Yongping Bai

Deciphering the mechanism of corona discharge treatment of BOPET film

The effect of corona discharge treatment on biaxially oriented polyethylene terephthalate (BOPET) film was investigated. The BOPET film and corona treated BOPET film were characterized by ATR-FTIR, XPS, SEM and AFM. It was found that many polar functional groups were generated on the surface of corona treated BOPET film and that this surface was etched after corona discharge treatment. Based on the results of the observations and analysis, a mechanism for the corona discharge treatment of BOPET film is proposed and the reactions that occur upon this treatment are put forward in detail.

Temperature-dependent decaying mechanism of BOPET corona films

BOPET corona films undergo a decrease in surface energy with time, a so called decaying effect, which has become a serious and widely known problem which prohibits their downstream industrial applications and needs to be carefully understood. Herein, the decaying behaviors and dynamics of decaying BOPET corona films in hot air were studied carefully by measuring water contact angle and surface tension and variable angle XPS. It was found that the molecular mechanism for the decaying effect involves migration of polar groups from the surface to the interior, and the decaying process is highly dependent on temperature. In addition, it was also found that such a temperature-dependent decay process is related to the glass transition of BOPET, and the glass transition temperature (Tg) can be predicted through analysis of the dynamics.

Influence of selected photoinitiators type II on tack, peel adhesion, and shear strength of UV-crosslinked solvent-borne acrylic pressure-sensitive adhesives used for medical applications

This article describes the photoreactive UV-crosslinkable solvent-borne acrylic pressure-sensitive adhesives (PSA) containing unsaturated copolymerizable photoinitiators and their synthesis. The solvent-borne acrylic PSA were synthesized in ethyl acetate as a solvent, and the copolymerizable photoinitiators type II, known as hydrogen abstractors, were incorporated into acrylic polymer chain during conducted radical polymerization process. The synthesized solvent-borne acrylic PSA containing different unsaturated photoinitiators were investigated to evaluate their relevant and significant properties such as tack, peel adhesion, and shear strength after UV exposure.

The functionalization of fluoroelastomers: approaches, properties, and applications

This review seeks to give an overview of different approaches to prepare functional fluoroelastomers for modern industries. These approaches can be divided into three main families of alternatives. The first extensively describes the preparation of telechelic fluoroelastomers based on chemical degradation. Carboxyl-terminated fluoroelastomers are usually achieved via a typical degradation process, which then can be changed into various functional group-terminated fluoroelastomers. The second deals with functionalization of fluoroelastomers through grafting reactions. Conventional strategies, such as radical polymerization, dehydrofluorination and sulfonation, are used to graft single or faintness functional monomers onto fluoroelastomers. Reversible deactivation radical polymerization, however, provides quantitative copolymers containing unique functional groups. The third alternative route, namely functionalized copolymerization, concerns two main types: functionalization of an initiator and functionalization of monomers. In several cases, both will be utilized to synthesize special functional fluoroelastomers. In addition to the three approaches, the properties and applications of processed fluoroelastomers are illustrated to explore their functions and influences after functionalization.

Synthesis and properties of soap-free P(2-EHA-BA) emulsion for removable pressure sensitive adhesives

Pressure sensitive adhesives (PSAs) are materials that can adhere strongly to solid surfaces under a light contact pressure for a short time. Soap-free emulsion polymerization of 2-ethylhexyl acrylate and n-butyl acrylate has been performed in the presence of a reactive emulsifier SR-10 to obtain high adhesion properties of PSAs. The particle size distribution was quite narrow with an average diameter of 137 nm. The FT-IR spectrum showed that the CC bonds contained in the monomers disappeared during the reaction. The DSC result showed that all the monomers were well copolymerized. The 180° peel strength could reach 183.2 N m−1 when SR-10 was 2 wt% and the ratio of 2-EHA to BA was 4 to 1. The tack was 13 #. The shear holding time was more than 100 h. The removable PSA tapes produced from the resulting soap-free emulsion showed good adhesion properties and stabilities, which are suitable for practical applications.

Fluorinated polyurethane based on liquid fluorine elastomer (LFH) synthesis via two-step method: the critical value of thermal resistance and mechanical properties

Until now, only few hydroxy-terminated fluorinated monomers were reported as soft segment. In this work, based on a novel hydroxy-terminated liquid fluorine elastomer (LFH), a series of FPUs were synthesized via a two-step method. Flexible soft segment polytetrahydrofuran glycol (PTMG) was applied as the second soft segment. FTIR and GPC results indicated that the fluorinated groups were introduced into the structures of copolymers, and all the monomers were copolymerized successfully. TGA, DMTA and conventional mechanical analysis show that FPU gains optimal thermal stability and mechanical properties when the dosage of LFH is increased to a critical value of 18 wt%, even after the cured films being immersed into hot water and oil. Additionally, the surface properties of FPUs can be highly changed as a small amount of fluoride (6 wt%) is introduced into the structures of copolymers, due to the effect of fluorine enrichment. Consequently, LFH can effectively improve the thermal stability, mechanical properties, water resistance and organic solvent resistance of polyurethane within limits. Besides, these mentioned controllable properties of FPU can be achieved by changing the dosage of LFH. This work will help to achieve the best balance between performance and cost in industrial production.

