Automotive Interior Research Articles

Rheology and FTIR-based tools for analyzing thermal-induced physical aging of polyurethane coatings for automotive interior plastic parts

Polyurethane (PU) coatings for automotive interior parts are frequently exposed to high temperatures, particularly in extreme environments such as deserts and equators, which cause thermal aging. Although both physical and chemical processes are involved in aging, most previous studies have focused on thermal-induced chemical degradation of PUs. Herein, the physical aging of PU coatings was investigated in the aging temperature range of 80–130 °C based on rheological and spectroscopic analyses. Dynamic mechanical analysis indicated that the thermal aging of PUs is strongly correlated with the glass transition temperature (Tg) of the hard segment (HS). For PU consisting of acrylic and ester polyols and hexamethylene diisocyanate trimer, the thermal aging at 80–130 °C increases the Tg of HS from 91 (fresh) to 118–126 °C (aged films). In particular, the aging was accelerated above the Tg. While the Tg of 130 °C-aged films exceeds 110 °C in 1 d of the aging, that of 80 °C-aged films reached over 110 °C in 7 d of the aging. This result is ascribed to the densification of hard domains: 1.7-fold higher activation energy (391 kJ mol−1) of 130 °C-aged PU than that of fresh PU (234 kJ mol−1) indicates the restricted segmental motion of HS in densified domains. In addition, constructing a two-dimensional gradient map of FTIR can be used to determine whether aging involves physical or chemical processes.

Impact of Zinc Oxide Addition on Oil Palm Empty Fruit Bunches Foamed Polymer Composites for Automotive Interior Parts

The sustainable use of agricultural waste to generate valuable products while minimizing environmental burdens is increasing rapidly. Multiple sources of fibers have been intensively studied concerning their application in various fields and industries. However, few publications have extensively discussed the property's performance of oil palm empty fruit bunches (OPEFB) composites. With main properties similar to composites currently listed for industrial applications, OPEFB is worth listing as a potential composite for industrial applications and non-structural material alternatives. OPEFB-reinforced polymer composites are expected to be applied to automotive interior parts. This study aims to determine the effect of adding zinc oxide (ZnO) and polyurethane on OPEFB-reinforced polymer composites for automotive interior parts. This composite was produced using the hand lay-up method with 70% resin, 15% OPEFB fiber, 15% polyurethane as a blowing agent, and four variations of ZnO at 5%, 10%, 15%, and 20%. The OPEFB particle sizes are 40, 60, 80, and 100, respectively. The composite was examined to determine mechanical, morphology, chemical, and thermal characteristics. It was observed that the addition of 20% ZnO caused ZnO agglomeration, weakening the interfacial bond between OPEFB particles, polyester, polyurethane, and ZnO filler. Overall, the results showed that adding ZnO and polyurethane to the composite increased tensile, compressive, flexural, and impact strength, as well as thermal stability with more significant values up to 160%, 225%, 100%, 100%, and 4.3%, respectively. This result depicted that the best composition was specimens with 15% ZnO and 149 microns OPEFB fibers particle size. It is considered a promising candidate to be applied in automotive interior components.

Analytical and parametric analysis of interface stress behaviour in nanoclay/polymer composite

Nowadays, nanoclay-reinforced polymers are one of the most widely used nanocomposites due to their high aspect ratio, higher contact area and their unique properties. These composites are used in a number of industrial applications, such as construction (building sections and structural panels), automotive (gas tanks, bumpers, interior and exterior panels), chemical processes (catalysts), pharmaceutical (as carriers of drugs and penetrants), aerospace (flame retardant panels and high performance components), food packaging and textiles, etc. Their interphase properties are essential for determining their proper design and safety application when applying large mechanical loads on them. In this work, a parametric analysis is performed to investigate how the change in the interphase properties influences the interphase shear stress (ISS) and interphase peel stress (IPS) in a nanoclay/polymer nanocomposite structure, subjected to axial load. The two-dimensional (2D) stress-function method is applied, which results in obtaining an analytical solution for ISS and IPS. The implemented parametric analysis shows how varying of the interphase mechanical properties (Young's modulus and Poisson's ratio) and their geometric properties (thickness and length) influence the value of the model interphase stresses. It was found, that increasing the value of Young modulus of the interphase does not change significantly the value of the model ISS, as well as the value of IPS, in the considered nanoclay/polymer structure. On the other hand, increasing the value of the interphase layer thickness becomes important for the value of ISS and IPS after 25nm. It turned out, that the interphase layer length is the most appreciable parameter, influencing both the model ISS and IPS. The obtained results could be useful for the proper design and safety application of similar nanoclay/polymer composites in industry.

