In vivo bioactivity of herbal‐drug‐incorporated nanofibrous matrixes

Aloe‐vera‐incorporated polycaprolactone nanofibrous matrixes were prepared by an electrospinning method. These developed matrixes were evaluated for their water absorption capacity, water vapor permeability, and contact angle, and, in an in vivo animal model, wound‐healing ability. The incorporation of the herbal drug made the matrixes hydrophilic with improved water retention and permeability properties. The in vivo studies were carried out in a rat model and showed improved results with respect to healing. Thus, this study confirmed that the developed matrixes could be used for wound‐healing applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42178.     

Effect of five saturated fatty acids on the properties of sweet‐potato‐starch‐based films

To fully explore the influences of saturated fatty acids (SFAs) on the properties of sweet‐potato‐starch (SPS)‐based films, five SFAs were chosen to add to SPS. The SPS‐based films were prepared by casting. The microstructure, mechanical, optical, water vapor barrier, and thermal properties of the films were investigated. The 2.0% (w/w, on the basis of starch) SFA significantly changed the SPS pasting characteristics in the peak viscosity, breakdown, and other feature point viscosity values as determined by a Rapid Visco Analyser. The amylose molecular weights decreased as measured by high‐performance size exclusion chromatography. A thermal study with differential scanning calorimetry suggested that the addition of SFA increased the onset temperature and peak temperature. Scanning electronic microscope (SEM) images showed a continuous and uniform structure in the films with SFA. The SPS–SFA composite films showed lower light transmission and elongation at break than the control. Compared with the control films, the addition of SFA increased the tensile strength and decreased the water vapor permeability of the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41380.     

Cytotoxicity and cellular uptake evaluation of mitoxantrone‐loaded poly(lactic acid‐co‐lysine) arginine–glycine–aspartic acid nanoparticles

The purpose of this study was to evaluate the in vitro characteristics of poly(lactic acid‐co‐lysine) arginine–glycine–aspartic acid (PLA–PLL–RGD) nanoparticles (NPs) loaded with mitoxantrone. PLA–PLL–RGD NPs with a particle size of 200 nm were prepared with a modified emulsification solvent‐diffusion method. The encapsulation efficiency of the mitoxantrone‐loaded NPs was 85%. In vitro release experiments showed that the release of the drug was prolonged and sustained, and approximately 60.2% of the mitoxantrone was released in the first week. The released drug was integrated to achieve desired drug‐release profiles and still possessed bioactivity according to a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2h‐tetrazolium bromide assay, which indicated that mitoxantrone‐loaded NPs were more cytotoxic against Michigan Cancer Foundation 7 (MCF‐7) breast cancer cells than mitoxantrone. Furthermore, the association processes of NPs with MCF‐7 cells, including binding and effective internalization, were investigated in vitro. The cellular uptake of the NPs was qualitatively studied with confocal laser scanning microscopy and was confirmed with flow cytometry analysis. These experimental results indicated that PLA–PLL–RGD NPs could be used as drug carriers for mitoxantrone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

In vitro and in vivo investigational studies of a nanocomposite‐hydrogel‐based dressing with a silver‐coated chitosan wafer for full‐thickness skin wounds

A nanocomposite reservoir‐type hydrogel dressing of poly vinyl alcohol (PVA) was fabricated by a freeze–thaw method and loaded with silver‐nanoparticle‐coated chitosan wafers (Ag–CHWs). The Ag–CHWs were synthesized by a sonication technique with silver nitrate (AgNO₃) and chitosan powder. Scanning electron microscopy images showed silver nanoparticles (AgNPs) with a size range of 10 ± 4 nm on the surface of the chitosan wafers, and the antibacterial efficacy (minimum inhibitory concentration) of the Ag–CHWs was measured against Pseudomonas aeruginosa (32 µg/mL), Staphylococcus aureus, (30 µg/mL) and Escherichia coli (32 µg/mL). The antimicrobial PVA hydrogel showed an improved tensile strength (～0.28 MPa) and gel content (～92%) in comparison with the blank hydrogels. Full‐thickness‐excision wound studies of the nanocomposite dressing on Wistar rats revealed enhanced wound contraction, improved inflammation response, re‐epithelization rate, neoangiogenesis, and granulation tissue formation in comparison to the control group. A flexible, biocompatible, nanocomposite reservoir dressing not only established the chitosan as a stabilizer but also proved the efficacious and safe utility of AgNPs toward chronic wound management. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43472.     

