Thermoplastic Polyolefin Research Articles

Structural Characterization of Polysaccharides Isolated from Panax notoginseng Medicinal Residue and Its Protective Effect on Myelosuppression Induced by Cyclophosphamide.

This study aims to establish the isolation and purification method of polysaccharides from medicinal residue of Panax notoginseng (PPN). The structure and protective effect of PPN on myelosuppression mice were investigated. One neutral polysaccharide (NPPN) and five acidic polysaccharides (APPN I, APPN II-A, APPN II-B, APPN III-A, and APPN III-B) were obtained. The results confirmed that NPPN, APPN I and APPN II-A are glycan with 1, 4 main chains. APPN III-A is a glycan. APPN II-B and APPN III-B are homogalacturonan pectin with 1, 4 main chains. This study demonstrated that NPPN played a bone marrow protective role in myelosuppression mice induced by cyclophosphamide. NPPN could relieve cell cycle arrest, reduce the apoptosis rate of marrow cells, and improve granulocyte-macrophage colony-stimulating (GM-CSF), thermoplastic polyolefin (TPO) and erythropoietin (EPO) serum level, which contributes to promoting the proliferation of hematopoietic cells.

Systematic analysis and nanoscale chemical imaging of polymers using photothermal-induced resonance (AFM-IR) infrared spectroscopy

In this work, a reliable and time-saving protocol for the measurement of polymers using photothermal-induced resonance (AFM-IR) at the nanoscale was developed and applied to 4 industrially relevant polymers: a polypropylene-based reactor thermoplastic polyolefin (rTPO), linear low density polyethylene (LLDPE) for molding and two recycled post-consumer polypropylene/polyethylene blends. In addition to the morphology obtained through AFM, we were able to identify and image the major components of each polymer, including the mineral fillers (talc and calcium carbonate) present in each blend using nanoscale spatial resolution infrared imaging. The protocol developed allows the quick analysis and identification at the nanoscale of the major components of a blend without having previous knowledge of the sample composition, a major advantage when compared to other traditionally used imaging techniques such as TEM and SEM.

Valorization of Recycled Tire Rubber for 3D Printing of ABS- and TPO-Based Composites.

Vulcanized and devulcanized ground tire rubber microparticles have been used as a minor phase in acrylonitrile butadiene styrene copolymer (ABS) and thermoplastic polyolefins (TPO) for the development of materials with desired functionalities by 3D printing. These polymers have been selected because they (i) present part of the plastic waste generated by the automotive industry and (ii) have totally different properties (ABS for its stiffness and robustness and TPO for its softness and ductility). The study aims to improve the circular economy of the automotive industry by proposing a promising route for recycling the generated tire rubber waste. In this respect, emergent technology for plastic processing such as 3D printing is used, as part of the additive manufacturing technologies for the prolongated end of life of recycled plastics originated from automotive waste such as ABS and TPO. The obtained results revealed that (i) the composites are suitable for successful filament production with desired composition and diameter required for successful 3D printing by fused deposition modeling, and that (ii) the optimization of the composition of the blends allows the production of materials with interesting mechanical performances. Indeed, some of the investigated ABS-recycled rubber tire blends exhibit high impact properties as TPO-based composites do, which in addition exhibits elongation at break higher than 500% and good compression properties, accompanied with good shape recovery ratio after compression.

Comparing the effects of ultraviolet radiation on four different encapsulants for photovoltaic applications in the Atacama Desert

