The three-phase structure of isotactic poly(1-butene)

A detailed analysis of the three-phase structure of isotactic poly(butene) was conducted by conventional and temperature-modulated calorimetry. The development of the crystalline, mobile amorphous, and rigid amorphous fractions was analyzed as a function of thermal history, upon isothermal and non-isothermal crystallization. It was found that, under the chosen experimental conditions, the amount of rigid amorphous phase (w_RA) in PB-1 ranges from w_RA = 0.14 to 0.23, with higher values formed when the polymer is crystallized at low temperatures or at high cooling rates from the melt. Comparison of total and frequency-dependent reversing heat capacity curves suggested that the rigid amorphous phase of isotactic poly(1-butene) vitrifies after completion of the crystallization process and that its full mobilization takes place at around 50 °C. The exact temperature of complete devitrification is slightly affected by the thermal history of the material. An effort to link the mechanical properties of PB-1 to the three-phase structure was attempted, and a correlation of Young's modulus with the solid fraction at the temperature of analysis, composed of crystalline and rigid amorphous phases, was proposed.     

An AFM study on the structure and melting behavior of melt-crystallized isotactic poly(1-butene)

Spherulites with closely packed edge-on lamellae and lathlike flat-on crystals of melt crystallized isotactic poly(1-butene) in ultra-thin films at different temperatures were studied by AFM in taping mode. Starting from these different crystals, the melting processes of them after aging at room temperature for different periods of time were monitored. Through selective melting of the thermally less stable Form II crystals, the solid phase transformation of iPB-1 from Form II to I was discussed. Based on the obtained results, it is concluded that nucleation of the iPB-1 stable Form I crystals is the rate-determining step of the Form II to I conversion. Moreover, from the facts that (i) nucleation of the stable Form I crystals starts most likely at crystalline side surfaces or corners, and (ii) the phase conversion rate of the melt grown flat-on crystals is much faster than that of the solution grown single crystals, we suggest that residual local thermal stresses exist at the edges of the microcrystallites and stacking regularity of the crystalline lamellae play a very important role in generating the nuclei of the iPB-1 Form I crystals.     

GMA/St多组分单体熔融接枝高全同聚1-丁烯

采用Haake转矩流变仪研究了甲基丙烯酸缩水甘油酯(GMA)-苯乙烯(St)多组分单体熔融接枝高全同聚1-丁烯(iPB).考察了温度,过氧化二异丙苯(DCP),GMA,St用量对接枝的影响.结果表明:在180℃下,DCP用量为0.8 phr时,接枝率最高;DCP用量一定时,随着GMA用量增加,接枝率增加,熔体流动速率减...     

Rheology,polymorphic crystal transformation,thermal, and mechanical properties of long-chain branched isotactic poly(1-butene)

Effects of long-chain branches (LCBs) on the rheology, crystal polymorphism, polymorphic transformation, and corresponding thermal and mechanical properties at different crystallization conditions, of isotactic poly(1-butene) (iPB-1) are systematically studied. The complex viscosity decreases and tangent increases with the increase of LCB concentration, and they inversely correlate with gels. The low branched samples crystallize into pure Form II by compression molding and cooling the melt to room temperature at a low crystallization cooling rate, whereas the moderate-to-highly branched samples crystallize into mixtures of Forms II and III, with a 1–30% fraction of crystals of Form III. The transformation of Form II into Form I in low branched iPB-1 was not significantly decelerated at different crystallization cooling rates, which is important in thermoforming, foaming, and extrusion blowing processes. Upon heating, Form III in highly branched iPB-1 with gels does not cold-crystallize into Form II even at a low heating rate. The low-to-highly branched samples mainly in Form I exhibit high yield strength, high melting temperature, and lower ductility, while the highly branched iPB-1 containing gels and mixtures of Forms I, III, and I′ possess brittleness. Under stretching, Form III predominantly transforms into Form I via a solid–solid crystal transition. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48411.     

