Atactic Polypropylene Research Articles

A Dynamic Mechanical Analysis on the Compatibilization Effect of Two Different Polymer Waste-Based Compatibilizers in the Fifty/Fifty Polypropylene/Polyamide 6 Blend.

This study aims to examine the 50/50 polypropylene/polyamide 6 (iPP/PA6) system molded under confined flow conditions, both in its original state and after being modified by two different interfacial agents. This study provides two main insights. Firstly, it focuses on a polymer blend close to phase inversion. Secondly, it investigates the impact of using two different types of interfacial agents (derived from polymer waste) to enhance the compatibility between iPP and PA6. Dynamic Mechanical Analysis (DMA) has been employed to achieve these objectives. It is important to note that the investigation of the 50/50 iPP/PA6 system is a crucial focus predicted in previous studies, where a series of mechanical properties were evaluated using Box-Wilson design of experiments (DOEs) over the whole compositional range on the iPP/PA6 binary system. Thus, two interfacial modifiers, namely succinic anhydride (SA)-grafted atactic polypropylene with terminal, side, and bridge SA grafts (aPP-SASA) and succinyl-fluoresceine (SF) with bridge succinic anhydride grafting atactic polypropylene (aPP-SFSA), were employed. The authors obtained and characterized these agents. The quantity of these agents used in the blend was identified as a critical coordinate in prior studies conducted by the authors. The processing method used, compression molding under confined conditions, was chosen to minimize any orientation effect on the emerging morphology. All characterization procedures were performed on samples processed by contour machining to retain the blend morphologies as they emerged from the processing stage. Results from WAXS and SAXS synchrotron tests concluded there were no changes in the crystal morphology of the iPP or the PA6 in the blends nor any co-crystallization process throughout the compositional range. These findings, and the long period fits on the PP crystalline phase for the fifty/fifty blends we are discussing, will support the present DMA study. Finally, the efficiency of these interfacial modifiers has been concluded, even in this unfavorable scenario.

Synthesis of High-Molecular-Weight Polypropylene Elastomer by Propylene Polymerization Using α-Diimine Nickel Catalysts.

The α-diimine late transition metal catalyst represents a new strategy for the synthesis of atactic polypropylene elastomer. Taking into account the properties of the material, enhancing the molecular weight of polypropylene at an elevated temperature through modifying the catalyst structure, and further increasing the activity of α-diimine catalyst for propylene polymerization, are urgent problems to be solved. In this work, two α-diimine nickel(II) catalysts with multiple hydroxymethyl phenyl substituents were synthesized and used for propylene homopolymerization. The maximum catalytic activity was 5.40 × 105 gPP/molNi·h, and the activity was still maintained above 105 gPP/molNi·h at 50 °C. The large steric hindrance of catalysts inhibited the chain-walking and chain-transfer reactions, resulting in polypropylene with high molecular weights (407~1101 kg/mol) and low 1,3-enchainment content (3.57~16.96%) in toluene. The low tensile strength (0.3~1.0 MPa), high elongation at break (218~403%) and strain recovery properties (S.R. ~50%, 10 tension cycles) of the resulting polypropylenes, as well as the visible light transmittance of approximately 90%, indicate the characteristics of the transparent elastomer.

Aluminiumalkylinduzierte Isomerisierung von Gruppe IV meso Metallocen Komplexen

AbstractBei der Synthese von Gruppe IV Metallocen‐Präkatalysatoren für die Polymerisation von Propylen werden im Allgemeinen zwei verschiedene Isomere gebildet: Das racemische Isomer, das isotaktisches Polypropylen (iPP) produziert und das meso‐Isomer, das ataktisches Polypropylen (aPP) produziert. Aufgrund seiner vergleichbar schlechten physikalischen Eigenschaften ist die Anwendung von aPP sehr begrenzt. Um Mischungen beider Polymere zu vermeiden, was die mechanischen und thermischen Eigenschaften von iPP zu verschlechtern würde, müssen die meso Metallocenkomplexe mühsam von den racemischen Komplexen getrennt werden, was die Metallocen‐basierte Polymerisation von Propylen industriell weit weniger attraktiv macht als das Ziegler/Natta‐Verfahren. Um dieses Problem zu umgehen, haben wir ein Isomerisierungsprotokoll zur Umwandlung von meso Metallocenkomplexen in ihre racemischen Analoga entwickelt. Dieses Protokoll steigerte die Ausbeute an iPP um 400 %, wobei die hervorragenden physikalischen Eigenschaften des Polymers beibehalten wurden; es war sowohl auf Hafnocen‐, als auch auf Zirkonocenkomplexe, sowie auf verschiedene Methoden zur Aktivierung des Präkatalysators anwendbar. Durch gezielte Variation der Liganden wurden Methoxygruppen an den Indenylsubstituenten als die für eine Isomerisierung verantwortlichen Strukturmotive gefunden ‐ dieser experimentelle Nachweis wurde durch Dichtefunktionaltheorieberechnungen bestätigt. Flüssig‐Injektion‐Feld‐Desorption‐Ionisierung‐Massenspektrometrie, sowie 1H‐ und 29Si‐Kernresonanzstudien ermöglichten den Vorschlag eines Isomerisierungsmechanismus.

