Analysis of volatile combustion products and a study of their toxicological effects

An experimental program was conducted to study the thermochemical, flammability and toxicological characteristics of uncoated and coated polyisocyanurate foams. The coatings used were fluorinated copolymer and an intumescent material. Flammability testing methods included the XP-2 chamber smoke test, ASTM D-1692, infrared photography, Bureau of Mines penetration test, and a JP-4 fuel combustion chamber. The results of these tests are presented in a companion paper. Combustion and pyrolysis gases were analyzed by gas chromatography and mass spectrometry. The LD-50 and LD-100 tests were performed on Sprague-Dawley rats housed in an environmental chamber. The isocyanurate foam, flourinated-copolymer-coated foam, and the intumescent-coated foam were found to have excellent flammability and insulation characteristics, although smoke development was substantial. The LD-50 values for Sprague-Dawley rats, based on a two-week survival, were approximately 2.0 gm/ft³ for all three materials. Examination indicated an absence of any significant cause of death except carbon monoxide poisoning.     

Toxicity of pyrolysis and combustion products of poly-(vinyl chloride)

The pyrolysis and combustion products of poly-(vinyl chloride) and those of some of its polymer, especially of vinyl chloride with vinylidene chloride, were analysed using gas chromatography and gas chromatography mass spectrometry. The toxic effect of the individual products on the human organism was evaluated and presumed total toxicity of the poly-(vinyl chloride) combustion products (0.3g PVC products per m³) was determined.     

掺塑料废纺燃烧特性分析

文章针对单一废纺、塑料及废纺与塑料配料分别进行燃烧特性分析,结果表明纯废纺发热量低且变化较大无法满足稳定窑况的需求,塑料发热量较高同时氯离子也较高,不利于成品质量控制,两者以特定的比例配合不仅提升能燃烧性能,同时能降低氯离子的危害,热分析结果研究表明塑料燃烧过程包含在废纺燃烧过程之中,两者最大燃烧速率接近,不会出现分段燃烧导致燃烧不集中的现象,放热稳定集中。     

混合废塑料裂解液相产物的分析

通过SH/T 0558色谱模拟蒸馏技术和成分检测分析混合废塑料裂解得到的液相产物。详细介绍了SH/T 0558色谱模拟蒸馏技术快速测定裂解油馏程的方法,采用nC_9、nC_(10)混合物作为裂解油模拟蒸馏的内标物,使用常规峰面积归一分析方法,经过处理产生色谱模拟蒸馏的测定报告。该方法样品用量少,操作简便,分析速度快,结果精确,最大相对标准偏差为0.75%,能够较好的模拟裂解油馏程。混合废塑料热裂解和催化裂解得到的液相产物中汽油和柴油的含量较高,油品质量较好。对混合废塑料热裂解和催化裂解所获得的两种油样进行饱和烃、芳烃和烯烃成分检测,有催化剂参与后烯烃+芳烃的总量为85.2%,其汽油辛烷值很高,可作为高标号优质汽油组分。     

Toxicity of the pyrolysis and combustion products of poly(vinyl chlorides): A literature assessment

Poly(vinyl chlorides) (PVC) constitute a major class of synthetic plastics, Many surveys of the voluminous literature have been performed. This report reviews the literature published in English from 1969 through 1984 and endeavors to be more interpretive than comprehensive. PVC compounds, in general, are among the more fire resistant common organic polymers, natural or synthetic. The major products of thermal decomposition include hydrogen chloride, benzene and unsaturated hydrocarbons. In the presence of oxygen, carbon monoxide, carbon dioxide and water are included among the common combustion products. The main toxic products from PVC fires are hydrogen chloride (a sensory and pulmonary irritant) and carbon monoxide (an asphyxiant). The LC₅₀ value calculated for a series of natural and synthetic materials thermally decomposed according to the NBS toxicity test method ranged from 0.045 to 57 mg l^?1 in the flaming mode and from 0.045 to > 40 mg l^?1 in the non-flaming mode. The LC₅₀ results for a PVC resin decomposed under the same conditions were 17 mg l^?1 in the flaming mode and 20 mg l^?1 in the non-flaming mode. These results indicate that PVC decomposition products are not extremely toxic when compared with those from other common building materials. When the combustion toxicity (based on their HCI content) of PVC materials in compared with pure HCI experiments, it appears that much of the post-exposure toxicity can be explained by the HCI that is generated.     

Effects of metallic coating on the combustion toxicity of engineering plastics

Experiments were conducted on 34 plastic materials having a variety of metallic coatings to determine the toxicity of their thermal decomposition products. Mice were exposed for 30 min in a dome exposure chamber to the products obtained by ramp-heating the samples from 200°C to 800°C. An LC₅₀ value was obtained for each material. Postmortem examinations were conducted on all dead mice, and on survivors after 14 days, to determine the gross pathological effects of exposure; particular attention was devoted to pulmonary pathology. The exposure protocol chosen has been extensively criticized, but it is very useful to study the effects of stress on mice, which was the most important part of this work. Experiments were made involving unrestrained mice in groups of four, restrained mice in groups of four and unrestrained single mice. The LC₅₀ values for single unrestrained mice were greater, by factors of 2–3, than those for four restrained mice, with the differences being shown to be statistically significant. This suggests that stress on the test animals will tend to reduce the LC₅₀ values in bench-scale smoke toxicity tests. The LC₅₀ values for all of the materials tested were equal to or higher than the value of 8 mg1^?1 representative of the contribution of carbon monoxide to post-flashover fires. Moreover, no ‘supertoxicants’ were found in the smoke of any of the materials tested. Finally, the coatings did not adversely affect the smoke toxicity of the substrate materials by a factor higher than 2–3 in any of the cases investigated. Uncoated polyethylene was the most toxic substrate material tested (LC₅₀ = 16 mgl^?1) and uncoated NORYL® resin was the least toxic (LC₅₀ = 91mgl^?1). Metallic coatings involving Cu, Ni, graphite, and Zn typically had no statistically significant effect on the smoke toxicity of the substrate materials, although Ni coatings increased the smoke toxicity of ABS I and of white polycarbonate structural foam, by factors of 2–3. Overall smoke toxicities were well correlated with production of carbon monoxide (r=0.84) and carbon dioxide (r=0.82); oxygen levels and chamber temperature did not vary beyond acceptable limits. The materials tested generating the more toxic smokes (including polyethlene, polystyrene, and several polycarbonates) produced severe lung damage at low concentrations. The LC₅₀ of these materials was also typically greater than predicted on the basis of CO production. Other materials (including several coating on NORYL® resin and Lexan® polycarbonate) produced pulmonary damage at higher concentrations amd had LC₅₀ values more closely correlated with CO production. None of the polyurethane materials tested produced severe lung damage at the concentrations employed.     

