Polybutene-1 Research Articles

Effect of thermal treatments on the laser sinterability of cryogenically milled polybutene-1

This paper demonstrates how thermal treatments can be used to enable the laser sintering (LS) of polybutene-1 (PB-1). One of the major issues with the examined PB-1 grade is the limited thermal operating window. At temperatures slightly below 90 °C crystallisation is too fast, resulting in warpage during processing. Above 90 °C, however, the powder becomes increasingly sticky, limiting the maximum bed temperature that can be applied in a laser sintering station. In this work, the problem is remediated by annealing the powder at 115 °C, which creates a more perfect crystal structure with a sharper melting onset. An alternative treatment of melting, slowly cooling and aging the sample at room temperature creates a powder with a stabilised crystal structure, which has a sharp melting onset at 120 °C and thus also a broader thermal window. Test parts were created on an LS machine validating the increase in processability.

Fractionated and Confined Crystallization of Polybutene-1 in Immiscible Polypropylene/Polybutene-1 Blends

In this work, the crystallization of immiscible polypropylene (PP)/polybutene-1 (PB) blends, in particular the effect of crystal morphology of PP (HTC, high Tm component) on the subsequent crystallization behavior of PB (LTC, low Tm component) was studied. Herein, we firstly indicated that PP/PB blends were not completely compatible but characterized as the LCST-like phase diagram above the melting temperature of PP. Crystallization of PP at different crystallization temperatures brought about different PP crystal morphologies and PB was segregated and confined at different locations. Much larger-sized domain of PB component appeared in PP spherulites resulting from the effects of non-negligible phase separation and the slower PP crystallization rate as PP crystallized at high temperature. As temperature continued to fall below Tm of PB, the fractionated and confined crystallization of PB occurred in the framework of PP spherulites, reflected by the decreased crystallization temperature (Tc) of PB and the formation of form I′ beside form II. Notably, if PP previously crystallized at high Tc, fractionated crystallization of PB became predominant and confined crystallization of PB became weak due to the much wider droplet-size distribution of PB domains.

Interfacial nucleation in iPP/PB-1 blends promotes the formation of polybutene-1 trigonal crystals

The formation of trigonal Form I′ crystals of polybutene-1 (PB-1) directly from melt has drawn much attention in past decades. In this study, we investigate the fractionated crystallization behavior of PB-1 within droplets formed by blending PB-1 with an excess of isotactic polypropylene (iPP) employing DSC, SEM, in situ synchrotron WAXD and FT-IR. When PB-1 is dispersed into a large number of small size droplets, the heterogeneous nucleation of Form II crystals can be inhibited because the number of droplets is larger than that of active nucleation sites for Form II (i.e., active heterogeneities originally present in bulk PB-1). The nucleation of the finely dispersed PB-1 droplets does not occur homogenously, but at the interface with the iPP matrix, which induces the crystallization of the droplets into Form I′. The crystallization rate of Form I′ at different temperatures was determined by Fourier transform infrared spectroscopy. It was found that trigonal Form I′ crystallizes faster when the content of PB-1 in the blend is lower, and the specific interfacial surface area is larger. The opposite effect has been observed for the kinetics of the metastable Form II formation. It is therefore suggested that Form I′ crystallization is driven by the nucleation of PB-1 at the crystalline iPP surface, which competes with the crystallization of Form II induced by nucleating heterogeneities present in PB-1 droplets.

Identification of polybutene-1 (PB-1) in easy peel polymer structures

Polybutene-1 (PB-1) is dispersed via extrusion in polyethylene (PE) based sealing layers to achieve ‘easy peel’ properties. PB-1 forms islands there. During opening of packagings with such sealing layers, cohesive fracture occurs within the sealed area along these PB-1 islands. The aim of this study was to find suitable methods for the identification of PB-1 in such PE based sealing layers. For this investigation PE-LD films with 3, 6, 9, 12 and 15 wt.-% PB-1 were extruded. FTIR spectroscopy and FTIR microscopy are suitable methods to identify low concentrations PB-1 in PE-LD layers in opposite to GC-FID and DSC. Raman spectroscopy is a suitable method to distinguish PB-1 from PE-LD.

