Influence of modified wood fibers on the mechanical properties of wood fiber-reinforced polyethylene

Wood fiber of aspen was used as a reinforced filler in linear low-density polyethylene (LLDPE). To improve the compatibility between the wood fiber and the LLDPE matrix, the wood fiber was treated with titanate coupling agents (i.e., TC-PBT and TC-POT) or grafted by acrylonitrile. Both treatments resulted in an improvement in the mechanical properties of the resultant composites compared with the composites filled with the untreated wood fiber. Moreover, the grafting method displayed a more obvious benefit than that of titanate coupling methods to the mechanical property improvement. This was attributed to the crystalline structure of the wood fiber to be destroyed by grafting acrylonitrile, and the amorphous fiber was easily deformed to enhance fiber adhesion at the LLDPE matrix. In addition, the effect of the concentration of the filled wood fiber and the amount of coupling agent or grafting ratio on the mechanical properties of composites are discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1561–1568, 1997     

纳米碳酸钙表面改性技术研究进展

综述了纳米碳酸钙的干法表面改性工艺（以钛酸酯、铝酸酯、硼酸酯、磷酸酯等为偶联剂）和湿法表面改性工艺［以硬脂酸(盐)、磷酸盐、磺酸盐和缩合磷酸、季胺盐类等为表面活性剂］及表面改性剂的特点。还介绍了包括母料填料、复合偶联剂、反应性单体、活性大分子及聚合物、等离子体、超分散剂等在内的各种表面改性新技术,并对改性碳酸钙未来的研究方向进行了展望。     

Use of silanes and copolymers as adhesion promoters in glass fiber/polyethylene composites

Two organofunctional silanes and three functionalized copolymers were used as adhesion promoters in glass fiber/polyethylene‐reinforced composites. The performance of the coupling agents was investigated by mechanical property measurements, scanning electron microscopy, and dynamic mechanical analysis. Coupling achieved with the poly(ethylene‐g‐maleic anhydride) copolymer proved to be the most successful compared with the other copolymers (ethylene/vinyl alcohol, ethylene/acrylic acid) and silane agents (γ‐methacryloxypropyltrimethoxy, cationic styryl). The combined coupling performance of the silanes and copolymers examined in this study appears to be controlled by the coupling performance of the copolymer. Effective coupling was reflected in increased mechanical properties. Increased fiber/matrix adhesion is not always associated with effective coupling because structural changes occurring at the interface region can result in a deterioration of the material property. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2877–2888, 2001     

‘Elasticisation’ and plasticisation of PVC with ethylene-vinyl acetate copolymers

Copolymers of ethylene and vinyl acetate (E-VA) of a certain composition can be used for the improvement of impact properties (elasticisation) of PVC as well as under certain conditions (grafting) for the preparation of flexible PVC (plasticisation). Products of interesting properties are prepared by blending E-VA (up to ～ 12%) with PVC or more advantageously by grafting vinyl chloride on special E-VA types. Graft copolymerisation by the suspension method allows the synthesis of E-VA/PVC systems in all ratios (up to 80% E-VA); these polymers are compatible over the whole range in contrast to the blends. Studies on the grafting efficiency of some monomers show that vinyl chloride can be grafted readily on E-VA. The grafting process is performed on a technical scale to give PVC types with E-VA contents up to 50%. Products with 6–8% E-VA should be classified as impact-modified suspension PVC. Flexible types (40–60% E-VA) have properties of flexible PVC with the plasticiser chemically incorporated, but may also be blended with unmodified PVC to give impact-improved formulations. The properties of the elasticised PVC (8% E-VA) mainly depend on the vinyl acetate (V-OAc) content of the E-VA and its molecular weight. Levapren® 450 P (45% V-OAc; mol. wt. ～ 100,000), a solution process copolymer, has good elasticising efficiency in blends and graft copolymers with PVC. PVC/E-VA products may be processed with or without addition of uncombined PVC into rigid or flexible PVC by the usual methods of PVC technology, e.g. extrusion, injection moulding, blow-moulding and calendering. Competitive modifiers, such as acrylonitrile-butadiene-styrene copolymers, methacrylate-butadiene-styrene copolymers, acrylates or chlorinated polyethylene, are compared with E-VA. Levapren® 450 P shows high efficiency as an impact modifier even in low concentration, giving good processability and ageing behaviour. Glass-clear high-impact PVC cannot be obtained by E-VA modification. Some electron microscopy studies to characterise the distribution of E-VA in the resin phase (PVC) are described; these showed the presence of a two-phase system.     

