Preparation of Ethylene-Vinyl Acetate Copolymer/ Iron-Containing Oxide Composites and Study of Their Fire Safety

聚乙烯-醋酸乙烯酯/鐵氧化物複合材料製備及其火安全性研究

Student thesis: Doctoral Thesis

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Author(s)

  • Lei WANG

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date28 Aug 2014

Abstract

Ethylene-vinyl acetate copolymer (EVA) is a commonly used polyolefin material, which can be used as hot melt adhesives, packaging, wire and cable insulation, carpet and so on. However, its flammability and large amounts of toxic gas and smoke appeared during the combustion process severely restrict the development of ethylene-vinyl acetate copolymer in the relevant fields. In order to expand the application of ethylene-vinyl acetate copolymer, developing flame retardancy ethylene-vinyl acetate copolymer material is very important. In this research thesis, halogen-free flame retardant technology, developed in recent decades, was reviewed systematically, and the feasibility of the application of the halogen-free flame retardant technology in ethylene-vinyl acetate copolymer was studied. The cause of the retarding combustion of several iron oxides in ethylene-vinyl acetate copolymer was explored. During the burning, toxic gas and smoke from these ethylene-vinyl acetate copolymer composites in the oxygen-rich conditions were discussed by a steady-state tube furnace test platform (SSTF).

1. Iron hydroxide (β-FeOOH) and phenyl dichloridophosphate modified iron hydroxide (β-FeOOPDCP) nanoparticles were prepared. Then, they were applied to an ethylene-vinyl acetate copolymer to prepare a series of EVA/β-FeOOH and EVA/β-FeOOPDCP composites. Thermal gravimetric tests showed that char residue from composites was significantly improved. Cone calorimeter tests indicated that the addition of β-FeOOH or β-FeOOPDCP nanoparticle, in some extent, decreased peak heat release rate and total heat release. Thermal gravimetric-Fourier transforms infrared spectrometry (TGA-FTIR) test demonstrated that during the pyrolysis process, the addition of β-FeOOH or β-FeOOPDCP nanoparticle reduced the volatiles form EVA matrix. The residue char after the combustion was conducted by XRD test. At the same time, DMA tests showed β-FeOOH or β-FeOOPDCP nanoparticle could improve the glass transition temperature (Tg) and the storage modulus of EVA effectively. In the aging test, it was found that 5%β-FeOOPDCP might have a very little effect on the photodegradation of EVA matrix.

2. β-FeOOH and β-FeOOPDCP nanoparticles were used as co-additives in ethylene-vinyl acetate copolymer/magnesium hydroxide composites to prepare ethylene-vinyl acetate copolymer/magnesium hydroxide/iron hydroxide (EVA/Mg(OH)2/β-FeOOH) and ethylene-vinyl acetate copolymer/magnesium hydroxide/phenyl dichloridophosphate modified iron hydroxide (EVA/Mg(OH)2/β-FeOOPDCP) composites. The results of TGA indicated that β-FeOOH or β-FeOOPDCP in the composite could effectively improve the thermal stability and the amount of residue char at high temperatures under nitrogen condition. MCC tests showed that magnesium hydroxide with iron hydroxide or phenyl dichloridophosphate modified iron hydroxide could significantly reduce peak heat release rate (PHRR), total heat release (THR) and heat release capacity (HRC) of the composite. Only substituted 1%Mg(OH)2, β-FeOOH or β-FeOOPDCP nanoparticle could improve the LOI value of EVA/Mg(OH)2 system from 26±0.5 to 35±0.5 and 39±0.5, respectively; UL-94 value increased from V-2 to V-0 level. SEM studies illustrated that the addition of β-FeOOPDCP nanoparticle system could form more robust char than other systems, which effectively prevented the spread of heat and combustible volatiles to improve the flame retardancy. Meanwhile, TGA-FTIR test demonstrated that the addition of β-FeOOPDCP nanoparticle could reduce the amount of total volatile products, hydrocarbons, acetic acid and CO. Thus, the introduction of β-FeOOH or β-FeOOPDCP nanoparticle could reduce fire hazards. Based on these, the reason for retarding the combustion was proposed.