Catalytic property of poly(ethylene terephthalate-co-isophthalate) synthesized with a novel Sb/Al bimetallic compound catalyst

In this paper, the hydrolysis process of aluminum subacetate (AlSA) was studied by Fourier transform infrared (FT-IR), 27Al nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and particle size distribution analysis, and poly(ethylene terephthalate-co-isophthalate) (PETI) was synthesized by using a compound catalyst made of its hydrolysate, γ-AlOOH, and ethylene glycol stibium (EGSb). Meanwhile, the effects of the γ-AlOOH addition stage on the catalytic effect and the relative properties of the polyester were investigated. The results showed that the Sb and Al compound catalyst had obvious synergistic effects on the process of the polyester polycondensation. With the same dosage of catalyst, the usage of EGSb and the polycondensation time were reduced by 60% and 18.6%, respectively, and the diethylene glycol content in the polyester also decreased by using the compound catalyst, compared with that obtained when only using the EGSb catalyst. The use of γ-AlOOH could play a catalytic role and also shows a unique crosslinking center, which could improve the melting point and glass transition temperature.

UV-initiated crosslinking of photoreactive acrylic pressure-sensitive adhesives using excimer-laser

UV-initiated crosslinking technology is well established in the market and allows the production of a wide range of ultraviolet (UV)-crosslinkable pressure-sensitive adhesives (PSA) with interesting features. The balance between such properties as adhesive and cohesive strengths within the crosslinked self-adhesive coatings is critical for their performance. The UV crosslinking of acrylic PSA, especially for following properties: tack, peel adhesion, and shear strength of self-adhesive polymer layers, has been investigated using UV excimer-laser and UV lamp as UV sources. It was observed that after UV crosslinking of acrylic PSA using excimer-laser in comparison with typical UV lamp, high-quality PSA products with excellent properties, such as tack, peel adhesion, shear strength, and shrinkage were received.

Interface manipulation of CO2–philic composite membranes containing designed UiO-66 derivatives towards highly efficient CO2 capture

Both material choice and filler/organic interface are crucial in mixed matrix membranes (MMMs) for sub-nano-size gas separations and yet, the interface–performance relationship is still a subject of intense debate due to challenging interfacial detection. Herein, two UiO-66-type MOFs (amino-functionalized UiO-66-NH2 and isopropenyl-functionalized UiO-66-MA) are incorporated in cross-linked CO2–philic polyethylene oxide (PEO) matrix based on judicious material screening for CO2 capture. The reactive material UiO-66-MA is stitched together with methacrylate-capped PEO in situ during UV-induced copolymerization to generate highly efficient gas transport passages with conceivably good interfaces. Poor interface is observed by substituting UiO-66-MA with non-reactive UiO-66-NH2 in MPCM (MOF/polymer composite membrane). The interfacial conditions of CO2–philic MPCMs are carefully assessed via advanced physicochemical characterizations for clarifying the correlation between interface and separation performance. The reactive material UiO-66-MA containing MPCM with good interface demonstrates higher gas permeability (up to 1450 barrers) with similar selectivity (up to 45.8 for CO2/N2) when compared to non-reactive UiO-66-NH2 containing MPCM. The mixed gas test also shows high CO2 permeability of 1439 barrer and CO2/N2 selectivity of 37.6 in our MPCM. We also observe unexpected suppressed plasticization/swelling behaviour in UiO-66-MA containing MPCM and enhanced plasticization in UiO-66-NH2 containing MPCM through analysis of gas separation performance in the range of 1–10 atm, which might be utilized as a potential interface assessment tool for nanocomposites. Moreover, the performances of our CO2–philic MPCMs can be optimized further to surpass the (2008) Robeson Upper Bound for highly efficient sustainable CO2 capture.

Thermal stability and surface properties of acrylic PSAs modified by hexafluorobutyl acrylate

Abstract The article attempted to prepare special acrylic adhesives with preferable adhesion property and better thermal stability by introducing a fluorinated monomer. The FT-IR result showed that fluorinated monomers and acrylic monomers participated in copolymerization successfully. Furthermore, fluorinated groups performed good compatibility with acrylic resins, based on differential scanning calorimetry curve. According to the TG test under different heating rates, the activation energy of PSAs containing different content of fluorinated monomers was calculated to evaluate the effect of hexafluorobutyl acrylate on heat resistance of PSAs. Then, the findings of contact angle test revealed that the fluorinated PSAs also had rather lower surface energy than ordinary PSAs. Finally, the results of peel strength measurements indicated that the fluorinated PSAs demonstrated excellent adhesion property on various materials, especially low surface energy substrates.