相对分子质量对全同聚1-丁烯熔体流变行为的影响

采用恒速型双筒毛细管流变仪研究了不同相对分子质量的全同聚1-丁烯(iPB)在较宽剪切速率范围的稳态剪切流变行为。讨论了剪切速率、温度及相对分子质量对iPB熔体黏弹性、非牛顿指数、黏流活化能及挤出物表观的影响。结果表明:在实验剪切速率范围内,iPB是典型的假塑性流体,相对分子质量越大非牛顿指数越小,熔体的黏弹性和黏流活化能越大,挤出物临界剪切速率越小;升高温度能降低熔体的黏弹性。iPB熔体的非牛顿性随温度变化及黏流活化能随剪切速率变化均因相对分子质量的不同而略有差异。     

负载钛-三异丁基铝体系催化1-丁烯聚合 Ⅱ.聚1-丁烯的结构与性能

负载钛－Ａｌ（ｉ－Ｂｕ）３催化合成的聚１－丁烯,经溶剂萃取分离和１３Ｃ－ＮＭＲ测试表明为全同立构和无规立构的混合物,全同立构含量约６７％,熔点为９７℃。ＰＢｔ生胶的拉伸强度９．７ＭＰａ,断裂伸长率４９０％,永久变形小于１００％,邵尔Ａ型硬度８７,是一种热塑性弹性体材料     

Mesophase formation in poly(propylene-ran-1-butene) by rapid cooling

The effect of random insertion of low amount of 1-butene of less than about 11 mol% into the isotactic polypropylene chain on structure formation at non-isothermal crystallization at different rate of cooling was investigated by X-ray scattering, density measurements, and atomic force and polarizing optical microscopy. Emphasis is put on the evaluation of the condition of crystallization for replacement of lamellar crystals by mesomorphic nodules on increasing the cooling rate/supercooling. In the polypropylene homopolymer, mesophase formation occurs on cooling at rates larger about 150–200 K s⁻¹, while in case of poly(propylene-ran-1-butene) mesophase formation is observed on cooling at a lower rate of about 100 K s⁻¹. It is suggested that the lowering of the critical rate of cooling for mesophase formation in poly(propylene-ran-1-butene) is due to a reduction of the maximum rate of formation of monoclinic/orthorhombic crystals at low supercooling, compared to the homopolymer. The data of the present study allowed the establishment of a non-equilibrium phase diagram which shows ranges of existence of phases as a function of the cooling rate on solidification the quiescent liquid and the concentration on 1-butene co-units.     

陈化方式对负载钛催化合成聚1-丁烯的影响

以TiCl4(简称Ti)／Al(i-Bu)3(简称A1)为催化剂,合成了聚1-丁烯热塑性弹性体,考察了催化剂的陈化温度、陈化时间以及陈化1-丁烯(Bt)用量对转化率、聚合物重均相对分子质量的影响。结果表明．采用0℃下Ti-Al-Bt三元陈化方式制备的催化剂可以有效地提高单体的转化率,降低Al的用量。最佳陈化条件为：Bt／Ti(摩尔比)60,Al／Ti(摩尔比)20,0℃,20min。0℃陈化时,试样的重均相对分子质量比室温陈化的高;三元陈化试样的重均相对分子质量比二元陈化的高。在室温和0℃陈化时．陈化时间较短,试样的重均相对分子质量变化不大;随陈化时间的延长,试样的重均相对分子质量下降。     

An unusual branching in single crystals of isotactic poly(4-methyl-1-pentene)

Single crystals of low M_w poly(4-methyl-1-pentene) (P4MP1) in its form I display an unusual streaking of their diffraction pattern. The crystals also frequently give rise to composite diffraction patterns made of two patterns rotated by 37°. The streaking indicates a structural disorder, namely a shift of nearby layers along the a or b axis by one quarter of the unit-cell edge. The daughter crystals, rotated by 37°, are produced on the edges of the parent crystals via an epitaxial growth that is a direct consequence of the structural disorder.     

