Particleboard From Rubber Wood Flakes with Polymeric MDI Binder

The use of rubber wood (Hevea brasiliensis) flakes for particleboard with polymeric diisocyanate (pMDI) as a binder was investigated. The effects of binder content in surface/core layers, cure temperature, cure time, and flake moisture on the properties of rubber wood particleboards were studied. The properties of the particleboard were compared with those of phenol-formaldehyde (PF) binder. The particleboard prepared from rubber wood flakes with pMDI binder gave high quality particleboards that had durability under severe conditions, low water absorption and thickness swelling, and a high modulus of rupture, modulus of elasticity, and internal bond strength. Moreover, pMDI binder could be cured at low temperatures, within a short time, and the binder consumption was small. The scanning electron micrographs of the rubber wood particleboard prepared from the high moisture content flakes showed the best, very tight packing characteristics

Superabsorbent polymers and superabsorbent polymer composites

ABSTRACT: This article briefly describes the general aspects and cross-linking polymerization of superabsorbent polymers (SAPs) and superabsorbent polymer composites (SAPCs). Research and development of SAPs has become very active after the Northern Region Laboratory of the United States Department of Agriculture invented the first SAP, used as a soil conditioner. Based on the advancements in organic/inorganic syntheses, SAPs are produced and used in a wide range of applications for fluid absorption. The rapid growing nanotechnology has led to more explorations of SAPs and SAPCs for applications in biomedical, biotechnology and advanced technologies. Examples of research work of SAPs and SAPCs published in refereed, reviewed articles are introduced

KAPOK I: CHARACTERISTCS OF KAPOK FIBER AS A POTENTIAL PULP SOURCE FOR PAPERMAKING

The potential use of kapok fiber for pulping and papermaking has been investigated. The kapok fibers were cooked using the optimal dosage of sodium hydroxide determined from the experiments. Then, the pulp was refined with two passes using a disc refiner and mixed with commercial hardwood pulp and/or softwood pulp at different blend ratios to make papers. It was found that addition of the kapok pulp to the mixed pulps improved the tensile and burst strengths of the sheets but decreased the tear resistance and elongation. Water repellency of the sheets prepared from the kapok pulp mixed with the commercial pulps was also improved. These results indicate that kapok fiber can be a quality pulp source for papermaking, especially for packaging paper requiring strength and water repellency

Influences of carbon nanotubes and graphite hybrid filler on properties of natural rubber nanocomposites

Natural rubber (NR) vulcanizates reinforced by carbon nanotubes (CNT, 3 phr), graphite particles (GP) and CNT/GP hybrid filler (varied GP 0–50 phr) were prepared. The stress relaxation behaviors of various filled samples were characterized by the novel temperature scanning stress relaxation (TSSR) technique to elucidate the state and degree of filler dispersion based on initial relaxation modulus, bound rubber, and thermal stability. The incorporation of CNT/GP hybrid filler in NR matrix improved relaxation modulus, bound rubber, and thermal stability of the nanocomposites. The CNT particles in the hybrid composites prevented the re-agglomeration of dispersed GP after mixing by a thermodynamic effect. It was found that a combination of 3 phr CNT and 30 ph GP gave superior properties to NR vulcanizates. That is, good dispersion and distribution of CNT and GP in the NR matrix provided further significant improvements in electrical conductivity and dielectric constant of the nanocomposites. The NR nanocomposites with high conductivity and low dielectric constant seems to be a semi-conductive substrate to be used in many electrical devices

Mesostructure evolution during storage of rubber films from washed cream latex and skim latex

Fresh field latex (FL) of Hevea brasiliensis was centrifuged to separate the major compartments: (i) the cream, (ii) the skim plus the C-serum, and (iii) the bottom fraction. Cream was dispersed in distilled water to prepare cream washed latex or CL sample. Skim was collected together with C-serum to prepare the skim latex or SKL sample. Then, films were made from FL, CL and SKL. The mesostructure (macromolecular structure and aggregates or gel) of the natural rubber films was studied by size exclusion chromatography coupled to a multiangular light scattering detector (SEC-MALS). The mesostructure was analyzed on fresh films and on films stored in the laboratory for three months (slow structuring). This study showed that FL and CL films had bimodal elution profiles of long and short polyisoprene chains as revealed by the two peaks on the chromatograms at low and high elution volumes, respectively. On the contrary, SKL films exhibited unimodal elution profiles at low elution volume and a highly abnormal molar masses elution profiles. After 3 months storage, the mesostructure of FL evolved dramatically especially the number-average molar masses (MO, which increased by 60%. The mesostructure of CL films evolved at a lesser extent and, the mesostructure of SKL films exhibited no significant change. These results indicated (i) the skim rubber particles are not prone to slow structuring during storage in presence of serum and (ii) some constituents either in the serum or/and in the bottom fraction could still be present with cream and be involved in the slow structuring of cream particles latex