The performance of photovoltaic modules is highly dependent on the properties of the materials used to build them and is particularly sensitive to the type of encapsulant in the case of harsh outdoor environments. In this study, we compared the effects of ultraviolet (UV) radiation, under laboratory accelerated aging conditions, of four encapsulants: thermoplastic olefin, thermoplastic polyurethane, silicone, and ethylene vinyl acetate. The operation of the indoor ultraviolet chamber, using a mercury/xenon arc lamp as a radiation source, was related to the Atacama Desert ultraviolet conditions to estimate the corresponding time under outdoor conditions. The total indoor experiment time corresponded to 24.7 years of UV-B and 1.34 years UV-A irradiation. Transmittance in the ultraviolet–visible range, together with Raman spectra were analyzed to assess the effect of ultraviolet degradation. The aged encapsulants showed a transmittance reduction between 2% and 5% and a displacement in the ultraviolet cut off to higher wavelengths of around 5 nm. This information was used to compute the potential effect on the photogenerated current density of crystalline silicon photovoltaic modules, which decreased between 1% and 4%. Raman spectroscopy indicated the degradation of the encapsulants’ polymer structure as an increment in the fluorescence of the spectra, above 50%, and modifications in the relative intensities of the encapsulant́s active Raman modes.

Investigation of structure-morphology-function relationship of plastomers used to produce low mold shrinkage thermoplastic olefins

Thermoplastic Polyolefins (TPOs) are one of the most commonly used polymeric materials in automotive industry due to their better elastomeric properties compare to commercial polyolefins. Thermoplastic polyolefin (TPO), or olefinic thermoplastic elastomers are prepared by mixing a polyolefin usually copolymer polypropylene and a plastomer in certain fraction in order to improve elastomeric properties. One of the most challenging problems in automotive industry during the production of these materials is to control the mold shrinkage of TPOs since the parts having very high aspect ratio such as bumper, exterior trims, glass run channel are produced by those materials. Therefore, this paper intends to produce TPO formulations with minimum mold shrinkage by focusing on to optimize the mechanical properties. For that purpose, TPO formulations were prepared by melt blending of plastomers having different physical/mechanical properties into a polyolefin phase. The relationship between structure of plastomer and the function of final product TPO was tried to be explained by structural characterization and molecular dynamic (MD) simulations. In terms of mold shrinkage values and mechanical properties the optimum TPO compound is found to be “sample A” containing 70% plastomer with medium crystallinity and 30% copolymer PP. It shows low mold shrinkage values in parallel (0,19%) and perpendicular (0,2%) to flow direction and optimum tensile strength (13,4 MPa), tear strength (74,4N/mm) and elongation at break (815%) results. Findings of this study is useful in understanding the micro-events taking place during compound process of PP with plastomers, and to explain the necessary PP-plastomer ratio with desired mechanical traits.

An Investigation on Some Mechanical Properties of the Tuft Carpets Produced by Homopolymer, Copolymer and Thermoplastic Polyolefin Mixed Polypropylene Bulked Continuous Filament Yarns

There are several parameters that affect the mechanical properties of carpets such as yarn characteristic and carpet construction. Yarn material is one of the most important factors which determine the usage performance of carpets by consumers. This study investigated the mechanical behaviours of carpets produced from polypropylene (PP) bulk continuous filament (BCF) yarns with not only homopolymer but also copolymer and thermoplastic polyolefin mixed. In this respect, ten carpet samples produced by different type of BCF yarns as pile were examined. Experimental results indicated that mixing polypropylene homopolymer with copolymer or thermoplastic polyolefin resulted with improvement in thickness loss and resilience properties. In addition, thermoplastic polyolefin included yarn exhibited higher performance compared to copolymer mix in both dynamic and static loading. PP BCF yarn type had considerable influences on compressibility behaviours of carpets, whereas there was no significant effect on tuft withdrawal force.

Dynamic Semicrystalline Networks of Polypropylene with Thiol-Anhydride Exchangeable Crosslinks.

Thermoplastic polyolefins (TPOs) crosslinked by dynamic covalent bonds (xTPOs) have the potential to be the most utilized class of polymer in the world, with applications ranging from household and automotive to biomedical devices and additive manufacturing. xTPO combines the benefits of thermoplastics and thermosets in a “single material” and potentially avoids their shortcomings. Here, we describe a new two-stage reaction extrusion strategy of TPOs with a backbone consisting of inert C–C bonds (polypropylene, PP), and thiol-anhydride, to dynamically crosslink PP through thiol-thioester bond exchange. The degree of PP crosslinking determines the rubber plateau modulus above the melting point of the plastic: the modulus at 200 °C increases from zero in the melt to 23 kPa at 6% crosslinking, to 60 kPa at 20%, to 105 kPa at 40%. The overall mechanical strength of the solid xTPO plastic is 25% higher compared to the original PP, and the gel fraction of xTPO reaches 55%. Finally, we demonstrate that the crosslinked xTPO material is readily reprocessable (recycled, remolded, rewelded, and 3D printed).