复合引发剂引发GMA熔融接枝聚1-丁烯

采用复合引发剂用Haake流变仪研究了甲基丙烯酸缩水甘油酯(GMA)-苯乙烯(St)多组分单体熔融接枝高全同聚1-丁烯(iPB)。用傅里叶变换红外光谱对接枝物进行了分析,并分别考察了复合引发剂比例、GMA用量、引发剂总用量和St用量对接枝的影响。结果表明:在复合引发剂引发下,GMA和iPB可熔融接枝,接枝率最高可达1.74%;St作为共单体可明显提高GMA的接枝率和接枝效率,当n(St)/n(GMA)为1.5时,接枝率为单独使用GMA时的2.3倍。     

Direct melt-crystallization of isotactic poly-1-butene with form I′ using high-pressure CO2

In this work, we found a new method to obtain isotactic poly-1-butene (iPB-1) with form I′ through direct melt-crystallization using high-pressure CO₂. The non-isothermal melt-crystallization behaviors of iPB-1 under atmospheric N₂ and 0.5-10 MPa CO₂ at cooling rates ranging from 0.25 to 5 °C/min were carefully studied using high-pressure differential scanning calorimeter (DSC) and analyzed using the modified Avrami method. Wide-angle X-ray diffraction (WAXD) measurements showed that the crystal structure of non-isothermally melt-crystallized iPB-1 changed from form II under atmospheric N₂ and 0.5-8 MPa CO₂ to form I′ under 10 MPa CO₂. In-situ high-pressure Fourier transform infrared (FTIR) was also used to investigate the non-isothermal melt-crystallization at CO₂ pressure up to 18 MPa at the cooling rate of 1 °C/min. Likewise, it was found that form II crystallized under atmospheric N₂ and 0.5-8 MPa CO₂, and form I′ melt-crystallized directly at CO₂ pressures higher than 10 MPa, which was confirmed by the followed DSC and WAXD characterizations on the iPB-1 films after FTIR measurements. The crystal morphology of the melt-crystallized iPB-1 films, characterized by using polarized optical microscopy (POM), showed that the Maltese cross pattern of iPB-1 spherulite became more diffuse with increasing CO₂ pressure, and the spherulite size decreased abruptly at the CO₂ pressure of 10 MPa.     

Differences in association behavior of isotactic and atactic poly(methacrylic acid)

In this paper we show by light scattering techniques that polymer tacticity introduces an opposite association behavior in the case of aqueous solution of poly(methacrylic acid) in the presence of 0.1 M NaCl. Aggregates of highly stereoregular isotactic poly(methacrylic acid), iPMA, are disrupted by shear and gradually reform in solution at rest, whereas those of the usual atactic form, aPMA, multiply as a result of mechanical stress (phenomenon of negative thixotropy) and gradually decrease in number after its cessation. The aggregates have characteristics of microgel particles and may act as precursors for temperature induced gelation at higher concentrations. According to the shape parameter ρ (∼0.6 and ∼0.70 for iPMA and aPMA, respectively) iPMA aggregates have a denser core than aPMA ones. Additional differences between both isomers are demonstrated at higher degrees of neutralization, α_N, through the analysis of the polyelectrolyte slow mode, which was identified for all α_N > 0.25 with iPMA but only for α_N = 1 with aPMA.     

