Effect of Recycling on the Rheological Properties and Foaming Behaviors of Branched Polypropylene

2003 ◽  
Vol 22 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Hani E. Naguib ◽  
Jin Wang ◽  
Chul B. Park ◽  
Anjan Mukhopadhyay ◽  
Norbert Reichelt
Keyword(s):  
Rheological Properties ◽  
Loss Modulus ◽  
Expansion Ratio ◽  
Melt Strength ◽  
Single Screw ◽  
Foam Morphology ◽  
Virgin Sample ◽  
Foaming Behavior ◽  
Branched Polypropylene ◽  
Density Results

The effects of recycling of branched polypropylenes on their rheological properties and foamability are studied in this paper. The rheological properties and foamability of branched polypropylene are compared with those of the virgin sample. The main purpose of the study was to explore the possibility of using recycled materials to make the acceptable foam products. The recycled polypropylenes showed the lower melt strength due to the lowered molecular weight and disentanglement of molecules. However, the high-shear viscosities of the virgin and recycled resins exhibited almost the same values whereas the zero-shear rate viscosity was lower for recycled ones. The rheological behavior of the resins was correlated to the foaming behavior. It was observed that the contribution of the storage modulus (G’) was more pronounced than the loss modulus (G”). The foam morphology of recycled branched polypropylene and the virgin material was studied at various processing temperatures using a single-screw tandem foam extrusion system. The volume expansion ratio and cell population density results were correlated with the rheological data. Despite the noticeable drop in the melt strength, it was found that the foamability did not significantly deteriorate by recycling.

scholarly journals Tuning High and Low Temperature Foaming Behavior of Linear and Long-Chain Branched Polypropylene via Partial and Complete Melting

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 44
Author(s):  
Mu Sung Kweon ◽  
Mahmoud Embabi ◽  
Maksim E. Shivokhin ◽  
Anvit Gupta ◽  
Xuejia Yan ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Processing Parameters ◽  
Expansion Ratio ◽  
Key Factors ◽  
Complete Melting ◽  
Foaming Behavior ◽  
High And Low Temperatures ◽  
Branched Polypropylene ◽  
Long Chain ◽  
Long Chain Branched Polypropylene

While existing foam studies have identified processing parameters, such as high-pressure drop rate, and engineering measures, such as high melt strength, as key factors for improving foamability, there is a conspicuous absence of studies that directly relate foamability to material properties obtained from fundamental characterization. To bridge this gap, this work presents batch foaming studies on one linear and two long-chain branched polypropylene (PP) resins to investigate how foamability is affected by partial melting (Method 1) and complete melting followed by undercooling (Method 2). At temperatures above the melting point, similar expansion was obtained using both foaming procedures within each resin, while the PP with the highest strain hardening ratio (13) exhibited the highest expansion ratio (45 ± 3). At low temperatures, the foamability of all resins was dramatically improved using Method 2 compared to Method 1, due to access to lower foaming temperatures (<150 °C) near the crystallization onset. Furthermore, Method 2 resulted in a more uniform cellular structure over a wider temperature range (120–170 °C compared to 155–175 °C). Overall, strong extensional hardening and low onset of crystallization were shown to give rise to foamability at high and low temperatures, respectively, suggesting that both characteristics can be appropriately used to tune the foamability of PP in industrial foaming applications.

Effects of pressure drop rate and CO2 content on the foaming behavior of newly developed high-melt-strength polypropylene in continuous extrusion

2020 ◽  
pp. 0021955X2094311
Author(s):  
Eric Kim ◽  
Mu Sung Kweon ◽  
Sandra Romero-Diez ◽  
Anvit Gupta ◽  
Xuejia Yan ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Strong Dependence ◽  
Expansion Ratio ◽  
Average Cell Size ◽  
Average Cell ◽  
Melt Strength ◽  
Pressure Drops ◽  
Foaming Behavior ◽  
Die Temperature ◽  
Drop Rate

We report systematic studies on the foamability of our novel high-melt-strength long-chain branched polypropylene under supercritical CO2. Continuous foaming experiments were conducted using a tandem extrusion system and a set of filamentary dies with similar pressure drops but different pressure drop rates. The foam expansion was controlled by varying the temperature at the die exit. Under identical CO2 loadings, the expansion ratio plotted as a function of die temperature exhibited similar shapes across multiple pressure drop rates. However, the shape of the curve varied across different amounts of CO2, under which the highest achievable expansion ratio occurred at a lower die temperature with increasing CO2 content. The cell density displayed strong dependence on both the pressure drop rate and the amount of dissolved CO2. The effect of the latter became more apparent at lower pressure drop rates. The average cell size decreased with increasing CO2 loading but generally showed weak dependence on pressure drop rate except at the highest value.

