A thermoplastic polyurethane (TPU) series for automotive panels with high durability have been newly synthesized using the reacting process based on polyester polyol (BTG), polycaprolactone triol (PCL), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 1,4-butanediol chain extender as a function of NCO/OH ratio (NCO index). The dependence of varying NCO index of synthesized TPUs on tensile strength and hardness have evaluated. To form PU foams with suitable rigidity and uniform skin-pores, the optimal synthetic process was controlled precisely by the amount of solvent, foaming agent, silicone surfactant, and catalysts content. A considerable NCO index dependence was observed in the range of 0.96 ≤ NCO index ≤ 0.99 at almost same molecular weight. When NCO index of TPU was 0.98, mechanical properties achieved maximum value due to the uniform open cell structure of molding PU foam. With the ratio of NCO/OH increasing, the hardness of PU foam also increased until 0.98 NCO index while the hardness of 0.99 NCO index decreased. The designed TPU with 0.98 NCO could be a promising formulation for molding foams of automotive skin panels and seating.

Urethane acrylate (UA) was synthesized from various di-polyols, such as poly(tetrahydrofuran) (PTMG, Mn = 1000), poly(ethylene glycol) (PEG, Mn = 1000), and poly(propylene glycol) (PPG, Mn = 1000), for use as a polymer binder for paint. Polymethyl methacrylate (PMMA) and UA were blended to form an acrylic resin with high transmittance and stress-strain curve. When PMMA was blended with UA, a network structure was formed due to physical entanglement between the two polymers, increasing the mechanical properties. UA was synthesized by forming a prepolymer using di-polyol and hexamethylene diisocyanate, which were chain structure monomers, and capping them with 2-hydroxyethyl methacrylate to provide an acryl group. Fourier transform infrared spectroscopy was used to observe the changes in functional groups, and gel permeation chromatography was used to confirm that the three series showed similar molecular weight and PDI values. The yellowing phenomenon that appears mainly in the curing reaction of the polymer binder was solved, and the mechanical properties according to the effects of the polyol used in the main chain were compared. The content of the blended UA was quantified using ultravioletvisible spectroscopy at a wavelength of 370 nm based on 5, 10, 15, and 20 wt%, and the shear strength and tensile strength were evaluated using specimens in a suitable mode. The ratio for producing the polymer binder was optimized. The mechanical properties of the polymer binder with 5–10 wt% UA were improved in all series.

In the current study, an acrylic polymer binder applicable to road signs was successfully developed by mixing various acrylic, acrylate-type, and photoinitiator-based monomer species at different acrylate series/silicone acrylate ratios. An amorphous acrylic monomer was used, and the distance between the polymers was increased to improve transparency. The binder was designed with the purpose of reducing the yellowing phenomenon due to resonance by excluding the aromatic ring structure, which is the main cause of yellowing. The optical properties of the binder were determined according to the content of n-butyl methacrylate/methyl methacrylate and the composition of the crosslinking agent in the formulation. Allyl glycidyl ether and dilauroyl peroxide were used to improve the yellowing problem of benzoyl peroxide, an aromatic photoinitiator. Adding a silicone-based trivalent acrylic monomer, 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), was also found to have a significant effect on the transparency, shear properties, and water resistance of the binder. When 15 wt% TMSPMA was added, the best water repellency and mechanical properties were exhibited. The surface morphology of the improved binder and the peeling part were confirmed using field emission scanning electron microscopy. The acrylic polymer developed in this study can be applied in the coating and adhesive industries.

Triol acrylic-urethane (t-AU) was synthesized from an addition reaction using trimethylolpropane, hexamethylene diisocyanate, and 2-hydroxyethyl methacrylate. The novel acrylic-urethane polymer was applied to a high-performance binder to prepare a reliable road marking paint. Acrylic-urethane polymer binder formulations were designed to optimize the effect of t-AU on the physical properties. The t-AU content in the formulation affected the adhesion and optical properties. The improvement in the adhesive performance and transparency ability for road markings was attributed to the optimal chemical structure or design of the acrylic-urethane polymer. The synthesis of t-AU was confirmed by Fourier transform infrared spectroscopy, and molecular weight and polydispersity index (PDI; PDI = M_w/M_n) measurements. The tensile and shear strength, hardness, gel fraction, crosslink density, contact angle, and transmittance of the acrylic-urethane polymer binder (AUP) were evaluated by curing at room temperature using a redox initiator system. An optimized AUP by adding 5 wt.% t-AU provides a viable alternative to high-performance binders in road marking paints.