Injection-molded Polypropylene Research Articles

Crystallization degree dependent effective thermo-elastic and thermal properties of an injection molded polypropylene component. Part 1: Multiscale simulation scheme and effective lamella properties

Crystallization degree dependent effective thermo-elastic and thermal properties of an injection molded polypropylene component. Part 1: Multiscale simulation scheme and effective lamella properties

Effects of Ramie Fiber/Boron Nitride Exposure on the Mechanical Characteristics of Injection-Moulded Polypropylene Composites for Automated Structural Applications

Hybrid fiber/ceramic to polymer matrix combination provides better tensile strength, improved flexural strength, good fracture toughness, durability, improved corrosion resistance, better chemical stability and good thermal behaviour reason; the composites are applied for high strength-to-weight ratio automotive structural applications. The present hybrid polypro-pylene composite is made with constant weight percentages of ramie fiber (chemically treated) and boron nitride (BN) particles (50nm) via an injection moulding machine configured with a hot press. Influences of ramie fiber (biodegradable) and BN on yield-tensile, elongation, and microhardness behaviour of hybrid polypropylene composite was experimentally studied with a statistical significance of 5 % followed by three trials. The composite of polypropylene is fabricated with 12 wt% of ramie (biodegradable) fiber along with BN of 6 wt% of BN and is exposed to superior yield & tensile strength, elongation percentage, and microhardness performance; it is superior to the value of unreinforced polypropylene. The yield & tensile strength & microhardness of polypropylene/12 wt% ramie fiber/ 6 wt% BN are 59.4±0.5MPa, 72.4±0.6MPa, 41.5%, and 53±0.2HV respectively. This polypropylene hybrid nanocomposite with 12 wt% and 6 wt% ramie (chemically treated) fiber and BN is recommended for automated structural application due to its enhanced tensile strength, microhardness, and improved elongation behaviour.

Properties of Multiple-Processed Natural Short Fiber Polypropylene and Polylactic Acid Composites: A Comparison

Natural fiber composites have gained increasing attention due to sustainability considerations. One often neglected aspect is the potential for the mechanical recycling of such materials. In this work, we compounded injection-molded polypropylene (PP) and polylactic acid (PLA) short cellulose fiber composites with fiber shares up to 40 percent by weight. Both matrix materials were reinforced by the addition of the fibers. We investigated a trifold full recycling process, where we subjected the materials produced in the first place to compounding, injection molding, testing, and shredding, and then repeated the process. Although the materials’ properties assigned to degradation were found to decrease with progressive recycling, attractive mechanical properties could be preserved even after the third reprocessing cycle.

Analysis of the Embodied Energy of Different Grades of Injection-Molded Polypropylene

Analysis of the Embodied Energy of Different Grades of Injection-Molded Polypropylene

Machine learning prediction of the mechanical properties of injection-molded polypropylene through X-ray diffraction analysis

ABSTRACT Predicting the mechanical properties of polymer materials using machine learning is essential for the design of next-generation of polymers. However, the strong relationship between the higher-order structure of polymers and their mechanical properties hinders the mechanical property predictions based on their primary structures. To incorporate information on higher-order structures into the prediction model, X-ray diffraction (XRD) can be used. This study proposes a strategy to generate appropriate descriptors from the XRD analysis of the injection-molded polypropylene samples, which were prepared under almost the same injection molding conditions. To this end, first, Bayesian spectral deconvolution is used to automatically create high-dimensional descriptors. Second, informative descriptors are selected to achieve highly accurate predictions by implementing the black-box optimization method using Ising machine. This approach was applied to custom-built polymer datasets containing data on homo- polypropylene and derived composite polymers with the addition of elastomers. Results show that reasonable accuracy of predictions for seven mechanical properties can be achieved using only XRD.