Constructing a double-percolated conductive network in a carbon nanotube/polymer-based flexible semiconducting composite

Conductive polymer composites featuring double-percolated network structures have attracted widespread interest. Constructing such a structure and controlling the trans-phase migration of the conductive filler remain the main challenges for the application of these conductive polymer composites. In this study, we report a novel two-step “in situ microfibrillation” and “microfiber coalescence” strategy that includes melt-drawing and a compressive annealing process to achieve a stable, double-percolated network of a polybutene-1 (PB-1)/polystyrene (PS)/multiwalled carbon nanotubes (MWCNTs) ternary system. Triggered by the compressive annealing treatment, inter-fiber coalescence led to the formation of an interconnected network, resulting in excellent conductive performance (volume resistivity down to 4.6 × 103 Ω·cm) with a MWCNT dosage as low as 1 wt%. Surface energy calculations and experimental evidence both indicated that the selective distribution of the MWCNTs in the PS phase resulted from the preferential surface wetting behavior and π-π interactions between the MWCNTs and PS, which also immobilized the MWCNTs, even at elevated temperatures. This work established a facile and scalable technology for constructing double-percolated structures in multiphase systems, thus providing access to intriguing functionalities and applications.

Intercrystalline Links Determined Kinetics of Form II to I Polymorphic Transition in Polybutene-1

The effect of intercrystalline links containing tie molecules and entangled loops on polymorphic transition from form II to form I in polybutene-1 (PB-1) of different molecular weights has been investigated by differential scanning calorimetry and small-angle X-ray scattering techniques. The PB-1 samples were isothermally crystallized at a range of temperatures to develop metastable form II crystalline modification of different lamellar thickness, long spacing, and number of intercrystalline links in the amorphous phase. Tammann’s two-stage crystal nuclei development method was applied to promote a faster polymorphic transition from form II to I; that is, form I nuclei were developed at the early low temperature stage, and form I crystals were formed at the later high temperature stage. At a given annealing condition, the transition rate in the high molecular weight sample is found to increase with the increase of the prior form II crystallization temperature, while it shows a negative correlation between...

Control of Chain Orientation in Blends of Polypropylene and Polybutene‐1

An extruded sheet having unique molecular orientation is developed using a miscible blend of isotactic polypropylene (PP) and isotactic polybutene‐1 (PB). Blends containing a small amount of N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide are extruded from a ribbon‐shaped die onto a chill roll at various temperatures. It is found that form‐I crystals of PB become oriented in the flow direction, whereas β‐form crystals of PP become oriented perpendicular to the flow direction. The molecular orientation is the most obvious for the blend containing 60 wt% of PB extruded at a chill roll temperature of 80 °C. The anisotropy in the tensile modulus of the obtained extruded sheet is reduced by its extraordinary molecular orientation. image

Solvent vapor annealing induced polymorphic transformation of polybutene-1

Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials. In this paper, we addressed the effects of solvent vapor annealing, including chloroform and water vapor, on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1 (PB-1) by means of in situ Fourier transform infrared spectroscopy (FTIR). The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity. Also, a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.

Kinetics of Nucleation and Growth of Form II to I Polymorphic Transition in Polybutene-1 as Revealed by Stepwise Annealing

Kinetics of II to I polymorphic transformation in isotactic polybutene-1 (PB-1) and its annealing temperature and time dependencies have been investigated by means of differential scanning calorimetry and in situ wide-angle X-ray diffraction techniques. The PB-1 samples were isothermally crystallized into metastable form II crystalline modification followed by annealing at a lower temperature (Tl) and at a higher temperature (Th) subsequently or at a single temperature (Ts) to promote polymorphic transition from form II to I. This solid-to-solid phase transition was shown to be a two-step process including nucleation and growth suggested by the result that more form I was obtained after being annealed at Tl and Th than annealed at Ts for the same period. Annealing at Tl benefits nucleation due to internal stress induced by unbalanced shrinkage of amorphous and crystalline phases because of their different thermal expansion coefficients, while annealing at Th is beneficial to growth owing to rapid segmenta...

Influence of thermal history on crystalline morphologies of isotactic polypropylene in its miscible blends with polybutene‐1

ABSTRACTThe miscibility behaviors in blends of isotactic polypropylene (iPP) and polybutene‐1 (PB) have been studied using in‐situ FTIR imaging. The heterogeneous melt of 3/7 iPP/PB blends were formed at 250, 220, and 180°C and then quenched to the same crystallization temperature of iPP at 125°C, respectively. Evolution processes of composition distribution during crystallization were monitored according to their characteristic peaks, and the results suggest a trend from local concentration to uniform dispersion of PB fraction. Further studies of the PB fraction as the distance from the growth front of iPP spherulite indicate an irreversible phase behavior with the progress of thermal history. The cyclic melting and crystallization favor the mixing of iPP/PB blend. Meanwhile, the nonlinear growth rate of iPP spherulite is mainly responsible for compatible promotion of iPP/PB blend, which hinders the transportation of iPP chains to its growth front. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43282.

