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.     

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     

Self-nucleation of isotactic poly(1-butene) in the trigonal modification

Isotactic poly(1-butene) (i-PBu) is a polyolefin of industrial relevance which exhibits an interesting polymorphism. Upon cooling from the relaxed melt at atmospheric pressure, a tetragonal phase (Form II) develops. However, being metastable, this structure slowly evolves upon aging in the stable trigonal modification (Form I). Another trigonal modification, denoted Form I′, can also crystallize directly from the melt if proper conditions are met, e.g., high pressure, low tacticity, ultrathin samples etc. In this work, we aim to verify whether, by acting on the nucleation stage via a proper thermal history, the direct formation of the trigonal polymorph from the melt in a bulk sample is possible. Nucleation of i-PBu has been tailored by means of the self-nucleation technique, imposed on previously aged samples (Form I). DSC and temperature-resolved WAXS show that different crystallization pathways can be observed, depending on the residual concentration of Form I self-nuclei. With decreasing self-nucleation temperature we first encounter “cross-nucleation” of the tetragonal crystal on trigonal nuclei, followed by concomitant crystallization of Form II and Form I′ and eventually the sole formation of the trigonal modification (Form I′).     

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.     

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...     

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     

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。     

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。     

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。     

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     

Synthesis of branched poly(lactide) using polyglycidol and thermal, mechanical properties of its solution-cast film

Branched poly(lactide)(PLA)s with various lengths of graft chain were synthesized by ring-opening polymerization of l- or d-lactide (l- or d-LA) in bulk using polyglycidol as a macroinitiator. The properties of polymer films of branched PLLA or PDLA obtained and their stereocomplex were investigated through thermal analysis and tensile testing. The branched PLLA or PDLA film exhibited a lower glass transition temperature (T_g), melting temperature (T_m), crystallinity, Young's modulus and a higher strain at break than the corresponding linear PLLA or PDLA film. The branched PLLA/branched PDLA stereocomplex film showed a high maximum stress and a high Young's modulus keeping its high strain at break. Moreover, the usefulness of branched PLLA or PDLA as a plasticizer of linear PLLA was investigated with 1:9 blend or stereocomplex film prepared from the branched PLLA or branched PDLA and linear PLLA. The blend or linear PLLA/branched PDLA stereocomplex film showed a higher strain at break compared with linear PLLA film. The mechanical properties of the blend or linear PLLA/branched PDLA stereocomplex film could easily be controlled by changing the molecular weight of branched PLA.     

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     

Processability,rheology, and thermal,mechanical, and morphological properties of postconsumer poly(vinyl chloride) bottles and cables

The processability, rheology, and thermal, mechanical, and morphological properties of three different commercial poly(vinyl chloride) (PVC) compounds blended with postconsumer PVC bottles and PVC cables were examined with respect to the recycled PVC content. The addition of PVC bottle recyclates [recycled bottles (RBs)] into virgin PVC bottle (VB) and virgin PVC pipe (VP) compounds caused a progressive reduction in the average torque. No thermal degradation or color change in the RB‐blended PVC compounds used was detected through carbonyl and polyene indices from IR analysis. The rheological properties for VP compounds were more sensitive to RB addition than those of VB compounds. The extrudate swell ratio did not change with the RB content. The decomposition temperature for the VB and VP compounds increased at 60–80% RB, whereas the glass‐transition temperature was unaffected by the RB loading. The 20 and 80 wt % RB loadings were recommended for the VB and VP compounds, respectively, for the optimum impact strength, the blends showing ductile fracture with a continuous phase. At the optimum impact and tensile properties, introducing RB recyclates into the VB compounds gave better results than the VP compounds. The hardness and density of the VB and VP compounds did not change with the RB content. The RB property change was comparatively faster than that of recycled PVC pipes. Adding the PVC cable recyclate [recycled cable (RC)] to virgin PVC cable (VC) had no obvious effect on the torque value of the RC/VC blends. The decomposition temperatures of the RC/VC blends stabilized at 20–60% RC and tended to decrease at 80% RC. The ultimate tensile stress was improved by the addition of the RC compounds, whereas the hardness and density of the VC compounds were unaffected by the RC content. It was concluded that the optimum concentrations of PVC recyclates to be added to virgin PVC compounds were different from one property to another and also depended on the type of virgin PVC grade used. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2738–2748, 2003     

Mesophases in polyethylene, polypropylene, and poly(1-butene)