A Mixed Numerical-Experimental Method to Characterize Metal-Polymer Interfaces for Crash Applications

Metallic (M) and polymer (P) materials as layered hybrid metal-polymer-metal (MPM) sandwiches offer a wide range of applications by combining the advantages of both material classes. The interfaces between the materials have a considerable impact on the resulting mechanical properties of the composite and its structural performance. Besides the fact that the experimental methods to determine the properties of the single constituents are well established, the characterization of interface failure behavior between dissimilar materials is very challenging. In this study, a mixed numerical–experimental approach for the determination of the mode I energy release rate is investigated. Using the example of an interface between a steel (St) and a thermoplastic polyolefin (PP/PE), the process of specimen development, experimental parameter determination, and numerical calibration is presented. A modified design of the Double Cantilever Beam (DCB) is utilized to characterize the interlaminar properties and a tailored experimental setup is presented. For this, an inverse calibration method is used by employing numerical studies using cohesive elements and the explicit solver of LS-DYNA based on the force-displacement and crack propagation results.

Mechanical properties and foaming behavior of polypropylene/elastomer/recycled carbon fiber composites

AbstractResearch on lightweight products for transportation industry, to address fuel efficiency and lower carbon footprint, has attracted great attention due to public environmental awareness. Polymer composites containing carbon fiber are boosted by automotive original equipment manufacturers (OEMs) as a replacement for steel. However, their high cost has generated interest to find cost‐effective alternatives. In this report, a recycled carbon fiber and an elastomer are introduced to polypropylene impact copolymers to modify matrix properties in terms of strength and toughness. Fractography analysis is carried out to elucidate the failure mechanisms governing the mechanical performance of the compatibilized carbon fiber reinforced thermoplastic polyolefin (TPO) composites. The results suggest that for the TPO composites, toughened by an ethylene‐1‐octene copolymer, the complex interplay of intrinsic and extrinsic toughnesses in impact resistance is predominantly governed by the presence of the fibers. Incorporating 20 wt% recycled carbon fibers into the matrix resulted in an improvement of the heat distortion temperature (HDT) by 100 °C, and ~ 3.5 and ~ 11.5 times enhancements in tensile strength and stiffness, respectively. Moreover, microcellular foams with expansion ratios higher than 11 and 5 were achieved for the neat samples and reinforced composites, respectively, confirming the foamability of composites with such a high carbon fiber content.

Life cycle assessment on PERC solar modules

With the pursuit of high photoelectric conversion efficiency in the photovoltaic market, passivated emitter and rear cell (PERC) modules has become the new market mainstream. The environmental impact of PERC modules requires life cycle assessment (LCA) methods to analyze. The SimaPro software was used to calculate the environmental impacts, such as global warming potential (GWP), human toxicity potential – cancer effects (HTP-CE), human toxicity potential-non-cancer effects (HTP-nCE), freshwater ecotoxicity potential (FEcP), freshwater eutrophication potential (FEuP) and abiotic depletion potential (ADP) of mono-facial and bifacial (dual-glass encapsulation and transparent back-sheet encapsulation) PERC modules prepared using 158.75 mm, 166 mm and 210 mm silicon wafers. The rear side gain of a bifacial module increases its electricity generation in the Use stage, and thereby making bifacial module achieve better environmental performance than mono-facial module. In order to improve the rear side gain of bifacial module, it is usually necessary to select an appropriate ground reflective material in system design. The LCA results show that the waterproof membrane TPO (Thermoplastic Polyolefin) is a very good choice, and white gravel and grassland can also be considered in landscape design point of view. Whether to choose dual-glass encapsulation or transparent back-sheet encapsulation, has little effect on the overall environmental impact of bifacial modules. In addition, adding recycling in the photovoltaic industry chain can significantly reduce the overall environmental impact of photovoltaic modules, especially in the indicators such as ADP, HTP-CE and FEuP.

