Flame Retardancy, Smoke Suppression Effect and Mechanism of Aryl Phosphates in Combination with Magnesium Hydroxide in Polyamide 6

The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis（diphenyl phosphate） （BDP） and resorcinol bis（diphenyl phosphate） （RDP）] combined with magnesium hydroxide （MH） in polyamide 6 （PA6） have been investigated. Combining 5 wt% BDP, 50 wt% MH imparts a limiting oxygen index （LOI） of 40.9% and UL94 V-0 rating to PA6, meanwhile the peak rate of smoke release （pRSR）, total release of smoke （TSR） and Izod notched impact strength are 41%, 33% and 233% relative to the corresponding value of 55 wt% MH without BDP, respectively. Dynamic mechanical analysis （DMA） indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP. Furthermore, based on the comprehensive analysis of thermogravimetry （TG）, cone calorimeter and SEM-EDX investigations, possible flame retardancy and smoke suppression mechanisms were revealed. Besides the fuel dilution and barrier effect of MH, the combination of MH and RDP shows an additional flame inhibition effect. The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.

Built-up Effect of Core Material for Microencapsulated Flame Retardant Containing Dimethyl Methyl Phosphate

The flame retardants containing organophosphorus compounds have extensively been used in the flame retarding of polymer materials. Among others, dimethyl methyl phosphate (DMMP) was applied in flame retarding of polyurethane owing to its so much merit. However, the water-soluble property of DMMP restricted its application in textile fabric. The flame retarding system containing DMMP will be microencapsulated to form a novel flame retardant that could be used in textiles. We have studied the built–up effect of DMMP with some inorganic compounds to improve the afterflame and afterglow suppression in the flame retarding system. The experimental data indicated that inorganic compounds containing various non-metal elements P, N, B and metal ions Mg2+, Al3+, Ca2+, Zn2+, Cu2+, Mn4+ could be applied in flame retarding systems as additives to effectively suppress afterflame or afterglow.

Comparative Study on the Properties of Inorganic Silicate and Organic Phenolic Prepolymer Modified Poplar Wood by Vacuum Cycle Pressurization

To enhance mechanical properties and improve flame retardancy and smoke suppression of fast-growing poplar wood in wood applications,the wood was impregnated and modified.An organic phenolic prepolymer and inorganic sodium silicate was used as contrasting impregnation modifiers and wood samples were impregnated by a bionic“respiration”method with alternating positive and negative pressure.The weight percentage gain,density increase ratio,mechanical properties(bending and compressive strength and hardness),and water absorption rate of inorganic and organic-impregnated modified poplar wood(IIMPW and OIMPW,respectively)were compared and these properties in IIMPW were found to be higher than those of OIMPW with the exception of the water absorption rate which was lower than the OIMPW.This was attributed to the superior absorption of sodium silicate that also improved the impregnation,reinforcement,and dimensional stability in the IIMPW.The chemical structure,crystalline structure,internal morphology,flame retardancy,smoke suppression,and thermal stability of IIMPW and OIMPW were characterized by FT-IR,XRD,SEM,CONE,and TGA.FT-IR and XRD results showed that,although IIMPW cellulose crystallinity reduced the most,more chemical bonds were come into being in IIMPW,which explained the better physical and mechanical properties of IIMPW.Compared with OIMPW,IIMPW had better flame retardant and smoke suppression performance.

Pavement structure and materials design for sea-crossing bridges and tunnel:Case study of the Hong Kong-Zhuhai-Macao Bridge

With the continuous development of bridge and tunnel construction technologies,large-scale sea-crossing bridges and tunnels have gradually become the preferred choice for regional traffic.The construction technology of Hong Kong-Zhuhai-Macao Bridge(HZMB),one of the most representative sea-crossing passageways,is instructive for the construction of other large sea-crossing infrastructures.At present,the pavement design method of sea-crossing passageways lacks pertinence as it still refers to specifications for design of common pavement.Therefore,it is necessary to consider the bridge and tunnel pavement of HZMB as a typical example to analyze key technical problems encountered in its design,construction and operation.Novel solutions for material selection and structural design built upon the analysis of such critical problems should thus follow up.Based on comprehensive literature research,it can be found that environmental variability,tunnel closure,structural differential settlement and expansion deformation are the key technical problems faced by pavement of sea-crossing passageways.In view of the environmental variability,the steel deck-paving material and structure design of GMA-10 t SMA-13 is innovatively proposed.As for the closure of immersed tube tunnel,warm-mix flame retardant asphalt mixture is used to control pavement design through key indexes such as temperature and limit oxygen index.Regarding the deformation of immersed pipe joints,BJ200 asphalt seamless expansion joint material is introduced,which effectively satisfies the multi-directional deformation between pipe joints and ensures the smoothness of the road surface and driving comfort.For segmental joints,double-layer waterproof-coiled material is used to effectively prevent reflective cracks while ensuring the continuity of asphalt concrete pavement.Therefore,this paper provides a panel of ideas and methods for the pavement design of the same type of sea-crossing passageways.