Reducing Moisture Absorption in Polypropylene Nanocomposites for Automotive Headlamps Using Hydrophobicity-Modified Graphene/Montmorillonite.

Polypropylene (PP) is used as a housing material in automotive headlamps but can cause fogging as a result of absorbed moisture and temperature differences between the exterior and interior of the housing. In this study, PP was combined with a graphene/montmorillonite hybrid (MMT-G) to yield a nanocomposite with reduced moisture absorption. Crucially, the modified nanofiller had low hydrophilicity and good compatibility with the PP matrix. Notably, the water contact angle of the MMT-G improved by 676%. Furthermore, the maximum moisture absorption of the PP/MMT-G nanocomposites was reduced by up to 11.22% compared to that of commercial PP composites, and the weight of the headlamp housing was decreased by 3.6%. Therefore, the designed nanocomposites are expected to help mitigate headlamp fogging while slightly reducing the housing weight.

Light control using vertically aligned dichroic dye films for windshield antireflection in automotive displays.

A vertically aligned dichroic dye (VA-Dye) film, whose absorption axis is perpendicular to that of its substrates, was laminated on a display panel in which the absorption axis of the top polarizer was set to 0°. In the vertical viewing angle of the display panel, the absorption axes of the top polarizer and dichroic dye are at right angles to each other, and, so, the light emitted from the display panel can be blocked. In the horizontal viewing angle of the display panel, the absorption axes of the top polarizer and dichroic dye are parallel to each other so that the light emitted from the display panel can be transmitted. Based on these polarization optics, we achieved complete elimination of light emitted in the upward or downward direction of the display panel, while the light emitted to the left and right is transmitted. We also added a designed optical compensation film using a positive biaxial (+B) retarder to the VA-Dye film so that the light emitted in the upward and downward directions of the display panel could be blocked in a wide viewing angle range (not only in the vertical direction, but also in the diagonal direction). The display panel using the VA-Dye film with the +B retarder showed excellent optical performance, such as significantly lower transmittance over a wide viewing angle range in the upward direction and relatively higher transmittance compared to that of a reference panel without the VA-Dye film. In addition, the VA-Dye film can be manufactured with a lower thickness, easier fabrication, and lower cost when compared with other technologies.

Durability and Service Life Prediction of Fluorocarbon Elastomer under Thermal Environments.

This study investigated the service life prediction of fluorocarbon elastomers that are used in automotive vapor fuel hoses under thermal environments. The changes in mechanical properties such as the tensile strength, elongation, compression set (CS), and hardness according to thermal aging were investigated for two types of ternary fluoroelastomers. Destructive tests of the tensile strength and elongation showed large variations in the mechanical properties under the same condition because there is no continuity of samples. In contrast, nondestructive tests of the CS and hardness showed little variations in the mechanical properties under the same condition. The elongation, CS, and hardness were selected as the physical parameters for service life prediction as they showed a tendency according to the aging temperature, which is an accelerating factor. The effective activation energy derived using each physical parameter was 74.91-159.6 kJ mol-1, and the service life was 17.8-140 × 103 h based on B10. In this study, hardness, which has a small deviation between samples, is considered appropriate as mechanical parameter for predicting the service lifetime.

Tribological Properties of Polyamide 46/Graphene Nanocomposites.

Polyamide 46 (PA46) is used in various automotive parts because of its excellent heat resistance and mechanical properties. This study aims to improve the frictional properties of PA46 using the lubricating ability of graphene. Nanocomposites are prepared via two mixing methods: Graphene powder is compounded directly with PA46 pellets through a twin-screw extruder, or PA46 powder is added to graphene dispersion for self-adsorption, and subsequently, it is dried and compounded with PA46 through the twin-screw extruder. Application of the nanocomposite in the friction field is evaluated via the pin-on-disk method. The coefficient of friction of the nanocomposite prepared by self-adsorption is lower than that of the nanocomposite prepared by direct compounding. The mechanical properties of the nanocomposite fabricated by self-adsorption are superior to those of other materials. This can be attributed to the uniform dispersion of graphene and the strong attractive force between the PA46 matrix and graphene.

Synthesis of polyurethane foam from ultrasonically decrosslinked automotive seat cushions.

In this study, we have investigated the recycling of flexible polyurethane foam (PUF) using an ultrasonic reactor. Waste PUF of automotive seat cushions were subjected to ultrasonic horn oscillation of various amplitudes at different flow rate. Successful decrosslinking of ultrasonically treated waste PUF was confirmed by thorough characterizations such as gel fraction, crosslink density, and thermal property. Decrosslinked PUFs were blended with the virgin PUF in various proportions to prepare the recrosslinked PUFs. Automotive seat cushions made of the blended PUFs exhibit enhanced comfort than that of the virgin PUFs by lowering the hardness and hysteresis loss and increasing the sag factor.

Drug release characteristics from nanoclay hybrids and their dispersions in organic polymers.

This study establishes and compares structure-property-processing relationships on three drug delivery systems containing an anionic active pharmaceutical ingredient (API) in the following excipient carriers: (a) an inorganic anionic nanoclay, (b) pH responsive acrylic polymers, and (c) combinations thereof. The effects of the excipients on the APIs dissolution rate were studied from their release profile in simulated body fluids (SBFs) with different pH. In the API-nanoclay system, calcination of the clay followed by its reconstitution in an API solution was successfully used to intercalate the API in its amorphous state in the clay. As a result, the API showed increased apparent solubility vs. its crystalline form with its release mechanism from the clay being predominantly diffusion controlled and depending on the pH of the SBFs. In melt mixed ternary polymer systems containing the above hybrids, as a result of an additional diffusional step due to presence of nanoplatelets, the API showed a more controlled release vs. polymer systems that contained only API. By comparison to the low pH SBF, the ternary system in the pH 7.4 SBF showed a reduced diffusion contribution due to the presence of clay platelets, the latter unaffected by the high pH value. Reasonable agreement was found with predictions from literature diffusion/erosion models. It is confirmed that hot melt mixing offers opportunities to produce systems with enhanced API apparent solubility. The presence of nanoclays can also increase the API's apparent solubility and affect its release in a controlled manner.

Synthesis of highly monodisperse polystyrene microspheres via dispersion polymerization using an amphoteric initiator.

The highly monodisperse polystyrene (PS) microspheres were produced by dispersion polymerization using an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057). The polymerization characteristics were investigated and compared with conventional initiators, 2,2-azobis(isobutyronitrile) (AIBN) and benzoyl peroxide (BPO). The monodisperse PS microspheres having the coefficient of variation (C(v)) of diameter all less than 4% are obtained at very low stabilizer, poly(vinyl pyrrolidone) (PVP) concentrations of 1 and 2 wt%. It is found that the size dependence of the VA-057 system, D(n) proportional, variant [VA-057](0.267), is less sensitive than a conventional initiator system. When the same amount, 2 wt%, of AIBN, BPO, and VA-057 is used under the identical PVP concentration of 2 wt%, the D(n)/C(v)'s are 1.95/11.57, 1.47/22.44, and 2.08 microm/2.50%, respectively. The uniformity of particles was characterized employing an optical analyzer, Turbiscan. For the VA-057 system, the back scattering intensity is linearly reduced with time having a constant sedimentation rate of 48.98 microm/min throughout the settling process. The uniformity of PS particles in the VA-057 system stems from (1) the higher rate of polymerization in early stage of polymerization, followed by significantly faster reduction of the rate, and (2) good dispersion stability of primary particles. Therefore, it is found that the use of an amphoteric initiator, VA-057, is promising for producing monodisperse particles in dispersion polymerization.