Influence of fly ash on thermo-mechanical and mechanical behavior of injection molded polypropylene matrix composites

Polypropylene composites find widespread application in industries, including packaging, plastic parts, automotive, textiles, and specialized devices like living hinges known for their remarkable flexibility. This study focuses on the manufacturing of polypropylene composite specimens by incorporating varying weight percentages of fly ash particles with polypropylene using a twin-screw extruder and injection molding machine. The composites were comprehensively tested, evaluating tensile, compressive, and flexural strength, solid-state and polymer melt properties, modulus, damping, and thermal response. The findings reveal that the compressive strength of polypropylene increases up to 2 wt% of added fly ash particles and subsequently exhibits a slight decline. Tensile strength demonstrates an increase up to 1 wt% of fly ash, followed by a decrease with a 2 wt% addition, and then a subsequent increase. Flexural strength shows improvement up to 3 wt% fly ash addition before declining. The storage modulus curve is categorized into three regions: the glassy region (up to 0 °C), the glass transition region (0–50 °C), and the glass transition region of polypropylene (>50 °C), each corresponding to different molecular motions. Weight loss curves exhibit similar trends, indicating uniform pyrolysis behavior attributed to consistent chemical bonds. Plastic degradation commences around 440 °C and concludes near 550 °C. Additionally, elemental mapping of fly ash composition identified various elements such as O, Si, K, Mg, Ca, Cl, Na, P, Al, Fe, S, Cu, Ti, and Ni. These findings offer valuable insights into the mechanical and thermal properties of polypropylene composites reinforced with fly ash, rendering them suitable for a wide range of industrial applications necessitating strength and durability across temperature variations.

Tribological and Micro-Mechanical Properties of Injected Polypropylene Modified by Electron Radiation

Today, more and more importance is given to the improvement of polymer materials’ wear resistance, i.e., their micro-mechanical and tribological properties, which could widen their application in practice. The properties of materials can be modified by several methods, among them exposure to electron radiation. This study focuses on the effect of varying radiation intensity (15 kGy to 99 kGy), depth of penetration, and subsequent structure modification of injection-molded polypropylene on tribological and micro-mechanical properties. Electron radiation influences the structure of individual layers, thus improving or degrading their properties. Hence, the depth of penetration can be examined by instrumented hardness tests and scratch tests. Due to irradiation, surface properties and wear resistance increased by up to 105% (from 38 MPa to 78 MPa). As the results show, an increase in mechanical properties was recorded in the direction towards the center of the sample (from 72 MPa to 82 MPa). Micro-mechanical tests were also confirmed by the observation of cross-linking changes (gel test) as well as crystallinity increases (wide-angle X-ray diffraction and microtome cuts). This finding could have a significant effect on the manufacturing and subsequent modification of injection-molded polypropylene parts, which opens new possibilities in practice for this material. The increased surface wear resistance enables the use of parts for which the durability and abrasion resistance of the surface are demanded, especially in applications facing exposure to long-term cyclical loads (e.g., gears).

Rapid, One-Step Sample Processing for Label-Free Single-Cell Proteomics.

Sample preparation for single-cell proteomics is generally performed in a one-pot workflow with multiple dispensing and incubation steps. These hours-long processes can be labor intensive and lead to long sample-to-answer times. Here we report a sample preparation method that achieves cell lysis, protein denaturation, and digestion in 1 h using commercially available high-temperature-stabilized proteases with a single reagent dispensing step. Four different one-step reagent compositions were evaluated, and the mixture providing the highest proteome coverage was compared to the previously employed multistep workflow. The one-step preparation increases proteome coverage relative to the previous multistep workflow while minimizing labor input and the possibility of human error. We also compared sample recovery between previously used microfabricated glass nanowell chips and injection-molded polypropylene chips and found the polypropylene provided improved proteome coverage. Combined, the one-step sample preparation and the polypropylene substrates enabled the identification of an average of nearly 2400 proteins per cell using a standard data-dependent workflow with Orbitrap mass spectrometers. These advances greatly simplify sample preparation for single-cell proteomics and broaden accessibility with no compromise in terms of proteome coverage.

An Approach to the Impact Simulation on Foamed Injection Molded Polypropylene Parts: An Example of Application in the Automotive Industry.

An approach to the simulation of foamed injection molded Polypropylene parts subjected to impact loading is presented in this paper. The proposed method, which considers strain-rate-dependent material properties and the possible occurrence of fracture, is, in particular, suitable for parts manufactured with core-back technology. The method was developed to be used within the functionality of a commercial Finite Element solver using a shell-type element mesh. The material model is based on a three-layer structure, with two compact skin layers and a foamed core layer made of expanded material. The properties of the foamed material are assumed as those of the compact grade scaled by a suitable factor, which is identified via inverse engineering on a set of bending tests executed on specimens having different foam densities. The fracture of the material is then predicted using a damage model which considers the effects of triaxiality. The approach is then validated on industrial parts from the automotive sector, subjected to impact in a component test. Despite the simplicity of the presented approach, which makes this method suitable for industrial applications and especially for early-stage design, the validation shows a sufficiently accurate simulation of part behavior under the impact, with a reasonable prediction of damage and fracture.

