Synthesis and Structure–Property Relationships of Polypropylene-g-poly(ethylene-co-1-butene) Graft Copolymers with Well-Defined Long Chain Branched Molecular Structures

Coupling Kinetic Modelling with SAOS and LAOS Rheology of Poly(n-Butyl Acrylate)

A kinetic model based on fundamentals of radical polymerization and literature known rate parameters for the polymerization of n-butyl acrylate is validated against molecular analysis and rheological data. The model is used to predict conversion, molar mass distribution, and branching densities in form of short and long chain branching. Rheological measurements of synthesized model polymers are evaluated along the Carreau-Yasuda and Van Gurp-Palmen presentations, allowing to detect small differences in the degree of long chain branching. Contributions of anharmonics to viscoelastic response in large amplitude oscillations are small and differences between the products are dominated by the differences in molar mass.

Improving Rheological and Mechanical Properties of Various Virgin and Recycled Polypropylenes by Blending with Long-Chain Branched Polypropylene

Blends of two long-chain branched polypropylenes (LCB-PP) and five linear polypropylenes (L-PP) were prepared in a single screw extruder at 240 °C. The two LCB-PPs were self-created via reactive extrusion at 180 °C by using dimyristyl peroxydicarbonate (PODIC C126) and dilauroyl peroxide (LP) as peroxides. For blending two virgin and three recycled PPs like coffee caps, yoghurt cups and buckets with different melt flow rate (MFR) values were used. The influence of using blends was assessed by investigating the rheological (dynamic and extensional rheology) and mechanical properties (tensile test and impact tensile test). The dynamic rheology indicated that the molecular weight as well as the molecular weight distribution could be increased or broadened. Also the melt strength behavior could be improved by using the two peroxide modified LCB-PP blends on the basis of PODIC C126 or PEROXAN LP (dilauroyl peroxide). In addition, the mechanical properties were consistently enhanced or at least kept constant compared to the original material. In particular, the impact tensile strength but also the elongation at break could be increased considerably. This study showed that the blending of LCB-PP can increase the investigated properties and represents a promising option, especially when using recycled PP, which demonstrates a real "up-cycling" process.

Morphological and mechanical properties of biodegradable poly(glycolic acid)/poly(butylene adipate-co-terephthalate) blends with in situ compatibilization

In the present work, the biodegradable blends of poly(glycolic acid) (PGA) and poly(butylene adipate-co-terephthalate) (PBAT) with in situ compatibilization using 4,4'-methylenebis(phenyl isocyanate) (MDI) were prepared. The combined results of FTIR, DSC, SEM, DSC, POM, TGA and rheology demonstrated that the MDI was successfully reacted with PGA/PBAT, the complex viscosity and storage moduli (G') of the blends were increased. Melt elasticity and viscosity of the blends were also increased on increasing the concentration of PBAT. SEM results indicated that the compatibility was improved by in situ compatibilization. Due to the apparent differences in melting temperature (T m) between PGA and PBAT, the morphology of the dispersed phase evolved from a spherical structure to in situ microfiber when the content of PBAT was up to 60% during injection molding. The interfacial adhesion between PGA and PBAT was strengthened, consequently, the impact strength of the blend was sharply increased from 9.0 kJ m-2 to 22.2 kJ m-2. On account of the chain extension effect, the crystallinity, crystallization temperature and crystallization size were decreased, which was also of benefit for the improvement of toughness. Meanwhile, the thermal stability of the PGA was improved through blending with PBAT. A novel biodegradable blending material with enhanced toughness and thermal stability was prepared.

Polyolefin graft copolymers through a ring-opening metathesis grafting through approach

A series of polyethylene-g-atactic polypropylene graft copolymers were synthesized by grafting through copolymerization of a cyclooctene terminated aPP macromonomer with cyclooctene monomer and subsequent hydrogenation.

