Improvement of hydrophilicity of polypropylene by liquid-phase mutual irradiation of acrylics

N-butanol was found to promote the inclusion of methyl acrylate and methyl methacrylate in polypropylene, but did not affect the uptake of acrylic acid in the polymer. Polymerization of the monomers was, however, not significantly affected by the use of this swelling agent. The monomer exchange process followed by a liquid phase mutual irradiation has proved to be very effective in enhancing the polymerization of all three monomers on polypropylene. Optimum radiation doses for effective polymerization of the monomers were found to be around 3.2 Mrad for methyl acrylate and around 4.8 Mrad for methyl methacrylate and acrylic acid. Surface wettability of the film and moisture regain of the fiber were tremendously improved with all monomers regardless of the swelling agent and temperatures. Also, a low radiation dose of 1.6 Mrad was as effective as the higher doses. Methyl acrylate and methyl methacrylate modified fibers showed no marked changes in strength and elongation, but did result in a harsher hand. Acrylic acid modified fibers increased greatly in elongation, decreased to a greater extent in strength, and softened in hand.     

Chemical conversion of wood to thermoplastic material

A chemically modified wood meal (CE-wood) was prepared by cyanoethylation in the presence of alkaline salts. The temperature T_f at which the wood could flow was measured by a simple mechanical flow tester. The CE-wood demonstrated thermal flow at around 250°C. The T_f value decreased with increasing cyanoethyl content of the wood. Treatment of the wood meal before cyanoethylation with sodium periodate or sodium chlorite lowered T_f. The flow temperature was also decreased by blending the CE-wood with appropriate synthetic polymers or plasticizers. Treatment of CE-wood with chlorine solution was found to be the most effective method of lowering T_f. The T_f value of the slightly chlorinated CE-wood (Cl content=2%) was about 100°C lower than that of the original CE-wood. The lowering of T_f for CE-wood by treatment with chlorine may be interpreted in terms of the plasticizing effect of chlorination on the lignin moiety in the wood.     

Dental restorative composites containing methacrylic spiroorthocarbonate monomers as antishrinking matrixes

In this work, the synthesis of two new antishrinking methacrylic monomers of spiroorthocarbonate type, SOC-IP-UDMA and SOC-UDMA, is discussed, along with studies of their performance as polymeric matrix in dental composites. The monomers were photoactive with components of a conventional resin composite. In order to study the photocuring kinetics of these SOC monomers, a real-time test was performed using FTIR spectroscopy. It was found that SOCs promoted higher double bond conversions (DC) than conventional methacrylic monomer bis-GMA (48%), reaching a DC value of 68% for SOC-UDMA and 75% for SOC-IP-UDMA. The shrinkage stress that accompanies curing of dental composites was measured by a universal testing machine. These new monomer SOCs are capable of reducing the shrinkage up to 51.1% and 27.7% for both methacrylic monomers when they were compared with bis-GMA as control. Also, a dynamical mechanical analysis was conducted on the dental composites, obtaining a higher modulus and a range of T _g values from 80 to 100 °C. Others parameters like flexural properties, solubility, and sorption water were determined, obtaining values better than or equal to the parameters established by the standard ISO 4049. These monomers can be considered as alternative matrixes to replace bis - GMA in dental composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47114.     

Swelling and Network Parameters of Oil Sorbers Based on Alkyl Acrylates and Cinnamoyloxy Ethyl Methacrylate Copolymers