Effect of mold temperature and additive migration on scratch behavior of TPOs at elevated temperatures

Scratch performance of thermoplastic olefins (TPOs) has been considered one of the required properties for automotive applications. The scratch resistance of TPOs can be enhanced by utilization of commonly used slip additives such as erucamide. When TPOs are injection molded, the mold temperature impacts the migration of the slip additive toward the surface and the surface crystallinity of the TPOs, which has been shown to influence scratch resistance. In order to evaluate the effect of the mold temperature and erucamide migration on scratch behavior at elevated temperatures, this research has adopted the ASTM D7027/ISO 19252 linearly increasing normal load scratch test methodology to investigate the scratch behavior of the model TPOs at 25 °C, 50 °C, and 75 °C. This study provides a comprehensive understanding on the effects of mold temperature, slip additive, elevated testing temperature, and thermal aging on scratch behavior of TPOs.

The encapsulation of intumescent flame retardants by poly-siloxane for thermoplastic polyolefin: Fire safety and water resistance

The flammability of thermoplastic polyolefins (TPO) is a prior concern related to fire disasters. The fire safety strategy for TPO has not been settled because of serious waterproof property deteriorations caused by the presence of flame retardant additives. This work reported an encapsulation of conventional intumescent flame retardant (IFR) additives by a poly-siloxane (Si-IFR) and its application in TPO composites. The fire behavior characterization revealed that the peak heat release rate and smoke density of the TPO/Si-IFR sample was decreased by 26.5% and 24.0% respectively compared with that of the TPO/IFR sample. The flame retardant mechanism analysis suggested that the poly-siloxane coated IFR formed compact char layers through Si-O structures and nano-silica attachment on the carbonous layer. Notably, the flame retardancy and mechanical property for the TPO/Si-IFR sample were almost unchanged after being soaked in water for 7 days at 70°C. Consequently, this work proved that the poly-siloxane encapsulated IFR was an effective additive for producing flame retardant and water resistant TPO composites.

Verifying the reliability of the steam-jet test on coated thermoplastic olefin substrates by a semi-quantitative peel test

The steam-jet test is a standard method to evaluate adhesion of coated lacquer on different substrates in automotive industry. Besides metals, most common for exterior parts is coated injection molded talc filled thermoplastic olefin (TPO). This material often shows high spreading and partially substrate participation in its failure modes. To examine the validity of the steam-jet test on coated TPO, different adhesion qualities are produced by varied flame treatment of the substrate and subjected to the well-known steam-jet test as well as to the peel test. The peel test requires a fabric, embedded inside the coating to measure the peel force, when pulling off the lacquer. Surface characterization is done by XPS and light microscopy. We show that the steam-jet test does not allow even qualitative differentiation between the two best adhering samples. The error is of the order of magnitude of the mean value. By contrast, the peel test showed that the binding force to the substrate is higher than its interior strength and therefore both best adhering samples provide similar peel forces. As a result, the steam-jet test was found to have significant weaknesses in testing coated talc filled thermoplastic olefins.

Damp heat resilient thermoplastic polyolefin encapsulant for photovoltaic module encapsulation