Evaluating the Injection Moulding of Plastic Parts Using In Situ Time-Resolved Small-Angle X-ray Scattering Techniques.

In this study, we describe the design and fabrication of an industrial injection moulding system that can be mounted and used on the NCD-SWEET small-angle X-ray scattering beamline at ALBA. We show how highly useful time-resolved data can be obtained using this system. We are able to evaluate the fraction of the material in the mould cavity and identify the first material to solidify and how this varies with the injection temperature. The design follows current industrial practice and provides opportunities to collect time-resolved data at several points within the mould cavity so that we can build up a 4D perspective of the morphology and its temporal development. The quantitative data obtained will prove invaluable for the optimisation of the next generation of injection moulding techniques. This preliminary work used results from the injection moulding of a general-purpose isotactic polypropylene.

Post-Molding Shrinkage, Structure and Properties of Cellular Injection-Molded Polypropylene.

Cellular injection molding is a common method of modifying polymer materials aimed at reducing the sink marks on moldings’ surfaces while reducing their weight. However, the dimensions of polypropylene (PP) samples as well as their mechanical properties after the injection molding process change as a result of re-crystallization. Knowledge of dimensional accuracy and awareness of the change in mechanical properties of products during conditioning are very important aspects in the polymer processing industry. The aim of this study was to assess the changes in the value of processing shrinkage and the size of the sink marks of porous PP moldings depending on the degree of porosity and the time since they were removed from the injection mold cavity. Studies of the structure and mechanical properties of moldings were carried out after several conditioning time intervals. The maximum conditioning time of samples was 840 h at 23 °C. Based on the analysis of the test results, it was found that the cellular injection molding process with the holding phase reduces the nucleation of gas pores, which results in a smaller reduction of sink marks than in the case of samples produced without the holding phase. However, PP moldings with a porosity degree equal to 8.9% were characterized by a higher shrinkage value after 1 h of conditioning, compared to moldings with porosity equal to 3.6%. The extension of the conditioning time also resulted in an increase in the value of linear shrinkage and the properties determined during tensile tests of solid and porous samples. Furthermore, in the case of samples with the highest porosity, the impact strength was reduced by about 30% after 840 h of conditioning compared to results obtained after 1 h.

Design and performance of a flow sensor CoroQuant used with emergency lung ventilator CoroVent during COVID-19 pandemic

At the time of COVID-19 pandemic onset in spring 2020 a project CoroVent was initiated with the aim to design and produce emergency lung ventilators and distribute them to hospitals. No flow and tidal volume sensors were available for the project. The lack of tidal volume sensors was a consequence of the rapidly increased demand for mechanical lung ventilators and their consumables. The aim of the study was to develop a special flow sensor CoroQuant for the CoroVent ventilators. The sensor based on pneumotachographic principle, manufactured by the plastic injection moulding of polypropylene, meets the requirements for precision of tidal volume measurement defined by international standard ISO 80601-2-12 for mechanical lung ventilators. CoroVent ventilators with CoroQuant sensors were distributed to 27 hospitals in the Czech Republic for free upon the requests from the medical facilities and started to be clinically used, thus preventing lack of lung ventilators in hospitals in the Czech Republic.

Study on the Properties of Chemical Foaming Injection Molded Polyolefin/Chitosan Composites

Chitosan is a biodegradable material with good biocompatibility. It can be used in medicine, foodstuff, the chemical industry and heavy metal adsorption. In this study, an exothermic foaming agent (Azodicarbonamide) injection molded was added to polypropylene (PP), maleic anhydride (MA) grafted PP (PPgMA) and Chitosan composites. MA served as a compatibilizer due to the poor bonding between PP and chitosan. This study investigated the effects of the modifier and chitosan loading on the tensile strength, thermal properties and morphology in chemical foam injection-molded PP and PPgMA composites. The results showed that the tensile strength decreased with the addition of chitosan, but Young’s modulus increased with the added chitosan loading. The enhancement was significant for foam injection molding. The cell size decreased and the cell density increased with the addition of chitosan for the PP/PPgMA composites. The thermogravimetric analysis (TGA) results showed that the thermal degradation could be decreased with the addition of chitosan in both the PP and PPgMA composites. The use of foamed chitosan composites will be further investigated in the removal of heavy metal in waste water.