Characterization of polypropylene–poly(1-butene)–hydrogenated olygo(cyclopentadiene) ternary blends

Ternary blends containing polypropylene (PP), poly(1-butene) (PB), and hydrogenated oligo(cyclopentadiene) (HOCP) have been studied using microscopic calorimetric and dynamic mechanical techniques, with no phase separation having been observed in the melt for all the considered compositions. The morphology of the crystallized blends and spherulite growth rate of the PP component appeared to be influenced by the blend composition. The presence of one or two T_gs revealed by dynamic mechanical thermal analysis (DMTA) on quenched or crystallized blends has suggested that demixing phenomena can occur during the crystallization of the components. The blend composition has been found to affect the overall crystallization rate and the equilibrium melting temperature of the PP component. A parameter describing the enthalpic interactions between the PP component and the diluent fraction evidenced that the addition of HOCP to PP and PB increases the stability of the ternary blend. The above results suggest that the three components can form a miscible blend in the melt. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1659–1665, 1997     

Isotactic poly(1-butene)/hydrogenated oligo(cyclopentadiene) blends: Miscibility,morphology, and thermal and mechanical properties

The article discusses the influence of the oligomeric resin, hydrogenated oligo(cyclopentadiene) (HOCP), on the morphology and properties of its blends with isotactic poly(1-butene) (PB-1). PB-1 and HOCP are found to be partially miscible in the melt state. Solidified PB-1/HOCP blends contain three phases: (1) a crystalline phase formed by PB-1 crystals; (2) an amorphous PB-1-rich phase; and (3) an amorphous HOCP-rich phase. The optical micrographs of the solidified blends show a morphology constituted by microspherulites and domains of the HOCP-rich phase homogeneously distributed in the intraspherulitic region. DSC and DMTA results show two glass transition temperatures (T_g), different from the T_g values of the plain components. The lower T_g is attributed to the PB-1-rich phase, and the higher T_g, to the HOCP-rich phase. The tensile properties were investigated at 25 and 80°C. At 25°C, the PB-1-rich phase is rubbery and the HOCP-rich phase is glassy, so the addition of HOCP to PB-1 arouses a noteworthy hardening of the samples and this brings an increase of the Young's modulus, E′ (although the blend crystallinity lessens), and decreases of stresses at yielding point (σ_y) and at rupture (σ_r). The 90/10 and 80/20 blends show high values of elongation at rupture (ε_r). At 80°C, the blends show decreases of E′ and σ_r values with the HOCP content. These decreases are attributed to the rubbery state of the phases and reduction of the blend's crystallinity. At 80°C, all the blends show a high value of ε_r. This phenomenon is attributed to the fine-size domain dispersion of the phases and to sufficient densities of tie molecules and entanglements. Finally, the partial miscibility behavior proposed in this article is compared with the miscibility hypothesis reported elsewhere. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1369–1381, 1998     

Morphology and supermolecular structure of polypropylene–poly(1-butene)–hydrogenated oligo(cyclopentadiene) ternary blends

Ternary blends containing polypropylene, poly(1-butene), and hydrogenated oligo(cyclopentadiene) have been studied using microscopic, calorimetric, and X-ray diffraction techniques. While no phase separation was found to occur in the melt for all the considered compositions, demixing phenomena were observed by scanning electron microscopy in the ternary blends after crystallization of both polyolefins. On the other hand, a homogeneous surface without the presence of separate domains was observed for blends quenched avoiding the crystallization of polypropylene. The composition has been found to affect the crystallization and the melting properties of the ternary blends and the crystal modification of polypropylene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1878–1882, 1998     

Crystallization and orientation behaviors in isotactic polystyrene and poly(2,6-dimethylphenylene oxide) blends

The crystallization and orientation behavior in the miscible iPS/PPO blends were studied aiming at producing oriented materials consisting of iPS crystals and amorphous PPO chains. Oriented films of iPS/PPO blends were prepared by drawing the melt-quenched blend films. The films were heat-treated under constraint at the drawing temperature so as to crystallize the molecular chains of iPS in the oriented state. The crystallinity and the crystal orientation in the drawn annealed films were studied by the wide-angle X-ray diffraction (WAXD), and the orientation behaviors of molecular chains were analyzed by polarized FTIR spectroscopy. WAXD diagrams show the presence of the highly oriented crystalline structure of iPS in the drawn annealed films of pure iPS and iPS/PPO=7/3 blend. The polarized FTIR spectra of drawn annealed films suggest that the molecular orientation of the amorphous chains of PPO and iPS is markedly relaxed by the heat treatment, although the orientation of iPS with 3₁ helical structure was retained during the oriented crystallization. It was concluded that the drawn annealed samples of the iPS/PPO=7/3 blend consist of highly oriented iPS crystals and nearly isotropic amorphous materials. The mechanical properties of the oriented iPS/PPO blends were measured not only in the stretching direction but also perpendicular to the stretching direction. It was shown that the ultimate strength in the perpendicular direction is 4-5 times higher in the drawn annealed film of iPS/PPO=7/3 blend than in the drawn annealed iPS. The improvement in the vertical strength in the blend is discussed in relation to the structural characteristics of the iPS/PPO blend.     

