Solvatochromism as an alternative for contact angle measurements in the characterisation of modified polymer surfaces

Polyolefine surfaces have been pre-treated by UV/ozone and UV/water methods. The increase in polar groups on a polymer surface and the contribution of these polar groups to the adhesion of the polymer has been investigated by using contact angles and tensile strength tests. Because contact angle measurements do not give information about the specific polar groups on the surface we have used solvatochromic analyses to identify specific polar groups. The results showed that solvatochromic analyses is a promising method to discriminate between different kinds of polar groups and therefore solvatochromic surface characterisation may become an important surface analytical tool in adhesive technology.     

Study on Adhesive Resin of Aluminum-Plastic Pipes

Polyolefin was chemically improved during extrusion by reactive extruding technology, and on its main chain was grafted a polar monomer, thus a stronger chemical bond was formed between the polyolefin and polar materials, which can enhanced the adhesive power on the interface of the two polymers.     

Polymer matrix of polyethylene porous films functionalized by electrical discharge plasma

The polyethylene porous films were treated by dielectric surface barrier discharge (DSBD) plasma at atmospheric pressure in oxygen (O₂) or nitrogen (N₂), and by radio-frequency discharge (RFD) plasma in air at reduced pressure 46 Pa. The surface energy of films was carried out by direct measurements of contact angles of six testing liquids. The strength of adhesive joints in the system modified polyethylene porous films - polyacrylate was measured by peeling of the joints under the angle of 90°. The significant increase of the surface energy and its polar component of polyethylene porous films modified by all types of plasma were observed. The higher strengths of adhesive joints were found for modification of polyethylene porous films by radio-frequency discharge plasma in comparison with modification of the films by barrier discharge plasma.     

Adhesion of acrylate-based water dispersion to polypropylene hybrid fabrics

The increase in the content of crosslinking agent and surfactant in acrylate-based water dispersion results in an increase of surface parameters e.g. total SFE and its polar component, interfacial and mechanical work of adhesion of polyacrylate to PP hybrid fabrics. UV irradiation of polyacrylate coating in the course of accelerating ageing has the same effect on surface and adhesive properties as a crosslinking agent or surfactant and leads to a considerable growth of the total SFE, its polar component, interfacial and mechanical work of adhesion. The increase in the interfacial and mechanical work of adhesion with the increase of the crosslinking agent and/or surfactant content in acrylate-based water dispersion is higher for PES/PP fabrics compared to the PA/PP system. The adhesive properties of the film obtained from acrylate-based water dispersion are substantially influenced by the presence of a surfactant and a crosslinking agent.     

Surface and bulk modification of polyolefins by functional aryl nitrenes as highly reactive intermediates

Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV‐irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene‐propylene and ethylene‐octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene‐propylene‐copolymers, less than half of it to ethylene‐octene‐copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers.     

UV‐Induced Tetrazole‐Thiol Reaction for Polymer Conjugation and Surface Functionalization

A UV‐induced 1,3‐dipolar nucleophilic addition of tetrazoles to thiols is described. Under UV irradiation the reaction proceeds rapidly at room temperature, with high yields, without a catalyst, and in both polar protic and aprotic solvents, including water. This UV‐induced tetrazole‐thiol reaction was successfully applied for the synthesis of small molecules, protein modification, and rapid and facile polymer–polymer conjugation. The reaction has also been demonstrated for the formation of micropatterns by site‐selective surface functionalization. Superhydrophobic–hydrophilic micropatterns were successfully created by sequential modifications of a tetrazole‐modified porous polymer surface with hydrophobic and hydrophilic thiols. A biotin‐functionalized surface could be fabricated in aqueous solutions under long‐wavelength UV irradiation.     

High-performance polyolefin composites by chemical modification

The paper will give a short introducing survey on the present state of polyolefin and copolyolefin cross linking. The combination of high-density polyethylene (PEHD) and polypropylene (PP) with elastomers, particularly with ethylene-propylene terpolymer (EPDM), results in high-impact strength PP (HI-PP) and in thermoplastic elastomers (TPE) considered as high-performance polyolefin composites (HP-POC). By filling of PEHD and PP, HP-POCs with increased stiffness, modulus, and abrasion resistance can be produced. They are cost - advantageous substitutes for construction materials as, for example, ABS. Possibilities and limits are demonstrated by own investigations in this field. Best mechanical properties are obtained by reinforcement with fibres, particularly with glass fibres. Requirement for superior parameters is a chemical coupling between glass-fibre surface or glass-fibre size, respectively, and the PP matrix. A new adhesive agent on the basis of siloxane allows to reach high strength and toughness of the composites. The effect seems to be due to a better mutual penetration of the adhesive agent, the size, and the PP matrix. Outlooks will be given on the further development of HP-POC in the field of reinforcement and reactive combination with other polymers.     