Effect of crystallization and packing pressure on the development of residual stresses on injection molded polypropylene samples

Effect of crystallization and packing pressure on the development of residual stresses on injection molded polypropylene samples

Effect of inhomogeneous mold cavity surface temperature rapid self-cooling on β phase contents and mechanical properties of injection-molded polypropylene

A dynamic self-cooling inhomogeneous temperature gradient field was applied instead of steady-state temperature at the mold cavity surface to study the effect of different cooling rates on the crystallization progress after the melt flow. The results showed that both the crystallinity and the β phase content increased with the gradient of the inhomogeneous mold temperature. When the mold temperature gradient of the high-temperature and the low-temperature sides increased from 0 to 40 °C, the size of the shish-kebab in the shear layer and the amount of small β phase spherulites in the transition layer increased. During the melt flows, a cavity temperature gradient higher than 30 °C was required to increase the stability of β phase in the transition layer. The yield stress and the elongation at break increased with the temperature gradient, but decreased at the temperature gradient of 45 °C.

Effect of Gas Counter Pressure on the Surface Roughness, Morphology, and Tensile Strength between Microcellular and Conventional Injection-Molded PP Parts.

Microcellular injection-molded parts have surface defect problems. Gas counter pressure (GCP) is one of the methods to reduce surface defects. This study investigated the effect of GCP on the surface roughness, morphology, and tensile strength of foamed and conventional injection-molded polypropylene (PP) products. GCP is generated by filling up the mold cavity with nitrogen during the injection-molding (IM) process. It can delay foaming and affect flow characteristics of microcellular and conventional injection-molding, which cause changes in the tensile strength, flow length, cell morphology, and surface quality of molded parts. The mechanism was investigated through a series of experiments including tuning of GCP and pressure holding duration. Surface roughness of the molded parts decreased with the increase in GCP and pressure holding duration. Compared to microcellular IM, GCP-assisted foaming exhibited much better surface quality and controllable skin layer thickness.

Investigation on surface roughness of injection molded polypropylene parts with 3D optical metrology

Investigation on surface roughness of injection molded polypropylene parts with 3D optical metrology

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

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.

Creep study of glass reinforced polypropylene: Effect of temperature and presence of notches

Short fibers reinforced injection molded parts are commonly used in the applications under sustained loads. This requires creep resistance and creep behavior predictions under both short- and long-term service conditions.This article studies the creep behavior of injection molded polypropylene with short glass fibers at different temperatures and in the presence of a notch. The produced samples were analyzed by means of FT-IR (Fourier-transform infrared spectroscopy) and TGA (thermogravimetric analysis) to obtain and indication on microstructure and fiber content, respectively. Visible light microscopy was used to analyze the fiber orientation. Mechanical properties were measured using tensile testing. Tensile creep testing in an internally fabricated lever-type creep machine at a controlled constant temperature was conducted on plain specimens and specimens with machined notch. Fracture surfaces were analyzed by means of SEM (Scanning Electron Microscopy).Both creep strength and time to failure decrease with increasing temperature following the power law models. Norton’s power law and Monkman-Grant’s relationship can estimate the time to rupture not only of plain specimens, but also notched, if the stress is amplified by the stress concentration factor. These results can potentially estimate lifetime of injection molded parts with stress concentrations at elevated temperatures.

Accessioning and automation compatible anterior nares swab design

The COVID-19 pandemic has resulted in an unparalleled need for viral testing capacity across the world and is a critical requirement for successful re-opening of economies. The logistical barriers to near-universal testing are considerable. We have designed an injection molded polypropylene anterior nares swab, the Rhinostic, with a screw cap integrated into the swab handle that is compatible with fully automated sample accessioning and processing. The ability to collect and release both human and viral material is comparable to that of several commonly used swabs on the market. SARS-CoV-2 is stable on dry Rhinostic swabs for at least 3 days, even at 42 °C, and elution can be achieved with small volumes. To test the performance of the Rhinostic in patients, 119 samples were collected with Rhinostic and the positive and negative determinations were 100 % concordant with samples collected using Clinical Laboratory Improvement Amendments (CLIA) use approved nasal swabs at a clinical lab. The Rhinostic swab and barcoded tube set can be produced, sterilized, and packaged cost effectively and is designed to be adopted by clinical laboratories using automation to increase throughput and dramatically reduce the cost of a standard SARS-CoV-2 detection pipeline.