Relationship between thermal degradation behavior and flame retardancy on polycarbonate–polydimethylsiloxane block copolymer

This article describes the thermal degradation behavior of polycarbonate–polydimethylsiloxane (PC–PDMS) block copolymer with dimethylsiloxane (DMS) block size 15 to 350 units, and the effects of the PDMS block size and the PDMS content on thermal degradation were studied. PC–PDMS block copolymer with DMS unit of 100 had the lowest value of maximum weight loss rate and the most residue containing silica in the other PC–PDMS block copolymers. The PDMS block size influenced PDMS dispersibility in PC and the moderate PDMS dispersion (? 50 nm) caused high flame retardancy for PC. The control of nanodispersion of PDMS caused the change of thermal degradation behavior and high flame retardancy in PC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1697–1705, 2006     

Flame retardancy of polycarbonate–polydimethylsiloxane block copolymer/silica nanocomposites

This report describes the flame retardancy and the thermal degradation behavior of polycarbonate–polydimethylsiloxane (PC–PDMS) block copolymer/silica nanocomposites. PC–PDMS block copolymer with dimethylsiloxane (DMS) block size 40 units increased the dispersibility of nanosized amorphous silica. Addition of the slight nanosized silica caused the increment of flame retardancy of PC–PDMS block copolymer, and the PC–PDMS block copolymer with 1.0 wt % PDMS had the highest limiting oxygen index value when the nanosized silica was added 0.5 wt %. The maximum rate temperature of the PC–PDMS block copolymer increased with the addition of silica and the maximum loss rate was the lowest when silica content is 0.5 wt %. The monodisperse nanosized silica had an effect that enhances the flame retardant mechanism of PDMS for PC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3862–3868, 2006     

Synthesis and characterization of perfectly alternating polycarbonate‐polydimethylsiloxane multiblock copolymers possessing controlled block lengths

An array of perfectly alternating polycarbonate‐polydimethylsiloxane (PC‐PDMS) multiblock copolymers possessing systematic variations in block molecular weights were successfully produced by coupling preformed PC and PDMS telechelic oligomers using hydrosilylation. Based on gel permeation chromatography results, the multiblock copolymers were essentially void of the oligomeric precursors. Despite the relatively large difference in solubility parameter between PC and PDMS, the multiblock copolymers exhibited significant partial miscibility between the two phases. As expected, the degree of partial miscibility was dependent on the molecular weight of the blocks with the extent of partial miscibility increasing with decreasing block molecular weights. Morphological characterization using small angle X‐ray scattering showed that, at a given PC block molecular weight, the uniformity of the two phase morphology increased with increasing PDMS block molecular weight, which is consistent with a decrease in the extent of phase mixing with increasing PDMS block molecular weight. POLYM. ENG. SCI., 54:1648–1663, 2014. © 2013 Society of Plastics Engineers     

Rheo-optical Fourier transform near-infrared spectroscopy of polydimethylsiloxane/polycarbonate block copolymers

A series of polydimethylsiloxane (PDMS)/polycarbonate (PC) block copolymers with varying compositions were investigated by simultaneous mechanical and Fourier transform near-infrared (FTNIR) spectroscopic (rheo-optical) measurements to study segmental orientation during elongation-to-break and cyclic elongation–recovery procedures. Depending on the composition and the block lengths of the copolymers, different orientational and recovery phenomena were observed for the hard (PC) and soft (PDMS) segments. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1349–1357, 1998     

Flammability resistance synergism in BPA polycarbonate–silicone block polymers

The synergism in limiting oxygen index found in BPA carbonate–dimethylsiloxane block polymers (BPAC/DMS) is correlated with a rise in yield of pyrolytic char and an improvement in char oxidation resistance. These changes in turn are related to a peaking of fractional silicon retention in the char at a resin composition of 50 mole % DMS. This behavior, the fine dispersion of silicon in the char, and analyses of the pyrolysates suggest that an important feature of char formation in the block polymers is a polycondensation reaction between pyrolysis products from the two blocks. In addition to the role of chars in withholding fuel from the flame, they are thought to function effectively as thermal insulators.     