Thermoplastics Reinforced with Wood Fillers: A Literature Review

Problems concerning the processing of thermoplastics reinforced with wood fillers are discussed. The high level of moisture absorption by the filler, its poor wettability, as well as the insufficient adhesion between untreated filler and the polymer matrix are reasons for the low tensile strength and high moisture sorption of composites. These shortcomings of composites can be prevented by the modification of the interface. The fiber-matrix compatibility and the composites properties can be improved by using some physical (e.g., steam explosion, corona, cold plasma) and chemical (cross-linking and acetylation of cellulose, grafting, use of coupling agents) methods. Modified wood-polymer interaction mechanisms are complex and specific for each definite system and processing conditions. Cellulose cross-linking and acetylation reduce hygroscopicity and swelling of wood and wood composites. Grafting of styrene to wood is effective for wood-polystyrene systems. The best coupling agent for wood-thermoplastics is polymethylenepolyphenyl isocyanate. Silanes coupling effect can be increased with additives to the polymer matrix. Optimizing of technological parameters of wood-thermoplastics processing is necessary.     

Application of poly(vinyl alcohol) with an alkyl end group containing anionic groups to coal–water slurry as a dispersant

Anionic groups were introduced with copolymerization of corresponding vinyl monomers with vinyl acetate into poly(vinyl alcohol) (PVA) with an alkylthio end group. The polymers were investigated as a dispersant for coal-water slurry (CWM). Anionic groups such as sodium sulfonate and sodium carboxylate enhance remarkably the ability of PVA with an alkylthio end group to disperse coal. Sodium polyacrylic acid with an alkyl end group also showed a good ability of dispersing coal. The order of the ability of dispersing coal in these polymeric dispersants along with sodium napthalene sulfonate formaldehyde condensate (NSF) varied by the kind of coal used. In cases of the polymeric dispersants, the fluidity of coal in terms of dependence of viscosity on shear rate also varied, from dilatency to thixotropy, in accordance with coal used. Impurities in coal as well as surface properties of coal particles might play important roles in the properties of CWM. © 1995 John Wiley & Sons, Inc.     

Makromolekulare Dispergatoren fü die Copolymerisation von Maleinsäureanhydrid mit 1-Olefinen und Vinylaromaten in Suspension

The suspension copolymerization of maleic acid anhydride (MAH) with 1-olefines, e.g. isobutylene and diisobutylene, or aromatic vinyl compounds, e.g. styrene and α-methylstyrene, can be accomplished in the presence of novel macromolecular dispersing agents, which are soluble in aliphatic hydrocarbons. By this method the copolymers are received as finely divided powders with a relatively uniform particle size. The systems MAH-isobutylene and MAH-diisobutylene are polymerized by using an excess of 1-olefine as a dispersing medium, whereas in copolymerizations of aromatic vinyl compounds with MAH aliphatic hydrocarbons are used as diluting agents, but not as solvents. Efficient dispersing agents are prepared by the chemical modification of the following alternating copolymers: MAH-1-olefine-copolymers, MAH-styrene-copolymers, MAH-vinylether-copolymers, MAH-vinylester-copolymers and MAH-(meth) allylalcohol-1-olefine-terpolymers.     

Effect of structure on mechanical properties of vinyl ester resins and their glass fiber‐reinforced composites

The article describes the effect of structure of vinyl ester resins (VE) on the mechanical properties of neat sheets as well as glass fabric‐reinforced composites. Different samples of VE were prepared by reacting ester of hexahydrophthalic anhydride (ER) and methacrylic acid (MAA) (1 : 1 molar ratio) followed by reaction of monomethacrylate terminated epoxy resin with glutaric (E) or adipic (F) or sebacic acid (G) (2 : 1 molar ratio). The neat VE were diluted with styrene and sheets were fabricated by using a glass mold. A significant reduction in the mechanical properties was observed by increasing the methylene content of resin backbone (i.e., sample E to G). Glass fabric‐reinforced composites were fabricated by vacuum assisted resin transfer molding (VARTM) technique. Resin content in the laminates was 50 ± 5 wt %. Increase in the number of methylene groups in the vinyl ester resin (i.e., increasing the bridge length) did not show any significant effect on limiting oxygen index (LOI) value (21 ± 1) of the laminates but tensile strength, tensile modulus, flexural strength, and flexural modulus all increased though these values are significantly lower than observed in laminates based on resin B. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of grafted copolymers via oxidized polypropylene

