Wen-Yen Chiang

The improvements in flame retardance and mechanical properties of polypropylene/FR blends by acrylic acid graft copolymerization

Abstract Acrylic acid (AAc) was grafted onto a polypropylene (PP) backbone by a mechanochemical graft copolymerization reaction initiated by benzoyl peroxide (BPO) in a twin screw extruder. The modified PP was then blended together with the flame-retardant additive (FR), tris(2,3-dibromopropyl) isocyanurate for flammability reduction. Antimony (III) trioxide was selected as a synergistic agent. The flammability of the blends, according to the limiting oxygen index (LOI), mechanical properties, and thermal degradation of these materials were all investigated with various amounts of AAc and FR. Although the flammability of the PP/FR blends was reduced by the addition of the FR, the tensile strength and impact strength were also decreased. A characteristic of FR as a plasticizer was found by measuring the variation of Izod impact strength vs FR content, and a phenomenon of antiplastization appeared. For PP-g-AAc/FR blends, the LOI, Tpi, tensile strength, impact strength, and Youngs modulus all increased because of the AAc grafting modification.

Approaches of interfacial modification for flame retardant polymeric materials

Two different flame-retardant materials are discussed in this study, one of which employed an inorganic flame retardant and the other a brominated flame retardant. Matrix grafting modification was employed to modify the former material and Pukanszkys formula was used to analyze the effect of grafting. On the other hand, four different coupling agents were employed for the latter material. The effect of these coupling agents on the materials is found to closely relate to the chemical structure and molecular weight of the coupling agents. The interfacial modifying mechanisms of matrix grafting and coupling agent are compared to each other in terms of the molecular structure of the materials.

Separation of water—alcohol mixture by using polymer membranes—6. Water—alcohol pervaporation through terpolymer of PVA grafted with hydrazine reacted SMA

The pervaporation separation of water—alcohol mixture was carried out using grafted terpolymer membrane at −10–50°C. PVA-g-ST/MA-Hz (III) terpolymer was prepared by graft copolymerization of styrene (ST)-maleic anhydride (MA) hydrazine (Hz) copolymer (ST-co-MA-Hz) (II) onto poly(vinyl alcohol) (PVA) by a condensation-coupling reaction through esterification that was performed between the hydroxy groups of PVA and the anhydride groups of ST-co-MA-Hz (II) copolymer. The ST-co-MA-Hz (II) copolymer was prepared by the chemical reaction of ST-co-MA (I) and Hz in dioxane. The ST-co-MA (I) copolymer was prepared by the copolymerization of MA and ST in dimethyl sulfoxide (DMSO) by using azobisisobutyronitrile (AIBN) as an initiator. In order to obtain a membrane high in both selectivity and permeation rates, a series of PVA-g-ST/MA-Hz were synthesized with different compositions. Water was permeated through membrane preferentially in all ranges of water—alcohol feed compositions in this study. The permeation rate decreased and the selectivity increased as the PVA content in membrane rose. The effects of the molecular size of the permeating species on both permeation and separation were also investigated.

Effect of the compatibilizers on flame-retardant polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) alloy

Polycarbonate (PC) blended with acrylonitrile–butadiene–styrene (ABS) has the maximum notched Izod impact strength, which is 58 kg cm cm-1 for PC/ABS1 and 66 kg cm cm-1 for PC/ABS2, at a ratio of 80/20 in this study. We selected the ratio of 80/20 to prepare flame-retardant PC/ABS alloys. The compatibility of flame-retardant PC/ABS alloy was examined by differential scanning calorimetry (DSC). The flame-retardant PC/ABS alloy had two values of the glass transition temperature (Tg), indicating that the alloy was not compatible. Three kinds of compatibilizers, methacrylate–butadiene–styrene (MBS), ethylene–vinyl acetate (EVA), and styrene–maleic anhydride (SMA) were used to improve the phenomenon. DSC measurement revealed that after compatibilization the alloy had only one value of Tg, meaning that the alloy became more compatible. Samples were frozen in liquid nitrogen to look at their morphology. We found that the domain sizes were reduced and the surface boundaries were closed and blurred, a feature that could promote the mechanical properties of the alloy. In this study, we also compared the effects of mechanical properties on differential compatibilizers for the flame-retardant PC/ABS alloy. Cycoloy 2800 is a commercial-grade flame-retardant product and was chosen to compare it with our prepared alloys in this study.

Synthesis and properties of maleimide-terminated polyurethane AB crosslinked polymers I. Polyurethane/allyl nonyl novolac resin ABCPs

Abstract Polyurethane (PU) and phenolic resin were prepared to form maleimide-terminated PU/allyl nonyl novolac resin ABCPs. The polyurethane was prepared from 4,4′-diphenyl methane diisocyanate (MDI) and poly(tetramethylene oxide) [PTMO] of various molecular weights. The composition, compatibility, mechanical and thermal properties of these inhomogeneous network polymers were investigated through differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), the tensile strength tester and transmission electron microscopy (TEM) micrographs. The results reveal that the miscibility makes only a little improvement but the tensile strength has clear improvement when the PU’s soft segment, i.e. PTMO, is higher, because of the entanglement between components.