Electrical conductivity and rheological properties of carbon black based conductive polymer composites prior to and after annealing

2021 ◽  
pp. 096739112110012
Author(s):  
Qingsen Gao ◽  
Jingguang Liu ◽  
Xianhu Liu
Keyword(s):  
Electrical Conductivity ◽  
Carbon Black ◽  
Percolation Threshold ◽  
Rheological Properties ◽  
Network Formation ◽  
Loss Modulus ◽  
Conductive Polymer ◽  
Complex Viscosity ◽  
Electrical Percolation ◽  
Electrical Percolation Threshold

The effect of annealing on the electrical and rheological properties of polymer (poly (methyl methacrylate) (PMMA) and polystyrene (PS)) composites filled with carbon black (CB) was investigated. For a composite with CB content near the electrical percolation threshold, the formation of conductive pathways during annealing has a significant impact on electrical conductivity, complex viscosity, storage modulus and loss modulus. For the annealed samples, a reduction in the electrical and rheological percolation threshold was observed. Moreover, a simple model is proposed to explain these behaviors. This finding emphasizes the differences in network formation with respect to electrical or rheological properties as both properties belong to different physical origins.

Impact of high-pressure homogenization on the microstructure and rheological properties of citrus fiber

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Dianbin Su ◽  
Xin-Di Zhu ◽  
Yong Wang ◽  
Dong Li ◽  
Li-Jun Wang
Keyword(s):  
Particle Size ◽  
High Pressure ◽  
Rheological Properties ◽  
Binding Capacity ◽  
Loss Modulus ◽  
High Pressure Homogenization ◽  
Carreau Model ◽  
Hydration Properties ◽  
Water Binding ◽  
Water Holding

Abstract Citrus fiber dispersion with different concentrations (5–25 g/kg) was treated by high-pressure homogenization (90 and 160 MPa) for two cycles. The particle size distribution, hydration properties of powders, morphology and rheological measurements were carried out to study the microstructure and rheological properties changes by high-pressure homogenization (HPH). In conclusion, the HPH can reduce the particle size of fiber, improve the water holding capacity and water binding capacity. Furthermore, fiber shape can be modified from globular cluster to flake-like slices, and tiny pores can be formed on the surface of citrus fiber. The apparent viscosity, storage modulus and loss modulus were increased by HPH whereas the activation energy was reduced. The Hershcel–Bulkley model, Carreau model and Power Law mode were selected to evaluate the rheological properties.

Thermal Property, Morphology, Mechanical and Rheological Properties of a Modified Bio-Polymers Prepared by Blending Poly(3-Hydrobutyrate-Co-4-Hydrobutyrate) with Chain Extenders

2010 ◽  
Vol 152-153 ◽  
pp. 924-930
Author(s):  
Mei Li ◽  
Zhi Qiang Li ◽  
Jun Xu ◽  
Dun Sheng Wei ◽  
Hong Wei Zhu ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Shear Viscosity ◽  
Loss Modulus ◽  
Freeze Fracture ◽  
Fracture Morphology ◽  
Steady Shear ◽  
Thermal Transitions ◽  
Remarkable Effect ◽  
Steady Shear Viscosity ◽  
Chain Extenders

Modified Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] was prepared by melt reactive blending P(3HB-co-4HB) with chain extenders (ADR-4367). Thermal transitions, spherulitic and freeze-fracture morphology, mechanical and rheological properties of the chain extended bio-materials were investigated. The results show that glass transition temperatures and crystallization temperatures increase, crystallinity and diameters of spherulites decrease, there are amorphous parts dispersed among the crystalline phase, and the bio-materials transfer from brittleness to toughness and ductility. Steady shear viscosity of the modified P(3HB-co-4HB) increases by about one order of magnitude, melts of the modified P(3HB-co-4HB) behave more viscoelasticity by storage modulus and loss modulus correlated with oscillatory shear frequency. Addition of ADR-4367 with contents of 4~6 wt% in the blends is enough to branching and coupling the co-polymer chains and brings remarkable effect on improving mechanical properties, steady shear viscosity and viscoelasticity.