A new and novel class of oxidized polypropylene containing bound peroxide functionalities can be used as polymerization initiators to produce polypropylene‐grafted copolymers. Upon heat treatment, the peroxide functionalities in the oxidized polypropylene act as a source of free radicals, reacting with the unsaturated double bonds of the monomer and initiating polymerization. The grafting reaction is carried out in the solid state in a reactor. The advantage of grafting via this new class of oxidized polypropylene is the elimination of expensive and environmentally unfriendly organic peroxides. A number of monomers have been grafted using oxidized polypropylene, including vinyl acetate, vinyl pyrrolidinone, methacrylic anhydride, and maleic anhydride. Oxidized polypropylene‐grafted copolymers are effective compatibilizers for PP/ETP blends and good coupling agents in glass‐ reinforced formulations. Preparation, characterization, and mechanical properties of terpolymers prepared from sequential grafting of oxidized polypropylene are also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Improvement in properties of poly(vinyl acetate): Emulsion with dibasic acids

We report an attempt to graft cis (maleic and citraconic) and trans (e.g., fumaric and mesaconic) unsaturated dibasic acids onto poly(vinyl acetate) in emulsion system, in the presence of an initiator and a small quantity of vinyl acetate. The resulting emulsions showed better adhesiveness, higher shear strength, and varied viscosity, and yielded relatively translucent films with faster drying properties. Grafting in the case of these acids was poor, but the cis acids were better grafted than the trans acids. Furthermore, saturated acids (e.g., oxalic and succinic acid) and an inorganic acid (boric acid) were only physically incorporated in the poly(vinyl acetate) emulsion (PVAc emulsion); the resulting product also showed similar improvement in the end properties.     

Surface functionalization of polyolefin films via the ultraviolet‐induced photografting of acrylic acid: Topographical characterization and ability for binding antifungal agents

The photoinduced graft copolymerization of acrylic acid with ultraviolet radiation onto films of poly(vinyl chloride), polypropylene, and polyethylene was studied. Benzophenone was used as the initiator for most of the experiments performed. The percentage of grafting was determined by gravimetric measurements, and the characterization of the grafted films was carried out by chemical analysis (Fourier transform infrared spectroscopy, volumetric titration, and dye adsorption). In all samples, the grafted yield increased with the ultraviolet exposure time. High levels of grafting were obtained at room temperature. In addition, optical and atomic force microscopy allowed the topography of the modified films to be studied as a function of the reaction time. The pendant functional groups that were grafted were then used to bind antifungal agents, such as natamycin and crystal violet, and the antifungal properties of the films were demonstrated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2254–2263, 2006     

Synthesis and characterization of polysaccharide based graft copolymer by using potassium peroxymonosulphate/ascorbic acid as an efficient redox initiator in inert atmosphere

Polysaccharide based graft copolymer (xanthan gum‐g‐4‐vinyl pyridine) was synthesized using potassium peroxymonosulphate/ascorbic acid redox initiator in inert atmosphere at 40°C. By studying the effect of the concentration of monomer, peroxymonosulphate (PMS), ascorbic acid (AA), xanthan gum (XOH), hydrogen ion along with effect of time and temperature on grafting characteristics: grafting ratio (%G), add on (%A), conversion (%C), efficiency (%E), homopolymer (%H), and rate of grafting (Rg), the reaction conditions for optimum grafting were determined. The optimum concentration of AA, H⁺ ion, 4‐VP for maximum grafting were found to be 10.0 × 10^?3 mol dm^?3, 2.5 × 10^?2 mol dm^?3, 10.0 × 10^?3 mol dm^?3, respectively. Maximum %G was obtained at minimum concentration of xanthan gum i.e., at 40.0 × 10^?2 g dm^?3 and at maximum concentration of PMS i.e., at 10.0 × 10^?3 mol dm^?3. The optimum temperature and time duration of reaction for maximum % of grafting were found to be 45°C and 120 min respectively. The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the xanthan gum‐g‐4‐vinyl pyridine is thermally more stable than pure gum. A probable mechanism was suggested for the graft copolymerization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Functional polymers for colloidal applications. X. Syntheses of graft-charged naphthalene–formaldehyde condensates and their ability to disperse dyes

