Influence of Phase Separation on Performance of Graft Acrylic Pressure-Sensitive Adhesives with Various Copolyester Side Chains

Influence of UV Polymerization Curing Conditions on Performance of Acrylic Pressure Sensitive Adhesives

Acrylic pressure sensitive adhesives (PSAs) were prepared by UV polymerization under varying curing conditions of both fast and slow curing, employing high- and low-intensity UV radiation, respectively. The influences of curing conditions and isobornyl acrylate (IBOA) content on PSA performance were comprehensively investigated by measurement of their rheological, thermal, and adhesive properties. In particular, rheological characterization was accomplished by several analytical methods, such as in situ UV rheology, frequency sweep, stress relaxation, and temperature ramp tests, to understand the effect of the UV curing process and IBOA content on the viscoelastic behavior of acrylic PSAs. The slow-cured samples were observed to form more tightly crosslinked networks compared to the fast-cured. On the other hand, at high loading levels of IBOA, in the case of slow curing, the sample exhibited a contrasting trend, having the shortest stress relaxation time and the highest energy dissipation; this was due to molecular chain scission occurring in the crosslinked polymer during UV polymerization. Consequently, we successfully demonstrated the influence of monomer composition of acrylic PSAs, and that of curing conditions employed in UV polymerization. This study provides valuable insights for the development of crosslinked polymer networks of acrylic PSAs for flexible display applications.

Polyolefin graft copolymers through a ring-opening metathesis grafting through approach

A series of polyethylene-g-atactic polypropylene graft copolymers were synthesized by grafting through copolymerization of a cyclooctene terminated aPP macromonomer with cyclooctene monomer and subsequent hydrogenation.

Change of Characterization and Film Morphology Based on Acrylic Pressure Sensitive Adhesives by Hydrophilic Derivative Ratio

Hydrophilic acrylic pressure-sensitive adhesives (PSAs) were synthesized by controlling the contents of 2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA), and 2-hydroxyethyl acrylate (HEA); especially, the characteristic change of the HEA content was analyzed. Surface contact angle of acrylic PSA film decreased from 77.87° to 70.23° in the case of Acryl-2 to Acryl-8 (below HEA 10 wt %). However, the surface contact angle of Acryl-10 to Acryl-40 (HEA 10 wt % to 40 wt %) increased up to 92.29°, indicating hydrophobicity. All acrylic PSA films showed high adhesive force above 1800 gf/25 mm. According to X-ray diffraction (XRD) measurement, hydrophilic acrylic PSAs exhibited amorphous property and it was confirmed that the morphology of acrylic PSA film was significantly affected by the flexibility of the polymer chain and the strength of hydrogen bonding. The affinity with hydrophilic materials for acrylic PSA films was evaluated by T-type peel test, confirming that the affinity with hydrophilic materials is determined by the hydrophilicity of the acrylic PSA film. The synthesized acrylic PSA film is non-toxic regardless of the hydrophilicity.

Stiffening, strengthening, and toughening of biodegradable poly(butylene adipate-co-terephthalate) with a low nanoinclusion usage

Simultaneous stiffening, strengthening, and toughening of biodegradable polymers, such as poly(butylene adipate-co-terephthalate) (PBAT) and others, is necessary for their use in packaging and agriculture applications. However, a high content of nanoinclusions is usually required, leading to a tradeoff between composite toughness and strength or stiffness in the reinforcement. Herein, we report an iterative reinforcement strategy that uses one nanocomposite to reinforce PBAT. An in-situ grafting polymerized cellulose nanocrystal (CNC)/PBAT (CNC-g-PBAT) nanocomposite consisting of ungrafted/free PBAT (PBAT_f) was used as an inclusion directly to reinforce a commercial PBAT. At an exceptionally low CNC usage of 0.02 wt.%, we achieved a simultaneous enhancement of the Young's modulus by 26 %, tensile strength by 27 %, elongation at break by 37 %, and toughness by 56 % over those for PBAT. To the best of our knowledge, such reinforcement efficiency is the highest among similar biodegradable polymer nanocomposites reported in the literature. The rheology, differential scanning calorimetry, and wide-angle X-ray diffraction measurements confirmed the mechanical reinforcement attributed to a synergistic contribution from PBAT_f and CNC-g-PBAT. In particular, the use of PBAT_f enhanced both stiffness and toughness of the composites, while the CNC-g-PBAT interacted within the polymer matrix and increased the crystallinity of the polymer matrix, leading to the strengthening and toughening effect. The strategy proposed here is greatly beneficial to producing high-performance biodegradable polymer nanocomposite films for packaging and agricultural applications using a very low amount of nanoinclusion.