.7 k J/m~2,与纯PP–R材料比较提高了175%,而对拉伸及弯曲强度影响较小。同时,加入增韧剂及成核剂均能诱导α晶向β晶转变,晶粒细化,进而改善其冲击韧性。     

Simultaneously improving the toughness,flexural modulus and thermal performance of isotactic polypropylene by α‐β crystalline transition and inorganic whisker reinforcement

Magnesium salt (M‐HOS) whisker and β‐nucleating agent were introduced into polypropylene and their effects on the crystalline structures, morphologies, mechanical properties, and thermal resistance of polypropylene (PP) were investigated. The results of wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and polar optical microscopy (POM) examinations suggested that the presence of the whisker did not cause any negative effect on the occurrence of β‐modification, and β‐phase became absolutely dominant form in β‐nucleated samples. The mechanical and thermal properties tests demonstrated that there is an excellent synergy between the β‐nucleating agent and the whisker. For PP composite containing 0.1 wt% of the β‐nucleating agent and 10 wt% of the whiskers, the Izod notched impact strength, elongation at break, flexural modulus, and heat deflection temperature were increased by 108, 194, 31, and 40%, respectively, compared with those of neat PP. By combining the toughening effect of α–β transition with the reinforcing effect of the whisker, simultaneous improvement in toughness, flexural modulus, and thermal performance of PP was successfully achieved. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

The effects of chemical structure and synthesis method on photodegradation of polypropylene

The effects of chemical structure and synthesis method on the photodegradation behavior of polypropylene (PP) were investigated in injection‐molded samples exposed to ultraviolet radiation (UV) at 60°C. For this purpose, three PP samples with different chemical structures were chosen: two homopolymerized PP samples (H₁P, synthesized by bulk polymerization; whereas H₂P was synthesized by Ziegler–Natta catalyst) and copolymerized PP sample (CP). The photodegradation was characterized by melt flow rate and mechanical properties and Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that CP possesses the most superior resistance to UV‐irradiation, followed by H₂P and then H₁P, which indicates that copolymerization with a small amount of ethylene monomer is an effective approach to obtain high stability of PP to UV‐irradiation, and synthesis methods of PP play an important role in the resistance to UV‐irradiation. Moreover, the effect of photodegradation on the thermal behaviors of H₂P was also investigated using X‐ray diffraction, differential scanning calorimetry, and dynamical mechanical thermal analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 270–279, 2005     

三种有机成核剂成核聚丙烯的非等温结晶动力学研究

采用DSC研究了聚丙烯（PP）和三种有机成核剂成核的PP在不同的降温速率下的非等温结晶动力学。用Avrami对DSC的测试结果进行了分析。结果表明,三种有机透明成核剂能显著提高PP的结晶温度和结晶速率。可以用修正Avrami方程的Jeziorny法来处理三种有机成核剂成核PP的非结晶等温结晶行为,处理结果表明：三种有机成核透明成核剂成核PP的半结晶时间减少,结晶动力学常数(Zc)增加,结晶速率增加;松香型成核剂能最快提高PP的结晶速率;同一降温速率下,三种有机成核透明剂成核PP的n值较纯PP减少,结晶成核方式发生了改变。     

POE和自制成核剂协同增透增韧PP的研究

以弹性体乙烯-辛烯共聚物(POE)和自制成核剂为助剂制备了高韧性、高透明聚丙烯(PP)材料.通过DSC、PLM、雾度等测试手段研究了不同POE含量的共混体系的结晶行为、力学和透明性能.结果表明:随着弹性体POE加入量的不断增加,PP的结晶度出现先增大后降低的变化趋势;弹性体POE在加入量较少(质量分数小于10%)时和成核剂具有协同成核效果,可以提高PP的结晶峰温度,提高结晶度,降低材料雾度;在POE质量分数为10%时,可以很好地改善体系的加工性能.     