N-(3-sodium propylsulfonate)-α-naphthylamine–formaldehyde condensates (NAFS) and O-(3-propylsulfonate)-α-naphthol–formaldehyde condensates (NOFS) are synthesized by condensation reactions followed by ring-opening reactions. Those condensates are used as dispersants to disperse dyes in water (C. I. Navy Blue 79 and C. I. Brown 1), and can be compared to the conventional dispersants [e.g., naphthalenesulfonate–formaldehyde condensates (NSF)]. The dispersing properties of the condensates were evaluated by scanning electron microscopy (SEM), sedimentation, as well as measurments of viscosity. For NAFS or NOFS, the sulfonate groups were grafted separately on the backbone of the condensate; however, for NSF, the sulfonate groups were anchored on the backbone of the condensate. The structural effects of those condensates were demonstrated by comparing the dispersing ability of these condensates, and the conventional condensates NAFS and NOFS exhibit better dispersing abilities than NSF for the Navy Blue 79 and Brown 1 dyes. © 1996 John Wiley & Sons, Inc.     

Dispersion of aluminum‐doped zinc oxide nanopowder in non‐aqueous suspensions

This study proposes appropriate dispersants for dispersing aluminum‐doped zinc oxide (AZO) nanopowder in the commonly used organic solvent‐dimethylacetamide (DMAC). The dispersion efficiencies and stabilization mechanisms of four DMAC‐soluble dispersants, poly(acrylic acid) (PAA), polyethyleneimine (PEI), poly(vinyl alcohol) (PVA), and poly(vinyl pyrrolidone) (PVP), are compared. The non‐polyelectrolyte‐based PVA and PVP surprisingly exhibit greater efficiency than the polyelectrolyte‐based PAA and PEI. This is because the nano AZO is soft‐agglomerated in DMAC and easily de‐agglomerated by the application of ultrasonic power; therefore, the increased viscosity contributed from additions of PVA and PVP efficiently prevent reagglomeration and sedimentation of the nanopowder. This stabilization mechanism is evidenced by an experimental analysis of zeta potentials and rheology and also by theoretical calculations based on Stokes’ law.     

Preparation and characterization of poly(vinyl alcohol)‐poly(vinyl pyrrolidone) blend: A biomaterial with latent medical applications

Aqueous solutions of poly(vinyl alcohol) and poly(vinyl pyrrolidone) are blended and films are produced by casting method with the further intention of being used as bio‐materials with latent medical application. Glutaraldehyde, 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt tetra‐hydrate are used as crosslinker agents, whereas lactic acid is the plasticizer in the blend. The obtained films are characterized by differential scanning calorimetry (DSC), mechanical properties, swelling and solubility behavior. DSC measurements show that the blends exhibit a single glass transition temperature indicating that they are miscible, even in the presence of the plasticizer and crosslinker agents. By the combination of all mentioned additives, a relevant enhancement of the swelling is observed, accompanied by a stabilization of the solubility during the tested time. Finally, mechanical properties show an appropriate performance in the studied parameters. As a consequence, the obtained films could be suitable for use as medium or long‐term implants. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interfacial Modification of Polystyrene‐block‐polybutadiene‐block‐polystyrene/Magnesium Hydroxide Composites, 1

Composites based on polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS triblock thermoplastic elastomer) and magnesium hydroxide (Mg(OH)₂) (5–60 wt.‐%) have been prepared by twin screw extrusion. Interfacial modifiers included dispersants, i.e., isostearic acid, oleic acid, stearic acid; and coupling agents, i.e., maleanised polybutadiene and vinyltriethoxysilane. In each case, approximately one monolayer of treatment was used. A dual bore motor driven extrusion rheometer was used for assessment shear and elongation flow behavior (Cogswell's method) over a shear rate range of 100 s^?1 to 5 000 s^?1. Untreated filler and filler treated with coupling agents gave composites that become increasingly pseudoplastic as filler level increased. Fatty acid structure was shown to have some influence over the level of melt viscosity reduction normally associated with such treatments; stearic acid gave the most pronounced reduction in melt viscosity possibly due to the tightly packed monolayer. Elongational flow properties, determined using Cogswell's method, indicated significant chain extension/branching of the bulk matrix when high levels of untreated filler were present and long range filler‐matrix interaction in composites modified with maleanised polybutadiene.

Elongational viscosity versus extensional stress (obtained by Cogswell's method) for SBS blended with filler surface treatments (□) unfilled matrix, and unfilled matrix plus (?) Hⁱst and (?) MPBD.     

