Post-polymerization Temperature Research Articles

Effects of postpolymerization time and temperature on the flexural properties and hardness profile of three-dimensional printed provisional resin

Background/purposeThree-dimensional (3D) printing technique was widely used for provisional restorations in clinical use. However, the effects of post-polymerization temperature and time on the flexural properties and hardness profile were not fully elucidated yet. The purpose of this study is to investigate the effects of post-polymerization temperature and time on the flexural properties and hardness profile of the provisional restoration. Materials and methods3D-printing provisional resin was printed and post-polymerized at various temperatures (room temperature, 40 °C, 60 °C and 80 °C) and periods (0, 15, 30, 60, 90 and 120 min of photopolymerization). Afterwards, the flexural strength, flexural modulus, surface hardness, and internal hardness at different depth were evaluated. ResultsThe group post-polymerized without concurrent heating had significantly shallow depth of cure comparing to the heating counterparts. The surface hardness of the groups post-polymerized at different temperatures did not show any difference. All groups with post-polymerization temperature at 40 °C, 60 °C and 80 °C and post-polymerization time ranged between 15 and 90 min, had curing depth between 3 and 4 mm. Group post-polymerized without concurrent heating has significantly shallow depth of cure comparing to the heating counterparts. ConclusionPost-polymerization at an elevated temperature, preferably 60 °C, is suggested. The wall thickness of the 3D-printing provisional prosthesis thinner than 3–4 mm is recommended.

A self-templating dilution strategy for preparation of hollow concave polystyrene nanoparticles in a styrene/ethanol-water ternary system

Hollow concave polymer particles have attracted wide attention due to their particular properties and applications, however, the controllable synthesis of hollow concave polystyrene nanoparticles (HC-PSNPs) based on soap-free emulsion polymerization via a one-pot method has not been achieved. Herein, based on a styrene/ethanol-water (St/EtOH-H2O) ternary system, a simple green self-templating dilution strategy was established to produce monodisperse HC-PSNPs. In the synthesis, the degree of concavity and opening size of HC-PSNPs can be controlled by adjusting polymerization parameters such as the pre-polymerization time (polymerization time before dilution) and dilution conditions (including dilution ratio and ethanol content of the diluents). Furthermore, one opening or multiple openings in the surface of HC-PSNPs can be controlled by varying the post-polymerization temperature (polymerization temperature after dilution). Based on our results and observations, we propose a plausible mechanism for the formation of HC-PSNPs.

Cationic starch-grafted-cationic polyacrylamide based graphene oxide ternary composite flocculant for the enhanced flocculation of oil sludge suspension

In this study, a novel, highly efficient and environmentally friendly ternary composites flocculant, namely, cationic starch-grafted-cationic polyacrylamide/graphene oxide (CS-g-CPAM/GO), was synthesized by ammonium persulfate initiation polymerization and condensation reaction. First, CS-g-CPAM was polymerized with cationic starch (CS), acrylamide (AM) and diallyl dimethyl ammonium chloride (DMDAAC), and CS-g-CPAM/GO was then synthesized by condensation reaction. The influence factors of graft polymerization were investigated, including total monomer concentration, initiator dosage, monomer mass ratio of mAM: mCS: mDMDAAC, post-polymerization temperature and post-polymerization time. The chemical structures and morphologies of the samples were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The CS-g-CPAM/GO was used to flocculate the oil sludge suspension, the effects of CS-g-CPAM/GO dosage, temperature and pH value on the flocculation performance were investigated, and the flocculation mechanism of CS-g-CPAM/GO was also analyzed. The results show that CS-g-CPAM/GO has outstanding flocculation effect, and CS-g-CPAM/GO flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.

Preparation and characterization of polymethyl methacrylate light-scattering material

In this paper, hydroxyl terminated polysiloxane was first prepared by ring-opening polymerization of octamethylcyclotetrasiloxane (D4), which was then modified with acryloyl chloride to obtain acryloyloxy polysiloxane. A light-scattering material was synthesized by copolymerization of acryloyloxy polysiloxane and methyl methacrylate (MMA). The results showed that the transmittance of the material was 88% and the haze was 93% when the ratio of MMA to light-scattering agent was 100:1, the amount of initiator was 0.3%, and the post-polymerization temperature was 50 °C. The TGA data indicated that the material had excellent heat resistance. Therefore, it has a wide range of applications in the field of light-emitting diodes.