This paper contains new views about the amorphous and partially ordered phases of the three polymers listed in the title. The discussion is based on information on structure, thermodynamic stability, and large-amplitude molecular motion. Polyethylene is the basic backbone of all alkene polymers, and the other two are the first members of the vinyl polymers which have stereospecifically placed alkyl side chains. Their multiphase structures consist of metastable crystals, mesophases, and surrounding rigid and mobile amorphous fractions. All these phases have sizes ranging from micrometer dimensions down to nanometers. Besides the phase structures, information about the molecular coupling between the phases must be considered. Depending on temperature, the polymer phases can vary from solid (rigid) to liquid (mobile). New knowledge is also gained by cross-comparison of the title polymers. The experimental information was gained from (a) various forms of slow, fast, and temperature-modulated thermal analysis to identify equilibrium and non-equilibrium states, (b) measurement of structure and morphology at various length scales, and (c) tracing of the large-amplitude molecular motion, the kinetics of order/disorder changes, and the liquid/solid transitions (glass transitions). It is shown that much more needs to be known about the various phases and their coupling to characterize a given polymer and to fine-tune its properties for a given application.     

Synthesis,characterization, and properties of long‐chain branched poly(butylene succinate)

Long‐chain branched poly(butylene succinate) were synthesized through a two‐step process of esterification and polycondensation, using 1,2,4‐butanetriol (1,2,4‐BT) as a long‐chain branching agent. The effect of long‐chain branches on the crystallization behaviors, rheological properties, and tensile properties was investigated systematically. The results of differential scanning calorimetry and polarized optical microscopy showed that with the increasing of 1,2,4‐BT segments, the crystallization temperatures and glass transition temperatures increase slightly, while the relative crystallinity degree decreases gradually. Also, the double‐banded extinction patterns with periodic distance along the radial direction were observed in the spherulites of long‐chain branched poly(butylene succinate), similar to that of linear poly(butylene succinate) (PBS). The result of wide‐angle X‐ray diffraction indicated that the incorporation of 1,2,4‐BT segments had little effect on the crystal structure of PBS. However, based on data from rheology and tensile testing, the viscoelastic properties of long‐chain branched PBS under shear flow were different from the linear PBS. For example, the complex viscosities, storage modulus, and loss modulus of long‐chain branched PBS at low frequency were significantly enhanced in comparison with those of linear PBS. In addition, long‐chain branched PBS showed higher tensile strength than that of linear PBS without notable decrease in the elongation at break when compared with linear PBS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic mechanical and thermal properties of plasticized poly(lactic acid)

The blends of low molecular weight triacetin (TAC) and oligomeric poly(1,3‐butylene glycol adipate) (PBGA) were used as multiple plasticizers to lubricate poly(lactic acid) (PLA) in this study. The thermal and mechanical properties of plasticized polymers were investigated by means of dynamic mechanical analysis and differential scanning calorimetry. Atomic force microscopy (AFM) was used to analyze the morphologies of the blends. Multiple plasticizers were effective in lowering the glass transition temperature (T_g) and the melting temperature (T_m) of PLA. Moreover, crystallinity of PLA increased with increasing the content of multiple plasticizers. Tensile strength of the blends decreased following the increasing of the plasticizers, but increased in elongation at break. AFM topographic images showed that the multiple plasticizers dispersed between interfibrillar regions. Moreover, the fibrillar crystallite formed the quasicrosslinkings, which is another cause for the increase in elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1583–1590, 2006     

Rheology,morphology, and mechanical and thermal properties of recycled PVC pipes

This article demonstrated the possibility of recycling PVC pipes by investigating the effect of adding PVC pipes (varying from 0 to 80 % wt) into two commercial PVC virgin grades on the rheological, morphological, mechanical, and thermal properties of the PVC blends. The results obtained showed an increase in the melt viscosity and no change in the die swell ratio as the concentration of the recycled PVC was increased. The die swell ratio was observed to increase with temperature, this being associated with the presence of gelation that occurred at high temperature. The optimum tensile and impact strengths were detected, the impact strength being explained by use of SEM micrographs of the fracture surface. The hardness result corresponded well to the density of the compounds. The glass transition, degradation, and heat-deflection temperatures were also found to shift with the recycled PVC loading. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2478–2486, 2001     

负载钛体系催化合成聚1-丁烯的结构与性能

对负载钛体系催化合成的聚1－丁烯（PBt)进行了结构表征和性能的测试。DSC测试表明，PBt有两个熔融峰，分别为43.5℃和112．4℃，玻璃化温度为－23．4℃；热－机械分析表明PBt的软化点为80℃，粘流温度为165℃；脆性温度为－21℃；PBt的物理交联点间平均相对分子质量为2400；应力－应变曲线呈典型的弹性体特征；PBt具有优良的耐酸碱性、良好的绝缘性和介电性，其介电损耗正切值介于极性和非极性材料之间；永久形变在90％－150％之间     

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。