Posts Tagged ‘polymerization’

EXOTHANES Highlighted on Dr. Bicuspid

Thursday, May 24th, 2012
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One of Esstech’s own, Jim Duff, had the opportunity to speak with Dr. Bicuspid’s Assistant Editor, Rob Goszkowski about EXOTHANE Elastomers.

These unique materials continue to gain popularity for their low volumetric shrinkage, low shrinkage stress and high conversion!  Click the following link to read the whole article.

http://www.drbicuspid.com/index.aspx?d=1&sec=sup&sub=rst&pag=dis&ItemID=310631

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LOW SHRINK, HIGH CONVERSION

Friday, November 11th, 2011
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EXOTHANE Elastomers

Do not sacrifice conversion and the risk of residual monomer contamination to achieve low-shrink properties.  New testing has demonstrated that EXOTHANE(TM) Elastomers have low shrinkage stress, low volumetric shrinkage, AND high conversion.

  • Exothane 8, 94% Conversion, 3% Shrinkage, high % elongation
  • Exothane 26, 96% Conversion, 4% Shrinkage, increased flexibility/toughness
  • Exothane 32, 97% Conversion, 3% Shrinkage, low color and low viscosity

This new data, in addition to superior toughness, tensilse strength and percent elongation make the EXOTHANE product line ideal form many applications including, low-shrink dental restoratives, non-curling industrial coatings, unique UV nail enhancements, tougher anaerobic adhesives and more.


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Polymerizing Thick Sections of BISGMA and TEGDMA

Monday, May 23rd, 2011
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Efficiency of 4,4′-bis(N,N-diethylamino) benzophenone for the polymerization of dimethacrylate resins in thick sections

Walter F Schroeder, Silvana L Asmussen, Wayne D Cook, Claudia I Vallo

Abstract

The efficiency of 4,4′-bis(N,N-diethylamino)benzophenone (DEABP) for the polymerization of dimethacrylate monomers in thick sections (12 mm) was studied. DEABP (λmax = 365 nm) represents a complete initiating system as it contains both ketone and amine functional groups. During irradiation, DEABP photobleaches at a fast rate causing deeper penetration of light through the underlying layers, but the photoinitiation efficiency (rate of polymerization per photon absorption rate) is relatively poor. As a result, irradiation of methacrylate monomers at 365 nm results in a slow average polymerization rate and a reduced monomer conversion for thick sections due to the light attenuation caused by the high absorptivity of DEABP and photolysis products. These results highlight the inherent interlinking of light attenuation and photobleaching rate in polymerization of thick sections.

Materials

The resins were formulated from blends of 2,2-bis[4-(2-hydroxy-3-
methacryloxyprop-1-oxy)phenyl]propane (bis-GMA)
and triethylene glycol dimethacrylate (TEGDMA) at mass fraction of 70:30.

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HEMA Incorporated in Tissue Engineering Scaffolds

Monday, January 24th, 2011
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Modification of polymer networks with bone sialoprotein promotes cell attachment and spreading

Wailen D. Chan, Harvey A. Goldberg, Graeme K. Hunter, S. J. Dixon,  Amin S. Rizkalla, Journal of Biomedical Materials Research Part A

ABSTRACT:

Biomaterials used for tissue engineering scaffolds act as temporary substrates, on which cells deposit newly synthesized extracellular matrix. In cartilage tissue engineering, polycaprolactone/poly(2-hydroxyethyl methacrylate) (PCL/pHEMA) polymer blends have been used as scaffold materials, but their use in osseous tissue engineering has been more limited. The objective of this study was to evaluate modification of PCL/pHEMA surfaces with bone sialoprotein (BSP), an extracellular matrix protein important in regulating osseous tissue formation. Modification of surfaces with BSP significantly enhanced osteoblastic cell attachment and spreading, without compromising proliferation. Thus, BSP-immobilization may be a useful strategy for optimizing scaffolds for skeletal tissue engineering.

INTRODUCTION:

Tissue regeneration requires a substrate that allows cells to adhere, proliferate, and eventually form their own matrix. Polymers from the polyester family, such as poly(lactic acid), poly(glycolic acid), or their copolymers, have been the most commonly used materials to fabricate scaffolds for skeletal tissue engineering applications.  More recently, another member of this family, poly(ε-caprolactone) (PCL) has also been considered for skeletal tissue engineering. Human primary osteoblasts demonstrate attachment and spreading on PCL surfaces.

