scholarly journals Free-Radical Bulk-Photopolymerization Process as a Method of Obtaining Thermally Curable Structural Self-Adhesive Tapes and Effect of Used Type I Photoinitiators

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2191 ◽  
Author(s):  
Konrad Gziut ◽  
Agnieszka Kowalczyk ◽  
Beata Schmidt
Keyword(s):  
Free Radical ◽  
Glycidyl Methacrylate ◽  
Butyl Methacrylate ◽  
Cross Linking ◽  
Type I ◽  
Fabrication Method ◽  
Thermal Curing ◽  
Scanning Calorimetry ◽  
Nmr Studies ◽  
Physico Chemical

A new fabrication method for thin (120 µm) thermally curable structural self-adhesive tapes (SATs) was demonstrated by utilizing a series of acrylic syrups (ASs) modified using Bisphenol A-based liquid epoxy resin. The acrylic syrups containing poly(butyl acrylate-co-butyl methacrylate-co-glycidyl methacrylate-co-2-hydroxyetyl acrylate-co-4-acryloyloxy benzophenone) were synthesized via free-radical bulk-photopolymerization (FRBP) process. Influence of different type I radical photoinitiators (PIs), i.e., α-hydroxyalkylphenones (HPs), acylphosphine oxides (APOs) and its mixtures (HPs/APOs and APO/APO) on selected physico-chemical features of obtained ASs was studied. It turned out that APO-type PIs are more effective in the FRBP process (NMR studies). Self-adhesive tests of SATs revealed that the monomers’ conversion in ASs have a significant influence on adhesion and tack. Moreover, the polymer structures formed at the UV cross-linking stage of SATs significantly affect the cross-linking degree of SATs during thermal curing (differential scanning calorimetry method). The highest values of overlap shear strength were achieved by SATs based on ASs with monomers’ conversion on the level 50–60%.

A comparative study on the effect of higher acrylate on cross-linkable PMMA used as environment friendly latexes

2020 ◽  
Vol 32 (2) ◽  
pp. 135-141
Author(s):  
Sweta Shukla
Keyword(s):  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Butyl Methacrylate ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
Environment Friendly ◽  
Glycol Diacrylate ◽  
Poly Propylene ◽  
Kinetics Of ◽  
Scanning Electron

The kinetics of emulsion polymerization of monomers methyl methacrylate (MMA)/ n-butyl methacrylate (BMA) was studied to investigate the effect of cross-linkable monomer poly(propylene glycol diacrylate) (PPGDA). The results showed that by the incorporation of PPGDA rate constant of reaction decreased. Fourier transform infrared spectroscopy and scanning electron microscope were used to characterize the synthesized polymers. The thermal analysis of samples was done by differential scanning calorimetry, and the results were compared by the previous studies with MMA/ n-butyl acrylate (BA) and MMA/2-ethylhexyl acrylate (EHA). The glass transition temperature ( T g) values show that the latexes prepared using BA and EHA as comonomer was suitable for binder purpose, but in the present study the T g is not suitable in case of BMA as higher acrylate comonomer. That may be due to more cross-linking in MMA-BMA-PPGDA. The results conclude that the BA and EHA can be used as the binder, but the use of BMA is limited for the binder in coating applications.

scholarly journals Model Systems for Evidencing the Mediator Role of Riboflavin in the UVA Cross-Linking Treatment of Keratoconus

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 190
Author(s):  
Mihaela Monica Constantin ◽  
Cătălina Gabriela Corbu ◽  
Sorin Mocanu ◽  
Elena Irina Popescu ◽  
Marin Micutz ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Type I Collagen ◽  
Tear Film ◽  
Model Systems ◽  
Cross Linking ◽  
Type I ◽  
Paramagnetic Resonance ◽  
Uva Irradiation ◽  
Physico Chemical ◽  
Mediator Role

Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.