Cinnamoyloxy ethyl methacrylate (CEMA) monomer was copolymerized with different monomer feed ratios of alkyl acrylate, such as dodecyl and octadecyl acrylate DDA and ODA, respectively. The monomers were copolymerized with different mole% to produce different compositions for each CEMA/alkylacrylate copolymer with low conversion. ¹HNMR was used to determine the copolymer compositions. The monomer reactivity ratios of each CEMA/alkylacrylate copolymer were determined using Fineman-Ross and Kelen-Tudos methods. CEMA was copolymerized with DDA or ODA and crosslinked using azobis isobutyronitrile (AIBN) as the initiator and 1% weight content of either 1,1,1-trimethylolpropane triacrylate (TPT) or 1,1,1-trimethylolpropane trimethacrylate (TPT_m) crosslinkers. The swelling parameters, such as the maximum oil absorbency (Q _max), characteristic oil sorbency (Q), characteristic swelling time (T), and swelling rate constant (k), were evaluated for the synthesized sorbers. The network parameters, such as the polymer solvent interaction (χ), effective crosslink density (υ _e), equilibrium modulus of elasticity (G _T), average molecular weight between crosslinks (M _c), and the theoretical crosslink density (υ _t), were determined and correlated with the structure of the synthesized sorbers.     

Fracture toughness of poly(lactic acid)/ ethylene acrylate copolymer/wood‐flour composite ternary blends

A fracture mechanics analysis based on the J‐integral method was adopted to determine the resistance of composites with various concentrations of wood‐flour and ethylene acrylate copolymer (EAC) to crack initiation (J_in) and complete fracture (J_f). The J_in and J_f energies of unmodified poly(lactic acid) (PLA)/wood‐flour composites showed the deleterious effect of incorporating wood fibers into the plastic matrix by significantly decreasing the fracture toughness of PLA as the wood‐flour content increased. The reduced fracture toughness of the matrix induced by adding brittle wood‐flour into PLA was well recovered by impact modification of the composites with EAC. Microscopic morphological studies revealed that the major mechanisms of toughening were through the EAC existing as separate domains in the bulk matrix of the composites which tended to act as stress concentrators that initiated local yielding of the matrix around crack tips and enhanced the toughness of the composites. © 2012 Society of Chemical Industry     

Radiation-induced grafting of methacrylic acid onto polyurethane in the presence of solvents

The radiation-induced grafting of methacrylic acid onto polyurethane has been carried out in the presence of solvents. The swelling of polyurethane was highest when the solubility parameter of the monomer solution was 11.0. The molecular weight of polyurethane did not change with the irradiation dose up to 30 Mrad in the absence of solvent. The irradiation in the presence of solvent, on the other hand, decreased the molecular weight. The grafting yield in CCl₄, benzene, and n-hexane decreased monotonously with the decrease in monomer concentration. The large decrease of the grafting yield in CCl₄ was proved to be due to the high possibility of chain transfer to CCl₄. When such solvents as water, methanol, and DMF were used, on the other hand, a maximum grafting yield was obtained when the monomer concentration was ca. 75%. The hydrogen bonding among polyurethane, methacrylic acid, and solvent was found to affect both the swelling and the grafting yield.     

Thermal and dynamic mechanical behavior of poly(vinyl chloride)/wood flour composites

Thermal and dynamic mechanical behaviors of wood plastic composites made of poly vinyl chloride (PVC) and surface treated, untreated wood flour were characterized by using differential scanning calorimetry and dynamic mechanical analysis. Glass transition temperature (T_g) of PVC was slightly increased by the addition of wood flour and by wood flour surface treatments. Heat capacity differences (ΔC_p) of composites before and after glass transition were markedly reduced. PVC/wood composites exhibited smaller tan δ peaks than PVC alone, suggesting that less energy was dissipated for coordinated movements and disentanglements of PVC polymer chains in the composites. The rubbery plateaus of storage modulus (E′) curves almost disappeared for PVC/wood composites in contrast to a well defined plateau range for pure PVC. It is proposed that wood flour particles act as “physical crosslinking points” or “pinning centers” inside the PVC matrix, resulting in the absence of the rubbery plateau and high E′ above T_g. The mobility of PVC chain segments were further retarded by the presence of surface modified wood flour. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Wood-Plastic Composite with Methylmethacrylate in Presence of Novel Additives

Wood–plastic composites (WPC) were prepared with kadom and mango wood of Bangladesh under Co-60 gamma irradiation using methylmethacrylate (MMA) as the bulk monomer mixed with methanol (swelling solvent) at different proportions in presence of a number of additives such as N-vinyl pyrrolidone, tripropylene glycol diacrylate, trimethylol propane triacrylate, copper sulfate, sulfuric acid, and urea. Composites prepared with urea, NVP, and CuSO₄ possess better tensile and protective properties.     