Ammonium persulfate-initiated polymerization of cationic starch-grafted-cationic polyacrylamide flocculant for the enhanced flocculation of oil sludge suspension

In this study, a novel, highly efficient and environmentally friendly flocculant, namely, cationic starch-grafted-cationic polyacrylamide (CS-g-CPAM), was synthesized by initiation polymerization of ammonium persulfate. First, CS-g-CPAM was polymerized with cationic starch(CS), acrylamide(AM) and diallyl dimethyl ammonium chloride (DMDAAC), and then the influence factors of graft polymerization were investigated, including total monomer concentration, initiator dosage, the monomer mass ratio of mAM: mCS: mDMDAAC, post-polymerization temperature and post-polymerization time. And the intrinsic viscosity of the CS-g-CPAM was measured by the one point method accurately. The chemical structures and morphology of the samples were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric and differential scanning calorimetry (TG-DSC), and scanning electron microscope (SEM). The CS-g-CPAM was utilized to flocculate the oil sludge suspension, the effects of CS-g-CPAM dosage, temperature and pH value on the flocculation performance were investigated. The results show that CS-g-CPAM has outstanding flocculation effect.

Plasma-induced synthesis of chitosan-g-polyacrylamide and its flocculation performance for algae removal

ABSTRACTChitosan (CS)-g-polyacrylamide (PAM) is a highly efficient and environmentally friendly flocculant, which was synthesized through plasma-induced graft copolymerization of CS and acrylamide (AM). The effects of monomer concentration, AM:CS ratio, discharge power, discharge time, post-polymerization temperature, and post-polymerization time on the intrinsic viscosity, grafting ratio, and grafting efficiency of CS-g-PAM were investigated. The optimum conditions of graft copolymerization were as follows: 20% monomer concentration, 7:3 AM:CS ratio, 40 W discharge power, 90 s discharge time, 50°C post-polymerization temperature, and 24 h post-polymerization time. The structural characteristics of CS-g-PAM were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. CS-g-PAM exhibited better flocculation efficiency than the commercially available PAM in both diatomite-simulated wastewater and low-turbidity algal water. The optimal turbidity removal efficiency for the diatomite-simulated wastewater was 99.9%, which was obtained with 6 mg L−1 of CS-g-PAM at pH 11.0 and 250 s−1 of velocity gradient. In low-turbidity algal water, the optimal removal efficiencies for chlorophyll-a, turbidity, and COD were 93.6%, 94.5%, and 98.2%, respectively.

Macroporous polymer particles via reactive gelation under shear: effect of primary particle properties and operating parameters.

Reactive gelation under shear is a recently developed procedure toward rigid macroporous polymeric particles that does not require the use of any porogen. A comprehensive study of the effect of individual parameters on the resulting material characteristics is presented. Primary particle properties are found to be pivotal, namely, the primary particles size, cross-linking degree, and outer shell composition. Operating parameters also play a significant role; specifically, the effects of applied shear rate, salt feeding rate, swelling degree of primary particles, waiting time before postpolymerization, and postpolymerization temperature are investigated. By varying the operating conditions, the size, internal structure, as well as porosity of the fabricated microclusters may be controlled. The pores are invariably micrometer-sized, with pore size distributions exhibiting adjustable maxima. Thanks to the sequential character of the procedure, different parameters may be tuned individually at different stages along the preparation route, allowing thus for high versatility in the control of different properties of the final material.

Temperature‐sensitive membranes prepared by the plasma‐induced graft polymerization of N‐Isopropylacrylamide into porous polyethylene membranes

AbstractA temperature‐responsive polymer, poly(N‐isopropylacrylamide) (PNIPAAm), was grafted onto porous polyethylene membranes by a plasma‐induced graft polymerization technique. A wide range of grafting was achieved through variations in the grafting conditions, including the postpolymerization temperature, time, monomer concentration, and graft‐reaction medium. The active species induced by plasma treatment was proven to be long‐living via a postpolymerization time of 95 h. Different solvent compositions, that is, water, methanol, benzene, and water/methanol, were used as reaction media, and water showed a much higher polymerization rate than the organic solvents. Based on the hydrophilicity of the active species, a mechanism explaining the solvent effect in plasma‐induced graft polymerization was examined. Characterizations by scanning electron microscopy, X‐ray photoelectron spectroscopy (XPS), and micro Fourier transform infrared showed that the grafted polymers were located on both the outer surface and inside pores of the membranes. The XPS analysis also confirmed that the polar amide groups tended to distribute more outward when grafted PNIPAAm was in its expanding state than when it was in its shrinking state. Water permeation experiments showed that the permeability of the grafted membranes varied dramatically with a slight temperature change in the vicinity of the lower critical solution temperature (LCST) of PNIPAAm. The effective pore radii of the grafted membranes above and below the LCST could be depicted by Hagen‐Poiseuille's law. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3180–3187, 2003