Preparation and characterization of block and graft copolymers using macroazoinitiators having siloxane units

α,ω-Amine terminated organofunctional polydimethylsiloxane (PDMS) was condensed with 4,4′-azobis-4-cyanopentanoyl chloride (ACPC) to prepare macroazoinitiators containing siloxane units. Interfacial polycondensation reaction at room temperature was applied: ACPC was slightly dissolved in carbon tetrachloride and it was poured on aqueous NaOH solution of PDMS. Block copolymers containing PDMS as a block segment combined with polystyrene (PS) have been derived by the polymerization of styrene monomer initiated by these macroazoinitiators. PS-b-PDMS block copolymers were characterized by using nuclear magnetic resonance and infrared spectroscopy. Thermal and mechanical properties of the block copolymers were studied by using thermogravimetric analysis, differential scanning calorimetry, and a Tensilon stress-strain instrument. The morphology of block copolymers was investigated by scanning electron microscopy. PDMS-g-polybutadiene (PBd) graft copolymers were also prepared by reaction of PBd with the above macroazo-initiator. Increase in the amount of macroazoinitiator in the mixture of PBd (52% w/w) leads to the formation of crosslinked graft copolymers. Molecular weights of soluble graft copolymer samples were between 450 and 600 K with a polydispersity of 2.0–2.3. © 1996 John Wiley & Sons, Inc.     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Versatile synthesis of self‐assembling ABA triblock copolymers with polymethyloxazoline A‐blocks and a polysiloxane B‐block decorated with supramolecular receptors

BACKGROUND: Self‐assembling amphiphilic block copolymers with incorporated, biologically relevant functionalities have received limited attention, partly due to the fact that biomolecules are not robust enough to synthetic manipulation, do not lend themselves readily to systematic studies due to their complexity and leach rather quickly from a vesicle or membrane when physically incorporated. Synthetic supramolecules are used as biomolecule mimics in functional membranes. RESULTS: Reaction conditions were established for the synthesis of a tosyl‐terminated siloxane end‐blocker, which serves as molecular weight control in the synthesis of polydimethylsiloxane (PDMS) and poly(dimethylsiloxane‐co‐methylhydrosiloxane) [P(DMS‐co‐MHS)] copolymers. Hydrosilylation reactions were investigated for the covalent coupling of synthetic supramolecules (18‐crown‐6 ether, hydroxybenzoate) to the polymer backbone using the methylhydrosiloxane repeat units as the anchor moiety. Using P(DMS‐co‐MHS) or derivatized P(DMS‐co‐MHS) copolymers as macroinitiator for the ring‐opening polymerization of 2‐methyl‐4‐hydroxy‐oxazoline led to the formation of poly[(dimethylsiloxane‐co‐methylhydrosiloxane)‐block‐oxazoline] [P(DMS‐co‐MHS‐b‐Ox)] ABA triblock copolymers with defined PDMS to PMHS ratios and controlled molecular weights. CONCLUSION: Derivatized P(DMS‐co‐MHS‐b‐Ox) ABA triblock copolymers synthesized using a novel versatile procedure undergo vesicle formation upon electroformation with vesicle diameters ranging from 2 to 10 µm. The size of the vesicle depends on the overall polarity of the macromolecule. Copyright © 2008 Society of Chemical Industry     

阻燃剂类型对聚碳酸酯阻燃性能的影响

分别选用溴化齐聚物、磺酸盐、聚硅氧烷混合物和磷酸酯阻燃剂对聚碳酸酯(PC)进行阻燃改性,研究了阻燃剂类型对PC阻燃性能的影响,同时探讨了试样厚度对阻燃性能测试结果的影响。结果表明,溴化齐聚物提升了PC的灼热丝起燃温度(GWIT),磺酸盐、聚硅氧烷混合物和磷酸酯降低了PC的GWIT;成炭对起燃的影响远小于热分解,决定GWIT高低的因素是热分解温度,热分解温度越高,GWIT越高。磺酸盐分解的SO2促使PC交联形成的产物为层碳或石墨化结构,不仅隔热、隔氧、阻止气体流通,还具有导电性,是真炭层,磺酸盐阻燃改性PC的相比电痕化指数由纯PC的175 V降低至150 V;聚硅氧烷混合物、磷酸酯及其分解物形成的“炭层”仅具有类似炭层的作用,无导电性,对PC的电痕化性能无影响。添加四种阻燃剂后PC的灼热丝可燃性指数、垂直燃烧等级均有不同程度的提升,针焰试验结果变好。随着试样厚度增加,溴化齐聚物阻燃PC的GWIT升高,磺酸盐和磷酸酯阻燃PC的GWIT降低,聚硅氧烷混合物阻燃PC的GWIT无明显变化。随着试样厚度增加,四种阻燃剂阻燃PC的其它阻燃性能整体变好,但磷酸酯阻燃PC的垂直燃烧等级仍为V–1级。     