A comparison of efficiency of two photoinitiators for polymerization of light‐cure dental composite resins

The purpose of the study was to compare the effect of two photoinitiators, (?)camphorquinone (CQ) and 1‐phenyl‐1,2‐propanedione (PPD) on curing performance of light‐cure dental composite resins. Bisphenol A‐glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) monomer mixture was used as the resin matrix. The resin matrix was mixed with CQ and/or PPD along with 0.25% of 4‐(dimethyl amino) phenethyl alcohol (DMAPEA) catalyst. The effect of photoinitiator on curing performance was evaluated and compared in terms of properties such as depth of cure, diametral tensile strength (DTS), flexural strength (FS), flexural modulus (FM), vickers hardness number (VHN), water sorption (WS), and solubility of cured composite. Statistical evaluation using Analysis of Variance (single factor) showed that the photosensitization efficiency of CQ and PPD are comparable. However, their combination showed synergistic effect for properties such as DTS and solubility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(L‐lactide). X. Enhanced surface hydrophilicity and chain‐scission mechanisms of poly(L‐lactide) film in enzymatic,alkaline, and phosphate‐buffered solutions

Attempts were carried out to enhance the surface hydrophilicity of poly(L ‐lactide), that is, poly(L ‐lactic acid) (PLLA) film, utilizing enzymatic, alkaline, and autocatalytic hydrolyses in a proteinase K/Tris–HCL buffered solution system (37°C), in a 0.01N NaOH solution (37°C), and in a phosphate‐buffered solution (100°C), respectively. Moreover, its chain‐scission mechanisms in these different media were studied. The advancing contact‐angle (θ_a) value of the amorphous‐made PLLA film decreased monotonically with the hydrolysis time from 100° to 75° and 80° without a significant molecular weight decrease, when enzymatic and alkaline hydrolyses were continued for 60 min and 8 h, respectively. In contrast, a negligible change in the θ_a value was observed for the PLLA films even after the autocatalytic hydrolysis was continured for 16 h, when their bulk M_n decreased from 1.2 × 10⁵ to 2.2 × 10⁴ g mol^?1 or the number of hydrophilic terminal groups per unit weight increased from 1.7 × 10^?5 to 9.1 × 10^?5 mol g^?1. These findings, together with the result of gravimetry, revealed that the enzymatic and alkaline hydrolyses are powerful enough to enhance the practical surface hydrophilicity of the PLLA films because of their surface‐erosion mechanisms and that its practical surface hydrophilicity is controllable by varying the hydrolysis time. Moreover, autocatalytic hydrolysis is inappropriate to enhance the surface hydrophilicity, because of its bulk‐erosion mechanism. Alkaline hydrolysis is the best to enhance the hydrophilicity of the PLLA films without hydrolysis of the film cores, while the enzymatic hydrolysis is appropriate and inappropriate to enhance the surface hydrophilicity of bulky and thin PLLA materials, respectively, because a significant weight loss occurs before saturation of θ_a value. The changes in the weight loss and θ_a values during hydrolysis showed that exo chain scission as well as endo chain scission occurs in the presence of proteinase K, while in the alkaline and phosphate‐buffered solutions, hydrolysis proceeds via endo chain scission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1628–1633, 2003     

Microstructure‐property relationships in a tissue‐engineering scaffold

Electrospinning can produce tissue‐engineering scaffolds possessing appropriate strength, biomimetic structure, economic appeal, and biocompatibility. To investigate how microstructural changes could potentially affect adherent mammalian cells, tensile samples were strained to 10, 40, and 80% extension, and adhered to double‐sided carbon tape to maintain specific states of strain. While establishing the stress–strain response, we invoked polymer sintering to help verify that the “point bonding” concept is more significant than previously realized at both the macroscopic and microscopic length scales. Sintering successfully established the effects of deliberate, extensive point bonding/localized “notch” generation on mechanical properties and microstructural response without requiring chemical changes within the structure. We also found that fibers experience significant hysteresis in terms of their orientation following exposure to high values of strain. Aligned fibers provide higher strengths (σ_ave = 2.8 ± 0.3 MPa vs. σ_ave = 1.29 ± 0.04 MPa for unaligned fibers) but considerably lower elongation [ε_ave = (30 ± 2)% vs. ε_ave = (102 ± 6)%]. Conversely, when strain occurs perpendicular to the aligned fiber direction total strain increases [ε_ave = (188 ± 6)%] while strength decreases (σ_ave = 0.38 ± 0.01 MPa). Elastic response to low strains appears to estimate ultimate tensile strength. In many ways, electrospun fibers behave similarly to classic interpretations of polymer chains in that when strained in both cases elements can rearrange and translate to align along the direction of loading. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Biological evaluation of chitosan‐based in situ‐forming hydrogel with low phase transition temperature