The effect of chemical treatment of wood and polymer characteristics on the properties of wood–polymer composites

The physical-mechanical properties and the microscopic structure of caixeta (Chrysophyllum viride) and slash pine (Pinus elliottii) impregnated with polystyrene (PS) were investigated. The influences of a pretreatment with hydrogen peroxide (H₂O₂) solutions utilized in the production of the wood–polymer composites (WPC) and the characteristics of polystyrene formed in situ on the properties of WPC were analyzed. The incorporation of polystyrene improved the compression and static bending properties of slash pine and caixeta. The micrographies confirmed that there were distinct but continuous phases of polymer and wood cell wall which granted the composites a better physical-mechanical behavior. The sensibilizing treatment with dilute hydrogen peroxide solution led to an increase in the viscosity average molecular weight (M _v) of polystyrene, and to the graft polymerization of the monomer, which, in turn, enhanced the stress properties of caixeta–polystyrene composites. Concentrated H₂O₂ solutions degraded caixeta wood, decreasing its tensile properties. Lower initiator concentration favoured higher molecular weight of polystyrene formed in pine wood. A fivefold increase in M _v of PS, however, had little effect on the compression properties of pine–polystyrene composites.     

Dimensional stability of wood–polymer composites

Wood–polymer composites (WPC) were prepared by impregnation of polymeric monomers in wood and in situ polymerization. Three polymeric chemicals were chosen for this study: methyl methacrylate (MMA), hydroxyethylene methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA). The effects of polymeric monomers and their combinations on moisture adsorption (M), anti–moisture adsorption efficiency (AME), liquid water uptake (D), water repellency efficiency (WRE), longitudinal, radial, tangential, and volumetric swelling properties (S) after soaking, and antiswelling efficiency (ASE) were investigated. It was found that M was different for different methacrylate combinations and depended not only on the composition of the impregnants, but also on wood properties. Liquid water uptake was similar regardless of the formulation of the WPC. Wood–polymer composites with high MMA content displayed enhanced dimensional stabilities, but WPCs with high HEMA content did not. Tangential and volumetric ASEs were strongly dependent on the type of treatment. Mold growth tests showed that wood treated with HEMA alone had no surface mold growth, and wood treated with MMA alone also showed less mold growth than did the control samples. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 5085–5094, 2006     

Crystallization and melting behavior of HDPE in HDPE/teak wood flour composites and their correlation with mechanical properties

The nonisothermal crystallization behavior and melting characteristics of high‐density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (?_f) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (T_m) and crystallization temperature (T_p) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE‐g‐MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ?_f in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Radiation-crosslinked polypropylene: Physical and dielectric properties

Irradiation of two stereoregular polypropylenes and a polyallomer via ⁶⁰Co in the presence of 3–8% allyl methacrylate (AMA) monomer, to does up to 5 Mrad, lead to an improvement in mechanical properties. With irradiation, heat resistance, tensile strength, and gel fractions increased, and creep compliance decreased. The decrease in creep compliance was revealed by measurements of irradiated samples at 185⁰C (at constant load and monomer level), a temperature above the T_m of polypropylene. Dielectric properties (dielectric constant K and dissipation factor tan δ) were virtually unaffected by irradiation of 0.3 to 5.0 Mrad in nitrogen when AMA was absent. In the presence of monomer, small but generally tolerable increases in tan δ resulted if the monomer concentration was not too great. To obtain improvements in mechanical properties while not simultaneously altering the dielectric losses, it was necessary to keep the AMA concentration to a maximum of 4%.     