Modification of polypropylene, blending with resole type phenol-formaldehyde resins

Abstract Resole type phenolic prepolymers were prepared with phenol, p-cresol, p-t-butylphenol and p-nonylphenol as the phenolic component. Small amounts of the prepolymers were blended with PP and structure, mechanical properties, electric and dielectric characteristics, as well as mould shrinkage of the blends were determined. The phenolic resin is dispersed as fine particles in the PP matrix and SEM studies indicate good adhesion between the components. In spite of the small amount of phenolic resin in the blend—max. 4 wt%—significant improvement of some of the properties, especially impact strength, was observed. Analysis of experimental data, calculation of interfacial interaction and comparison with literature data indicate that during homogenization chemical reactions take place between PP and the phenolic prepolymer. According to the analysis the reactions go through chinon methides and other chinoidal transformation compounds forming during resin cure. Although the presented tentative explanation must be verified with further experiments, the reaction of the components opens up new possibilities in PP modification.

The effect of maleic anhydride grafting on the flame retardation of plasma pretreated polyethylene

Abstract A rotating cylindrical-type argon plasma treatment system was used for pretreating low-density polyethylene (LDPE) to graft polar vinyl monomers. Maleic anhydride (MA) was used to graft onto plasma-treated LDPE (PLDPE) using UV-induced polymerization. The MA-grafted PLDPE (MA-g-PLDPE) was characterized by FT-IR spectra, SEM, TGA and ESCA measurement. The modified PLDPE was blended with a commercial flame-retardant additive (FR 44-94S), a coupling agent, lubricant and antioxidant to improve the flammability. The flammability of these blends increases with increasing amounts of FR 44-94S. However, the tensile strength and impact strength were decreased as the amount of FR 44-94S increased. From the results of notched Izod impact strength vs flame-retardant content, this flame-retardant seemingly exhibited plasticizer characteristics. As MA-g-PLDPE and FR 44-94S were blends, the mechanical strength, such as the tensile strength, impact strength, Youngs modulus and LOI increased because the grafted MA can enhance the affinity between matrix and additives.

The synthesis and properties of side‐chain liquid‐crystal polymers with a chiral center

The synthesis and mesomorphic properties of six monomers and six side-chain liquid-crystal polymers with a chiral center are described. The polysiloxanes were prepared by the hydrosilation of monomers with poly(hydromethylsiloxane)s. Most of the polymers exhibit a wide range of the chiral smectic C phase (SmC * ).

Synthesis and properties of simultaneous interpenetrating networks based on poly(urethane-epoxy)/allyl novolac resin

Poly (urethane-epoxy)/allyl novolac resin simultaneous interpenetrating networks (SINs) were prepared by crosslinking urethane-epoxy adduct with diamino diphenylmethane (DDM) and allyl novolac resin simultaneously. An urethane-epoxy adduct was synthesized by terminating the urethane prepolymer composed of 4,4′-diphenyl methane diisocyanate (MDI) and poly (tetramethylene oxide) (PTMO), whose molecular weight range falls in 600–700 (UT1), 900–1050 (UT2) and 1900–2100 (UT3) with glycidol (GL). The allyl novolac resin was derived from novolac type phenolic resin by substituting the hydroxy group on the aromatic ring with the allyl group. The thermal, mechanical and dynamical characteristics of these SINs were measured by differential scanning calorimetry (DSC), Instron tester and dynamical mechanical analysis (DMA), and correlated well enough with morphological observations from transmission electron microscopy (TEM). All these SINs exhibit a two-phase structure and a reasonable explanation is provided for the correspondence of the phase mixing and the specific mechanical properties.

Preparation and characterization of polyurethanes/allyl novolac resin simultaneous interpenetrating network

Abstract A series of interpenetrating networks (IPNs) of polyurethanes (PU) and allyl novolac resin were successfully prepared by mixing all the essential components at the same time so that these two polymer networks were constructed simultaneously. The major components included PU prepolymers and allyl novolac resin. The former components were prepared by reacting 4,4′-diphenyl methane diisocyanate (MDI) with poly (tetramethylene oxide) (PTMO) whose molecular weight range falls in 600–700 (for convenience this polymer is called as UT1), 900–1050 (UT2) and 1900–2100 (UT3) separately, and the latter component was synthesized by substituting the hydroxy group of phenolic resin with allyl group. The phenomena of phase mixing for these IPN polymers were investigated and confirmed through dynamic mechanical analysis (DMA), differential scanning calorimetric analysis (DSC) and transmission electric microscopy (TEM) analysis. The tensile strength of these IPNs was improved and was in accordance well with their structures, viscoelastic properties and morphology.