Biaxial reinforcements for polybutene-1 medical-tubes achieved via flow-design controlled morphological development of incorporated polystyrene: In-situ microfibrillation, alignment manipulation and performance optimization

Abstract By means of goal-directed flow designing and morphology controlling, this paper opened up an efficient method of continuously mass-producing biaxially reinforced polystyrene (PS)/polybutene-1(PB-1) tubes for medical application. The experimental results showed that the PS microfibers were in-situ formed by imposing a specific convergent flow onto the off-die PS/PB-1 blend melt, exhibiting excellent dispersion, high aspect ratio and good interfacial contact. As a result, the ultimate axial strength (UAS) of the microfibrillar PS/PB-1 tubes was enhanced from 29.9 MPa of conventional neat PB-1 tubes to 41.3 MPa. Moreover, by introducing the rotating mandrel or die to modify the flow to helical convergent flow, the formed PS microfiber deviated from axial direction to further improve hoop damage strength (HDS) performances. Particularly, via counter-helical convergent flow extrusion controlled by the counter-rotating mandrel and die system, the opposite-handed helical configuration of PS microfibers was brought out to eliminate the inter-fiber relative slip. As a result, the PS/PB-1 composite tubes exhibited remarkably reinforced mechanical performances in both UAS (40.3PMa) and HDS (34.9 MPa) tests, improved by 34.8% and 48.5% compared to Conv-E neat PB-1. These results suggest that such bi-axially reinforced microfibrillar tubes could be of benefit to ensure the structural integrity of artificial medical tubing systems.

Polybutene-1 tube with in situ microfibering polystyrene via helical convergent flow: an economical pathway to continuously fabricate biaxially reinforced polyolefin tubes for medical application

Polystyrene (PS) microfibers with high molecular orientation and helical alignment were in situ formed via helical convergent flow during polybutene-1 (PB-1) tubing processing to achieve performance improvements in both axial and hoop directions, which opened up an economical pathway for continuous fabrication of biaxially reinforced polyolefin tubes for medical application.

The impact of viscoelastic behavior and viscosity ratio on the phase behavior and morphology of polypropylene/polybutene‐1 blends

In this study, the influence of the viscosity ratio on the rheology, morphology, and interfacial interaction of polypropylene and polybutene‐1 (PB‐1) resins with various melt flow behaviors in the blend are investigated. A droplet‐matrix morphology is observed in the scanning electron microscope images for all formulations and the size of particles increased proportionally by increasing the viscosity ratio. Viscoelastic parameters of blends at various viscosity ratios and compositions are measured by small‐amplitude oscillation rheometry in the linear viscoelastic region. The Cole‐Cole plots showed a nearly semicircular arc for all compositions. This semicircular arc is observed while the viscosity ratio is lower than 1, and the Cole‐Cole plots deviated from the semicircular shape at PB‐1 content higher than 10 wt%. It is emphasized that, in addition to compatibility, the semi‐circularity of Cole‐Cole plots affects the size of the dispersed particles, which is under the influence of the viscosity ratio. It is found that the interfacial tensions of polypropylene and PB‐1 are not significantly different when changing the viscosity ratio and coarsening the morphology. The form relaxation times in the blends with lower viscosity ratios are shorter than the form relaxation times of the blends with higher viscosity ratios. J. VINYL ADDIT. TECHNOL. 21:94–101, 2015. © 2014 Society of Plastics Engineers

In-situ microfibrillation of polystyrene(PS)/polybutene-1 (PB-1) composites prepared via melt drawing:morphological evolution and properties