Aluminum Alkyl Induced Isomerization of Group IV meso Metallocene Complexes.

The synthesis of group IV metallocene precatalysts for the polymerization of propylene generally yields two different isomers: The racemic isomer that produces isotactic polypropylene (iPP) and the meso isomer that produces atactic polypropylene (aPP). Due to its poor physical properties, aPP has very limited applications. To avoid obtaining blends of both polymers and thus diminish the mechanical and thermal properties of iPP, the meso metallocene complexes need to be separated from the racemic ones tediously-rendering the metallocene-based polymerization of propylene industrially far less attractive than the Ziegler/Natta process. To overcome this issue, we established an isomerization protocol to convert meso metallocene complexes into their racemic counterparts. This protocol increased the yield of iPP by 400 % while maintaining the polymer's excellent physical properties and was applicable to both hafnocene and zirconocene complexes, as well as different precatalyst activation methods. Through targeted variation of the ligand frameworks, methoxy groups at the indenyl moieties were found to be the structural motifs responsible for an isomerization to take place-this experimental evidence was confirmed by density functional theory calculations. Liquid injection field desorption ionization mass spectrometry, as well as 1H and 29Si nuclear magnetic resonance studies, allowed the proposal of an isomerization mechanism.

Water Proofing System in Concrete Structures

Water proof structure is a design concept that aims to repel water and prevent any moisture from seeping into the materials used in construction. This type of structure is particularly important in areas prone to heavy rainfall or flooding, as it helps maintain the integrity and durability of the building. Water proof concrete is formulated with additives and admixtures that create a barrier against water infiltration, making it ideal for areas prone to high levels of humidity or moisture. By incorporating this technology into construction projects, builders can ensure that their structures remain protected from the damaging effects of moisture, such as mold growth, deterioration of building materials, and potential structural issues. The use of abstract damp proof concrete represents a forward-thinking approach to building design and can greatly enhance the durability and longevity of a building.Crystalline admix water proofing with water stops, water proofing with Atactic Polypropylene membrane, and injection are the water proofing systems most commonly used in basements. Using non-shrinking cementitious grout for waterproofing, concrete must have crystalline admixtures made of cementitious powder and water. For toilets in non-sunken places, water proofing with an elastomeric cementitious coating is used. In sunken areas, brick jelly cement concrete with inherent water proofing compound is used.In this paper it deals with the different types of water proofing system..

Helical polyamines.

Polymer microstructures rely on tacticity, yet exploration in polyamines has focused predominantly on atactic polymers. We introduce a method to synthesize a diverse library of ortho and para-cyanobenzenesulfonyl-activated-methyl aziridines using R, S, and racemic alaninol. Living anionic ring-opening polymerization of racemic sulfonyl aziridines yields soluble polymers, while enantiomerically-pure sulfonyl aziridines follow a dispersion polymerization with complete monomer conversion giving access to stereoblock copolymers. Removal of activation groups is achieved using dodecanethiol and tert-butylimino-tri(pyrrolidino)phosphorane to obtain isotactic or atactic linear polypropylene imines (LPPIs). High-purity L-PPIs are obtained in salt and neutral forms with high yields. Stereoblock copolymers of poly-R-block-S-polysulfonamides and respective polypropylene imine stereoblocks are synthesized, revealing helical structures in water influenced by the monomer type and sequence in CD spectroscopy. Molecular dynamics simulations confirm the helical nature of isotactic LPPIs in water. Bulk characterization demonstrates the first crystalline isotactic polyamines via spherulite growth in polarized light, atomic force microscopy and XRD analyses. In cell-transfection studies, the synthesized isotactic LPPIs exhibit lower toxicity and transfection efficiency than commercial hyperbranched polyethylene imine, with longer chains showing increased transfection efficiency. These isotactic polymers open avenues for complex macromolecular architectures with optically active polyamines akin to poly(amino acid)s but lacking hydrolytically cleavable amide links.