Solid wood processing with acetic acid when creating elements of automotive interior

Since the appearance of the first automobiles, the wood due to its advantages, such as ease of processing and noble appearance, has firmly entered the automotive world as a material for body engineering and interior finish. However, fairly rough operating conditions of the automobile (variable humidity, possible contact with water) require protection of wooden elements. This paper provides the results of a study of modified wood by acetylation with acetic acid. Experimental data showed that moisture absorption decreased depending on the duration of wood veneer treatment in glacial acetic acid from 43% to 21%. An increase in the limiting wetting angle value was found - 460, 580 and 690 as compared with the control sample (100). The mass gain after keeping the samples for 6, 12, 18, 24 and 30 hours in glacial acetic acid ranged from 1.2 to 4.8% by mass as compared to the control sample (due to the introduction of acetyl groups). Based on the results of acquired data, it can be concluded that this method of wood treatment allows reducing moisture absorption, minimizing swelling and, as a result, increasing the shape stability of wooden products for the automotive industry.

Development and application of nonwovens based on palm fiber as reinforcements of unsaturated polyester

This work aims to investigate the potential of nonwovens made from untreated (U) and alkaline/bleaching treated (T) palm, wool, and polyester fibers as reinforcing materials in polyester matrix for automotive interior applications. Four needle-punched nonwovens were developed and used with and without chloropropyltriethoxysilane (CPTS) treatment as polyester matrix fillers. Eight composite panels were made using the resin transfer molding machine process and compared to the matrix panel in terms of physical, mechanical, thermal, and climate resistance. The produced composite materials have smooth surfaces and provide consumers with four different aesthetically pleasing finishes. The physical results reveal that the UPalm/Wool and UPalm/Polyester nonwovens lower matrix density from 1223.3 Kg/m3 to 1022.3 and 1040.7 Kg/m3, respectively. The SEM images show that palm fibers are more adherent to the matrix after being treated with an alkaline/bleaching solution. This adhesion is also improved after nonwovens are treated with the CPTS precursor. The composite reinforced with CPTS-treated TPalm/Polyester nonwoven has the highest tensile strength and modulus (72.1 MPa and 3.76 GPa), which are 127% and 36% greater than those of the polyester matrix, respectively. The matrix’s flexural strength and modulus are also enhanced by 148% and 59%, respectively, after reinforcing with CPTS-treated TPalm/Polyester nonwoven. The use of TPalm/Wool and TPalm/Polyester nonwovens as polyester matrix fillers reduces their thermal conductivity from 0.125 W/(m.K) to 0.081 and 0.095 W/(m.K), respectively. Moreover, the climate aging results indicate that composites reinforced with CPTS-treated nonwovens are more stable to climate, implying their applicability and durability in automotive interior applications.

Environment-friendly Polyurethane Beads for Automotive Interiors

Environment-friendly Polyurethane Beads for Automotive Interiors

Experimental and finite element analysis on the sound absorption performance of wedge-like knitted composite

Limited by the single mechanism of sound absorption, most current sound-absorbing materials exhibit difficulties in balancing weight and acoustic performance. In this work, a flexible wedge-like knitted composite (WKC) realized by knitting and coating technology with multiple sound-absorbing mechanisms including porous sound absorption mechanism and wedge-like structure resonant mechanism is proposed. To study the influence mechanisms of coating and wedge structure on the sound absorption performance, experiment and finite element analysis were both conducted. By improving the porosity distribution through the addition of viscoelastic layer, the sound absorption coefficient (SAC) is enhanced by 239%, which is originated from the infiltrated silica gel into the fabric pores, increasing the complexity of the penetration path. The wedge structure plays a necessary role on enhancing the sound absorption coefficient under low frequency because the concave–convex surface of wedge generates stronger resonance of rear air cavity. The size effect of wedge shape is analyzed in terms of acoustic vibration angle and acoustic energy dissipation density. The increase of the acoustic vibration angle increases the reflection collision path and speed of sound vibration, which further enhances the energy dissipation. Therefore, the combination of viscoelastic coating layer and wedge structure effectively promote the sound absorption, especially at low frequency. This work provides guidance for the structural design and realization of innovative flexible sound absorbing materials, which is promising in application prospect of indoor curtain interiors, wall coverings and automotive interiors.