Novel regular network polyimide films from mellitic acid and aliphatic and aromatic diamines or diisocyanates

Novel regular network aliphatic-aromatic and aromatic polyimide films were prepared from mellitic acid (Y H) and aliphatic and aromatic diamines or diisocyanates. Prepolymers prepared by solution polycondensation were cast and successively post-polymerized to form a network. The resultant films were insoluble in any organic solvents. The heat distortion temperature ( T h ) and density of network polyimide films increased and then levelled off with increasing post-polymerization temperature and time. Polyimide films prepared from diisocyanates and Y H had higher T h values compared with those prepared from the corresponding diamines and Y H, which is due to the enhanced degree of reaction of the former films shown by infra-red spectroscopy. On increasing the length of the methylene chain in the diamine component, the T h values and densities decreased and the intensities of X-ray diffraction peaks increased for network aliphatic-aromatic polyimide films. The T h values of network polyimide films were somewhat higher than those of the corresponding linear polyimide films and network polyamide films. The 6′Y H film prepared from Y H and hexamethylene diisocyanate (6′) post-polymerized at 370°C for 1 h had a T h value of 316°C; and the OY H film prepared from Y H and 4,4′-diaminodiphenyl ether (O) post-polymerized at 370°C for 1 h had the highest T h value of 449°C among the polyimide films studied. Network polyimide films had much higher thermal resistance compared with the corresponding linear polyimide films at higher temperature, suggesting the preferred formation of carbonized structure.

Network polyester films from glycerol and dicarboxylic acids

AbstractThis paper presents information on the preparation of the network polyester films from glycerol (Yg) and aromatic dicarboxylic acids of phthalic anhydride (P), dimethyl isophthalate (I) and dimethyl terephthalate (T), as well as aliphatic dicarboxylic acids of adipic, sebacic, 1, 10‐decanedicarboxylic and 1, 12‐dodecanedicarboxylic acids, and their properties. Yg and dicarboxylic acid were polycondensed immediately before the gelation started. The prepolymers obtained were cast from DMF solution and successively post‐polymerized at various temperatures and times to form networks. The resultant films were transparent, flexible and insoluble in organic solvents. Heat distortion temperature (Th) measured by a penetration mode of thermomechanical analysis increased with increasing post‐polymerization temperature and time, and then leveled out. Th values corresponded well to the glass transition temperature (Tg) measured by differential thermal analysis (DTA). Th was 152°C, 162°C and 197°C for YgP, YgI and Yg T post‐polymerized at 270°C for 6 h, respectively. Th values of network films made from aliphatic dicarboxylic acids could not be observed until complete probe penetration occurs, as a result of thermal decomposition because the Tg is lower than room temperature. The degree of reaction estimated from the IR absorbance of hydroxyl and methylene groups was in the range of 60–80%. Two diffraction peaks appeared in the wide‐angle X‐ray scattering pattern, suggesting some ordered structure owing to the regular networks. Density decreased with increasing post‐polymerization time and temperature, in the order YgP > YgI > YgT. Network films made from aliphatic dicarboxylic acids had much lower tensile strength and Young's modulus, and greater elongation, than those made from dicarboxylic acids, as a result of the Tg being below room temperature.

Novel regular network wholly aromatic polyester and polyamide films

Novel regular network wholly aromatic polyester and polyamide films were prepared from trimesic acid (Y) and aromatic diols and aromatic diamines. Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and post-polymerized at various elevated temperatures and times to form networks. The resultant films were insoluble in any organic solvents. Heat distortion temperature T h of both polyester and polyamide films increased with increasing post-polymerization temperature and time. Polyester films of OY, prepared from Y and 4,4′-dihydroxybiphenyl ether (O) post-polymerized at 290°C for 18 h, and of BY, prepared from Y and 4,4′-dihydroxybiphenyl (B) post-polymerized at 340°C for 2 h, showed the highest T h (430°C) of the polyester films studied. Polyamide films of O′Y, prepared from Y and 4,4′-diaminobiphenyl ether (O′) post-polymerized at 350°C for 2 h, had the highest T h (444°C) of the polyamide films studied. The degree of reaction, a measure of network formation, increased with increasing post-polymerization time. X-ray diffraction patterns of these network polymer films exhibited broad but distinct diffraction peaks, suggesting the formation of some ordered structure owing to the regular network formed by symmetrical trimesic acid moiety. The density of polyester films decreased and that of polyamide films increased with increasing post-polymerization time. These network polymers had tensile strengths and Young's moduli lower than the network polyester film of 2GY prepared from Y and ethylene glycol (2G). Temperature profiles of both thermomechanical analysis and thermogravimetry of polyamide films exhibited higher thermal resistance than polyester films, suggesting the formation of a carbonized structure at higher temperature.