Study of a novel halogen‐free flame retardant system through TGA and structure analysis of polymers

Butadiene‐rubber toughened styrene polymers, such as acrylonitrile‐butadiene‐styrene (ABS) copolymer and high impact polystyrene (HIPS), are noncharring polymers. They are generally blended with polycarbonate (PC) or polyphenyleneether (PPE), which are char forming polymers, to improve char forming ability for styrenic blends containing conventional phosphate flame retardants. To achieve cost effective flame retardant system, PET was selected as a potential char‐source for ABS blends through the thermogravimetric analysis (TGA) and chemical structure analysis of various polymers. PET may contribute to the enhancement of flame retardancy of ABS/PET blends, especially in the presence of small amounts of phenol novolac (PN). The effective flame retardancy of this system is believed to be accomplished through the enhancement of interchain reactions by PN. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal and mechanical properties of tetramethyl-p-silphenylenesiloxanedimethylsiloxane block copolymer

Several kinds of $\text{tetramethyl}\text{-p-}\text{silphenylenesiloxane}\text{dimethylsiloxane}$ (TMPS/DMS) block copolymers having various compositions and segment lengths were synthesized by the polycondensation of p-bis(dimethylhydroxysilyl)benzene and silanol-terminated DMS oligomers of different degrees of polymerization, which were 19, 43, 300, 380 and 540 DMS monomer units. The compositions ranged from TMPS/DMS wt% ratio of 100/0 to 24/76. For these copolymers, differential scanning calorimetry was carried out to determine the melting temperatures, the heat of fusion and the crystallinities. The melting temperatures and the crystallinities of the block copolymers were found to decrease as DMS contents were increased from 11 to 76 wt% and as DMS segment lengths were decreased from 540 to 19. The crystalline parts of TMPS segment would be increased according to the long TMPS sequences which were obtained from the copolymerizations by using DMS oligomers with high degrees of polymerization such as 300, 380 and 540. The stress-strain behaviour and the dynamic mechanical behaviour were also investigated for these copolymers. The tensile strength was decreased and the percentage elongation was increased with increasing DMS content and segment length. In the case of the copolymers for which the DMS contents remained constant at 26 wt%, two major transitions were observed at around ?120° and ?10°C for the copolymers having DMS block sizes of 300, 380 and 540. But for the copolymers having those of 19 and 43 the two transitions merged together at ?50°C. The relaxations at ?120°C corresponding to the glass transition of DMS component and those at ?10°C are due to the amorphous TMPS phase which is separated from the DMS phase owing to the longer sequence length. The relaxation observed around ?50°C is due to the shorter sequence length of TMPS in the main chain plus the presence of more flexible DMS component. It may be suggested that the long sequence length causes large domains of hard and soft phases which consist of TMPS and DMS blocks respectively.     

润滑剂对PP/IFR复合材料性能的影响

以聚丙烯(PP)为基体树脂、FR–1420为无卤膨胀型阻燃剂,分别加入乙撑双硬脂酰胺(EBS)、聚乙烯(PE)蜡、硬脂酸锌(硬锌)、硅酮及聚偏氟乙烯(PVDF)等五种润滑剂来制备阻燃PP复合材料(PP/IFR),考察了润滑剂及其含量对PP/IFR的阻燃性能和力学性能的影响,并对材料的热分解行为及炭层结构进行了表征和分析。结果表明,FR–1420含量为21%,五种润滑剂含量在0.5%~2%范围内变化时,对PP/IFR复合材料的力学性能影响不大,而对阻燃性能产生了明显影响;EBS与阻燃剂产生对抗作用,不论添加量多少,都显著降低PP/IFR的阻燃性,垂直燃烧等级由V–0级降低至无级;PE蜡、硬锌、硅酮及PVDF的添加量都存在一个最大值,当低于最大值时,不会影响PP/IFR的阻燃性,垂直燃烧等级均为V–0级,而高于最大值时,则会降低PP/IFR的阻燃性;PE蜡、硬锌、硅酮及PVDF均会不同程度延后PP/IFR的起始分解温度,略微降低其成炭率。     