Encapsulated sour cherry pomace extract: Effect on the colour and rheology of cookie dough

2018 ◽  
Vol 25 (2) ◽  
pp. 130-140 ◽  
Author(s):  
Jovana Petrović ◽  
Biljana Pajin ◽  
Ivana Lončarević ◽  
Vesna Tumbas Šaponjac ◽  
Ivana Nikolić ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Wheat Flour ◽  
Soy Protein ◽  
Loss Modulus ◽  
Control Sample ◽  
Sour Cherry ◽  
Soy Proteins ◽  
Blue Colour ◽  
B Values ◽  
Cherry Pomace

In this study, the effect of encapsulated sour cherry pomace extract on the physical characteristics of the cookie dough (colour, textural and rheological properties) was investigated. Sour cherry pomace extract encapsulated in whey (WE) and soy proteins (SE) was incorporated in cookie dough, replacing 10% (WE10 and SE10) and 15% (WE15 and SE15) of wheat flour. The dough samples containing encapsulates had the grey-blue colour ( b* values significantly decreased compared to control sample). Due to the presence of anthocyanins, a* values of the dough colour increased significantly with the addition of encapsulates. The addition of soy protein encapsulate increased hardness, resistance to extension and viscosity of cookie dough and decreased deformation compliance ( J), while the addition of whey encapsulate caused dough softness, higher deformation compliance and lower values of viscosity compared to control sample. Values of storage and loss modulus, G′ and G″, significantly decreased when wheat flour was replaced with WE and increased when the flour was replaced with soy protein encapsulate. The addition of soy protein encapsulate resulted in higher cookie hardness.

Rheological properties of cholesteric liquid crystals as lubricant additives

2019 ◽  
Vol 33 (05) ◽  
pp. 1950014 ◽  
Author(s):  
A. Bindu Madhavi ◽  
S. Sreehari Sastry
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Loss Modulus ◽  
Flow Behavior ◽  
Lubricant Additives ◽  
Rheological Parameters ◽  
Practical Applications ◽  
Phase Transition Temperatures ◽  
Frequency Independent ◽  
Temperature Shear

Rheological properties of Cholesteryl n-valerate, Cholesteryl decanoate and Cholesteryl myristate which are esters of cholesterol have been studied. Phase transition temperatures and rheological parameters such as viscosity, elastic modulus G[Formula: see text], loss modulus G[Formula: see text] as functions of temperature, shear rate and time are investigated. In frequency sweep test, a higher transition crossover region has occurred for Cholesteryl myristate, whereas for Cholesteryl n-valerate a frequency-independent plateau prevailed for both the moduli. The occurrence of blue phase in Cholesteryl decanoate during temperature sweep measurements is an indication for the rheological support. The results for steady state have informed that cholesteric esters are having non-Newtonian flow behavior in their respective cholesteric phases. The power-law model has explained well the shear rate dependence of shear stress. A few practical applications of these esters as lubricant additives are discussed, too.

Effect of stretching speed on morphologies and properties of in situ microfibrillar POE/PLA composites

2020 ◽  
pp. 089270572093917
Author(s):  
Jing Sun ◽  
Anrong Huang ◽  
Shanshan Luo ◽  
Min Shi ◽  
Heng Luo ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Rheological Properties ◽  
Loss Modulus ◽  
Weight Ratio ◽  
Poly Lactic Acid ◽  
Electron Microscopic ◽  
Dynamic Rheological Properties ◽  
Scanning Electron Microscopic ◽  
Ethylene Octene Copolymer

In situ microfibrillar ethylene–octene copolymer (POE)/poly(lactic acid) (PLA) composites (MFCs) with different phase morphologies were prepared by controlling the stretching speed and maintaining the weight ratio of POE/PLA of 80/20. Four different stretching speeds were employed to study the effect of PLA microfibrillar morphology on tensile, crystalline, and rheological properties of MFCs. Scanning electron microscopic images revealed that the morphology of PLA phase was strongly influenced by stretching speed. MFCs with highest aspect ratio and smaller diameter of PLA microfibrils were obtained with a stretching speed of 60 rpm. The PLA microfibrils with high aspect ratio had the best reinforcement effect on MFCs. The dynamic rheological properties indicated that the MFCs achieved higher storage modulus and loss modulus at the stretching speed of 60 rpm.