Characterization of Water Repellent and Flame Retardant Finished Cotton Canvas Fabric for Bivouac Tents

Water repellency and flame retardancy have applications in many fields, such as automotive interiors, indoor decorations, upholstery, outdoor clothing and tents. Cotton, having superior qualities, is considered one of the best raw materials for tent manufacture. The study has undertaken the application of different water repellent and flame retardant chemicals on 100% cotton canvas fabric to be used as bivouac tents. The purpose was to find suitable water repellent and flame retardant chemicals that can be applied in a single bath or in a two-step process to give the desired repellency and retardancy effect. Initially, two screening sets were carried out, which aided in the identification of best-performed chemicals to be used in the combined application of water repellent and flame retardant. In the combined application, the fabric was finished using two approaches. In the first approach, both repellent and retardant chemicals were prepared in a single bath, and in the second approach, the fabric was first finished with flame retardant chemicals and then finished with water repellent chemicals. In both the approaches, the finished fabric was evaluated by a cone test, a hydrostatic pressure head test and a flammability test against locally set requirements. It is concluded that the procedure of single bath water repellent and flame retardant finishes (SBWRFR1b) showed reduced pickup percentage (60%) and resulted in better water repellency and flame retardancy properties, in comparison to other procedures and series of recipes.

Impact of Evening Light Exposures with Different Solid Angles on Circadian Melatonin Rhythms, Alertness, and Visual Comfort in an Automotive Setting.

Future automotive interior lighting might have the potential to go beyond decorative purposes by influencing alertness, circadian physiology, and sleep. As the available space in the interior of an automobile for lighting applications is limited, understanding the impact of various luminous surface sizes on non-image-forming effects is fundamental in this field. In a laboratory study using a within-subject design, 18 participants were exposed to two bright light conditions with different solid angles and one dim light condition in a balanced, randomized order during the course of the evening. Our results demonstrate that both light conditions significantly increased subjective alertness and reduced salivary melatonin concentration but not cognitive performance compared to dim light. The solid angle of light exposure at constant corneal illuminance only affected visual comfort. While subjective alertness can be increased and melatonin can be attenuated with rather small luminaires, larger solid angles should be considered if visual comfort is a priority.

Recycled Multi-Material Packaging Reinforced with Flax Fibres: Thermal and Mechanical Behaviour.

In this work, the use of a recycled mix stemming from the treatment of multilayer aseptic packaging used in the food and beverage industry is proposed as the matrix for short fibre composites reinforced with flax fibres, to generate value-added materials in contrast to the more common end-of-life scenario including energy recovery. This is expected to be a preferred choice in the waste hierarchy at the European level. A commercially available material (EcoAllene) obtained from multilayer packaging recycling was compounded with short flax fibres up to 30 wt.% by twin screw extrusion, with a view to enhancing its poor mechanical profile and broadening its applications. Composites were in depth analyzed by thermogravimetric analysis and differential scanning calorimetry, which highlighted the complex nature of this recycled product, a limited nucleation ability of flax fibres and a lower thermal stability due to the premature degradation of natural hemicellulose and cellulose, though featuring in any case onset degradation temperatures higher than 300 °C. Composites’ mechanical properties were assessed in tension, bending and impact conditions, with remarkable improvements over the neat matrix in terms of stiffness and strength. In particular, at 30 wt.% fibre content and with 5 wt.% of maleated coupling agent, an increase in tensile and flexural strength values by 92% and 138% was achieved, respectively, without compromising the impact strength. The effectiveness of flax fibres confirmed by dynamo-mechanical analysis is beneficial to the exploitation of these composites in automotive interiors and outdoor decking applications.