The aims of current study were to choose a method for preparing sterile chitosan‐α,β‐glycerophosphate (CS‐α,β‐GP) in situ‐forming hydrogel which had potential applications in tissue engineering and evaluated its biocompatibility and degradation characteristics. The results of sterilization stability tests indicated that sterile formulations could be obtained by ultraviolet irradiation of CS powders, 0.22 µm filtration of α,β‐GP and lactic acid solutions, and sterile preparation of CS‐α,β‐GP formulations. The obtained sterile CS‐α,β‐GP formulations showed low hemolysis rates and low BSA adsorption at physiological conditions. When injected in vivo the CS‐α,β‐GP sol turned into gel implant in situ and could be degraded gradually. A minimal inflammatory reaction which could not be found by macroscopic evaluation was induced after injection and new capillary formation was found around the hydrogel humps, making the CS‐α,β‐GP hydrogel worthwhile to be considered for tissue engineering and biomedical applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41594.     

Fabrication and improved performance of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) for packaging by addition of high molecular weight natural rubber

The packaging industry is searching for alternative materials to attain environmental sustainability. Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate (PHBV) is a semicrystalline polymer that meets this sustainability goal since it is bioderived and biodegradable. However, its brittle nature and relatively high water permeation and transmission rates make it unsuitable for packaging applications. In addition, PHBV has poor mechanical, thermal, and rheological properties above 160 °C, limiting its use in cast sheets and thermo‐formed packaging applications. To improve these properties, new blends of PHBV with high molecular weight natural rubber at 5, 10, 15, and 25% by weight were fabricated, and physico‐chemical properties of the blends were characterized. The rubber in the blends aided in the following: increased thermal stability since the complex viscosities of the blends were improved by one log over pure PHBV at 170 °C, created more uniform melting peaks attesting to improved homogeneity, decreased water permeation to a level similar to that of traditional thermoplastics; increased the elongation at break, and stabilized the Young's modulus. Therefore, these blends can potentially be used in‐place of traditional, petroleum‐based thermoplastics in cast sheets and thermoforms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43937.     

Nondegradative microextrusion of resorbable polyesters for pharmaceutical and biomedical applications: The cases of poly‐lactic‐acid and poly‐caprolactone

In recent years biodegradable polymers, particularly polyesters such as the poly(lactic acid) (PLA) and polycaprolactone (PCL), have gained high interests for their applicability in the biomedical and pharmaceutical fields where they're used for manufacturing various different resorbable devices, from tissue engineering scaffolds to controlled drug release systems. Despite many positive characteristics, processability of these materials still remains a critical issue as they easily tend to degrade during manufacturing. In this article we aimed to assess microextrusion as a nondegradative process for manufacturing PLA and PCL. The results we experimentally obtained, that are hereby presented, set a new point in the on‐going debate on degradation during processing of resorbable polymers as they allow to affirm that microextrusion leaves unmodified molecular weight distributions without producing any evident reductions in mean molecular weight. Microextrusion thus represents a risk‐free high molecular weight polymer processing solution for obtaining nondegraded products within pharmaceutical and biomedical production lines, such as for scaffolds for tissue engineering applications or drug delivery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Hydrolytic degradation and crystallization behavior of linear 2‐armed and star‐shaped 4‐armed poly(l‐lactide)s: Effects of branching architecture and crystallinity