An overview of water proofing system in concrete structures

Water Proofing is one of the methods to prevent leakage problems in buildings. For toilets, terraces, water tanks, and outdoor spaces, several methods of water proofing are suitable. Due to the concrete's tendency to shrink, fractures typically occur in the screed of the roof. However, the surface fracture will be partially repaired by casting the concrete in panels. This also happens due to temperature variation. Crystalline admix water proofing with water stops, water proofing with Atactic Polypropylene membrane, and injection are the water proofing systems most commonly used in basements. Using non-shrinking cementitious grout for waterproofing, concrete must have crystalline admixtures made of cementitious powder and water. For toilets in non-sunken places, water proofing with an elastomeric cementitious coating is used. In sunken areas, brick jelly cement concrete with inherent water proofing compound is used. Waterproofing without insulation and waterproofing with insulation are typically used in terraces. There are typically two different types of buildings: Air-conditioned buildings and Non Air-conditioned buildings. Buildings with air conditioning need to be insulated. Extruded polystyrene with geotextile mat is used as over deck insulation. Injection grouting is used in water tanks on the side walls and base slab. On the top surface of the slab and the outside face of the wall throughout the whole area, holes must be drilled using a pneumatic hammer in a zigzag pattern. Generally artificial area and extended basement needs to treat with proper water proofing system. Membrane is used to waterproof the landscape regions. Soil is used to fill in landscaped areas, and there will be a drainage layer to remove water. Materials should be made entirely of recycled polypropylene. In this paper it deals with the different types of water proofing system.

Polymer Waste-Based Highly Efficient Maleated Interfacial Modifier in iPP/SCF Composites—Some Notes on the Role of Processing in Their Thermal and Dynamic Mechanical Properties

This work has a two-fold objective. First, it attempts to present the excellent efficiency of a maleated interfacial agent (obtained by the authors by using atactic polypropylene industrial waste) when used as interfacial additive in polypropylene/short carbon fiber composites (iPP/SCF). Second, in this paper, we pay attention to the role played by processing in the final properties of the composite. This work has been performed by considering the emerging crystalline morphologies generated by the different shear forces that the molten material suffers depending on the molding method employed. The interfacial agent analyzed here consists of an atactic polypropylene containing succinic anhydride grafts obtained through a chemical modification process performed in solution. It incorporates different types of succinic grafts, such as succinic bridges between aPP chains and backbone and terminal grafts (aPP-SASA) in its structure, and contains 5.6% (5.6 × 10-4 g/mol) of grafted polar groups in total. The adhesion of the polyamide SCF sizing and the succinic units is followed by Field Emission Scanning Electronic Microscopy (FESEM) and Synchrotron Infrared Microscopy (SIRM). However, the main objective of this work is the study of the thermal and the dynamic mechanical behavior of the materials of a series of both compression- and injection-molded samples to ascertain the enhanced interfacial interactions in the material and further comparison between the results obtained by both processing operations. Therefore, we detect improvements of 200% in stiffness and 400% in the viscous response of the same SCF content composites caused by aPP-SASA, depending on the processing method used.

Experimental and numerical investigation of roll pave blended with Atactic Polypropylene

In this study, the asphalt mix is modified by using Atactic PolyPropylene (APP)and made as a roll pave in the form of a prefabricated single unit of 300 mm x 300 mm x 20 mm. A four different roll pave is made by varying the APP content starting from 0 %, 6.5 %, 10 %, and 15 %. This roll pave is tested for density, deflection, and skid resistance for the varying APP contents. The 6.5 % APP content in the roll pave gives optimum. In general addition of APP in asphalt mixes increase the performance of roll pavement rather and it should be tested before it reaches road application. The roll pave is the best concept for repair works rather than laying of the new road. The numerical model created for the roll pave using ABAQUS gives a good agreement with experimental failure patterns.