In-situ Polystyrene (PS)/Polybutene-1 (PB-1) microfibrillar composites were prepared by applying “melt drawing” technique. The phase morphology, crystal structure, and mechanical performances of the produced sheets were investigated. The mechanical tests showed distinct rise of samples’ strength and modules with the increasing of melt drawing ratio (MDR). And, the discernible differences in mechanical performances between the PS added and neat PB-1 systems were also detected. The 2D-WAXD results proved that by increasing the melt drawing ratio (MDR), the orientation degree of PB-1 and PS/PB-1 composites increased gradually indicating the formation of highly oriented PB-1 crystals. Interestingly, as a respond to the external drawing field, the morphologies of PS phase dispersed in the PB-1 matrix were transformed from isotropic spherical droplets to anisotropic microfibers at high aspect ratio during the melt-drawing process. Different from the widely reported mechanism for cool-drawing microfibrillation, in this study, PS phase firstly assembled together due to its fine fluidity, and then deformed to form microfiber structure as observed in SEM pictures. Accordingly, new mechanism for in-situ microfibrillation of PS/PB-1 composites during melt drawing was proposed as: “coalescing”, “deforming”, “needle-like tails growing and propagating” and “microfibrillating”. As a result, the as-prepared microfibrillar composites at high value of MDR (4.89) exhibited superior mechanical performances (120.2 MPa in tensile strength) than that of as-prepared neat PB-1 samples (91.4 MPa). The reinforcing effect of PS microfibers on the PS/PB-1 composites was also confirmed through annealing experiments. This study illustrate the morphological evolution mechanism and morphology-property relationship in PS/PB-1 systems and indicate a technique to transform “defects” into “reinforcements”.

Lamellar thickness and stretching temperature dependency of cavitation in semicrystalline polymers.

Polybutene-1 (PB-1), a typical semicrystalline polymer, in its stable form I shows a peculiar temperature dependent strain-whitening behavior when being stretched at temperatures in between room temperature and melting temperature of the crystallites where the extent of strain-whitening weakens with the increasing of stretching temperature reaching a minima value followed by an increase at higher stretching temperatures. Correspondingly, a stronger strain-hardening phenomenon was observed at higher temperatures. The strain-whitening phenomenon in semicrystalline polymers has its origin of cavitation process during stretching. In this work, the effect of crystalline lamellar thickness and stretching temperature on the cavitation process in PB-1 has been investigated by means of combined synchrotron ultrasmall-angle and wide-angle X-ray scattering techniques. Three modes of cavitation during the stretching process can be identified, namely “no cavitation” for the quenched sample with the thinnest lamellae where only shear yielding occurred, “cavitation with reorientation” for the samples stretched at lower temperatures and samples with thicker lamellae, and “cavitation without reorientation” for samples with thinner lamellae stretched at higher temperatures. The mode “cavitation with reorientation” occurs before yield point where the plate-like cavities start to be generated within the lamellar stacks with normal perpendicular to the stretching direction due to the blocky substructure of the crystalline lamellae and reorient gradually to the stretching direction after strain-hardening. The mode of “cavitation without reorientation” appears after yield point where ellipsoidal shaped cavities are generated in those lamellae stacks with normal parallel to the stretching direction followed by an improvement of their orientation at larger strains. X-ray diffraction results reveal a much improved crystalline orientation for samples with thinner lamellae stretched at higher temperatures. The observed behavior of microscopic structural evolution in PB-1 stretched at different temperatures explains above mentioned changes in macroscopic strain-whitening phenomenon with increasing in stretching temperature and stress-strain curves.

Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

Abstract In this article, a new rotational extrusion processing system was adopted for manufacturing of polybutene-1 (PB-1) pipes, and the effects of mandrel rotation speed on their structures and mechanical performances were studied. The experimental results showed that besides the conventional axial extrusion flow field, a hoop shear stress field imposed to the melt, which was generated by the introduction of mandrel rotation, could lead the combined stress apart from the axial direction of the pipes to induce the molecular orientation deviated from the axial direction. Thus, the axial orientation of PB-1 was restrained, which was revealed by thermal shrinkage measurements and polarized infrared spectra. Moreover, it was also found and confirmed by scanning electron microscopy and two-dimensional wide-angle X-ray diffraction that orientation mainly existed in the amorphous region rather than the crystal region. Differential scanning calorimetry tests showed that the mandrel rotation could facilitate the formation of more perfect crystals and higher crystallinity. As a result, compared with the PB-1 pipe produced by conventional extrusion, the hoop strength of the PB-1 pipes manufactured at a mandrel rotation speed of 8 rpm increased from 20.2 to 24.9 MPa, achieving a mechanical balance in both axial and hoop directions.