Poly(2-hydroxyethyl methacrylate) (pHEMA) is another polymer that has been used extensively as a biomaterial in drug delivery and soft-tissue applications. pHEMA gels have a propensity to calcify after prolonged implantation periods, leading to the suggestion that pHEMA could be used for filling bone or dental defects…

PREPARATION:

PCL/pHEMA semi-interpenetrating networks (sIPN’s) were prepared by combining HEMA monomer (Esstech, Essington, PA), a low-molecular-weight PCL (CAPA 2302, 3000 g/mol; Solvay Interox, Warrington, UK), and a high-molecular-weight PCL (CAPA 6506, 50,000 g/mol; Solvay Interox) in a 5.5:2.5:1 weight ratio, respectively. PCL and HEMA monomer were mixed together and placed in an oven at 60oC to facilitate melting and dissolution of PCL in HEMA monomer. After melting, the compositions were thoroughly mixed to ensure a homogenous distribution. Camphorquinone (Esstech) was added to the mixtures at 0.2% by weight of HEMA monomer. The mixtures were sonicated for approximately 8 min to evenly dissolve the camphorquinone. 1 mL polypropylene syringes (∼4 mm internal diameter) were subsequently filled with PCL/HEMA monomer compositions and cured using a Triad 2000 light-curing system (Dentsply, York, PA).


Article first published online: 31 MAR 2010, DOI:  10.1002/jbm.a.32715, Copyright 2010 Wiley Periodicals, Inc.

Volume 94A, Issue 3, pages 945–952, 1 September 2010

Link:  http://onlinelibrary.wiley.com/doi/10.1002/jbm.a.32715/abstract


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Effect of Varying Filler Content in BisGMA:TEGDMA Composites

Friday, September 10th, 2010
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Contraction stress related to composite inorganic content

F. Gonçalvesa, Y. Kawanob, R.R. Bragaa

Dental Materials Volume 26, Issue 7, Pages 704-709 (July 2010).

Objectives: The role of inorganic content on physical properties of resin composites is well known. However, its influence on polymerization stress development has not been established. The aim of this investigation was to evaluate the influence of inorganic fraction on polymerization stress and its determinants, namely, volumetric shrinkage, elastic modulus and degree of conversion.

Methods: Eight experimental composites containing 1:1 BisGMA (bisphenylglycidyl dimethacrylate):TEGDMA (triethylene glycol dimethacrylate) (in mol) and barium glass at increasing concentrations from 25 to 60vol.% (5% increments) were tested. Stress was determined in a universal test machine using acrylic as bonding substrate. Nominal polymerization stress was obtained diving the maximum load by the cross-surface area. Shrinkage was measured using a water picnometer. Elastic modulus was obtained by three-point flexural test. Degree of conversion was determined by FT-Raman spectroscopy.

Results: Polymerization stress and shrinkage showed inverse relationships with filler content (R2=0.965 and R2=0.966, respectively). Elastic modulus presented a direct correlation with inorganic content (R2=0.984). Degree of conversion did not vary significantly. Polymerization stress showed a strong direct correlation with shrinkage (R2=0.982) and inverse with elastic modulus (R2=0.966).

Significance: High inorganic contents were associated with low polymerization stress values, which can be explained by the reduced volumetric shrinkage presented by heavily filled composites.

Link:  http://www.demajournal.com/article/PIIS0109564110000801/fulltext


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Esstech to detail FIT 852 at IADR 2010 Barcelona

Wednesday, June 30th, 2010
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X-726-0000 Serves as HEMA Alternative and Improves Degree of Conversion

Wednesday, March 31st, 2010
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Polymerization Shrinkage and Stress Development in Amorphous Calcium Phosphate/Urethane Dimethacrylate Polymeric Composites

J.M. Antonucci, W.F. Regnault, and D. Skrtic

Journal of Composite Materials, Feb 2010; vol. 44: pp. 355 – 367. DOI: 10.1177/0021998309345180

Abstract: This study explores how substituting a new high molecular mass oligomeric poly(ethylene glycol) extended urethane dimethacrylate (UDMA) (PEG-U) for 2-hydroxyethyl methacrylate (HEMA) in photo-activated UDMA resins affects degree of vinyl conversion (DC), polymerization shrinkage (PS), stress development (PSSD) and biaxial flexure strength (BFS) of their amorphous calcium phosphate (ACP) composites. The composites were prepared from four types of resins (UDMA, PEG-U, UDMA/HEMA, and UDMA/PEG-U) and zirconia-hybridized ACP. Introducing PEG-U improved DC, while not adversely affecting PS, PSSD, and the BFS of composites. This improvement in DC is attributed to the long, more flexible structure between the vinyl groups of PEG-U and its higher molecular mass compared to poly(HEMA). The results imply that PEG-U has the potential to serve as an alternative to HEMA in dental and other biomedical applications.

…material research program supported by FDA, NIST, and ADAF. Generous contribution of UDMA, PEG- U, and HEMA monomers from Esstech, Essington, PA, USA, is gratefully acknowledged. Polymerization Shrinkage and Stress in ACP Composites 365 The authors also…

This version was published on February 1, 2010

Link: http://jcm.sagepub.com/cgi/content/abstract/44/3/355


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