Examples of recycled vinyl products

We describe examples in which we have demonstrated the feasibility of collection, separation, cleaning, and manufacture of several recycled products. We show that vinyl in municipal solid waste can be recycled into bottles, drainage pipe, and drainage pipe fittings with good appearance and properties. We also demonstrate the feasibility that vinyl wire and cable can be recycled into a variety of applications, including wire and cable traffic cones and drainage pipe with good appearance and properties.     

小桐子壳热解及其挥发性产物特性分析

选用小桐子壳作为原料,采用热重-红外联用(TG-FTIR)和热裂解-气相色谱质谱联用(Py-GC/MS)技术,研究小桐子壳的热解特性以及300~800℃热解过程中产物的组分信息和有机化合物中官能团随温度的变化情况,同时利用Coast-Redfern积分法求解不同升温速率下的动力学参数。结果表明,小桐子壳的热解过程分为干燥(30~100℃)、预热解(100~258℃)、热解(258~420℃)和炭化(420~900℃)四个阶段。随升温速率升高,小桐子壳的最大质量损失率依次增加,升温速率的升高对小桐子壳热分解速率具有促进作用。随热解温度升高,吸收峰处存在明显的强度变化,CO2、醛酮类等化合物的吸收峰强度逐渐降低甚至消失;小桐子壳热解过程中的气体产物成分主要为CO, CO2, H2O等,主要挥发性有机产物为苯酚、羰基化合物、愈创木酚类等,热解温度由400℃升至700℃时,酚类化合物的峰面积比例从35.94%升至59.59%、羰基化合物的峰面积比例从36.90%降到11.87%。小桐子壳热解动力学参数n=1时,其反应表观活化能最大为61.34 kJ/mol,且三个升温速率的拟合相关系数均在98%以上。小桐子壳热解动力学参数n≠1时,选取相关系数最大时的n值为反应级数,则n=0.2,反应活化能E为47.64 kJ/mol,指数前因子A为0.83。随升温速率的升高表观活化能依次递减,且拟合相关系数均在97%以上。     

Photodegradable vinyl plastics. I. Effect of N-halogen additives

The addition of small amounts of N-halogen compounds to polystyrene (PS), Polypropylene (PP), and polyethylene (PE) enhanced the photodegradability of the resultant plastic films. The effectiveness of the additives varied with their structure and with the polymer. A comparison of N-Bromosuccinimide (NBS) with several known photoinitiators showed it to be superior in effectiveness to all but one. Films were irradiated with a 275-watt RS sunlamp for 66–200 hr. Degradation was measured by increase in carbonyl absorbance at 1750–1695 cm^?1 using infrared spectroscopy and by change in viscosity. PS containing NBS underwent a greater molecular weight loss than unmodified PS after UV exposure as determined by viscosity measurements.     

Pyrolysis of mixed plastics for the recovery of useful products

Thermal and catalytic pyrolysis of polystyrene (PS) with low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), poly-ethylene terephthalate (PET) plastics were carried out in a 25 cm³ stainless steel micro reactor at around 430–440 °C under 5.5–6.0 MPa of N₂ gas pressure for 1 h. Three reactions of each plastic with PS were conducted in the ratio of 1:1, 1:2 and 1:3. The amount of PS was varied to explore its role and reactivity. In all coprocessing reactions, ratio 1:1 afforded the best yields in the form pyrolytic oils. SIM distillation of hexane soluble portion showed that the low boiling fractions were not found and fractions were obtained only after 96 °C + boiling point. It could be due to the vaporization of high volatile components. In most of the binary pyrolysis, light cycle oil (LCO) fractions have low recovery than heavy cycle oil (HCO). GC identified some very important chemical compounds present in the liquid products obtained from the pyrolysis of mixed plastics. The results obtained from this study have shown usefulness and feasibility of the pyrolysis process of the mixed plastics as an alternative approach to feedstock recycling.     

Screening flame retardants for plastics using microscale combustion calorimetry

Microscale combustion calorimetry (MCC) was evaluated as a screening test for efficacy of flame-retardant additives in polymers. The MCC method separately reproduces the gas and condensed phase processes of flaming combustion in a nonflaming laboratory test and forces them to completion to obtain intrinsic/material combustion properties. At flame extinction, these MCC combustion properties are comparable in magnitude and effect to the extrinsic factors (sample size and orientation), physical behavior (dripping, swelling), and chemical processes (flame inhibition, charring) associated with flame retardancy. Consequently, MCC properties by themselves cannot correlate flame resistance of plastics over a broad range of flame-retardant chemical composition. POLYM. ENG. SCI., 47:1501–1510, 2007. © 2007 Society of Plastics Engineers