Effect of MWCNT carboxyl functionalization on the shear rheological and electrical properties of HMS-PP/MWCNT foams

2020 ◽  
pp. 0021955X2094309
Author(s):  
Olavo S Bianchin ◽  
Guilherme HF Melo ◽  
Rosario ES Bretas
Keyword(s):  
Impedance Spectroscopy ◽  
Rheological Properties ◽  
Polarized Light ◽  
Multiwall Carbon Nanotubes ◽  
Dynamic Mechanical Properties ◽  
Dielectric Constants ◽  
Scanning Calorimetry ◽  
Cellular Density ◽  
Foaming Behavior ◽  
High Dielectric

Different concentrations of multiwall carbon nanotubes (MWCNT) and carboxyl functionalized MWCNT (MWCNT-COOH) were added to a high melt strength polypropylene (HMS-PP) to produce foams with high dielectric constants, using azodicarbonamide (AZO) as blowing agent. The AZO foaming behavior and the crystallization, thermal properties, steady state and oscillatory shear rheological properties of the nanocomposites were analyzed by polarized light optical microscopy (PLOM), differential scanning calorimetry (DSC), thermogravimetry analyses (TGA) and parallel plate rheometry. The morphology, the dielectric and dynamic mechanical properties (DMTA) of the foams were also studied by scanning electron microscopy (SEM), impedance spectroscopy and bending method, respectively. A decrease in crystallite size and an increase in the HMS-PP overall crystallinity promoted by the presence of both types of MWCNTs was observed, as well as an increase in the crystallization temperatures. From these results and from the analyses of the rheological properties, it was possible to predict that the 5 wt.% MWCNT foam would have the lowest bubble growth rate, the 1.5 wt.% MWCNT-COOH the highest, while the 3 wt.% MWCNT-COOH composition would have the slowest bubble stability (and consequently the highest cellular density) and the 1.5 wt.% MWCNT-COOH the fastest. Also, it was possible to predict that only the 5 wt.% MWCNT-COOH foam would have a percolated and electrically conductive structure. All these predictions were confirmed by the resultant morphology and impedance spectroscopy results. The highest mechanical damping was displayed by the 3 wt.% MWCNT-COOH foam, while the lowest by the 5 wt.% MWCNT-COOH foam. Regarding the dielectric properties, the 1.5 wt% MWCNT-COOH foam was found to be the most suitable to be used as a capacitor material; this foam was also the less dense of all the samples.

Microcellular PP-CaCO3 Nanocomposites: Relationship Between Nanocomposite Morphology and Foam Morphology

Materials ◽  
2005 ◽  
Author(s):  
Han-Xiong Huang ◽  
Jian-Kang Wang
Keyword(s):  
Expansion Ratio ◽  
Polymeric Nanocomposites ◽  
Screw Extruder ◽  
System Effect ◽  
Foam Morphology ◽  
Caco3 Content ◽  
Twin Screw ◽  
New Material ◽  
Carbon Dioxide Co2 ◽  
The Relationship

Polymeric nanocomposites exhibit high potential as a new material for carbon dioxide (CO2) foaming. In this paper, a polypropylene (PP)/nano-calcium carbonate (nano-CaCO3) composite was selected to investigate the relationship between nanocomposite morphology and foam morphology. Nanocomposites were prepared using a twin-screw extruder with screw including both shearing and mixing elements. Nanocomposites with different morphology via changing the nano-CaCO3 content were then foamed by using supercritical CO2 in a batch system. Effect of nano-CaCO3 content on the volume expansion ratio, and cell coalescence were studied.

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