Green Propylene and Polypropylene Production from Glycerol: Process Simulation and Economic Evaluation

To reduce dependence on fossil fuels in Brazil, biodiesel production has grown in recent years, resulting a large surplus of glycerol, which is obtained as a byproduct. Therefore, it is essential to seek new applications so that glycerol can be more efficiently used and add value to the biodiesel production chain. Based on this scenario, this work aims to carry out a technical-economic feasibility analysis regarding the process of transforming glycerol into propylene by hydrogenolysis and the subsequent polymerization of this product into atactic homopolymer polypropylene. To fulfill this objective, computer simulations of these processes were performed in Aspen Plus v8.8, with the support of information available in the literature. Glycerol hydrogenolysis showed high production costs when compared to other propylene production routes. The polymerization process proved to be economically viable, but its integration with the hydrogenolysis process generated polypropylene with an uncompetitive price compared to the price found in the market. The main problems for the viability of this route were identified as the large excess of hydrogen necessary for the hydrogenolysis reaction and the high costs of glycerol and effluent disposal.

Evaluation of Atactic Polypropylene (APP) geomembranes used as liners for salt ponds

This study focused on evaluating the longevity of Atactic Polypropylene (APP) used as a geomembrane (GM) to line ponds that collect runoff water from salt handling facilities. Samples of APP were exhumed from the ponds that have been in service for 6-, 25-, and 44-years and evaluated in the laboratory. Tests were conducted to analyze the surface cracks and textures, tensile properties, puncture resistance, and ability to hold water (permeability). Control tests were conducted with virgin APP GM. Results were compared based on the difference in the age of the APP, location of where the APP samples were obtained within the side slope of the pond (i.e., submerged, and above water level), and orientation of the side slope in relation to the sun (e.g., east, west, north, or south). Based on the field observations and laboratory evaluations, it was determined that exposure to sunlight accelerates the degradation more so than the chemical degradation that occurs due to the salt content within the pond water. The samples exhumed from the north slope (south-facing) had more severe degradation due to high solar radiation energy deposition.

Perfectly Isotactic Polypropylene upon In Situ Activation of Ultrarigid meso Hafnocenes.

For more than 40 years, the synthesis of C2 -symmetric indenyl-based racemic metallocenes for the isoselective polymerization of propylene relied on a tedious separation of the produced rac and meso isomers. Status quo, latter are considered wasteful as they produce atactic polypropylene (aPP) rather than isotactic polypropylene (iPP) if activated with methylaluminoxane (MAO). Unexpectedly, the in situ activation of meso hafnocene I yielded perfectly isotactic polypropylene. We verified an isomerization of the meso compound to the corresponding racemic one upon triisobutylaluminum (TIBA) addition via nuclear magnetic resonance (NMR) spectroscopy and established an easy and convenient polymerization protocol, enabling productivities comparable to pure rac-I if applied to pure meso-I or a mixture of both isomers. With this established isomerization protocol, the potential yield of iPP was enhanced by more than 400 %. This protocol was also shown to be applicable to other meso hafnocenes and some initial mechanistic insights were received.

Migration of Microplastics and Phthalates from Face Masks to Water.

Since the outbreak of COVID-19, face masks have been introduced in the complex strategy of infection prevention and control. Face masks consist of plastic polymers and additives such as phthalates. The aim of this study was to evaluate the migration of microplastics (MP) and phthalates from face masks to water. Four types of masks including FFP2 masks and surgical were studied. Masks were first characterized to determine the different layers and the material used for their fabrication. Then, masks were cut into 20 pieces of 0.5 cm2, including all their layers, placed in water, and the migration of MP and phthalates was evaluated according to the conditions stated in EU Regulation No 10/2011 on plastic materials and articles intended to come into contact with food. For MP, the morphological analysis (shape, dimension, particle count) was performed using a stereomicroscope, while the identification of both masks and MP released was conducted using μ-Fourier-transform infrared spectroscopy (µ-FT-IR). Migration of phthalates was assessed by ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometer (UPLC-MS/MS). Face masks analyzed in the present study were made of atactic polypropylene (PP) as stated by the manufacturer. The μ-FT-IR confirmed that PP and polyamide (PA) were released as fragments, while both PP and polyester (PES) were released as fibers. In addition, 4 phthalates were identified at concentrations between 2.34 and 21.0 µg/mask. This study shows that the migration study can be applied to evaluate the potential release of MP and phthalates from face masks to water and could give a hint for the potential impact of their incorrect disposal on the aquatic resources.