Photodegradation of talc-filled polypropylene

Injection-molded talc-filled polypropylene (PP) composites have been exposed to ultraviolet (UV) radiation in the laboratory for periods up to 26 weeks. The extent of chemical degradation has been assessed by means of Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and the results correlated with the mechanical properties. In the early stages of exposure, the photo-oxidation is faster in the talc-filled composites than in the unfilled polymer, but this trend is reversed for exposures longer than ∼12 weeks. Scanning electron microscopy (SEM) inspection has revealed that surface cracks caused by photodegradation in the filled PP occur in the surface exposed to the UV source only, resulting in much less deterioration in tensile properties when compared with the unfilled polymer which degrades significantly at the unexposed surface also. Measurements of melting temperatures by differential scanning calorimetry (DSC) gave a consistent picture of degradation with that obtained by FTIR and GPC studies. DSC analyses have also shown that an increase in the melting enthalpy for both the unfilled and filled grades occurs during exposure.     

Study on the Crystallization Properties of Polypropylene/Montmorillonite Composites

The crystalline size of polypropylene (PP) filled with montmorillonite (MMT) was studied by X-ray diffraction (XRD). The isothermal crystallization behavior of polypropylene was studied by means of differential scanning calorimetry (DSC). The Avrami equation was used to describe the isothermal crystalline kinetics of PP/MMT composites. The result showed that the addition of MMT decreased the crystalline size L _hkl of the polymer. MMT was used as nucleating agent during isothermal crystallization process of polypropylene. The addition of montmorillonite decreased the crystallization time of the polypropylene and the melt point was raised. The value of Avrami exponent n was related with the crystallization temperature. The value of Avrami pre-index factor k of PP/MMT composite was decreased with increasing crystallization temperature. The value of half crystallization time t _1/2 of PP/MMT composite was less than that of PP at a given crystallization temperature, signifying that montmorillonite acted as nucleating agent, accelerated the overall crystallization process.     

纳米粒子/聚烯烃复合材料的结晶性能研究

报道了无机纳米粒子／聚烯烃复合材料的结晶性能研究。探索了有机成核剂苯甲酸纳、纳米二氧化钛、纳米碳酸钙对聚丙烯(PP)、高密度聚乙烯(HDPE)及其共混物的结晶形态影响，并用差示扫描量热计分析了PP，HDPE和HDPE／PP及其纳米复合材料的结晶性能。结果表明，HDPE／PP共混使HDPE的熔点(Tm)下降，PP的Tm保持不变；成核剂的加入均会使材料的Tm向低温侧移动且结晶度下降；无机纳米粒子对材料晶粒细化作用大大优于有机成核剂，纳米二氧化钛的晶粒细化作用最佳。     

PP/纳米TiO_2复合材料的结晶行为研究

采用傅里叶红外光谱仪(FT-IR)表征了改性前后纳米TiO2粉体的表面特征。通过熔融共混法制备了PP/纳米TiO2复合材料。通过力学性能测试、DSC热分析和POM照片观测,对PP/纳米TiO2复合材料的力学性能和结晶行为进行了研究。结果表明:纳米TiO2对PP既增强又增韧;纳米TiO2在PP结晶过程中具有异相成核剂的作用,能够提高PP结晶度和加速PP结晶,可明显细化PP晶粒。     

成核剂1,3-2,4-二（3,4-二甲基）亚苄基木糖醇的合成及其对聚丙烯的改性

以3,4-二甲基苯甲醛和木糖醇为原料合成1,3-2,4-二（3,4-二甲基)亚苄基木糖醇（DMDBX）,将DMDBX作为成核剂使用溶液沉淀法制备DMDBX质量分数分别为0、0.1%、0.3%、0.5%、0.7%、0.9%的聚丙烯（PP）样品,采用红外光谱仪、差示扫描量热仪、X射线衍射仪和偏光显微镜等方法,研究了DMDBX对PP结晶结构和结晶性能的影响。结果表明,DMDBX是PP的有效α晶型诱导剂,DMDBX的加入能诱导大量球晶生成,导致结晶峰尖锐,结晶温度区间变窄,结晶度提高15％左右,FT-IR、X射线衍射和DSC等分析结果一致。在PP中添加0.3%～0.5％DMDBX时,聚丙烯的改性效果最好,结晶度达到最大值。采用修正Avrami方程Jeziorny法处理非等温结晶动力学结果表明,添加DMDBX的PP Avrami指数约为3,说明DMDBX起到了异相成核的作用,使PP结晶过程的成核和生长方式发生了改变。     

