Fire and thermal properties of PA 66 resin treated with poly-N- aniline- phenyl phosphamide as a flame retardant
Wenyan Lyu
ABSTRACT In this study, a halogen-free phosphorous–nitrogen synergistic flame retardant, poly-N-aniline-phenyl phosphamide (PDPPD), was synthesized. The Fourier transform Infrared spectroscopy, nuclear magnetic resonance spectroscopy, and elements analysis data confirmed the structure of PDPPD. The essential flame retardant of FR PA66 was polymerized with PA66 pre-polymer and PDPPD pre-polymer, prepared from PDPPD and adipic acid. The limit oxygen index and UL-94 test results of the flame retardant of FR PA66 reached 28% and V-0, respectively, when the contents of PDPPD pre-polymer were 4.5 wt%. The thermogravimetric and differential scanning calorimetry results demonstrated that the initial decomposition temperature of flame retardant of FR PA66 was 43 °C lower than that of pristine PA66 from 385 to 342 °C; however, the peak decomposition temperature was 36 °C higher than that of pure PA66 from 437 to 473 °C, when the contents of PDPPD pre-polymer reached 4.5 wt%. Flame retardant mechanism was studied by cone calorimeter and SEM-EDX, confirming that the HRR, THR, and TSP decreased slightly, and PDPPD functions according to the gas phase flame retardant mechanism.
KEYWORDS: flame retardant; thermal properties; PA66 resin;
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phosphorous; nitrogen 1. INTRODUCTION Recently, flame retardant composites have attracted increasing attention [1]. Traditionally, brominated and chlorinated compounds are used for preventing the flammability of polymers. However, because of the environmental problems [2] considering the generation of toxic, corrosive, and halogenated gases, the release of toxic, endocrine disrupting chemicals in combustion should be avoided, thus necessitating the need of halogen-free flame retardant composites [3]. Therefore, phosphorus- and nitrogen-containing compounds are mostly used for replacing brominated and chlorinated compounds in flame retardant composites including phosphorus-containing curing agents [4,5] and reactive comonomers [6]. The common phosphorus- and nitrogen-containing flame retardants are red phosphorus (RP)[7] and melamine cyanurate [8]. However, the conventional flame retardants have some disadvantages such as a certain flame retarding level is achieved; therefore, a higher loading of additive is necessary at the expense of the mechanical properties of the flame-retardant materials [9,10]. Moreover, the commonly used flame retardant systems, which hardly withstand temperatures through the process of heating at >200 °C, cannot be incorporated into such engineering plastics. Consequently, it is essential to develop new and highly effective flame retardant systems to meet the constantly changing demand of new regulations and standards. In this study, a polymeric halogen-free phosphorous–nitrogen flame retardant, poly-N- aniline-phenyl phosphamide (PDPPD), was synthesized via the polycondensation between A and B. Then, the flame retardant of FR PA66 was prepared by the polymerizing between PA66 pre-polymer and PDPPD pre-polymer, which was synthesized from PDPPD and adipic acid. 2. EXPERIMENTAL 2.1 Materials All the starting materials and solvents were commercially available and used without further purification. Reagent grade B (B) was obtained from Shandong HongYu Chemical Plant. A was purchased from Shanghai Experiment Reagent Co., Ltd. Adipic acid, triethylamine, acetic acid, diethyl ether, and ethyl alcohol of A.R. grade were provided by Nanjing Reagent Chemical Co., Ltd. PA66 pre-polymer was provided by AnShan GuoRui Chemical Co., Ltd. 2.2 Synthesis of PDPPD The synthetic route of PDPPD is shown in Scheme 1.