Investigation of radiation grafting of vinyl acetate onto (tetrafluoroethylene–perfluorovinyl ether) copolymer films

A study has been made of radiation-induced grafting of vinyl acetate (VAc) on to (tetrafluoroethylene–perfluorovinyl ether) copolymer (PFA). Effects of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield were investigated. In this grafting system, ammonium ferrous sulphate (Mohr′s salt) was added to the monomer-solvent mixture to minimize the homopolymerization of VAc and the most suitable concentration was found to be 2.0 wt%. It was found that the dependence of the initial grafting rate on monomer concentration is of the order 1.5. The degree of grafting tends to level off at high irradiation doses due to the recombination of formed free radicals without initiating graft polymerization. Some properties of the prepared graft copolymer such as swelling behaviour, electrical conductivity, thermal and mechanical properties were also investigated. The electrical conductivity was improved by hydrolysis of poly(vinyl acetate) in the grafted chains to their respective vinyl alcohols. The tensile properties were improved by grafting; however, the elongation percent decreased. The DTA data showed thermal stability of such graft copolymers for temperatures up to 300°C, but stability decreased at higher temperatures.     

Surface grafting modification of fibrous silicates with polyvinylpyrrolidone and its application in nanocomposites

Chemical surface modification of fibrous silicate with polyvinylpyrrolidone (PVP) or its derivates via grafting‐from and grafting‐to methods was investigated. The grafting‐from method was based on the immobilization of reactive end functional groups of silane coupling agents on silicate surface, followed by chain growth via radical polymerization of N‐vinylpyrrolidone (NVP) to form grafted polymers with different molecular weight. In the grafting‐to method, a novel copolymer PVP‐171 with side functionalized groups and designed molecular weight was synthesized by radical polymerization of NVP and vinyltrimethoxysilane (DB171) and then bonded to the surface of fibrous silicates. Evidences from FTIR, XPS, TGA, and BET test indicate that there are ～ 68,000 reactive sites per square meters on the surface with the grafted vinyl concentration of 59 mequiv per 100 g of clay. XRD patterns and SEM images demonstrate that grafting modification was bound on the silicate surface and make the surface rough with the increase of graft‐loading quantity. In contrast with grafting‐to approach, grafting‐from approach facilitates the dispersion of silicates in PET composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of alginate‐g‐vinyl sulfonic acid with a potassium peroxydiphosphate/thiourea system

Alginate‐g‐vinyl sulfonic acid graft copolymer was synthesized through the graft copolymerization of vinyl sulfonic acid (VSA) onto alginate with an efficient system, i.e., potassium peroxydiphosphate (PDP)/thiourea in an aqueous medium. The effects of the concentration of thiourea, PDP, hydrogen ion, alginate, and VSA along with the time and temperature on the graft copolymerization were studied by the determination of the grafting parameters (grafting ratio, add‐on, conversion, grafting efficiency, and homopolymer). The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the alginate‐g‐vinyl sulfonic acid is thermally more stable than alginate. Water swelling capacity, metal ion sorption, flocculation, and resistance to biodegradability studies of synthesized graft copolymer have been performed with respect to the parent polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Acid‐synergized grafting of sodium styrene sulfonate onto electron beam irradiated‐poly(vinylidene fluoride) films for preparation of fuel cell membrane

The role of acid addition in synergizing radiation induced grafting of sodium styrene sulfonate (SSS) onto electron beam‐irradiated poly(vinylidene fluoride) (PVDF) films as a single‐step route for preparation of proton exchange membranes containing sulfonic acid groups was systematically investigated. The grafting reaction, known for its poor kinetics, was studied using SSS diluted in various solvents and solvent/acid solutions of different concentrations and volumes. The addition of acid solution was found to marvelously synergize the grafting reaction from very low values (e.g., 0.5%) to achieve high degrees (e.g., 65%) of grafting and such synergetic effect depends on the type, concentration and volume of the added acid. The degree of grafting was also found to be function of the monomer concentration and the irradiation dose at constant acid concentration and volume. The obtained membranes were investigated with Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), and X‐ray diffractometry (XRD). The results of present study reveal that grafting of SSS to levels suitable for fuel cell application onto PVDF film is only possible by adding aqueous acids solution. Moreover, the addition of acid makes this shorter single‐step method more economical route for preparation of proton exchange membranes for fuel cells. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010