Highly branched polymethacrylates prepared efficiently: brancher-directed topology and application performance

A series of highly oil-soluble and branched polymethacrylates are prepared via ATRcP of 2-ethylhexyl methacrylate and divinyl brancher with high efficiency, focusing on the brancher effect on the structure-performance of the polymers.

Influence of Different Types of Peroxides on the Long-Chain Branching of PP via Reactive Extrusion

Long-chain branching (LCB) is known as a suitable method to increase the melt strength behavior of linear polypropylene (PP), which is a fundamental weakness of this material. This enables the modification of various properties of PP, which can then be used-in the case of PP recyclates-as a practical "upcycling" method. In this study, the effect of five different peroxides and their effectiveness in building LCB as well as the obtained mechanical properties were studied. A single screw extruder at different temperatures (180 and 240 °C) was used, and long-chain branched polypropylene (PP-LCB) was prepared via reactive extrusion by directly mixing the peroxides. The peroxides used were dimyristyl peroxydicarbonate (PODIC C126), tert-butylperoxy isopropylcarbonate (BIC), tert-Butylperoxy 2-ethylhexyl carbonate (BEC), tert-amylperoxy 2-ethylhexylcarbonate (AEC), and dilauroyl peroxide (LP), all with a concentration of 20 mmol/kg. The influence of the temperature on the competitive prevalent reactions of degradation and branching was documented via melt mass-flow rate (MFR), rheology measurements, and gel permeation chromatography (GPC). However, via extensional rheology, strain hardening could be observed in all cases and the mechanical properties could be maintained or even improved. Particularly, PODIC C126 and LP signaled a promising possibility for LCB in this study.

New effort to synthesize star isotactic polypropylene

Star isotactic polypropylenes with adjustable arm numbers of 3–8 were synthesized via an efficient arm-first approach with two facile steps.

Isothermal and Non-Isothermal Crystallization Studies of Long Chain Branched Polypropylene Containing Poly(ethylene-co-octene) under Quiescent and Shear Conditions

Isothermal and non-isothermal crystallization behaviours of the blends of long chain branched polypropylene (LCB PP) and poly(ethylene-co-octene) (PEOc) with different weight ratios were studied under quiescent and shear flow using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and rheological measurements. Experimental results showed that the crystallization of the LCB PP/PEOc blends were significantly accelerated due to the existence of the long chain branches (LCBs), the blends being able to rapidly crystallize even at 146 °C. The addition of PEOc that acts as a nucleating agent, could also increase the crystallization rate of LCB PP. However, the crystallization rate of LCB PP was reduced when the PEOc concentration was more than 60 wt %, showing a retarded crystallization growth mechanism. The morphology of the binary blend was changed from a sea-island structure to a co-continuous phase structure when the PEOc concentration was increased from 40 to 60 wt %. In comparison with linear isotactic iPP/PEOc, the interfacial tension between LCB PP and PEOc was increased. In addition, flow-induced crystallization of LCB PP/PEOc blends was observed. Possible crystallization mechanisms for both LCB PP/PEOc and iPP/PEOc blends were proposed.

Synthesis and structure–property relationships of SIS-g-PB copolymers and their application in hot-melt pressure-sensitive adhesives

Grafting polybutadiene blocks onto epoxidized styrene-b-isoprene-b-styrene (ESIS) copolymers results in significant improvement of ESIS-based adhesives performance while retaining polarity.

Copolymerization of propylene with Si-containing α,ω-diolefins: how steric hindrance of diolefins affects long chain branch formation

A series of long chain branched isotactic polypropylenes (LCBPPs) were in situ synthesized by copolymerization of propylene with diallylsilanes. The substituent groups can efficiently suppress the cyclization of the diolefin and significantly improve LCB formation efficiency.

Preparation and characterization of long chain branched polycarbonates with significantly enhanced environmental stress cracking behavior through gamma radiation with addition of difunctional monomer

A series of long chain branched polycarbonates (LCB-PCs) was prepared with unique topological structures and significantly enhanced ESC properties.