聚烯烃分离膜表面改性研究进展

综述了聚烯烃类分离膜表面改性研究的主要进展,着重介绍了高能辐射接枝、光引发接枝、等离子体接枝、表面臭氧处理、以及超临界CO2状态下接枝等表面改性方法的特点,分析了改性后聚烯烃膜的性能,并对聚烯烃分离膜表面改性进行了展望。     

Surface Energy and Adhesive Properties of Polyamide 12 Modified by Barrier and Radio-Frequency Discharge Plasma

Summary. The polyamide 12 foil with sufficient surface and adhesive properties to other substrates can be prepared by discharge plasma modification. For improvement of bonding and printing of polymer a surface barrier discharge plasma in N₂ and O₂ as well as a radio-frequency discharge plasma in air has been studied. A significant increase in surface energy of the polymer as well as in strength of adhesive joint to more polar polymer was found. The chemical changes of PA 12 modified by plasma were analyzed using fourier transform infra red – attenuated total reflection (FTIR–ATR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements. The observed changes of surface properties of the polymer due to aging were not important.     

Surface Energy and Adhesive Properties of Polyamide 12 Modified by Barrier and Radio-Frequency Discharge Plasma

The polyamide 12 foil with sufficient surface and adhesive properties to other substrates can be prepared by discharge plasma modification. For improvement of bonding and printing of polymer a surface barrier discharge plasma in N₂ and O₂ as well as a radio-frequency discharge plasma in air has been studied. A significant increase in surface energy of the polymer as well as in strength of adhesive joint to more polar polymer was found. The chemical changes of PA 12 modified by plasma were analyzed using fourier transform infra red – attenuated total reflection (FTIR–ATR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurements. The observed changes of surface properties of the polymer due to aging were not important.     

A novel photoadditive for polyolefin photostabilization: hindered amine light stabilizer

Hindered‐amine light stabilizers were surface anchored to polyethylene and polypropylene thin films by: i) direct photo‐grafting of 1,2,2,6,6‐pentamethyl piperidinyl‐4‐acrylate onto the surface and ii) by reacting of 1,2,2,6,6‐pentamethyl‐4‐piperidinol with succinic anhydride functionalized polyolefin surface. The samples were exposed to UV irradiation in air and the oxidative‐degradation of the polymers was studied with FT‐IR spectroscopy. The photo‐stability of surface anchored Hindered‐amine stabilizers (HAS) was compared with films stabilized with commercial HAS by melt blending. The results of the study evince superiority of surface anchored HAS over that of melt blended polyolefins.     

烯烃聚合催化剂的研究进展

获得高性能聚烯烃材料是化学家们不断的追求。烯烃聚合催化剂的结构对其催化性能有重要影响,而聚烯烃的改性则能够改善聚合物实际应用中表面形貌、本体性能中存在的缺陷,如通过改性可增加聚合物韧性、降低聚合物表面的摩擦系数或提升表面能等。 本文系统总结了金属烯烃聚合催化剂研究进展,包括Ziegler-Natta催化剂、茂金属催化剂、非茂金属催化剂的结构及调控策略,探讨了位阻效应、双金属协同效应以及其他效应对催化效果的影响。     

Shielded molecularly imprinted polymers prepared with a selective surface modification

Uniformly sized, molecularly imprinted polymers (MIPs) of bisphenol A (BPA), one of many potential endocrine disruptors, were prepared by selective surface modification and immobilized at intervals of functional monomers with 4,4′‐methylenebisphenol as a pseudotemplate. MIPs for BPA were prepared with 4‐vinyl pyridine immobilized at the most effective interval and with ethylene glycol dimethacrylate monomer as a functional crosslinker. The prepared MIPs were surface‐modified with both polar and ionic monomers with different modification methods and then evaluated to reveal their selectivity and retention characteristics. Some of the modified MIPs showed significant selectivity for BPA retention when they were used as high‐performance liquid chromatography (HPLC) stationary phases, in comparison with ordinary MIPs. This effect of molecular imprinting was retained even after the surface modification of MIPs. The MIPs employed as pretreatment media for a column‐switching HPLC system provided a detection limit as low as 1 ng/L (ppt) by electrochemical detection. Actual samples, including Suwannee River natural organic matter (NOM), were analyzed for BPA, and BPA was quantitatively detected in NOM even with the combination with widely used UV detection because of the effective removal of interference afforded by an effective surface modification of the MIPs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2048–2060, 2005     

聚烯烃的化学接枝改性

综述了化学接枝改性聚烯烃的三种方法,即溶液法,熔融法及固定相法,并讨论了接枝单体的选择,接枝机理和接枝物的性能表征。     

Elastomers based on PEF-3A oligomer

The kinetics of curing epoxyurethane oligomer PEF-3A by curing agents of different chemical nature has been studied by differential scanning calorimetry. The reactivity of PEF-3A has been found to be higher than that of epoxide resins owing to the polar urethane groups in its molecule. The strength of the adhesive joint has been shown to increase after modification of PEF-3A-based compositions by orthophosphoric acid.     