Flame‐retardant olefin block copolymer composites with novel halogen‐free intumescent flame retardants based on the composition of melamine phosphate and pentaerythritol

A series of halogen‐free intumescent flame retardants (IFR) based on home‐made melamine phosphate and pentaerythritol system (MPPER) including polyamid 12, basic nickel carbonate (NiCO₃·2Ni(OH)₂·4H₂O), lanthanum oxide (La₂O₃), and expandable graphite compounding with MPPER, were adopted for flame retarding olefin block copolymers (OBC). Flame‐retardant effects and thermal stabilities of OBC‐IFR composites were investigated by limiting oxygen index, vertical burning test (UL‐94), and thermogravimetry analysis along with the analysis of morphological structures of the char residue by scanning electron microscopy. The mechanical properties and the flame‐retardant mechanism of the final composited materials have been also discussed. The loading of suitable amount of IFR can improve effectively the flame retardancy of the OBC with tolerable decrease in mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40066.     

A flame‐retardant composite foam: foaming polyurethane in melamine formaldehyde foam skeleton

A composite foam, polyurethane–melamine formaldehyde (PU/MF) foam, was prepared through foaming PU resins in the three‐dimensional netlike skeleton of MF foam. The chemical structure, morphology, cell size and distribution, flame retardancy, thermal properties and mechanical properties of such composite foam were systematically investigated. It was found that the PU/MF foam possessed better fire retardancy than pristine PU foam and achieved self‐extinguishment. Moreover, no melt dripping occurred due to the contribution of the carbonized MF skeleton network. In order to further improve the flame retardancy of the composite foam, a small amount of a phosphorus flame retardant (ammonium polyphosphate) and a char‐forming agent (pentaerythritol) were incorporated into the foam, together with the nitrogen‐rich MF, thus constituting an intumescent flame‐retardant (IFR) system. Owing to the IFR system, the flame‐retardant PU/MF foam can generate a large bulk of expanded char acting as an efficient shielding layer to hold back the diffusion of heat and oxygen. As a result, the flame‐retardant PU/MF foam achieved a higher limiting oxygen index of 31.2% and exhibited immediate self‐extinguishment. It exhibited significantly reduced peak heat release rate and total heat release, as well as higher char residual ratio compared to PU foam. Furthermore, the composite foam also showed obviously improved mechanical performance in comparison with PU foam. Overall, the present investigation provided a new approach for fabricating a polymer composite foam with satisfactory flame retardancy and good comprehensive properties. © 2018 Society of Chemical Industry     

Development of thin layer polymers to concentrate and detect aquatic contaminants

Poly(dimethylsiloxane) (PDMS) and a poly(DMS‐styrene) block copolymer were compared as extraction and optical detection media for hydrophobic compounds in water and water/ethanol solutions. Partitioning to both polymers increased exponentially with increased percent water in ethanol. Partition coefficients to the copolymer were 10–30‐fold higher than to PDMS. Ultraviolet absorbance spectra of pyrene showed a 4‐nm red‐shift in copolymer versus PDMS, providing evidence of π–π interactions, accounting for greater partitioning. The extinction coefficient coefficient of pyrene at 334 nm was twice as high in the copolymer as in PDMS. The combination of higher affinity for polycyclic aromatic hydrocarbons with higher absorbance make poly(DMS‐styrene) copolymers promising material for extraction and in situ detection of hydrophobic aromatic compounds in water. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface properties of block and graft polystyrene–polydimethylsiloxane copolymers