PEB/St-AN悬浮接枝共聚反应机理的研究

研究了乙烯-1-丁烯共聚物（PEB）与苯乙烯-丙烯腈（St-AN）悬浮接枝共聚体系的反应行为随反应时间的延长而变化的规律。核磁共振氢谱（1 H-NMR）分析表明反应产物由未接枝PEB、接枝共聚物PEB-g-SAN和非接枝共聚物SAN构成,无交联产物存在。体系在反应的最初阶段接枝共聚反应速率高于非接枝共聚反应速率。凝胶渗透色谱（GPC）分析表明,在整个反应过程中发生了未接枝PEB和PEB-g-SAN主链的降解反应。共聚反应在反应时间为240min时结束,此后发生少量未接枝PEB和PEB-g-SAN结合的反应,导致产物的橡胶接枝率逐渐提高、产物与SAN树脂共混物的缺口冲击强度逐渐上升、以及用SEM分析证实的共混物增韧机理由空穴化的脆性断裂向高度剪切屈服的韧性断裂转变。     

Unusual crystallization behavior of isotactic polypropylene and propene/1-alkene copolymers at large undercoolings

During the investigation of the crystallization of metallocene isotactic polypropylene and copolymers with low amount of 1-butene and 1-hexene at large undercoolings, an unexpected behavior has been found. Random copolymers crystallize faster than the homopolymer between 80 and 40 °C, while at high temperatures the overall crystallization rates follow the expected trend. On the basis of structural and morphological evidences we suggest that the overall structuring kinetics of the homopolymer is slowed down by the concomitant formation of mesophase and monoclinic structures. This effect is absent in the copolymers because the branched counits retard the development of mesophase.     

Crystallization and phase transformation kinetics of poly(1-butene)/MWCNT nanocomposites

Poly(1-butene)/MWCNT nanocomposites were prepared by simple melt processing technique. Crystallization, crystal-to-crystal phase transformation and spherulitic morphology were studied using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and optical microscopy (OM). The non-isothermal crystallization exhibited higher values of Z_t derived from Avrami theory and lower values of F(T) obtained from Avrami-Ozawa analysis, while the isothermal crystallization revealed a significant increase in crystallization temperatures and lower crystallization half times compared to pristine PB. The observed changes in the crystallization kinetics were ascribed to the enhanced nucleation of PB in the presence of MWCNT. The nucleating activity calculated from the non-isothermal crystallization data revealed that the MWCNTs provide an active surface for the nucleation of PB. The optical micrographs exhibited significantly smaller crystallites with disordered morphology for the nanocomposites compared to the well defined spherulitic morphology for pristine PB. The rate of phase transformation from kinetically favored tetragonal to thermodynamically stable hexagonal form was noticeably enhanced as evidenced by the reduction in the half time for phase transformation from 58 h to 25 h for PB reinforced with 7% MWCNT.     

聚1-丁烯结晶度的实验测定

用差示扫描量热法(DSC)和密度法测定了聚1-丁烯的结晶度,并对2种方法测得的结晶度进行了线性拟合。结果表明,用密度法测得的结晶度相对于DSC法测得的结晶度要高,2种方法所测得的结晶度有较好的线性关系。