Effect of comonomer type and concentration on the equilibrium swelling and volume phase transition temperature of N‐isopropylacrylamide‐based hydrogels

The effect of incorporating a hydrophilic monomer into poly(N‐isopropylacrylamide) (polyNIPA) hydrogels on the equilibrium swelling and the volume phase transition temperature is reported here. A nonionizable monomer (acrylamide) and three ionizable monomers (itaconic acid, 2‐ethoxyethyl monoitaconate, and 2,2‐(2‐ethoxyethyl) monoitaconate) were studied. Hydrogels with larger swelling capacity than that of the polyNIPA hydrogel were obtained. With the exception of the hydrogel containing 2,2‐(2‐ethoxyethyl) monoitaconate, which did not exhibit the de‐swelling phenomena, the rest showed a volume phase transition. The hydrogels containing 85 wt % acrylamide and 15 wt % comonomer presented the higher shrinking ratio. For some compositions, the T_c of the polyNIPA hydrogel was within the desired temperature range (38–41°C) for controlled‐drug delivery in the human body. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughening of wood particle composites—Effects of sisal fibers

Sisal fibers were added to wood particle composites to enhance their toughness. The selected matrix was a commercial styrene diluted unsaturated polyester thermoset resin. Fracture tests were carried out using single‐edge notched beam geometries. Stiffness, strength, critical stress intensity factor K_IQ, and work of fracture W_f of notched specimens were determined. The incorporation of sisal fibers into wood particle composites significantly changed the fracture mode of the resulting hybrid composite. For the neat matrix and the wood particle composites, once the maximum load was reached, the crack propagated in a catastrophic way. For hybrid composites, fiber bridging and pull‐out were the mechanisms causing increased crack growth resistance. Addition of a 7% wt of sisal fibers almost doubled the K_IQ value of a composite containing 12% wt of woodflour. Moreover, the W_f increased almost 10‐fold, for the same sample. In general, the two composite toughness parameters K_IQ and W_f increased when the fraction of sisal fibers was increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1982–1987, 2006     

Development and characterization of high-performance polybenzoxazine composites

To develop high-performance composites with high temperature resistance, two newly synthesized polybenzoxazines were successfully cured with carbon fiber to obtain composites with 60 vol% fiber. Results from differential scanning calorimetry studies were used to modify the benzoxazine monomers to improve processability in terms of melting point and solubility. The density and void content of these composites were measured. Dynamic mechanical tests were performed to determine the glass transition temperature (T_g) and the activation enthalpy of the glass transition process for these two composites. The effect of cure temperature on the T_g of the composites was investigated. Thermal characteristics were studied by means of dynamic mechanical analysis in terms of isothermal aging, decomposition temperature from thermogravimetric analysis, and storage moduli change at high temperatures. Mechanical evaluations of these composites were conducted by flexural and interlaminar shear tests. The mechanical and thermal properties of these two composites exceed bismaleimide composites and compete with polyimide composites, while exhibiting easier processability than polyimides.     

Swelling behavior of anionic acrylamide-based hydrogels in aqueous salt solutions: Comparison of experiment with theory

A series of hydrogels were prepared from acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) monomers with 0–80 mol % AMPS and using N,N′-methylenebis(acrylamide) as the crosslinker. The swelling capacities of hydrogels were measured in water and in aqueous NaCl solutions. The volume swelling ratio q_v of hydrogels in water increases sharply when the mole fraction f_c of AMPS increases from 0 to 0.06. At higher values of f_c from 0.06 up to 0.18, no change in the swelling capacities of hydrogels was observed; in this range of f_c, q_v becomes nearly constant at 750. However, as f_c further increases, q_v starts to increase again monotonically over the entire range of f_c. At a fixed value of f_c, the swelling ratio of hydrogels decreases with increasing salt concentration in the external solution. The results of the swelling measurements in aqueous salt solutions were compared with the predictions of the Flory–Rehner theory of swelling equilibrium. It was shown that the theory correctly predicts the swelling behavior of hydrogels up to 80 mol % charge densities. The method of estimation of the network parameters was found to be unimportant in the prediction of the experimental swelling data. The network parameters used in the simulation only correct the deficiency of the swelling theory. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 567–575, 1998     