A Study on Over-Molded Copper-Based Flexible Electronic Circuits.

Over-molding has been proposed in recent years as an integrated functional flexible circuit board in a plastic part. This method uses the conventional process for film insert technology. Over-molding has attracted significant attention across many industries due to its potential to deliver different electrical functions in a variety of different part geometries, especially in automotive interiors and home appliances. While it has great application potential, manufacturing challenges continue throughout foil fabrication and injection molding. This raises challenges for designers and researchers responsible for maintaining the reliability of such electronic flexible circuits. Therefore, the purpose of this research paper is to improve some of the over-molding process parameters. On 0805 and 1206 over-molded zero-ohm resistors, electrical, mechanical, and failure characterization was performed. Those components were mounted in parallel, perpendicular, and 45° angled arrangements on two different polymer substrates, polyimide (PI) and polyethylene terephthalate (PET) using lead-free solder, low-melt solder, and conductive adhesive paste. Moreover, as an over-molding material, polycarbonate (PC) with medium viscosity was used. The effect of using different mold shapes (corner mold, 2 mm flat mold, and 3 mm flat mold) and injection molding process parameters (injection speeds and melt temperature) was studied.

In situ nanofibrillar fully-biobased poly (lactic acid)/poly (ethylene 2,5-furandicarboxylate) composites with promoted crystallization kinetics, mechanical properties, and heat resistance

To save resources and improve energy efficiency, an efficient, economical, and environmentally friendly technology is needed to produce high-performance poly (lactic acid) (PLA). However, the poor heat resistance of PLA greatly restricts its application in packaging materials and other fields. Herein, a scalable and efficient method was developed to fabricate high-performance PLA by combining bio-based nanofibrillar reinforcing material. In-situ nanofibrillar PLA/ poly (ethylene 2,5-furandicarboxylate) (PEF) composites were successfully obtained using a fast and straightforward melt extrusion and spinning process. PEF nanofibers with a high aspect ratio were well dispersed in PLA matrix with an average diameter of 80 nm, which dramatically enhanced the rheological properties, crystallization kinetics, and dynamic mechanical properties of PLA. Unprecedently, such fully bio-renewable PLA/PEF nanofibers composites exhibited excellent heat resistance. With the addition of 3 wt% PEF, the heat resistance of PLA was significantly increased from approximately 59.6 to 157 ℃. This environmentally-friendly in-situ nanofibrillar PLA/PEF composites with high heat resistance will potentially broaden the application of PLA in areas like packaging materials and automotive interiors.

Tactile and visual perception of plastic textures for car interiors: Psychophysical and affective dimensions

Surface textures play an important role in the perception of consumer products. In car interiors, they are a major contributor to the perceived quality of a vehicle. However, limited attention has been paid to the affective responses elicited by touch and observation of a textured surface. Here we report an investigation in which Kansei Engineering was used to explore the perception of texturized plastic surfaces, both in its psychophysical and affective dimensions, as well as the influence of the textures’ physical parameters. In a controlled study, 21 subjects were asked to touch 18 samples of two types of plastics, commonly used in car interiors, Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS), under tactile (only touch) and visual-tactile (touch and vision) conditions. Participants were asked to rate the samples according to 8 descriptors of psychophysical and affective nature. Results show a relation between perceived roughness and the positive/negative valence of the affective response. Importantly, this relation is moderated by the visual appearance of the textures, when these are visible. Both psychophysical and affective dimensions were modelled through height parameters of the texture elements and a variable describing the type of material. The present findings are relevant for the understanding of visual-tactile perception of textures and have implications in the design of textured components for automotive car interiors.