3. Learning from the outstanding performance of phenyl dichloridophosphate modified iron hydroxide (β-FeOOPDCP) nanoparticles in ethylene-vinyl acetate copolymer, lanthanum ferrite (LaFeO3) nanoparticle was applied in ethylene-vinyl acetate copolymer and ethylene-vinyl acetate copolymer/iron oxide (Fe2O3), ethylene-vinyl acetate copolymer/lanthanum oxide (La2O3) and ethylene-vinyl acetate copolymer/lanthanum ferrite (LaFeO3) composites were prepared. TGA tests showed that the adding of LaFeO3 nanoparticle improved thermal stability and amount of the residue char at high temperatures; The results from microscale combustion calorimeter (MCC) testing indicated that LaFeO3 nanoparticle could reduce the peak heat release rate (PHRR), heat release capacity (HRC) and total heat release (THR) values of ethylene-vinyl acetate copolymer (EVA); The tests about the residue char illustrated the addition of LaFeO3 nanoparticle raised the amount of ordered carbon of the material. TGA-FTIR test indicated that during the pyrolysis process, LaFeO3 significantly reduced the amount of flammable volatiles generated from EVA matrix. In the aging test, the results showed that 5%LaFeO3 might also have a very little effect on the photodegradation of EVA matrix.

4. LaFeO3 nanoparticle was used as a co-additive in ethylene-vinyl acetate copolymer/intumescent flame retardant (EVA/APP/PER) composite. Then ethylene-vinyl acetate copolymer/intumescent flame retardant/iron oxide (EVA/APP/PER/Fe2O3), ethylene-vinyl acetate copolymer/intumescent flame retardant/lanthanum oxide (EVA/APP/PER/La2O3) and ethylene-vinyl acetate copolymer/intumescent flame retardant/iron oxide/lanthanum oxide (EVA/APP/PER/Fe2O3/La2O3) composites were also prepared. TGA tests showed the addition of Fe2O3, La2O3, the mixture (Fe2O3 and La2O3) and LaFeO3 improved the thermal stability of ethylene-vinyl acetate copolymer/intumescent flame retardant (EVA/APP/PER) composite under nitrogen atmosphere. Only replaced 0.5% intumescent flame retardant (APP/PER), Fe2O3, La2O3, the mixture (Fe2O3 and La2O3) and LaFeO3 all could raise the UL-94 value of EVA/IFR system from V-2 to V-0 level. Cone calorimeter tests demonstrated that adding these oxides could effectively reduce the peak heat release rate (PHRR) and total heat release (THR). LaFeO3 had the best effect. The char residue was measured by SEM, indicating that the addition of different oxides had great impacts on the morphology of char residue; Elements from char residue were analyzed by XPS. The results indicated that the addition of LaFeO3 could significantly improve the thermal stability of EVA retardant composites at high temperatures. Based on these, this flame retardant mechanism was proposed.

5. According to international standards, a steady-state tube furnace test platform (SSTF) was used to study toxic gas and smoke from three groups of samples, including the first group: EVA, EVA/β-FeOOH, EVA/β-FeOOPDCP and EVA/LaFeO3; the second group: EVA, EVA/Mg(OH)2, EVA/ Mg(OH)2/β-FeOOPDCP and EVA/Mg(OH)2/LaFeO3; the third group: EVA, EVA/APP/PER, EVA/APP/PER/β-FeOOPDCP and EVA/APP/PER/LaFeO3 composites. The study showed that under the oxygen-rich condition, in the thermal or combustion process of ethylene-vinyl acetate copolymer, the consumption of oxygen mainly came into carbon dioxide; β-FeOOPDCP and LaFeO3 could, to a certain extent, reduce the amount of toxic gas and smoke of the composites.

    Research areas

  • Ethylene-vinyl acetate copolymer, Magnesium hydroxide, Intumescent flame retardant, Co-additive, Mechanism