An Additive Model to Predict the Rheological and Mechanical Properties of Polypropylene Blends Made by Virgin and Reprocessed Components

Mantia, Francesco Paolo La; Mistretta, Maria Chiara; Titone, Vincenzo

doi:10.3390/recycling6010002

Cited by 10 publications

(14 citation statements)

References 11 publications

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“…and, then, the reduction of the Newtonian viscosity means a reduction of the molecular weight, which can be calculated using Equation (3) [22] as follows:…”

Section: Resultsmentioning

confidence: 99%

Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester

Titone

Correnti²,

Mantia

2021

Polymers

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This work is focused on the influence of moisture content on the processing and mechanical properties of a biodegradable polyester used for applications in injection molding. The pellets of the biodegradable polyester were exposed under different relative humidity conditions at a constant temperature before being compression molded. The compression-molded specimens were again placed under the above conditions before the mechanical testing. With all these samples, it is possible to determine the effect of moisture content on the processing and mechanical properties separately, as well as the combined effect of moisture content on the mechanical properties. The results obtained showed that the amount of absorbed water—both before processing and before mechanical testing—causes an increase in elongation at break and a slight reduction of the elastic modulus and tensile strength. These changes have been associated with possible hydrolytic degradation during the compression molding process and, in particular, with the plasticizing action of the moisture absorbed by the specimens.

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“…and, then, the reduction of the Newtonian viscosity means a reduction of the molecular weight, which can be calculated using Equation (3) [22] as follows:…”

Section: Resultsmentioning

confidence: 99%

Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester

Titone

Correnti²,

Mantia

2021

Polymers

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“…The Newtonian viscosity is a strong function of the molecular weight (see Equ ( 5)) [17]: 3.4 and then, the molecular weight of the sample photo-oxidized can be calculated Equation ( 6 As reported before, the decrease of the molecular weight enhances the crystalliz rate and the crystallinity degree. In Figure 3 the thermograms of the same sample reported.…”

Section: Characterization Of Photo-oxidized Ppmentioning

confidence: 96%

“…It has been already shown that if P(M i ) is the value of the generic property of a mono-polymer blend having recycled fractions until the i-th photo-oxidized polymer, [17]:…”

Section: Modelingmentioning

confidence: 99%

“…Recently [17], we used the typical industrial operation of blending virgin polymer with the same polymer reprocessed several times to compare an additive model to predict rheological and mechanical properties with experimental results. We concluded that the model was effective when applied to blends where the recycled component undergoes only a modification of the molecular structure.…”

Section: Introductionmentioning

confidence: 99%

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Rheological, Mechanical and Morphological Characterization of Monopolymer Blends Made by Virgin and Photo-Oxidized Polypropylene

2021

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In this work, monopolymer blends of virgin polypropylene and photo-oxidized polypropylene were prepare and characterized. The polypropylene samples were subjected to accelerated ageing to simulate the effects of outdoor exposure of polypropylene. After exposure, samples were pelletized and mixed with the same virgin polymer. The rheological, mechanical and morphological characterization was conducted on both the polymers and the blends. Both viscosity and mechanical properties decrease with increases in the content of recycled, photo-oxidized components and of the level of degradation of this component. In addition, the experimental data were compared with a model that takes into account both the effect of the change of the molecular weight and of the presence of oxygenated groups.

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“…The management of waste plastic is a vital issue that must be addressed on a global scale through policy and proper waste management. After some careful research [19][20][21][22], the blending of raw and reprocessed PP has become routine and the process usually involves adding 10% to 30% recycled material to raw components to avoid any serious changes in the mechanical properties or process ability of the product. These reprocessed PP blends have the same properties and are very similar to virgin PP; the only clear change is a decrease in the molecular weight caused by the repetitive melt processing operations.…”

Section: Introductionmentioning

confidence: 99%

Number of Times Recycled and Its Effect on the Recyclability, Fluidity and Tensile Properties of Polypropylene Injection Molded Parts

Huang

Peng

2021

Sustainability

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The ease with which modern plastics can be injection molded makes them very suitable for the production of many different products and, today, plastics are often used as substitutes for metal. Polypropylene (PP) is one of the most widely used thermoplastics globally since it is very useful, cost-effective and flexible for molding. However, the amount of harm to the environment caused by plastic waste has become phenomenal and the recycling of plastics has become a serious aspect of environmental protection. PP, as the most commonly used plastic material, was selected for use in this study. It has a melt flow index of 15 g/min and its recyclability, fluidity, and physical properties, as well as manufacturing conditions, were explored in relation to the number of times the material could be recycled (TR). A cavity pressure sensor was used to measure the viscosity index of the recycled plastic after multiple cycles of plasticizing and injection, part molding, scrap-recycling, and crushing. A paperclip-shaped test specimen was used to determine PP fluidity and crystallinity of specimens with different TRs. Tensile tests were used to detect differences in the tensile strength between specimens made from Raw-PP and recycled PP. The results showed that PP that had been recycled several times had a higher melt flow index, material fluidity, melting peak area, crystallinity, crystallization rate, and crystallization temperature. Repeated injection and recycling of the material had reduced the length of the molecular chains and broadened the molecular weight distribution. This improved the fluidity and increased crystallinity. The increase in fluidity made cavity filling easier, reducing the cavity pressure as well as the viscosity index. The results of this study showed that the recycling of the PP could improve the physical properties of the products to a degree and also went some way to further the benefits of a circular economy. The recycling of injection-molded PP material can be added to renewable energy technologies and used in environmental impact assessment.

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An Additive Model to Predict the Rheological and Mechanical Properties of Polypropylene Blends Made by Virgin and Reprocessed Components

Cited by 10 publications

References 11 publications

Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester

Effect of Moisture Content on the Processing and Mechanical Properties of a Biodegradable Polyester

Rheological, Mechanical and Morphological Characterization of Monopolymer Blends Made by Virgin and Photo-Oxidized Polypropylene

Number of Times Recycled and Its Effect on the Recyclability, Fluidity and Tensile Properties of Polypropylene Injection Molded Parts

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