Effect of cross-linking on rheological properties and a model for flexibility-rigidity transition in SBS/PBMA LIPNs

2016 ◽  
Vol 36 (2) ◽  
pp. 149-156 ◽  
Author(s):  
Yanqing Ma ◽  
Fajun He ◽  
Heyun Wang ◽  
Huan Liu ◽  
Zhong Wei
Keyword(s):  
Rheological Properties ◽  
Polymer Networks ◽  
Interpenetrating Polymer Networks ◽  
Butyl Methacrylate ◽  
Particle Analysis ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
Latex Particles ◽  
Gel Content ◽  
Rigidity Transition

Abstract A series of latex interpenetrating polymer networks (LIPNs) with various cross-linking levels were prepared with polystyrene-polybutadiene-polystyrene (SBS) and butyl methacrylate (BMA) by emulsion polymerization. The gel content of the resultant latex particles ranged from 13.2% to 90.8%, with the amount of cross-linking agent increased. The structural, thermal and rheological properties of the latex particles were investigated by laser particle analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry and torque rheometry. Furthermore, in order to study the effect of gel content on the flow properties, a model is shown to predict the existence of a flexibility-rigidity transition of SBS/PBMA LIPNs as the amount of cross-linking agent increased. Torque data were interpreted in terms of shear rate, shear stress and viscosity. The relationship between gel content of SBS/PBMA LIPNs and polyvinyl chloride compositions and their effect on plasticization performance were determined, and the predictions of the model have good agreement with their flexibility-rigidity transition.

scholarly journals Epoxy-Based Structural Self-Adhesive Tapes Modified with Acrylic Syrups Prepared via a Free Radical Photopolymerization Process

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 189
Author(s):  
Konrad Gziut ◽  
Agnieszka Kowalczyk ◽  
Beata Schmidt ◽  
Krzysztof Kowalczyk ◽  
Mateusz Weisbrodt
Keyword(s):  
Shear Strength ◽  
Free Radical ◽  
Dynamic Viscosity ◽  
Glycidyl Methacrylate ◽  
Bulk Polymerization ◽  
Butyl Methacrylate ◽  
Crosslinking Degree ◽  
Mixing Speed ◽  
Molecular Weights ◽  
Free Radical Photopolymerization

New modifiers (i.e., acrylic syrups; ASs) of epoxy-resin-based thermally curable structural self-adhesive tapes (SATs) were prepared via a free radical bulk polymerization (FRBP) of n-butyl acrylate, butyl methacrylate, glycidyl methacrylate, and hydroxybutyl acrylate. In the process, two kinds of UV-photoinitiators (i.e., monoacylphosphine oxide/Omnirad TPO and bisacylphosphine oxide/Omnirad 819) and various mixing speed of the monomers mixture (200–1000 rpm) were applied. The TPO-based syrups exhibited a lower copolymers content (10–24 wt%), dynamic viscosity (<0.1 Pa·s), molecular weights (Mn and Mw, and polydispersity (1.9–2.5) than these with Omnirad 819. Additionally, the higher mixing speed significantly reduced monomers conversion and viscosity of ASs as well as molecular weights of the acrylate copolymers. These parameters influenced the properties of thermally uncured (e.g., adhesion) and thermally cured SATs (shear strength of aluminum/SAT/aluminum overlap joints). Better self-adhesive features were observed for SATs-TPO (based on ASs with lower monomers conversion, Mn and Mw); however, a slightly higher shear strength was noted for the thermally cured SAT-819 (ASs with higher monomers conversion, Mn and Mw). An impact of polydispersity of the acrylate copolymers as well as crosslinking degree of thermally cured SATs on the mechanical strength was also revealed.

Physico-Chemical Properties of Recombinant Desulphatohirudin

1990 ◽  
Vol 63 (03) ◽  
pp. 499-504 ◽  
Author(s):  
A Electricwala ◽  
L Irons ◽  
R Wait ◽  
R J G Carr ◽  
R J Ling ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Gel Filtration ◽  
Chemical Properties ◽  
Alpha Helix ◽  
Apparent Molecular Weight ◽  
Correlation Spectroscopy ◽  
Nmr Studies ◽  
Recombinant Hirudin ◽  
Physico Chemical ◽  
Recombinant Molecule

SummaryPhysico-chemical properties of recombinant desulphatohirudin expressed in yeast (CIBA GEIGY code No. CGP 39393) were reinvestigated. As previously reported for natural hirudin, the recombinant molecule exhibited abnormal behaviour by gel filtration with an apparent molecular weight greater than that based on the primary structure. However, molecular weight estimation by SDS gel electrophoresis, FAB-mass spectrometry and Photon Correlation Spectroscopy were in agreement with the theoretical molecular weight, with little suggestion of dimer or aggregate formation. Circular dichroism studies of the recombinant molecule show similar spectra at different pH values but are markedly different from that reported by Konno et al. (13) for a natural hirudin-variant. Our CD studies indicate the presence of about 60% beta sheet and the absence of alpha helix in the secondary structure of recombinant hirudin, in agreement with the conformation determined by NMR studies (17)

scholarly journals How to Improve Physico-Chemical Properties of Silk Fibroin Materials for Biomedical Applications?—Blending and Cross-Linking of Silk Fibroin—A Review