Additive effects of tripalmitin and low-density polyethylene on morphologies and tensile properties of polybutene-1/micro fibrous cellulose composite

Effects of tripalmitin (TP) and low-density polyethylene (LDPE) loading on morphologies and tensile properties of polybutene-1 (PB)/micro fibrous cellulose (MFC)/composite were studied. The scanning electron microscope (SEM) observation showed that the 10 % TP loading brought about good dispersity of the MFC in PB matrix. The TP worked as a good compatibilizer for the composite. The Young’s moduli of the PB/TP (10 %)/MFC (10 and 20 %) content were slightly lower than those of the corresponding PB/MFC under 0, 48 and 96 h aging treatments at r. t., and that of the PB/TP (10 %)/MFC (50 %) specifically decreased up to 73 %. The TP loading increased the PB crystal phase transformation rate, and its behavior suggested that there existed TP in the interface between the PB and MFC. The elongation at break values increased up to 281 % of the corresponding PB/MFC ones. The 30 % TP loading little improved the tensile properties of the composite as compared with the 10 % one. The 10 % LDPE loading brought about 5–51 % higher Young’s moduli than those of the corresponding PB/MFC without the aging treatment although the composite rapidly became embrittlement by the higher MFC content and aging. It was found that the LDPE loading highly improved the interface strength, in particular, without the aging treatment.

Effect of electron beam irradiation dose on the rheology, morphology, and thermal properties of branched polypropylene/polybutene‐1 blend

The aim of this work is to study the influence of electron beam irradiation on the structure of polypropylene (PP)/polybutene‐1 (PB‐1) blend in the branching process. The blend with 10 wt% of PB‐1 and 0.5 wt% trimethylolpropane trimethacrylate monomer is prepared and irradiated at different doses. The rheological properties of the melts in shear and extensional mode were evaluated, and their thermal behavior, crystalline structure, and morphology are studied by differential scanning calorimetry, wide‐angle X‐ray diffraction, and scanning electron microscopy. The presence of long chain branched structure is approved by higher zero‐shear viscosity (η0), longer relaxation time and pronounced strain‐hardening behavior in the within the range of dose tested. By increasing the irradiation dose and enhancing chain scission in the backbone and long chain branches, the decline in melting temperature, duplication of melting peak, and the decrease in zero‐shear viscosity were observed. The morphological study of the blends before and after irradiation revealed no considerable change in PB‐1 droplet size and their distribution in the PP matrix. The emulsion theoretical models could predict well the rheological behavior of all samples and no significant change was observed on the interfacial interaction of PP and PB‐1. POLYM. ENG. SCI., 54:1747–1756, 2014. © 2013 Society of Plastics Engineers

The role of PB-1 on the long chain branching of PP by electron beam irradiation in solid state and melt viscoelastic behavior

In this study, a long-chain branched polypropylene (LCB PP) was prepared by electron beam irradiation in the presence of polybutene-1 (PB-1) and a trifunctional monomer, trimethylolpropane trimethacrylate (TMPTMA). The effect of PB-1 on branching is evaluated by measuring the viscoelastic behavior in shear and extensional mode of deformation. Long-chain branched structure showed prominent higher zero-shear viscosity (η0) and storage modulus (G′), longer relaxation time and pronounced strain-hardening behaviors. It is found that 10wt% of PB-1 resin in PP matrix increase the efficiency of branching process which can be due to the effect of PB-1 resin in facilitating the mobility of macro-radicals generated during irradiation. At higher percentages, due to the high tendency of PB-1 resin to β-scission, the degradation reaction is more pronounced than its mobilizing effect in branching process.

Additive effects of tripalmitin on morphologies and tensile properties of polybutene-1 and its composite with micro fibrous cellulose

Morphologies and tensile properties of polybutene-1 (PB)/tripalmitin (TP) blend and PB/micro fibrous cellulose (MFC)/TP composite were studied. The scanning electron microscope observation showed that the PB(70 %)/TP(30 %) had a microphase-separated structure. The DSC measurement showed that the crystallization of the PB part was affected by the TP existence. A new crystal structure was observed in the X-ray diffraction pattern of the PB(70 %)/TP(30 %). Quicker saturation of the PB crystal phase transformation from the metastable tetragonal (II) to the stable hexagonal (I) phase was observed in the PB(70 %)/TP(30 %) under the aging at r.t. The saturation controlled the Young’s modulus increment of the PB(70 %)/TP(30 %) in the aging process. The elongation at break value of the PB/TP increased by the loading of the TP, suggesting that the TP worked as the plasticizer. The thermogravimetry measurement of the PB(70 %)/TP(30 %) suggested that there existed an interaction between them. The TP addition provided a good dispersibility and ductility enhancement for PB/MFC composite. It was found that the TP worked as a good compatibilizer for the composite.