Molecular dynamics simulation of polypropylene: diffusion and sorption of H2O, H2O2, H2, O2 and determination of the glass transition temperature

Molecular dynamics (MD) simulations in the canonical (NVT) and the isothermal-isobaric (NPT) ensemble using COMPASS III molecular force fields were performed to study the penetrant diffusion of water (H2O), hydrogen peroxide (H2O2) and oxygen (O2) in isotactic polypropylene (iPP) and hydrogen (H2) in iPP and atactic polypropylene (aPP) for time intervals up to 11 ns and in the case of H2O2 up to 22 ns. We found robust cluster formation in the case of H2O and H2O2. Further, the diffusion coefficients for all these systems were estimated by mean-square displacement analysis. Our results are consistent with previously published experimental and computational data except for the diffusion of H2 in polypropylene where our results are one and two orders of magnitude higher, respectively. Grand Canonical Monte Carlo (GCMC) simulations were used to determine the sorption loading and saturation concentration of H2O, O2 and H2 in iPP, where we find good agreement for H2O with experimental results. By means of MD simulation the glass transition temperature (Tg) of iPP was estimated to 273.66 ± 4.21 K which is consistent with previously published experimental results.

Effect of Macro- and Microstructures on Catalytic Hydrogenolysis of Polyolefins

Polyethylenes of varying molecular weight and branch density, as well as polypropylenes of varying molecular weight and tacticity, were catalytically converted to lower-molecular-weight liquid products to showcase how these various properties in a mixed waste plastic stream could affect the final product. A Pt nanoparticle on a strontium titanate nanocuboid (Pt/STO) catalyst was used under solvent-free conditions in the presence of 170 psi of H2 at 300 °C for hydrogenolysis. The initial molecular weight of polyethylene was found to have a moderate effect on the yield to the final product (ranging from 55 wt% for Mn ∼ 7600 Da to 67 wt% for Mn ∼ 50,950 Da). The microstructure, defined as the length and density of branches in a polymer, of higher-molecular-weight polymers was the dominant factor in determining the yield (ranging from 67 wt% for Mn ∼ 50,950 Da for linear low-density polyethylene (LLDPE) with C2 branches to 97 wt% for Mn ∼ 38,850 Da for LLDPE with C6 branches). The same products (Mn = C29–C46, Đ = 1.1–1.6) and distribution of undesired light gases (C1–C4 ≈ 90 mol%, C5–C8 ≈ 10 mol%) are obtained from conversions of PE of varying molecular weight. The tacticity of polypropylene at a given molecular weight had a significant effect on the molecular weight of the final product, while not strongly affecting conversion. Hydrogenolysis of isotactic polypropylene (iPP) produced ≈C18 with a wider polydispersity (Đ ∼ 1.4) compared to the narrow ≈C64 (Đ ∼ 1.0) and ≈C54 (Đ ∼ 1.0) products from atactic (aPP) and syndiotactic (sPP) polypropylene, respectively. The stereochemistry of the methyl groups dictates the shape and structure of the polymer in the melt, which in turn affects how the hydrocarbon chain interacts with the catalyst surface, thereby impacting the number of C–C scissions. These results show how various characteristics such as the molecular weight and structure of a waste plastic stream could affect the final product.

High‐performance atactic polypropylene modified bitumen blends fabricated via conventional, hot, and in‐situ blending techniques

AbstractThis research presents an investigation on the incorporation of atactic polypropylene (APP) as a modifier in bitumen at weight concentrations from 0 to 30 wt%. An APP‐modified bitumen (APPMB) was prepared by conventional, hot, and in situ blending and characterized for mechanical, morphological, thermal, structural, and physical properties. APPMB specimens using maleic anhydride (MA) functionalized polymer at its optimized concentration of 20 weight percentage (wt%), along at several other concentrations, were prepared using in situ and hot blending methods using an overhead stirrer mixer at a blending temperature of 160°C for 2 h. Fourier transform infrared revealed a strong interaction of APP or APP‐g‐MA with bitumen. The ultimate compressive strength, acquired in Mega Pascal (MPa) units, was increased from 0.24 MPa at 5 wt% APP to 0.70 MPa at 20 wt% APP loading. Scanning electron microscopy micrographs manifested dispersed phases of APP in bitumen due to the high temperature and shearing application with overhead stirring. In situ and hot blended specimens exhibited better mechanical, thermal, and structure–property relations. This research highlights the novelty in terms of property optimization and advancements at a high‐weight percentage of the modifier (i.e., 20 wt%) along with emphasizing the comparison of three different fabrication techniques; however, the previous research manifested the advancements in the properties of polymer and bitumen blends at low concentrations of polymers.