Irradiation effects on thermal,surface, and physicomechanical properties of ethylene and vinyl acetate copolymer

The structural and thermal transitions for ethylene and vinyl acetate copolymer (EVA) samples irradiated by fast electrons at doses in the range of 2.5–25 Mrad were investigated by DSC and X-ray diffraction analysis. The parameters of chemical bonds in the amorphous phase of copolymer were determined. The change in the degree of crystallinity, melting temperature, and crystallite sizes before and after radiochemical modification were estimated. The obtained results were analyzed and corresponded to the physicomechanical properties of copolymers. The surface energy of copolymers before and after irradiation was defined. The strength of adhesive joints based on EVA from PET substrates and the influence of radiochemical modification of adhesive before joint formation on its strength were analyzed.     

Azobenzene‐Containing Block Copolymers as Light‐Induced Reworkable Adhesives: Effects of Molecular Weight,Composition, and Block Copolymer Architectures on the Adhesive Properties

We previously reported that ABA‐type triblock copolymers with azobenzene‐containing terminal blocks can be utilized as a light‐induced reworkable adhesive that enables repeatable bonding and debonding on demand. The reworkability was based on the photoisomerization of the azobenzene moiety and concomitant softening and hardening of the azo blocks. Our aim in this study is to investigate the effect of the composition, molecular weight, and block copolymer architectures on the reworkable adhesive properties. For this purpose, we prepared AB diblock, ABA triblock, and 4‐arm (AB)₄ star‐block copolymers consisting of polymethacrylates bearing an azobenzene moiety (A block) and 2‐ethylhexyl (B block) side chains and performed adhesion tests by using these block copolymers. As a result, among the ABA block copolymers with varied compositions and molecular weights, the ABA triblock copolymers with an azo block content of about 50 wt % and relatively low molecular weight could achieve an appropriate balance between high adhesion strength and low residual adhesion strength upon UV irradiation. Furthermore, the 4‐arm star‐block structure not only enhances the adhesion strength, but also maintains low residual adhesion strength when exposed to UV irradiation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 806–813     

Synthesis,characterization, processability,mechanical properties,flame retardant,and oil resistance of chlorinated acrylonitrile butadiene rubber

Novel chlorinated acrylonitrile butadiene rubber (Cl‐NBR) was prepared from NBR by the alkaline hydrolysis of chloroform by using phase‐transfer catalysis. The formation of Cl‐NBR was monitored by ¹H‐NMR, UV‐Vis, and Fourier transform infrared spectroscopic techniques. The percentage of chlorine attached to the rubber chain was estimated by Volhard method. The effect of polar groups on the structural and thermal properties of Cl‐NBR was analyzed by scanning electron microscopy, X‐ray diffraction analysis, differential scanning calorimetry, and thermogravimetric analysis studies. The flame retardant, oil resistance, cure behavior, and mechanical properties of chlorinated elastomer were also analyzed. The proton NMR revealed the attachment of chlorine in the backbone of NBR with new chemical shift values. The C‐Cl stretching of chlorinated NBR was confirmed from Fourier transform infrared. The UV spectrum also supported the formation of chlorinated unit in the NBR chain through the shifts and broadening of absorption peaks. The X‐ray diffraction analysis pattern indicated a decrease in the amorphous domain of NBR with an increase in the level of chemical modification. The increased glass transition temperature obtained from differential scanning calorimetry confirms the increased molecular rigidity of the chlorinated NBR and thermal transitions increased with increase in the level of chemical modification. The thermal stability of Cl‐NBR decreased with an increase in chlorine content. The flame and oil resistance of Cl‐NBR was greatly higher than pure NBR due to the increased polarity of modified rubber. The superior tensile strength of Cl‐NBR (4 times higher than pure NBR) and higher oil resistance find applications in pump diaphragms, aircraft hoses, oil‐lined tubing, and gaskets materials with the excellent flame resistant property.     

Surface modification of ultra‐high molecular weight polyethylene fibers by chromic acid

Ultra‐high molecular weight polyethylene (UHMWPE) fibers were modified by chromic acid. The effects of surface modification were evaluated with Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electron microscope (SEM). The results showed that both the content of O‐containing functional groups and surface roughness of modified fibers increased. The polar groups on the modified fiber surface decreased the contact angles with water and ethylene glycol, as evidenced by contact angle measurement. The tensile test results showed the strength and the elongation at break of UHMWPE fibers decreased but the modulus increased after chromic acid modification. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface Modification of Polyester Monofilaments by Atmospheric-Pressure Nitrogen Plasma

Polyester monofilaments were treated by a pulsed surface electrical discharge in nitrogen at atmospheric pressure, to increase their adhesion to an epoxy resin matrix. The treatment resulted in an eight-fold increase in adhesive strength, without any change in mechanical properties of the monofilaments. It is concluded that polar group interactions, rather than increased surface area, are responsible for the improved adhesive strength.