Thermoplastic polyolefin (TPO) is a non-crosslinking material used in photovoltaic module encapsulation. TPO thermal degradation and its weather stabilities are still not known. In this work, TPO laminates were prepared and subjected to extended damp-heat weather test. TPO encapsulant properties were studied and compared with the most commonly used encapsulant, Ethylene-Vinyl Acetate (EVA). Four times lower rate of transmittance loss and increment rate in the yellowness index values have been found for TPO compared to EVA laminate. Damp-heat induced degradation mechanism, and its components were studied using Raman and Fourier-transform-infrared (FTIR) spectroscopy. Raman spectra revealed that the carbonyl group loss rate at the edge is one order of magnitude higher than the center. FTIR has shown a higher rate of acetic acid and hydroxyl group formation in EVA as compared to the TPO. FTIR also demonstrated that TPO has a lower water absorption because of its nonpolar nature, whereas EVA shows more water absorption due to its polar nature. The rate of change in thermal properties of TPO and EVA encapsulants were studied through the heat-cool-heat cycle. A higher rate of increment in the degree of crystallinity is found for EVA as compared to the TPO encapsulant during the extended damp-heat acceleration test. This study helps to understand the TPO and EVA encapsulants degradation behavior, degradation components, and mechanism to the encapsulant researchers and PV module manufacturers when a PV module experiences the hot-humid conditions. This TPO may result in the industry adopting the different PV modules for fabricating.

Improving the Mechanical Properties of Thermoplastic Polyolefins Using Recycled Low-Density Polyethylene and Multi-Walled Carbon Nanotubes

Thermoplastic polyolefin (TPO) has gained considerable attention because of having a combination of rubbery and thermoplastic properties and ease of production. Their excellent weather resistance, low density, and relatively low cost make them attractive materials for the automotive, electrical, footwear industries and membranes for water treatment. Their main shortcomings are poor mechanical properties, especially at low temperatures because of the opposing trends of stiffness and toughness. In this paper, recycled low density polyethylene (RLDPE) was integrated with ethylene-propylene-diene rubber (EPDM) incorporating very low content of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) to improve the mechanical properties of the produced TPO nanocomposite. TPO has been prepared through the combination of 40, 50, and 60 wt.% RLDPE and 40, 50, and 60 wt.% EBDM. The improved TPO composition was then reinforced with 0.1, 0.3, and 0.5 wt.% MWCNTs-COOH to produce TPO nanocomposites. The compounding of TPO and its nanocomposites was done by melt mixing followed by heat pressing. Mechanical and thermal behaviors of the TPO nanocomposites were investigated. Tensile tests showed that the TOP (60-40) is the best improved concentration; the storage modulus of nanocomposites was enhanced by increasing MWCNTs-COOH concentration. In addition, modulus, stress/strain and toughness of TPO were enhanced by adding 0.5 wt.% MWCNTs-COOH. Thus, MWCNTs-COOH reinforced TPO due to not only its large aspect ratios but also due to its interaction with both the TOP matrix and the combatibilizer. The results of microstructural investigations of the prepared TPO nanocomposite using FTIR and TGA confirmed the interaction between MWCNTs-COOH and TPO matrix

Three‐dimensional multi‐ribbon interconnection for back‐contact solar cells

AbstractBack‐contact solar cells are an interesting technology with advantages over traditional two‐sided cells. A lack of standardized and low‐cost interconnection methods inhibits their market penetration. In an attempt to overcome this obstacle, this work introduces an interconnection technology, based on a fabric of encapsulant with incorporated metal ribbons. The encapsulant is tailored for this application by adding glass fibres to a thermoplastic polyolefin. For this tailored encapsulant, characterization experiments were conducted and results on viscosity and coefficient of thermal expansion are shown. Initial reliability testing on sample‐size modules with high‐efficiency interdigitated back‐contact (IBC) cells shows promising results, passing up to four times the IEC 61215 standard for thermal cycling.

Comparison of Degradation Behavior of Newly Developed Encapsulation Materials for Photovoltaic Applications under Different Artificial Ageing Tests.

The main focus of this work is to investigate the degradation behavior of two newly developed encapsulants for photovoltaic applications (thermoplastic polyolefin (TPO) and polyolefin elastomer (POE)), compared to the most widely used Ethylene Vinyl Acetate (EVA) upon exposure to two different artificial ageing tests (with and without ultraviolet (UV) irradiation). Additive composition, optical and thermal properties and chemical structure (investigated by means of Thermal Desorption Gas Chromatography coupled to Mass Spectrometry, UV-Visible-Near Infrared spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis and Fourier Transform-Infrared spectroscopy, respectively) of the analyzed polymers were monitored throughout the exposure to artificial ageing tests. Relevant signs of photo-oxidation were detectable for TPO after the UV test, as well as a depletion of material’s stabilizers. Signs of degradation for EVA and POE were detected when the UV dose applied was equal to 200 kW h m−2. A novel approach is presented to derive information of oxidation induction time/dose from thermogravimetric measurements that correlate well with results obtained by using oxidation indices.