Colorimetric Array Electronic Nose for Automotive Interior Material Odor Detection

This study aims to detect the odor intensity levels of automotive adhesive tapes accurately, efficiently, and non-destructively. A 35-array colorimetric sensing test paper was developed using a polyvinylidene fluoride (PVDF) laminated test paper as the substrate and an acid-base solvent to detect the odor substances volatilized from the automotive interior materials. Detection experiments results show that the main odor substances volatilized from the automotive tape samples were aldehydes, ketones, acids, and ethers, changing colors at the relevant spots of the corresponding test paper. Hierarchical clustering analysis (HCA), principal component analysis (PCA), and partial least squares regression (PLSR) show that the colorimetric array test paper could accurately identify the different odor intensities of the automotive tape samples. To test the detection level of the colorimetric electronic nose on the odor intensity of other automotive tapes, a separate automotive tape sample prediction utilizes the electronic nose. All predicted odor intensity values of the separate automotive tape sample deviated by less than 0.4 from the subjective evaluation results and by less than 0.5 from the subjective evaluation results. Thus, the objective prediction model based on the colorimetric electronic nose can be used for detecting automotive adhesive tapes with different odor intensities.

Methodology for Sound Quality Analysis of Motors for Automotive Interior Parts through Subjective Evaluation.

With the development of autonomous vehicles, activities in the indoor spaces of autonomous vehicles are diversifying. Therefore, as the operating range of the interior parts increases, the occupant becomes sensitive to the operating noise of autonomous vehicles. Therefore, to reduce operating noise, it is necessary to analyze the causal relationship between the mechanical/electrical noise characteristics of the motor and sound quality. In this paper, we propose a methodology to analyze the relationship between the noise frequency components and the sound quality of small motors used in automobile interior parts. Two types of motors were selected for this study, and noise measurements and analyses were performed by applying the design proposed in this study. Subjective sound quality evaluations were conducted using the 12 pairs of adjectives extracted from the survey. The results suggest that subjective sound quality evaluation scores should be converted to Z-scores to ensure the reliability of the statistical analysis. In addition, we present a critical sound quality value that can be used as a criterion for determining whether the sound quality is positive (good quality) or negative (bad quality). Sound quality regression models explain the causal relationship between rotational frequency components of the motor and subjective sound quality characteristics. Thus, a method for analyzing the effect of the rotational frequency component of the motor on the sound quality is presented, which suggests that it can be used as basic research data to improve the noise performance of the motor.

Novel Method for Failure Modes Detection in UV-Cured Clear Coated Polymer for Automotive Interior Mechatronic Devices.

Plastic parts used in automotive interior are difficult to coat, due to their low surface energies as well as their sensitivity to temperature and solvents, rendering the development of coating systems for such substrates challenging. Automotive customer requirements are explicit and clear, mainly focused on functional and surface defects. A new failure modes detection methodology of UV clear coated polymers for automotive interior, obtained by a multi-step manufacturing process, is proposed. The polymer complex parts analyzed in this paper are manufactured in various steps as follows: two components plastic injection molding, primer coating, laser engraving, and UV-cured clear coating. The failure modes detection methodology of the parts within each process step is investigated using different tests and analyses as follows: surface tension test, painting adhesion test, optical 3D measuring, energy dispersive X-ray analysis (EDX), and microscopy. A design of the experiments (DoE) based on the Taguchi technique with the aim to detect the influence of the main factors that lead to surface defects was performed. The proposed methodology is validated by a case study. The results showed that the mold temperature and the laser engraving current have a significant influence on the surface defect occurrence. Additionally, a possible contamination of the molding tool can generate the defects. A solution to reduce the occurrence of the failures was proposed, reducing the defect rate from 50% to 0.9%.

Microwave-assisted foaming and sintering high-strength and antistatic polypropylene bead foams by constructing conductive 3D skeleton structure

Polypropylene (PP) bead foam parts, one of the most widely used automotive interiors, are traditionally welded by high-pressure steam, while their large inter-bead gaps result in the poor mechanical properties. Herein, syndiotactic polypropylene (sPP) powders, with low melting point, coated with carbon nanotubes (CNTs) were adopted as the microwave absorbing medium to weld the surface of expanded isotactic polypropylene (EiPP) beads, which were initially prepared by supercritical carbon dioxide (scCO2) foaming. Then, the modified EiPP (EiPP coated with CNTs@sPP powders, denoted as mEiPP) composite foams were successfully fabricated by microwave-assisted foaming and sintering. The obtained foam part consisted of porous iPP bead structure (body) and interconnected CNTs@sPP pathway (3D skeleton), which showed superior mechanical properties with tensile strength of 4.07 MPa and compressive strength of 4.64 MPa (10 % strain). Due to the conductive 3D skeleton, the requirements of antistatic PP bead foams could be sufficed with the lower CNTs loading.