Morphology of poly(tetraoxane) prepared by radiation-induced polymerization in the solid state.

Morphology and crystal orientation of poly (tetraoxane) (PTEOX) prepared by γ-ray induced polymeriza tion of tetraoxane (TEOX) single crystal were studied. The two-step postpolymerization process was applied and the polymer yield was high. The polymer yield is rather low at the first step postpolymerization, but it significantly increased at the second step because of the presence of PTEOX formed at the first step. The role of the resulting polymer can be considered to act as spatial guide or a substrate for epitaxial growth when the polymer chain grows. The extended chain crystal is always formed by this polymerization method and the lamellar crystal is formed at postpolymerization temperature above 80°C, while the subcrystal is formed below 90°C. Though all samples show net-like texture, most of the molecular chains orients along the fiber axis, impling that these polymers are composed of the so-called “shish kebab” structure.

Radiation-Induced Copolymerization of Trioxane with 1,3-Dioxolane

Abstract Copolymerization of 1,3-dioxolane (DOX) with trioxane in the solid state was studied by radiation. The effects of radiation dose, DOX concentration, postpolymerization temperature and duration on the copolymer yield, and DOX incorporation were investigated and compared with published data.

Radiation-induced copolymerization of trioxane with tetrahydrofuran

Abstract Radiation-initiated copolymerization of solid trioxane (TOX) with tetrahydrofuran (THF) was investigated. The effects of radiation dose, THF concentration, and post-polymerization temperature and duration on copolymer yield and THF incorporation were studied. These results are compared with the results of TOX homopolymerization under identical conditions. Copolymer yield was lower than that of homopolymer. Only a fraction of charged THF entered into the polymer chain. THF content and radiation dose also altered the MW of the copolymer but it showed better thermal stability. The initial reaction rates of the copolymerization were determined and from these the activation energy was found to be 36.2 kcal mol −1 .

Radiation-Induced Copolymerization of Trioxane with Styrene Oxide

Abstract Copolymerization of trioxane (TOX) and styrene oxide (STO) induced by gamma radiation was studied under varying operating conditions to see the effects of radiation dose, STO concentration, postpolymerization temperature, and duration on the polymer yield. Charging 5% STO with TOX STO conversion was 65% but yield was only 23% compared with 62% for the homopolymer. Molecular weight, melting point, density, and thermal stability of the copolymer samples were determined.

NMR and ESR studies of the solid‐state polymerization of vinyl monomers. III. Methacrylic acid

AbstractThe kinetics of postpolymerization of γ‐irradiated methacrylic acid at 77°K has been investigated by wide‐line NMR and by ESR spectroscopy. The conversion yield was continuously measured in the temperature range of 260–280°K, from the narrowing of the NMR spectrum due to the progressive “amorphization” of the matrix, releasing the motion of monomer molecules. The rate of postpolymerization decays exponentially with time, independently of the recombination of free radicals. The local concentration of radicals remaining after prolonged annealing is actually the same as initially, showing that no recombination occurs in the microdomains of polymerization. The 13C NMR study of the poly(methacrylic acid) formed by solid‐state polymerization shows a predominent syndiotactic character, with an increasing contribution of isotactic sequences as the postpolymerization temperature is lowered.

Radiation‐induced postpolymerization of nitroethylene

AbstractRadiation‐induced postpolymerization of nitroethylene in 2‐methyltetrahydrofuran glass has been studied and discussed in reference to the results obtained from ESR measurements. No postpolymerization occurred at the temperature below −150°C. In the temperature range between −135°C and −78°C, the polymer yield decreased with increasing postpolymerization temperature. The polymer yield increased linearly with the increase of the preirradiation dose in the range below 0.9 × 106 r. The mean value for chain initiation was estimated to be about 1.3. The following correlations were observed between the results of the postpolymerization and ESR measurements. The postpolymerization started in the temperature range between −140°C and −135°C, where the ESR spectrum due to the anion radicals of nitroethylene disappeared. The polymer yield of the postpolymerization decreased with the photoirradiation at −196°C before warming the samples in parallel with the photobleachability of the anion radicals observed in the glassy mixture by the ESR method. It was concluded from these results that the radiation‐induced postpolymerization was initiated by the anion radicals of nitroethylene formed by the capture of electons.