Bridging the gap between rubbers and plastics: a review on thermoplastic polyolefin elastomers

Thermoplastic elastomers (TPE) are studied for their unique properties of being easily processes and recycled. This paper focuses on the wide scope of thermoplastic polyolefin elastomers (TPO/TPE-O) which is one of the major classes of TPE. The performance of TPO is the cumulative effect of polyolefins and rubbers with the ease of processing due to the presence of thermoplastics. The study focuses on the classification of TPO, their routes of synthesis, composites, applications, and its impact on environment. The mechanical blending of polyolefins and conventional rubber was carried out to manufacture TPO. In further developments, the polyolefin elastomers (POE) were synthesized by copolymerization techniques to overcome the drawback of mechanical blending techniques. Environment-friendly blends of TPO are synthesized using industrial and municipal waste which includes scrap rubber tires, marble waste-filled polypropylene, computer body waste, etc. This technology will help in reducing the issue of landfills. The composites of TPO have been studied using different types of fillers which may be synthetic or bio-based. These include talc, carbon black, carbon nanotubes (CNT), Kenaf fiber, pineapple leaf fiber, etc. TPO have found their use in encapsulation, in electrical insulation, roofing, medical devices, and the automobile industry. Also, impact of using TPOs on environment is discussed here qualitatively.

Properties and degradation behaviour of polyolefin encapsulants for photovoltaic modules

AbstractVarious types of next‐generation encapsulation films based on polyolefins have recently been introduced and could attract market attention. These material innovations can be classified as polyolefin elastomer (POE) and thermoplastic polyolefin (TPO) encapsulants, both of which consist of a polyethylene backbone with different side groups. The main advantage of these materials is the replacement of the vinyl acetate side groups of state‐of‐the‐art encapsulant ethylene vinyl acetate (EVA) so that acetic acid cannot be formed. The main objective of this paper is to investigate the material properties of next‐generation encapsulant films and compare them to an EVA reference. Two commercially available EVA alternatives (POE and TPO) have been selected. The material properties of single films as well as the electrical performance of test modules using these different encapsulants were investigated. The different films show comparable optical, thermal and thermo‐mechanical properties, with slight differences in UV transparency and melting temperatures. Only shear viscosity values are higher for TPO than for POE and EVA, which requires adaption of the photovoltaic (PV) module lamination parameters. The test modules comprising the different encapsulation films show minor differences in the electrical performance after manufacturing; upon accelerated aging, no significant power loss is observed. But compared to TPO or POE, after 3000 h of damp heat exposure, test modules with EVA show the beginning of corrosion effects at the silver grid and above the ribbons. Based on the results, it can be stated that the new polyolefin encapsulation materials show great potential to be a valid replacement for EVA.

Phase-field modeling of electric-thermal breakdown in polymers under alternating voltage

In this work, a phase-field model is presented to characterize the breakdown properties of polymers under alternating voltage. The breakdown status is described with a spatially and time dependent continuous variable, and the evolution of damage phase is driven by the electrostatic and thermal energy in the system. The relationship between breakdown strength and material properties such as permittivity and dielectric loss can be represented with the phase-field model. For thermoplastic polyolefin with low permittivity and dielectric loss, the electric breakdown is probably the dominant mechanism at room temperature. For other polymers, the breakdown characteristics may be dominated by the electrothermal mechanism. The dielectric loss of polymers increases with temperature, which intensifies the thermal energy and further reduces the breakdown strength. Dielectric loss of polymers with high glass transition temperature increases slowly, and they can keep high breakdown strength at high temperatures.