成核剂对聚丙烯力学性能的影响

研究了成核剂有机铝盐、苯甲酸钠和稀土及其母料浓度对聚丙烯力学性能的影响，通过偏光显微镜(PLM)和差示扫描量热仪(DSC)表征了成核剂的成核效果。结果表明，成核剂能较好地改善聚丙烯的力学性能，降低球晶尺寸，并诱导聚丙烯生成不同晶型。     

Morphology,Rheological Properties,and Crystallization Behavior of Polypropylene/Clay Nanocomposites

Polypropylene/clay nanocomposites (PP/I.44P, PPCNs) were prepared in a twin-screw extruder using maleic anhydride grafted polypropylene (MAPP) as a compatibilizer. The intercalation of polypropylene into nanoclay particles was studied using X-ray diffraction. Rheological properties of the nanocomposites were investigated using a rheometer. The enhanced complex viscosity at low frequency regime indicated that the melt elasticity and melt strength of the nanocomposites were improved by adding nanoclay. The non-isothermal crystallization behavior of the nanocomposites was studied using differential scanning calorimetry (DSC) at various cooling rates and was analyzed with the Avrami method. It was found that the nanoclay acted as a heterogeneous nucleating agent resulted in higher crystallization temperature and higher crystallization rate than neat PP. Polarized optical microscopy revealed that the spherulites in the nanocomposites were finer than in the neat system.     

Detecting crystallization structure evolution of polypropylene injection‐molded bar induced by nucleating agent

The crystallization structures of Polypropylene (PP) injection‐molded bars nucleated by nucleating agent were detected from the skin layer to the core zone, layer by layer. α‐phase nucleating agent 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988), β‐phase nucleating agent aryl amides compounds (TMB‐5), and their compounds were introduced into PP matrix, respectively. The relative content of β‐phase PP in the different zones of an injection‐molded bar was characterized and calculated by Wide angle X‐ray diffraction (WAXD) and Differential scanning calorimetry (DSC). The results show that, whether in pure PP or in nucleated PP, both β‐phase PP and α‐phase PP grow in the skin layer of the injection‐molded bar. However, in the intermediate layers and the core zone, the crystallization structures of PP are dependent on the used nucleating agent. β‐phase is the main crystallization structure of TMB‐5 (0.1 and 0.2 wt%) nucleated PP, and α‐phase in DMDBS (0.1 and 0.2 wt%) nucleated PP. Compounding nucleating agents with 0.1 wt% DMDBS and 0.1 wt% TMB‐5 induces PP crystallization almost in β‐phase; however, PP nucleated by 0.2 wt% DMDBS and 0.2 wt% TMB‐5 crystallizes exclusively in α‐phase. The crystallization mechanism of PP nucleated by compounding nucleating agents was further studied in this work. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Effect of cross‐linked LLDPE/PP blend (LLDPE‐PP) as compatibilizer on morphology,crystallization behavior and mechanical property of LLDPE/PP blends

Moderate cross‐linked blend (LLDPE‐PP) of linear low‐density polyethylene (LLDPE) and polypropylene (PP) with benzoyl peroxide (BPO) were prepared by the reactive melt mixing in HAAKE mixer. Effect of LLDPE‐PP as compatibilizer on the morphology, crystallization behavior and mechanical properties of LLDPE/PP (87/13) blends were studied using scanning electron microscopy (SEM), polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and mechanical testing machines. The results showed that LLDPE‐PP not only improved the interfacial adhesion between the LLDPE and PP but also acted as selective nucleating agent for crystal modification of PP. In the blends, the sizes of LLDPE and PP spherulites became smaller, and their melting enthalpies reduced in the presence of LLDPE‐PP. Furthermore, the mechanical properties of LLDPE/PP blends were improved with the addition of LLDPE‐PP, and when the concentration of LLDPE‐PP was 2 phr, the ternary blend had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of Modified Abietate Nucleating Agents on the Properties of Polypropylene

Two kinds of modified abietates, cocrystals of dehydroabietic acid with sodium dehydroabietate and tetrahydroabietic acid with sodium tetrahydroabietate, were prepared, respectively. The properties and crystallization behavior of polypropylene (PP) with the modified abietate cocrystals as nucleating agents were investigated by the measurement of mechanical properties and heat distortion temperature (HDT), testing of differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarizing light microscopy (PLM) observation. The results show that the heat distortion temperature (HDT), transmittance, crystallizing point, the degree of crystallinity, and mechanical properties, especially the flexural strength and modulus of PP are enhanced obviously, but the size of spherulites measured by polarizing optical microscopy decrease, by adding modified abietate cocrystals. By adding the modified abietates, the typical α-form monoclinic structure of PP was formed, which was proved by the results of X-ray diffraction. It is concluded that the modified abietates can be used as effective nucleating agents for PP.     