The surface compositions of a series of polystyrene‐b‐polydimethylsiloxane (PS‐b‐PDMS) and polystyrene‐g‐polydimethylsiloxane (PS‐g‐PDMS) copolymers were investigated using ATR‐FTIR and XPS technique. The results showed that enrichment of PDMS soft segments occurred on the surface of the block copolymers as well as on that of graft copolymers. And the magnitude order of the enrichment was as follows: PS‐b‐PDMS > PS‐g‐PDMS, which was attributed to the facilitating of the movement of the PDMS segments in PS‐b‐PDMS copolymer. Meanwhile, the solvent type and the contact medium had influence on the accumulation of PDMS on the surfaces. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

改性硅基杂化介孔材料阻燃PC/ABS研究

将自制的9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)接枝硅基杂化介孔材料(DM)、三苯基磷酸酯(TPP)和聚碳酸酯(PC)/丙烯腈-丁二烯-苯乙烯塑料(ABS)共混制得阻燃PC/ABS复合材料。研究表明,当DM和TPP的质量分数为2%和6%时,复合材料的氧指数为28%,并达到UL 94 V-0阻燃级别;锥形量热仪进一步分析证实PC/ABS/TPP/DM体系的最大热释放速率和总热释放量均有大幅度下降;通过对炭层形貌及结构的研究表明,DM和TPP具有很好的协效作用,在燃烧过程中能促进PC/ABS复合材料生成微观致密的炭层,增强了PC/ABS复合材料的热稳定性。     

新型磷硅阻燃剂的合成及其对PC/ABS的阻燃研究

以三氯氧磷、季戊四醇和二乙氧基氨丙基硅甲烷为原料合成了一种磷硅阻燃剂PN,并通过红外光谱和核磁共振测定了其结构。将PN与聚碳酸酯/(丙烯腈/丁二烯/苯乙烯)共聚物(PC/ABS)体系共混后研究了PN对PC/ABS体系热降解性能、阻燃性能和残炭形貌的影响。结果表明,PN能改善PC/ABS体系的高温热稳定性和残炭量,在燃烧时形成内表面发泡、外表面致密连续的膨胀炭层;且能提高PC/ABS体系的阻燃性能,当PN的添加量从0增加到30份时,PC/ABS共混材料的极限氧指数由21%增加到29%;当PN添加量超过20份后,共混材料的阻燃等级能够达到UL94V-1级。     

Flame retardancy finish with an organophosphorus retardant on silk fabrics

The paper mainly deals with flame retardancy of silk fabrics treated with a commercial organophosphorus flame retardant [N‐hydroxymethyl (3‐dimethyl phosphono) propionamide (HDPP), also known as Pyrovatex CP], using the pad‐dry‐cure‐wash method. The structures and properties of the treated and control sample are discussed. The Limiting Oxygen Index (LOI) value of the modified sample is above 30%. After 50 laundry cycles, it still has some flame retardancy left. HDPP and a cross‐linking agent (HMM) were bound to silk fabrics which is confirmed by FT‐IR spectra and amino analysis. The reaction degree of the flame retardant with silk is also high; almost all the tyrosine units have reacted, which can be confirmed by amino acid analysis. The reaction between flame retardant and silk only occurs in the amorphous region of silk fibre, which is confirmed by X‐ray diffraction analysis and amino acid analysis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis show that the flame retardant causes silk fabrics to decompose below its ignition temperature (600°C) and formed carbonaceous residue or char when exposed to fire. The char behaves as a thermal barrier to fire, so silk fabrics show good flame retardancy. The treatment has a little effect on the whiteness of the silk fabrics and the tensile strength of treated silk fabrics slightly decreased; both effects are negligible. Copyright © 2006 John Wiley & Sons, Ltd.     

高效复合阻燃聚碳酸酯的研究

阻燃剂间的协同作用正引起人们的广泛关注。以苯基硅树脂(PPSQ)与极少量的磺酸盐(SNN)和偏氟乙烯(PVDF)复合阻燃改性PC,研究了PC的极限氧指数(LOI)和UL94阻燃等随PPSQ用量变化的关系。2.0%PPSQ与0.1%的SNN0、.1%PVDF复合阻燃PC后达到了UL94 V-0@1.6 mm,协效作用十分显著。TG分析表明阻燃剂间的协同作用提高了PC的起始热降解温度和热降解速率,改变了PC的热降解途径,使降解产物交联生成坚硬的炭层而起到阻燃作用。