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1510
Author(s):  
Sylwia Grabska-Zielińska ◽  
Alina Sionkowska
Keyword(s):  
Silk Fibroin ◽  
Biomedical Applications ◽  
Magnetic Particles ◽  
Chemical Properties ◽  
Ternary Mixtures ◽  
Cross Linking ◽  
Advantages And Disadvantages ◽  
Physico Chemical ◽  
Binary And Ternary Mixtures ◽  
To Receive

This review supplies a report on fresh advances in the field of silk fibroin (SF) biopolymer and its blends with biopolymers as new biomaterials. The review also includes a subsection about silk fibroin mixtures with synthetic polymers. Silk fibroin is commonly used to receive biomaterials. However, the materials based on pure polymer present low mechanical parameters, and high enzymatic degradation rate. These properties can be problematic for tissue engineering applications. An increased interest in two- and three-component mixtures and chemically cross-linked materials has been observed due to their improved physico-chemical properties. These materials can be attractive and desirable for both academic, and, industrial attention because they expose improvements in properties required in the biomedical field. The structure, forms, methods of preparation, and some physico-chemical properties of silk fibroin are discussed in this review. Detailed examples are also given from scientific reports and practical experiments. The most common biopolymers: collagen (Coll), chitosan (CTS), alginate (AL), and hyaluronic acid (HA) are discussed as components of silk fibroin-based mixtures. Examples of binary and ternary mixtures, composites with the addition of magnetic particles, hydroxyapatite or titanium dioxide are also included and given. Additionally, the advantages and disadvantages of chemical, physical, and enzymatic cross-linking were demonstrated.

15N NMR studies provide insights into physico-chemical properties of room-temperature ionic liquids

2021 ◽  
Author(s):  
Christoph Wiedemann ◽  
David Fushman ◽  
Frank Bordusa
Keyword(s):  
Ionic Liquids ◽  
Room Temperature ◽  
Chemical Properties ◽  
Room Temperature Ionic Liquids ◽  
15N Nmr ◽  
Nmr Studies ◽  
Physico Chemical ◽  
Alternative Solvents

Ionic liquids (ILs) have gained a lot of attention as alternative solvents in many fields of science in the last two decades. It is known that the type of anion...

scholarly journals Synthesis and Characterization of N-Substituted Polyether-Block-Amide Copolymers

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 773
Author(s):  
Jyun-Yan Ye ◽  
Kuo-Fu Peng ◽  
Yu-Ning Zhang ◽  
Szu-Yuan Huang ◽  
Mong Liang
Keyword(s):  
Titanium Isopropoxide ◽  
Decomposition Temperature ◽  
Phenyl Isocyanate ◽  
Cross Linking ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Degradation Temperature ◽  
Melt Polycondensation ◽  
Structural Regularity

A series of N-substituted polyether-block-amide (PEBA-X%) copolymers were prepared by melt polycondensation of nylon-6 prepolymer and polytetramethylene ether glycol at an elevated temperature using titanium isopropoxide as a catalyst. The structure, thermal properties, and crystallinity of PEBA-X% were investigated using nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, wide angle X-ray diffraction, and thermogravimetric analysis. In general, the crystallinity, melting point, and thermal degradation temperature of PEBA-X% decreased as the incorporation of N-methyl functionalized groups increased, owing to the disruption caused to the structural regularity of the copolymer. However, in N-acetyl functionalized analogues, the crystallinity first dropped and then increased because of a new γ form arrangement that developed in the microstructure. After the cross-linking reaction of the N-methyl-substituted derivative, which has electron-donating characteristics, with poly(4,4′-methylenebis(phenyl isocyanate), the decomposition temperature of the resulting polymer significantly increased, whereas no such improvements could be observed in the case of the electro-withdrawing N-acetyl-substituted derivative, because of the incompleteness of its cross-linking reaction.

Sign in / Sign up

Export Citation Format

Share Document