“Linear” aliphatic polyesters composed of two poly(l ‐lactide) arms attached to 1,3‐propanediol and “star‐shaped” ones composed of four poly(l ‐lactide) arms attached to pentaerythritol (2‐L and 4‐L polymers, respectively) with number‐average molecular weight (M_n) = 1.4–8.4 × 10⁴g/mol were hydrolytically degraded at 37°C and pH = 7.4. The effects of the branching architecture and crystallinity on the hydrolytic degradation and crystalline morphology change were investigated. The degradation mechanism of initially amorphous and crystallized 2‐L polymers changed from bulk degradation to surface degradation with decreasing initial M_n; in contrast, initially crystallized higher molecular weight 4‐L polymer degraded via bulk degradation, while the degradation mechanism of other 4‐L polymers could not be determined. The hydrolytic‐degradation rates monitored by molecular‐weight decreases decreased significantly with increasing branch architecture and/or higher number of hydroxyl groups per unit mass. The hydrolytic degradation rate determined from the molecular weight decrease was higher for initially crystallized samples than for initially amorphous samples; however, that of 2‐L polymers monitored by weight loss was larger for initially amorphous samples than for initially crystallized samples. Initially amorphous 2‐L polymers with an M_n below 3.5 × 10⁴g/mol crystallized during hydrolytic degradation. In contrast, the branching architecture disturbed crystallization of initially amorphous 4‐L polymers during hydrolytic degradation. All initially crystallized 2‐L and 4‐L polymers had δ‐form crystallites before hydrolytic degradation, which did not change during hydrolytic degradation. During hydrolytic degradation, the glass transition temperatures of initially amorphous and crystallized 2‐L and 4‐L polymers and the cold crystallization temperatures of initially amorphous 2‐L and 4‐L polymers showed similar changes to those reported for 1‐armed poly(l ‐lactide). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41983.     

Physical characterization of a self‐healing dental restorative material

The objectives of this study were to determine the efficacy of self‐healing a highly filled composite and to investigate the physical properties of a model dental compound formulated to autonomically heal cracks. A visible light cured model resin consisting of TEGMA : UDMA : BisGMA (1 : 1 : 1) at 45% w/w with silane 0.7 μ glass was formulated with a self‐healing system consisting of encapsulated dicyclopentadiene and Grubbs' catalyst. The base resin was also formulated and characterized with the microcapsules alone, Grubbs' catalyst alone, and no healing additives. Fracture toughness (K_Ic) was assessed using single edge notch specimens in three‐point bend (n = 12). Data was analyzed with ANOVA/Tukey's at p ≤ 0.05. DMA was performed from ?140 to 250°C at 2°/min and 1 Hz. Storage and loss modulus, T_g and tan δ, was recorded for each material. The self‐healing material was loaded to failure, was left to sit for 7 days and then loaded a second time to failure to determine healing in the material. These specimens had a K_Ic = 0.69 ± 0.072 for a 57% average recovery rate of the original fracture toughness. The fracture toughness of the self‐healing material was statistically similar to the control. The modulus decreased in the composites with encapsulated dicyclopentadiene. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate copolymers for pH responsive and shape memory hydrogel

Multifunctional hydrogels combining the capabilities of cellular pH responsiveness and shape memory, are highly promising for the realization of smart membrane filters, controlled drug released devices, and functional tissue‐engineering scaffolds. In this study, lipase was used to catalyze the synthesis of medium‐chain‐length poly‐3‐hydroxyalkanoates‐co‐polyethylene glycol methacrylate (PHA‐PEGMA) macromer, which was used to prepare pH‐responsive and shape memory hydrogel via free radical polymerization. Increasing the PEGMA fraction from 10 to 50% (mass) resulted in increased thermal degradation temperature (T_d) from 430 to 470°C. Highest lower critical solution temperature of 37°C was obtained in hydrogel with 50% PEGMA fraction. The change in PEGMA fraction was also found to highly influence the hydrogel's hydration rate (r) from 2.8 × 10^?5 to 7.6 × 10^?5 mL·s^?1. The hydrogel's equilibrium weight swelling ratio (q_e), protein release and its diffusion coefficient (D_m) were all found to be pH dependent. Increasing the phosphate buffer pH from 2.4 to 13 resulted in increased q_e from 2 to 16 corresponding to the enlarging of network pore size (ξ) from 150 to 586 nm. Different types of crosslinker for the hydrogel influenced its flexibility and ductility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41149.     