Macroporous poly(N-isopropylacrylamide) networks

Summary Effects of the gel preparation temperature T _prep and the initial monomer concentration c on the swelling and the porosity properties of poly(N-isopropylacrylamide) (PNIPA) networks are described. PNIPA networks were prepared by free-radical crosslinking copolymerization of N-isopropylacrylamide and N,N'-methylene(bis)acrylamide (BAAm) in aqueous solutions. The crosslinker (BAAm) concentration in the initial monomer mixture was kept constant at 30 wt %. It was shown that macroporous PNIPA networks with a stable porous structure can be prepared at T _prep = 22.5°C and at an initial monomer concentration c > 5 w/v %. The PNIPA networks contain pores of about 0.1 μm in radius, corresponding to the interstices between the microspheres. The experimental data also show collapse of the porous structure in PNIPA networks formed at higher temperatures. Received: 30 January 2002 / Revised version: 16 May 2002 / Accepted: 1 June 2002     

Effect of gamma‐irradiation on the mechanical behavior of EPDM rubber‐recycled newsprint microfibers composites

Waste newsprint paper was collected from the local market and subjected to chemical pulping using 2 M NaOH. The fiber, after getting rid of water, was treated again using 2 M HCl solution for the same time period. The obtained newsprint microfibers (NPFs) were characterized by using scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier transform infrared spectra. Then the dried and grounded NPF batch was mixed with ethylene propylene diene monomer (EPDM) rubber using different concentrations ranged from 5 to 50 phr. The prepared composites were irradiated by using gamma rays at different doses from 20 to 100 kGy. The mechanical properties of prepared EPDM/NPFs composites such as tensile strength (Ts), elongation at break (E_b%), tensile modulus (M₁₀₀), toughness (T_t), and crosslink density (Cd) were measured as a function of fiber contents and irradiation dose. The results indicated that the tensile strength (Ts) increases with increasing microfibers contents up to 10 phr and irradiation dose up to 40 kGy, while E_b% decreases as the fibers content and irradiation dose increase. M₁₀₀ and Cd values increase with increasing fibers content up 50 phr fibers and irradiation dose up to 60 kGy. The results also concluded that the toughness values of EPDM/NPFs composites reach its maximum degree when using 10 phr NPFs concentration and 60 kGy irradiation dose. J. VINYL ADDIT. TECHNOL., 25:198–212, 2019. © 2018 Society of Plastics Engineers     

Properties of films obtained by UV-curing 4,4'-hexafluoroisopropylidenediphenoldihydroxyethylether diacrylate and its mixtures with the hydrogenated homologue

A new ultraviolet (UV)-curable acrylic monomer, 4,4'-hexafluoroisopropylidene-diphenoldihydroxyethylether diacrylate, was synthesized: it was cured as a film and its properties compared with those of its fully hydrogenated homologue. The introduction of two CF₃groups into the monomer did not change its reactivity in the UV-curing reaction, but increased the glass transition temperature (T_g) of the cured polymeric film, decreased its refractive index (n), and lowered its surface tension. The fluorinated and the hydrogenated monomers were completely miscible and give homogeneous films: the T_g and n values were found linearly dependent on the fluorinated monomer content. The surface properties were deeply influenced by the presence of fluorine; a surface enrichment of the fluorinated monomer was evidenced by X-ray photoelectron spectroscopy analyses on the surfaces of the films obtained from mixtures of the two monomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 979–983, 1997     

Non-toxic preservatives for wooden objects in sea water. I. Styrene monomer polymerised using gamma irradiation

Abstract

White pine wood was impregnated with styrene monomer and polymerised in situ using a γ-irradiation technique. Factors affecting the polymerisation of styrene in pine wood samples have been studied, including the irradiation dose and the addition of CCl₄. The produced wood polymer composites were tested against attack by wood borers in the Mediterranean Sea at Port Said and in the Suez region of the Red Sea. The duration of the exposure test was generally 17–18 months. The study presents a new system of treated wood which showed promising results in preventing attack by wood borers in marine regions that have a high population and intensity of such borers.