Polypropylene-polyhedral oligomeric silsesquioxanes (POSS) nanocomposites

In this paper, the influence of the functionalisation of polyhedral oligomeric silsesquioxanes (POSS) cages on the preparation and properties of polypropylene (PP) based nanocomposites is studied.POSS with different chain lengths (octamethyl-, octaisobutyl- and octaisooctyl-POSS) are taken in to account and melt mixed with PP. The resulting composites are characterised as regards thermal and morphological characteristics by means of DSC, TGA, SEM and X-ray diffraction.A good dispersion is obtained particularly at low loadings of POSS functionalised with longer organic chains.Important features are recognised as regards the crystallisation behaviour of PP by octamethyl- and octaisobutyl-POSS: The former acting as a nucleating agent and the second inducing PP polymorphism.     

Effect of spatial confinement on the development of β phase of polypropylene

The focus of this study was the effect of spatial confinement on the development of nucleating agent-induced β phase polypropylene (PP) in the dynamically vulcanized thermoplastic elastomers (TPVs) based on dynamically vulcanized PP/ethylene-propylene-diene rubber (EPDM) blend. The melting behaviors, crystalline structures and the morphologies of the blends were studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results indicate that the EPDM phase undergoes a series of changes from the dispersed phase to a continuous one, and again to the dispersed phase with increased content of curing agent, and the PP component always shows itself in a continuous phase. In this process, with the content of the nucleating agent unchanged, the content of β phase PP in the blends initially increases a little and then decreases with increasing PF (Phenolic resin) content. We believe spatial confinement provides a good explanation for the development of β phase PP.     

Preparation and nonisothermal crystallization behavior of polypropylene/layered double hydroxide nanocomposites

Polypropylene (PP)/layered double hydroxide (LDH) nanocomposites were prepared via melt intercalation using dodecyl sulfate anion modified LDH and maleated PP as compatibilizing agent. Evidently the interlayer anions in LDH galleries react with maleic anhydride groups of PP-g-MA and lead to a finer dispersion of individual LDH layers in the PP matrix. The nanostructure was characterized by XRD and TEM; the examinations confirmed the nanocomposite formation with exfoliated/intercalated layered double hydroxides well distributed in the PP matrix. The nonisothermal crystallization behavior of resulting nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates. In nonisothermal crystallization kinetics, the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the Avrami analysis and Jeziorny method well define the crystallization behavior of PP/LDH nanocomposite. Combined Avrami and Ozawa analysis (Liu model) also found useful. The results revealed that very small amounts of LDH (1%) could accelerate the crystallization process relative to the pure PP and increase in the crystallization rates was attributed to the nucleating effect of the nanoparticles. Polarized optical microscopy (POM) observations also support the DSC results. The effective crystallization activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis. Overall, results indicated that the LDH particles in nanometer size might act as nucleating agent and distinctly change the type of nucleation, growth and geometry of PP crystals.     

Study on Mechanical Properties and Crystallization Behavior of Polypropylene and Its Blends Modified by β Crystalline Form Nucleating Agent

The influence of β crystalline form nucleating agent (β nucleator) on the mechanical properties of homo-polymerized polypropylene (PPH), random-copolymerized polypropylene (PPR), block-copolymerized polypropylene (PPB), and PPH/PPR/PPB blends was studied. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were used to characterize the crystalline morphology and behavior. The results indicated that α crystalline form of polypropylene (PP) had transformed to β crystalline form by adding 0.5% β nucleator; in the meantime, the toughness of PP and its blends was enhanced. That is, 0.5% β nucleator helped to improve the notched impact strength of PPH, PPR, and PPH/PPR/PPB blends by 130%, 40%, and 40%, respectively, without losing the tensile strength and flexural strength.