Fully bio‐based poly(ɛ‐capolactone)/poly(lactide) alternating multiblock supramolecular polymers: Synthesis,crystallization behavior,and properties

Supramolecular poly(?‐capolactone)/poly(lactide) alternating multiblock copolymers were prepared by UPy‐functionalized poly(lactide)‐b‐ poly(?‐capolactone)‐b‐ poly(lactide) copolymers. The prepared supramolecular polymers (SMPs) exhibit the characteristic properties of thermoplastic elastomers. The stereo multiblock SMPs (sc‐SMPs) were formed by blending UPy‐functionalized poly(l ‐lactide)‐b‐ PCL‐b‐ poly(l ‐lactide) (l ‐SMPs) and UPy‐functionalized poly(d ‐lactide)‐b‐ PCL‐b‐ poly(d ‐lactide) (d ‐SMPs) due to stereocomplexation of the PLLA and PDLA blocks. Sc‐SMPs with low content of d ‐SMPs (≤20%) are transparent, elastic solids, while those having high d ‐SMPs content are opaque, brittle solids. The effects of l ‐SMPs/d ‐SMPs mixing ratios on thermal, crystallization behaviors, crystal structure, mechanical and hydrophilic properties of sc‐SMPs were deeply investigated. The incorporation of UPy groups depresses the crystallization of polymer, and the stereocomplex formation accelerates the crystallization rate. The used initiator functionalized polyhedral oligomeric silsesquioxanes causes a different effect on the crystallization of PLA and PCL blocks. The tensile strength and elongation at break of l _d /d _d ‐SMPs (d represents the initiator diethylene glycol) are significantly larger than that of l _p /d _p ‐SMPs (p represents the initiator polyhedral oligomeric silsesquioxanes), and their heat resistance and hydrophilicity can be also modulated by the l ‐SMPs/d ‐SMPs mixing ratios and the different initiators. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45575.     

In situ chemically crosslinked chitosan membrane by adipic acid

Adipic acid, which is nontoxic, was used to dissolve chitosan. The chitosan/adipic acid solution was used to prepare chitosan membrane. After being heated at 80–100°C, the membrane was in situ chemically crosslinked by adipic acid, as verified by Fourier transform infrared and wide‐angle X‐ray diffractometer analysis. The crosslinked membrane did not collapse even without treatment in alkaline solution. In addition, the in situ crosslinking reaction was studied. The crosslinking degree (CLD) was quantitatively calculated based on the mass of water produced. The results showed that CLD was positively related to both heating temperature and time. Results of kinetic of crosslinking reaction suggested that the amidation was in agreement with the first‐order rate equation and that the temperature effect could be described with the Arrhenius equation. The results of weight loss of chitosan membrane in phosphate‐buffered solution (pH = 7.4) indicated that the best water resistance of chitosan membrane was obtained at 90°C. In brief, a straightforward, nontoxic, environment‐friendly, and economical chemically crosslinking approach has been developed for chitosan materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrospray‐assisted fabrication of core‐shell arabinoxylan gel particles for insulin and probiotics entrapment

This work presents the fabrication and characterization of electro‐sprayed core‐shell particles that were composed of maize bran arabinoxylans (MBAX) with insulin in the core, and maize wastewater arabinoxylans (MWAX) with Bifidobacterium in the shell. Two concentrations of MBAX (3% and 6% w/v) and MWAX (6% and 10% w/v) were evaluated. The particles fabricated with MBAX at 6% (w/v) in the core and MWAX at 10% (w/v) in the shell were more stable, presented spherical shape and no aggregation being therefore selected to be loaded with insulin and probiotics. These particles presented a size of 2.9 mm. Scanning electron microscopy analysis of the particle cross section revealed the presence of both, a smooth (shell) and a porous (core) microstructure. Confocal laser scanning microscopy confirmed the core‐shell structure of the particles and the viability of the probiotic entrapped. Gastrointestinal simulation strongly suggests that these particles are not degraded in the stomach and small intestine and that 76% of the carried insulin is released in colon. These results indicate that insulin and Bifidobacterium encapsulation by tetraaxial electro spraying can be a feasible and adequate technique to produce arabinoxylan capsules containing both insulin and probiotics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46411.     