One‐step flame retardant/hydrophobic finishing on cotton fabric with ammonium salt of hexamethylenediamine ‐ N, N, N′, N′ ‐ tetra (methylphosphonic acid) doped silica sol

AbstractWith the rapid development of textile technology, single‐function textile finishing is difficult to meet the current needs of people for textiles. Textiles with flame retardancy, superhydrophobicity, UV resistance, and other functions are increasingly favored by people. At present, most of the preparation processes of multifunctional textiles are complex and time‐consuming. In this work, a flame retardant hexamethylenediamine tetramethylene phosphate ammonium salt of hexamethylenediamine ‐ N, N, N′, N′ ‐ tetra (methylphosphonic acid) (AHDTMPA) was synthesized using hexamethylenediamine tetramethylene phosphate (HDTMPA) and urea with aqueous solution as solvent. Then AHDTMPA and cetyltrimethoxysilane were added into the solution with methyl trimethoxysilane (MTMOS) and tetraethyl orthosilicate (TEOS) as precursors to obtain a multifunctional sol. Finally, the multifunctional cotton fabric can be obtained by immersing the cotton fabric in the multifunctional sol in one‐step. The limiting oxygen index (LOI) and water contact angle (WCA) value of the finished cotton fabric was 27.6% and 131.4°, respectively. The FT‐IR characterization results and the SEM analysis verified the synthesis of AHDTMPA. The micro calorimeter combustion (MCC) and thermo gravimetric (TG) analysis indicated that the finished samples had less heat release capacity and less weight loss. The smoke density test showed good smoke suppression of the finished cotton fabric. Moreover, the whiteness of finished samples was nearly unchanged. In this work, the flame retardant and hydrophobic multi‐functional cotton fabric was prepared by one‐step, and the method is simple and efficient. The prepared functional cotton fabrics can be widely used in home textile fabrics, automotive interior fabrics, clothing fabrics, flags, tents, and protective clothing.

Investigation on the Mechanical Properties of Flax/False Banana Hybrid Fiber-Reinforced Polymer Composite

The intent of this research is to develop new material from flax and false banana fiber hybrid reinforced polymer composite using polyester resin as a matrix to replace synthetic fiber-reinforced polymer composites for automotive interior bodies. The composite samples were fabricated based on the weight percentage of fibers/matrix and the orientation of the fibers that were combined with Taguchi’s experimental design using the hand layup fabrication process. And also, single flax and single false banana fiber-reinforced polymer composite was fabricated with the same composition and orientation alone. The composite was tested for tensile and flexural strength properties, and it had been discussed and specimens were prepared according to ASTM standards. As a result, false banana showed better flexural strength than false banana fiber-reinforced composite for tensile strength, whereas the hybrid composites of 25% of flax, 15% of false banana, and unidirectional orientation have shown the maximum tensile and flexural strength with a value of 113.4 MPa and 167.88 MPa, respectively.

Circularity in mixed-plastic chemical recycling enabled by variable rates of polydiketoenamine hydrolysis.

Footwear, carpet, automotive interiors, and multilayer packaging are examples of products manufactured from several types of polymers whose inextricability poses substantial challenges for recycling at the end of life. Here, we show that chemical circularity in mixed-polymer recycling becomes possible by controlling the rates of depolymerization of polydiketoenamines (PDK) over several orders of magnitude through molecular engineering. Stepwise deconstruction of mixed-PDK composites, laminates, and assemblies is chemospecific, allowing a prescribed subset of monomers, fillers, and additives to be recovered under pristine condition at each stage of the recycling process. We provide a theoretical framework to understand PDK depolymerization via acid-catalyzed hydrolysis and experimentally validate trends predicted for the rate-limiting step. The control achieved by PDK resins in managing chemical and material entropy points to wide-ranging opportunities for pairing circular design with sustainable manufacturing.