Para rubber wood particleboard (PB) was prepared using NR based adhesives and hot pressing processes. Two types of NR based adhesives were used; epoxidized natural rubber (ENR) and unmodified NR. The ENR latex was prepared using in situ performic epoxidation. Molecular weight of the ENR molecules was then reduced by incorporating of a reducing agent; sodium nitrite solution. A chain scission reaction and epoxidation simultaneous occurred via a chain‐scission parallel epoxidation mechanism. Sulphur and multifunctional amine (i.e., hexamethoxymethylmelamine) curing systems were used to cure the adhesives. It was found that the hexamethoxymethylmelamine gave the PB with higher tensile strength than that of the sulphur vulcanization system. Furthermore, the tensile strength increased with increasing concentration of citric acid in the compounding formulation. Adhesion of the ENR adhesive with Parawood sawdust was observed to imporve by reducing molecular weight of the ENR molecules. That is, the highest tensile strength of the PB was observed for the ENR adhesive with the lowest $ {\overline {M}_{n}} $ (i.e., 1.10 × 105). This may be attributed to the adhesive with lower molecular weight exhibited greater ability to wet or cover the wood particle surfaces. As a consequence, greater chemical interaction between the adhesive and the wood particles was observed. POLYM. ENG. SCI., 47:421–428, 2007. © 2007 Society of Plastics Engineers.

Factors underlying design of a new nitroxide, 2,2,5trimethyl-4-tert-butyl-3-azahexane-3-oxyl (TITNO), and its styrene alkoxyamine (Styryl-TITNO) for effecting nitroxide-mediated polymerization (NMP) at temperatures ≤90 °C are described. The rate coefficient, k d , for thermal dissociation of Styryl-TITNO was determined in the range 70−100 °C, giving Arrhenius parameters A d = 2.9 × 10 12 s −1 and E d = 104.1 kJ mol −1 . Due to the low value of E d , values of k d and the activation−deactivation equilibrium constant for NMP of n-butyl acrylate (BA) and styrene are much lower at any given temperature than for alkoxyamines of more established nitroxides. Good control of molecular weight and dispersity, with negligible contributions from termination, is achieved at 90 °C for BA and at 70 °C for styrene, thus, eliminating the complicating contributions from styrene thermal initiation. Hence, TITNO and Styryl-TITNO offer new opportunities for controlled NMP at temperatures much lower than has previously been attainable.

In this work, we present an easy way to vulcanize natural rubber using glutaraldehyde as a cross-linking agent. The effect of poly(methyl methacrylate) (PMMA) grafting along with cross-linking of natural rubber on the mechanical, thermal, and oil resistance properties was studied. The main objective of this work was to improve the properties of cured natural rubber (NR) based on glutaraldehyde (GA) as a curing agent by using modified NR. Cured NRg-PMMA with different grafting levels were studied systematically and compared with cured natural rubber. A remarkable improvement in the properties of natural rubber was obtained by grafting PMMA.Higher tensile strength without much reduction in elongation at break can be achieved by curing NRg-PMMA with glutaraldehyde. The natural rubber grafted with PMMA and subsequently cured with glutaraldehyde as a cross-linking agent was found to be a useful technique for improving the properties of natural rubber products. K E Y W O R D Sglutaraldehyde, graft copolymer, grafted PMMA, natural rubber, poly(methyl methacrylate), vulcanization How to cite this article: Kalkornsurapranee E, Yung-Aoon W, Thongnuanchan B, Thitithammawong A, Nakason C, Johns J. Influence of grafting content on the properties of cured natural rubber grafted with PMMAs using glutaraldehyde as a cross-linking agent.

Flame‐retardant blends of polyethylene‐octene elastomer (POE) and natural rubber (NR) filled with expandable graphite (EG) were melt‐mixed with azodicarbonamide to prepare elastomeric foams. The effect of the NR incorporation on the properties of EG filled POE foam was investigated. Gel content and microstructure observations revealed that the addition of NR into the POE/EG blend induced change in molecular structure, which produced a finer cellular structure during foaming. The compressive strength and elastomeric recovery of the POE/NR/EG blend foams were found to increase with increasing NR content. Based on the limiting oxygen index and horizontal burning measurements, all the POE/NR/EG blend foams were found to have good flame‐retardant properties. On the other hand, these POE/NR/EG blend foams exhibited higher combustion rates with an increasing NR content under high heat radiation and temperature in a cone calorimeter test. This study demonstrates that the combined use of NR as a modifier and EG as a flame retardant in POE foams provides an effective and practical method of obtaining well‐balanced improvements in cellular structure, mechanical properties, and flame resistance.

We investigated the reinforcement behavior of small amounts of chemically unmodified cellulose nanofiber (CNF) in eco-friendly natural rubber (NR) nanocomposites. For this purpose, NR nanocomposites filled with 1, 3, and 5 parts per hundred rubber (phr) of cellulose nanofiber (CNF) were prepared by a latex mixing method. By using TEM, a tensile test, DMA, WAXD, a bound rubber test, and gel content measurements, the effect of CNF concentration on the structure–property relationship and reinforcing mechanism of the CNF/NR nanocomposite was revealed. Increasing the content of CNF resulted in decreased dispersibility of the nanofiber in the NR matrix. It was found that the stress upturn in the stress–strain curves was remarkably enhanced when the NR was combined with 1–3 phr CNF, and a noticeable increase in tensile strength (an approximately 122% increase in tensile strength over that of NR) was observed without sacrificing the flexibility of the NR in the NR filled with 1 phr CNF, though no acceleration in their strain-induced crystallization was observed. Since the NR chains were not inserted in the uniformly dispersed CNF bundles, the reinforcement behavior by the small content of CNF might be attributed to the shear stress transfer at the CNF/NR interface through the interfacial interaction (i.e., physical entanglement) between the nano-dispersed CNFs and the NR chains. However, at a higher CNF filling content (5 phr), the CNFs formed micron-sized aggregates in the NR matrix, which significantly induced the local stress concentration and promoted strain-induced crystallization, causing a substantially increased modulus but reduced the strain at the rupture of the NR.