Improving UV Curing in Organosolv Lignin-Containing Photopolymers for Stereolithography by Reduction and Acylation

Despite recent successes in incorporating lignin into photoactive resins, lignin photo-properties can be detrimental to its application in UV-curable photopolymers, especially in specialized engineered resins for use in stereolithography printing. We report on chemical modification techniques employed to reduce UV absorption by lignin and the resulting mechanical, thermal, and cure properties of these modified lignin materials. Lignin was modified using reduction and acylation reactions and incorporated into a 3D printable resin formulation. UV–Vis absorption at the 3D printing range of 405 nm was reduced in all modified lignins compared to the unmodified sample by 25% to ≥ 60%. Resins made with the modified lignins showed an increase in stiffness and strength with lower thermal stability. Studying these techniques is an important step in developing lignin for use in UV-curing applications and further the effort to valorize lignin towards commercial use.

Pharmacokinetics Of Transbuccal Swab-Administered Naloxone-HCl Using A Novel Plant-Based Resin Formulation In Dogs

A proof-of-concept transbuccal swab delivery of naloxone-HCL study using a mucoadhesive, plant-based film-forming resin formulation demonstrated comparable blood levels to benchmark intramuscular (IM) injection in highly predictive dog model. Results from this study allow the potential to translate rapid onset in humans with therapeutic blood levels being reached in 2-3 minutes comparable to that observed with commercially available parenteral injections and intranasal administrations. The simplicity, ease of delivery and rapid effectiveness has the potential to meet the public health emergency needs in the rescue of opioid overdosing.

Characterization of Ceramic Waste Filled Unsaturated Polyester Resin

In this study, the composites of ceramic waste filler polyester were produced with ceramic waste as the filler and unsaturated polyester resin as the matrix. Various weight of filler loads (particle size [180 �m) were used; 0, 28.5, 41 and 50 wt% in view to better understand the effect of filler content on the mechanical, thermal properties and water absorption of the composites. Additionally, Fourier transform infrared spectroscopy was used to characterize the samples, from the findings, it is noticed an increase in the level of porcelain powder decreased the flexural strength and Hardness and increased the density. The results of water absorption have shown the composites absorbs fewer water. Thermal degradation indicates that the composite is more resistant to temperature than unsaturated polyester matrix due to the effect of porcelain powder incorporated. Moreover, the results reveal an opportunity for using the ceramic waste as filler in unsaturated polyester resin formulation.

Review on UV-Induced Cationic Frontal Polymerization of Epoxy Monomers

Ultraviolet (UV)-induced cationic frontal polymerization has emerged as a novel technique that allows rapid curing of various epoxy monomers upon UV irradiation within a few seconds. In the presence of a diaryliodonium salt photoinitiator together with a thermal radical initiator, the cationic ring opening polymerization of an epoxide monomer is auto-accelerated in the form of a self-propagating front upon UV irradiation. This hot propagating front generates the required enthalpy to sustain curing reaction throughout the resin formulation without further need for UV irradiation. This unique reaction pathway makes the cationic frontal polymerization a promising route towards the efficient curing of epoxy-based thermosetting resins and related composite structures. This review represents a comprehensive overview of the mechanism and progress of UV-induced cationic frontal polymerization of epoxy monomers that have been reported so far in literature. At the same time, this review covers important aspects on the frontal polymerization of various epoxide monomers involving the chemistry of the initiators, the effect of appropriate sensitizers, diluents and fillers.

Manufacture of thin rice straw particleboards bonded with various polymeric methane diphenyl diisocyanate/ urea formaldehyde resin mixtures

Reducing particleboard thickness is one of the major approaches to decrease consumption volume of particleboard for furniture manufacture. This study employed an adhesive mixture of polymeric methane diphenyl diisocyanate (PMDI) and urea formaldehyde (UF) to produce single-layer medium density thin rice straw particleboard. The effects of various PMDI/UF formulations as well as board density on mechanical properties and water resistance of rice straw particleboard were studied. The results indicated that the mechanical properties and water resistance of the thin rice straw particleboard were appreciably affected by resin formulation. The panels bonded with PMDI/UF adhesive mixtures had mechanical properties and water resistance far superior to those bonded with UF. Higher PMDI content levels in resin mixtures led to improved mechanical properties and water resistance. Density influenced mechanical properties and water resistance of the thin rice straw particleboard. Increasing the density of the panel could upgrade the mechanical properties of the thin rice straw particleboard. The experimental outcomes showed that PMDI/UF resin systems had potential to substitute for pure PMDI resin in producing thin rice straw particleboard, which could effectively lower manufacturing cost and bring economic efficiencies due to reduced amount of pricey PMDI.