Kinetics of surface grafting on polyisoprene latexes by reaction calorimetry

The two-component redox-initiation system, cumene hydroperoxide (CHP) and tetraethylene pentamine (TEPA), was used to polymerize dimethylaminoethyl methacrylate (DMAEMA) in the presence of synthetic polyisoprene latexes. The modified latex particles are postulated to possess a 'hairy layer' of surface-grafted poly(DMAEMA) chains formed via an abstraction reaction between cumyloxy radicals and the isoprene moieties present in the seed polymer. The modified latexes exhibited enhanced colloidal stability to low pH, and dynamic light scattering showed that the apparent particle size was sensitive to pH. The rate of polymerization was followed by reaction calorimety. No steady-state polymerization was observed, with a continual increase in the number of propagating chains at all initiator feed rates investigated. The data for particle size and colloidal stability, together with the calorimetric data, are consistent with radical production at the particle surface, and with abstraction near the interface being a rare event. Further, there is evidence that radical production by the redox couple is relatively slow. While this 'topology-controlled' reaction is responsible for the formation of the hairy layer and latex stability, the dominant polymerization process appears to be the formation of ungrafted poly(DMAEMA) in the water phase

Surface-Grafted Poly(acrylic acid) Brushes as a Precursor Layer for Biosensing Applications: Effect of Graft Density and Swellability on the Detection Efficiency

Carboxyl groups along poly­(acrylic acid) (PAA) brushes attached to the surface of a gold-coated substrate served as the precursor moieties for the covalent immobilization of amino-functionalized biotin or bovine serum albumin (BSA) to form a sensing probe for streptavidin (SA) or anti-BSA detection, respectively. Surface-grafted PAA brushes were obtained by acid hydrolysis of poly­(<i>tert</i>-butyl acrylate) brushes, formerly prepared by surface-initiated atom transfer radical polymerization of <i>tert</i>-butyl acrylate. As determined by surface plasmon resonance, the PAA brushes immobilized with functionalized biotin or BSA probes not only showed good binding with the designated target analytes but also maintained a high resistance to nonspecific protein adsorption, especially those PAA brushes with a high surface graft density. Although the probe binding capacity can be raised as a function of the graft density of the PAA brushes or the amount of carboxyl groups along the PAA chains, the accessibility of the target analyte to the immobilized probe was limited at the high graft density of the PAA brushes. The effect was far more apparent for the BSA–anti-BSA probe–analyte pair than for the much smaller biotin–SA probe–analyte pair. The impact of the swellability of the PAA brushes, as tailored by the degree of carboxyl group activation, on both the sensing probe immobilization and analyte detection was also addressed. This investigation demonstrated that PAA brushes having a defined graft density have a promising potential as a precursor layer for biosensing applications

Enhanced adsorptive composite foams for copper (II) removal utilising bio-renewable polyisoprene-functionalised carbon derived from coconut shell waste

Abstract A bio -renewable polyisoprene obtained from Hevea Brasiliensis was used to produce functionalised carbon composite foam as an adsorbent for heavy metal ions. Functionalised carbon materials (C-SO3H, C-COOH, or C-NH2) derived from coconut shell waste were prepared via a hydrothermal treatment. Scanning electron microscopy images showed that the functionalised carbon particles had spherical shapes with rough surfaces. X-ray photoelectron spectroscopy confirmed that the functional groups were successfully functionalised over the carbon surface. The foaming process allowed for the addition of carbon (up to seven parts per hundred of rubber) to the high ammonia natural rubber latex. The composite foams had open pore structures with good dispersion of the functionalised carbon. The foam performance on copper ion adsorption has been investigated with regard to their functional group and adsorption conditions. The carbon foams achieved maximum Cu(II) adsorption at 56.5 $${\text{mg g}}_{\text{foam}}^{-1}$$ mg g foam - 1 for C-SO3H, 55.7 $${\text{mg g}}_{\text{foam}}^{-1}$$ mg g foam - 1 for C-COOH, and 41.9 $${\text{mg g}}_{\text{foam}}^{-1}$$ mg g foam - 1 for C-NH2, and the adsorption behaviour followed a pseudo-second order kinetics model

Development of a Novel Antifouling Platform for Biosensing Probe Immobilization from Methacryloyloxyethyl Phosphorylcholine-Containing Copolymer Brushes

The immobilization of thiol-terminated poly­[(methacrylic acid)-<i>ran</i>-(2-methacryloyloxyethyl phosphorylcholine)] (PMAMPC-SH) brushes on gold-coated surface plasmon resonance (SPR) chips was performed using the “grafting to” approach via self-assembly formation. The copolymer brushes provide both functionalizability and antifouling characteristics, desirable features mandatorily required for the development of an effective platform for probe immobilization in biosensing applications. The carboxyl groups from the methacrylic acid (MA) units were employed for attaching active biomolecules that can act as sensing probes for biospecific detection of target molecules, whereas the 2-methacryloyloxyethyl phosphorylcholine (MPC) units were introduced to suppress unwanted nonspecific adsorption. The detection efficiency of the biotin-immobilized PMAMPC brushes with the target molecule, avidin (AVD), was evaluated in blood plasma in comparison with the conventional 2D monolayer of 11-mercaptoundecanoic acid (MUA) and homopolymer brushes of poly­(methacrylic acid) (PMA) also immobilized with biotin using the SPR technique. Copolymer brushes with 79 mol % MPC composition and a molecular weight of 49.3 kDa yielded the platform for probe immobilization with the best performance considering its high S/N ratio as compared with platforms based on MUA and PMA brushes. In addition, the detection limit for detecting AVD in blood plasma solution was found to be 1.5 nM (equivalent to 100 ng/mL). The results have demonstrated the potential for using these newly developed surface-attached PMAMPC brushes for probe immobilization and subsequent detection of designated target molecules in complex matrices such as blood plasma and clinical samples