First, A (3.348 g, 0.031 mol) and triethylamine (6.060 g, 0.060 mol) were added to a glass flask. Then, B (5.850 g, 0.030 mol) was added dropwise to the resulting reaction mixture over a period of 2 h, and the temperature was maintained at 5 °C. The reaction mixtures were carefully maintained at 80 °C for another 5 h. Finally, the reaction mixture was washed with diethyl ether, separated by reduced pressure suction filtration, and dried in a vacuum oven at 100 °C for 12 h to afford a white solid powder, namely, poly-N-aniline-phenyl phosphamide (PDPPD) in 93%
yield. 2.3 Polymerization of flame retarded of FR PA66 Adipic acid (14.61 g, 0.10 mol) was dissolved in ethyl alcohol (200 mL) and poured into a glass flask, followed by adding PDPPD (119.80 g, 0.10 mol) to the mixture solution. The reaction mixtures were carefully stirred at 200 rpm and heated gradually to 60 °C. The PDPPD pre-polymer was obtained by washing with ethyl alcohol, separated by reduced pressure suction filtration, and dried in a vacuum oven at 100 °C for 12 h. The synthetic route is shown in Scheme 2. The flame retardant of FR PA66 was obtained by the polymerization reaction by replacing the equivalent PA66 pre-polymer (1.5, 3, 4.5 wt%) with PDPPD pre-polymer under 1.7 MPa and 280 °C. The polymerization route is shown in Scheme 3. 2.4 Preparation of flame retardant of FR PA66 samples Prior to the melt injection, the flame retardant of FR PA66 was dried at 100 °C for 24 h. The PA66 resin pellets were injection molded into standard sample (80 × 10 × 4 mm3) for limit oxygen index (LOI) characterization and rectangular bars (3.2 × 100 × 7.1 mm3) for UL-94 vertical burning test, by using a TX-CA1 injection molding machine from Haitian Plastic Machinery Ltd (China) in the temperature range of 255–265 oC. The detailed formulations and physical constants of the flame retardant of FR PA66 are listed in Table 1. 2.5 Measurement method The FTIR of PDPPD was recorded using an FTIR-8400S (SHIMADIU) spectrometer in the range of 4000–500 cm-1 at a resolution of 1 cm-1 by the potassium bromide pellet technique. NMR spectra were acquired at room temperature using a Bruker EMX-10/12 spectrometer operating at 500 MHz (1H). The NMR samples were prepared by dissolving 20 mg of PDPPD in deuterated dimethyl sulfoxide (DMSO) (500 μL). The characteristic peaks of FTIR and NMR are listed in Table 2. Thermogravimetric analysis (TGA) was performed in a Pyris 1 thermal analyzer (PerKin Elmer). The sample (2.5 mg) was placed inside Al2O3 crucible, and the measurement was carried out in the range of 25–600 °C at a heating rate of 10 °C/min under nitrogen atmosphere.
The isomerization procedure was done in order to create dimethyl fumarate from dimethyl maleate. Dimethyl maleate and dimethyl fumarate are cis and trans isomers, respectively. This procedure was done via a free radical mechanism using bromine. The analysis of carvones reaction was done in order to identify the smell and optical rotation of the carvone samples that were provided. The odor was determined by smelling the compound and the optical rotation was determined using a polarimeter.
Discussion The reaction of (-)-α-phellandrene, 1, and maleic anhydride, 2, gave a Diels-Alder adduct, 4,7-ethanoisobenzofuran-1,3-dione, 3a,4,7,7a-tetrahydro-5-methyl-8-(1-methylethyl), 3, this reaction gave white crystals in a yield of 2.64 g (37.56%). Both hydrogen and carbon NMR as well as NOESY, COSY and HSQC spectrum were used to prove that 3 had formed. These spectroscopic techniques also aided in the identification of whether the process was attack via the top of bottom face, as well as if this reaction was via the endo or exo process. These possible attacks give rise to four possible products, however, in reality due to steric interactions and electronics only one product is formed.
Benzyl bromide, an unknown nucleophile and sodium hydroxide was synthesized to form a benzyl ether product. This product was purified and analyzed to find the unknown in the compound.
In this experiment we produced a Nylon-6,10 polymer from a reaction with a sebacoyl chloride (decanedioyl dichloride)/dichloromethane mixture and a mixture of water, 1,6-hexanediamine and sodium carbonate. The name ‘Nylon-6,10’ indicates that the diamine that it was made from has 6 carbons and the diacid it was made from has 10 carbons. The sodium carbonate was used in the preparation of Nylon-6,10 because it is a strong base that will lower the acidity of the solution and neutralize the hydrochloric acid that was produced as a by-product. The HCl was produced as a by-product instead of water because we used milder conditions by substituting decanedioyl dichloride for decanedioic acid. The decanedioyl dichloride is a better alternative because it is more reactive towards the
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German Chemist Hans von Pechmann first synthesized Polyethylene by accident in 1898 by heating diazomethane. His colleagues characterized the waxy substance polyethylene due to the fact that they recognized that it consisted of long ethene chains. It was then first industrially synthesized by accident in 1933 by applying extremely high pressure to ethylene and benzaldehyde. Over the years, development of polyethylene has increased due to the additions of catalyst. This makes ethylene polymerization possible at lower temperatures and pressures.1
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Synthetic plastics are used widely in food packaging, detergents, cosmetics, pharmaceuticals and other chemicals’ packaging. Almost 30% of the synthetic plastics are used for packaging applications in the world and this rate is expanding at 12% per annum. They have replaced traditionally used papers and cellulose products for packaging purposes because of owing better physical and chemical properties. Polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyurethane, poly(ethylene terephthalate), poly(butylene terephthalate) and nylon are most commonly used plastics. Plastics possess not only suitable thermal and mechanical properties but also better stability and durability. Plastics have attractive more public and media attention because of its durability and visibility in a litter as compared to other solid components. In 1993, total world consumption of this material was 107 million tons and it reached to 146 million tons in
"Polyesters - Terylene and PET." Polyesters - Terylene and PET. N.p., n.d. Web. 29 May 2014. .