Improving UV Curing in Lignin-Containing Photopolymers for Stereolithography by Chemical Reduction and Acetylation

Despite recent successes incorporating lignin into photoactive resins, lignin photo-properties can be detrimental to its application in UV-curable photopolymers, especially to customized, engineered resins for use in stereolithography printing. We report on chemical modification techniques employed to reduce UV absorption in lignin and the resulting mechanical, thermal, and cure properties in these lignin-containing materials. Pine lignin was modified using acetylation and reduction reactions and incorporated into a printable resin formulation. Modified lignin displayed enhanced printing properties because UV absorption at the 3D printable range was reduced in all acylated lignin from 25% up to greater than 60%. Resins made with the modified lignin showed increased stiffness and strength with lower thermal stability. Investigating these techniques is an important step in developing lignin for use in UV-curing applications and furthers the effort to valorize lignin toward commercial use.

Improving UV Curing in Lignin-Containing Photopolymers for Stereolithography by Chemical Reduction and Acetylation

Despite recent successes incorporating lignin into photoactive resins, lignin photo-properties can be detrimental to its application in UV-curable photopolymers, especially to customized, engineered resins for use in stereolithography printing. We report on chemical modification techniques employed to reduce UV absorption in lignin and the resulting mechanical, thermal, and cure properties in these lignin-containing materials. Pine lignin was modified using acetylation and reduction reactions and incorporated into a printable resin formulation. Modified lignin displayed enhanced printing properties because UV absorption at the 3D printable range was reduced in all acylated lignin from 25% up to greater than 60%. Resins made with the modified lignin showed increased stiffness and strength with lower thermal stability. Investigating these techniques is an important step in developing lignin for use in UV-curing applications and furthers the effort to valorize lignin toward commercial use.

Low-Dielectric Constant Nanoporous Epoxy for Electronic Packaging

Epoxide functionalized poly(propylene carbonate) (ePPC) was included in an epoxy resin formulation and thermally decomposed to create nanoporous epoxy film. The dielectric constant of the porous epoxy was lower than the epoxy formulation control. The introduction of 30% porosity in the epoxy lowered the dielectric constant from 3.78 to 2.76. A postporosity chemical treatment further lowered the dielectric constant. Hexamethyldisilazane (HMDS) was used to terminate the pore walls with the hydrophobic silane layer and reduce both the dielectric constant and tangent loss of the porous epoxy. Two different styrene maleic anhydride crosslinking agents were used in the epoxy formulation, styrene maleic anhydride 2000 (SMA2000) and styrene maleic anhydride 4000 (SMA4000). The effect of the maleic anhydride concentration within SMA on the electrical, mechanical, and thermal properties of porous epoxy film was evaluated. Epoxy films crosslinked with SMA2000 resulted in films with a higher dielectric constant compared to films prepared with SMA4000 due to higher mole fraction of maleic anhydride within SMA2000. However, SMA2000 crosslinked films yielded films with better mechanical and thermal properties. SMA2000 crosslinked films with 30% porosity had a coefficient of thermal expansion (CTE) of 35.2 ppm/K and glass transition temperature of 143 °C.

GO-modified flexible polymer nanocomposites fabricated via 3D stereolithography

Graphene oxide (GO) induced enhancement of elastomer properties showed a great deal of potential in recent years, but it is still limited by the barrier of the complicated synthesis processes. Stereolithography (SLA), used in fabrication of thermosets and very recently in “flexible” polymers with elastomeric properties, presents itself as simple and user-friendly method for integration of GO into elastomers. In this work, it was first time demonstrated that GO loadings can be incorporated into commercial flexible photopolymer resins to successfully fabricate GO/elastomer nanocomposites via readily accessible, consumer-oriented SLA printer. The material properties of the resulting polymer was characterized and tested. The mechanical strength, stiffness, and the elongation of the resulting polymer decreased with the addition of GO. The thermal properties were also adversely affected upon the increase in the GO content based on differential scanning calorimetry and thermogravimetric analysis results. It was proposed that the GO agglomerates within the 3D printed composites, can result in significant change in both mechanical and thermal properties of the resulting nanocomposites. This study demonstrated the possibility for the development of the GO/elastomer nanocomposites after the optimization of the GO/“flexible” photoreactive resin formulation for SLA with suitable annealing process of the composite in future.