Flame Time Research Articles

Phosphorylated poly(vinyl alcohol) surface coatings as intumescent flame inhibitor for polymer matrix composites

Flammability is one of the main drawbacks affecting polymer matrix composites (PMCs), limiting metal replacement in several applications. Phosphorus compounds demonstrated a great ability in contrasting fire spreading. Here, phosphorylated poly(vinyl alcohol) (PPVA) has been synthesized and used as an intumescent flame inhibitor coating for carbon fiber reinforced polymer (CFRP) laminates. The synthesized PPVAs, with a phosphorylation degree up to 7.5 %wt, were investigated by spectroscopic (NMR and IR) and thermal (TGA and DSC) analyses. Moreover, thermal degradation kinetics was also rationalized by applying differential and integrals methods: the phosphorus catalytic effect combined with radicals-coupling behaviour deriving from the phosphorus species developed during the combustion has been highlighted, confirming the inhibitor role of PPVAs. Cone-calorimeter tests, simulating a small-scale fire scenario, were carried out on poly(vinyl alcohol)-coated and PPVA-coated materials prepared by solvent casting. Results highlight the anti-flame properties of PPVAs, especially as effective flame inhibitors: up to −58 % in the time of flame (TOF). Instead, poly(vinyl alcohol) coatings lead to an overall worsening of the material fire behaviour, highlighting the crucial role of phosphorous to reduce flammability. Such promising results pave the way for the use of PPVA coatings to reduce the fire risk of flammable composites making them safer.

인도네시아 주요 조림수종의 연소특성

본 연구에서는 인도네시아 조림지에서 생장한 4수종의 효율적 활용방안을 마련하기 위해 콘칼로리미터법에 의해 연소특성을 조사하였다. 그 결과, 평균열방출량(<TEX>$HRR_{mean}$</TEX>)은 비중에 비례하였으며, 총열방출량(THR) 및 연소시간(FT) 등열관련 계수도 같은 경향을 나타냈다. Albizia는 열방출 시간이 짧았고, Mindi는 4수종 중 점화시간(TTI)과 연소시간(FT)이 길어져 4수종 중 연소속도가 늦었고, 열방출 시간도 가장 길게 이어져 결국은 Mangium 수종과 비슷한 총열방출률을 나타내는 것을 확인할 수 있었다. Albizia는 공시수종 중 가장 높은 비소화면적 값을 나타내어 연기발생비율이 높았고, 반대로 Mindi는 가장 낮은 비소화면적 값을 나타내 연기발생비율이 낮았다. 초기 연기방출률은 Albizia가 높았으나 이후에는 Gmelina와 Mangium 의 연기방출률이 높아져 총연기발생량이 높게 나타났다. Gmelina는 불완전연소로 인해 연소기간 중 가장 많은 일산화탄소 연기를 생성하였고, <TEX>$CO/CO_2$</TEX> 비율은 다른 수종에 비해 3배 이상 높았다. This study was performed to understand combustion properties four major Indonesian wood species such as Albizia, Gmelina, Mangium and Mindi were investigated by cone-calorimeter for better utilization of theses wood species. Heat release rate (HRR), total heat release (TSR), specific mass loss rate (SMLR), effective heat of combustion (EHC), time to ignition (TTI), flame time (FT), specific extinction area (SEA), smoke production rate (SPR) and CO compound production rate were measured. HRR, THR and FT were proportional to the density of woods. Albizia showed the highest HRR, while Mindi had the lowest HRR. For SPR, Albizia showed the highest value due to its higher SEA. On the other hand, Mindi had the lowest SPR due to a lower SEA value. The highest smoke emission was for Albizia at the beginning of combustion. After 300 seconds, smoke emission of Gmleina and Mangium was increased greatly. Mangium and Mindi showed the highest total carbon dioxide emission. Expecially, Gmelina released the highest carbon monoxide during the combustion period and presented three times higher <TEX>$CO/CO_2$</TEX> ratio than those of other species due to incomplete combustion.

Federalism Vindicated: University Desegregation in South Carolina and Alabama, 1962–1963

By the 1950s, two contrasting strategies of white leadership were emerging in the South: “massive resistance” and “moderation.” Both were equally committed in principle to a defense of segregation, but they employed different tactics: The former trumpeted “defiance,” the later counseled “delay.” The strategists of-“massive resistance,” who for a decade largely dominated politics in Alabama and Mississippi, were convinced that any concession, even a tactical one, would be a dangerous break in the dike of segregation. They believed that defiance could deter the federal government from enforcing the university desegregation decisions and Brown v. Board of Education of Topeka (1954; 1955). On the other hand, the strategists of “moderation,” who gained political ascendancy in South Carolina, maneuvered within the law, first to postpone implementation of Brown, and then to determine the minimum amount of desegregation that blacks would accept, which would not at the same time inflame white racists. In effect, they used skillful tactics of delay to “moderate” both white racism and black aspirations. Ultimately, they were more successful in achieving their objectives than the resisters, because they avoided sweeping federal interventions.