The Variance of the Polypropylene α Relaxation Temperature in iPP/a-PP-pPBMA/Mica Composites

By considering that the α relaxation related to the glass to rubber transition (obtained by dynamic mechanical analysis) of isotactic polypropylene (iPP) can be identified with the thermal history of the material (and so, with the processing step), this work deals with the changes in this transition temperature (Tα) in polypropylene/mica composites caused by the mutual effect of the other components (mica and interfacial additive). Here, the additive used is a p-phenylen-bis-maleamic grafted atactic polypropylene (aPP-pPBMA) obtained from polymerization wastes (aPP) by the authors. This additive contains 5.0·10−4 g.mol−1 (15% w/w) grafted pPBMA. In essence, this article has two different objectives: (1) To observe and discuss the changes in Tα of the polymer matrix (iPP) caused by the combined effect of the other components (mica and aPP-pPBMA); and (2) predicting the values for Tα in terms of both aPP-pPBMA and mica content for whatever composition in the experimental space scanned. This task was undertaken by employing a Box–Wilson experimental design assuming the complex character of the interactions between the components of the iPP/aPP-pPBMA/mica system, which define the ultimate properties of the composite.

Characterisation of carbon paste electrodes bulk-modified with surfactants for measurements in nonaqueous media

This article deals with carbon paste electrodes bulk-modified with surfactants for measurements in pure organic solvents where common carbon paste-based mixtures undergo disintegration. The electrodes of interest were prepared by mixing of selected carbon materials (namely: two types of graphite powder, glassy carbon powder, raw shungite powder, and multi-wall carbon nanotubes, with various binders (mineral oil, silicone oil, paraffin wax, vaseline, atactic polypropylene, and tricresyl phosphate), together with surfactants of choice (sodium dodecyl sulfate, cetylpyridinium chloride, benzethonium chloride, cetyltrimethylammonium bromide, didodecyldimethylammonium bromide, Triton X-100, and 1,3‒didecyl‒2‒methylimidazolium chloride). The corresponding studies were focused on the optimal composition of the individual pastes and their characterisation in organic solvents, when using cyclic voltammetry with model redox pairs (ferrocenium/ferrocene and quinone/hydroquinone). The results obtained suggest one that amount of the individual components depends predominantly on the type of carbon used. Key factors for selection of the proper surfactant are its polarity, chemical inertness, and electrochemical inactivity. For comparison, glassy carbon disc electrode was also used.

Efficient synthesis of thermoplastic elastomeric amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP)

The synthesis of amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP), with molecular weights (Mw) up to 2.0 MDa and narrow polydispersities is reported using remarkably efficient permethylindenyl-phenoxy (PHENI*) titanium complexes.

Mechanism of form I′ formation in polybutene-1/polypropylene blends

Isotactic polybutene-1 (PB) can crystallize into form I′ polymorph directly in its blends with isotactic polypropylene (iPP), but the mechanism remains controversial. In this work, by using Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), we investigated systematically cold crystallization of PB in its blends with iPP and with atactic polypropylene (aPP), one crystallizable and the other amorphous. It was found that form I′ was produced in both PB/iPP and PB/aPP blends, the higher the PP content, the greater the form I′ fraction, and iPP was found to be more effective in promoting form I'. However, in a PB/iPP blend containing 10 wt% iPP with the iPP fully crystallized at 120 °C, the PB crystallized into form II exclusively in the cold crystallization, at a faster rate than in neat PB. These experimental results indicate that in PB/iPP blends both confined nucleation mechanism and surface nucleation mechanism operate, but the former governs the PB polymorph formed. Under the confinement only the smaller form I′ nuclei are allowed, and the PP crystals then expedite the process via the surface nucleation mechanism.