Surface and degradation properties of thermoplastic blends from albumin and zein‐based plastics

The use of traditional petroleum‐based thermoplastics in food packaging applications pose an environmental hazard, as their lack of biodegradability creates waste that environmental systems are unable to cope with. To address this issue, the investigation of surface, biodegradation, and water solubility properties of the albumin and zein thermoplastic blends plasticized with glycerol and mixed with varying amounts of low‐density polyethylene (LDPE) is conducted. When subjected to soil burial, albumin as a bioplastic completely biodegrades within two months, while a zein‐based bioplastic is more resilient to attacks from microbes within the soil (4.34% of intial mass remains). If albumin and zein proteins are used in the production of thermoplastics in tandem with LDPE, it could be possible to produce a plastic that will naturally biodegrade over time, decreasing the environmental impact of the use of thermoplastics in medical and food packaging applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44646.     

Effect of reinforcement of sustainable β‐CaSiO3 nanoparticles in bio‐based epoxy resin system

The β‐CaSiO₃ nanoparticles (NPs) were prepared using calcium carbonate from egg shells and silica as precursors. These NPs were incorporated (1–4 wt %) into bio‐based epoxy resin to fabricate nanocomposites. Thermal and mechanical tests were carried out on these composites. The results of dynamic mechanical analysis showed significant improvement in the storage modulus of 1 and 2 wt % composites. The thermomechanical analysis data revealed ～19 and 20% of reduction in coefficient of thermal expansion for 1 wt % of CaSiO₃ before and after glass transition as compared to the neat epoxy system. Thermogravimetric analysis results also showed delayed thermal degradation of the composites by significant amounts (17–35°C) for 5% of decomposition, a proportional increase in residues corresponding to the loading concentrations. The flexure tests showed significant improvements in strength (17–36%), modulus (5–33%), and toughness for 1–4 wt % of reinforcement of β‐CaSiO₃ NPs. Theoretical calculations of the reinforcement effect on the flexure modulus of the composites agree well with the experimental values. The scanning electron micrograph of the fractured surfaces revealed better interfacial interactions in the composites and enhancements in crack path deflections over the neat specimen. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40867.     

Degree of conversion of a copolymer of an experimental monomer and methyl methacrylate for dental applications

The aim of this study was to determine the degree of double bond conversion of the copolymer of an experimental monomer and methyl methacrylate after photopolymerization. A mixture of an experimental monomer with four methacrylate groups and methyl methacrylate monomer (mass ratio 70 : 30) was polymerized by using various concentrations of light initiator system. The degree of conversion was determined with FTIR spectrometry. A photopolymerized 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy)‐ phenyl]propane/triethylene glycol dimethacrylate (mass ratio 40 : 60) copolymer was used as a control material for degree of conversion. The maximum degree of conversion for the experimental monomer/methyl methacrylate copolymer was 62% and was obtained with 2 wt % initiator concentration. It was comparable to that of the control polymer (64%). The results of this study suggest that the experimental monomer/methyl methacrylate system can be polymerized by light initiator system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1908–1912, 2004     

Effects of thermal aging on degradation mechanism of flame retardant‐filled ethylene–propylene–diene termonomer compounds

Ethylene–propylene–diene termonomer (EPDM) compounds filled with halogenated (Br and Cl) flame retardants (FRs) and Sb₂O₃ were prepared via melt mixing, and their thermal stability, weight loss, and elemental composition were investigated as a function of aging conditions (temperature: 120–380°C, period: ～100 h, and atmosphere: nitrogen and air). The thermal aging was done with thermogravimetic analysis under both isothermal and nonisothermal conditions and a convection oven. Scanning electron microscopy–energy dispersive spectroscopy was used to study the surface morphology and elemental composition of the thermally aged FRs‐filled EPDM compounds. For a better precision of compositional analysis, a laser‐induced breakdown spectroscopy (LIBS) was employed in this study. The thermal degradation behavior of EPDM compounds containing halogenated FRs was strongly dependent on the aging atmosphere (N₂ or air) and type of FRs. The weight loss of the EPDM compounds during thermal aging was found to be quite small in the temperature ranges below 190°C, while it was noticeable above the temperature. The LIBS technique can be an effective and promising analysis tools for analyzing the elemental components in a bulk rubber compound. Two possible mechanisms were proposed for the thermal degradation of the EPDM compounds containing brominated FR and Sb₂O₃. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41324.