Advanced Industrial and Engineering Polymer Research最新文献

Due to environmental concerns, some of the conventional halogenated flame retardants have been banned. In this context, both the industrial and academics have made efforts to develop more eco-friendly and sustainable flame retardant materials. Among new flame retardants, bio-based groups have attracted plenty of attention. In this review, varied types of bio-based flame retardants are systematically described, including the structural characteristics, flame retardant behaviors, and an overview of flame retardant mechanism. Recent research progress on various bio-based materials such as flame retardants (e.g., chitosan, lignin, phytic acid, polydopamine, Tannic acid, β-cyclodextrin, etc.) applied to different polymers are adequately summarized. Finally, the opportunities and challenges for the future development of bio-based flame retardants are briefly outlooked.

Wood is a combustible material. Not all types of wood, however, react to ignition and burning the same way. This can vary significantly depending on the type of wood, because the physical structure (morphology), density, as well as chemical composition of the wood can significantly affect its fire behavior. In this study, eight different types of tree species, four from the northern temperate zone and four from the tropical zone, were studied to determine their fire behavior. The results show different behaviors in all the species studied. It was found that although there is some correlation between density and positive fire behavior, these factors are not always determining.

The use of a waste material as flame retardant for polypropylene (PP), i.e. flue gas desulfurization (FGD) gypsum, has been studied. FGD gypsum has been used alone or in combination with melamine cyanurate (MC) and a phosphate ester (SolDP), which acts also as polymer plasticizer. Several formulations have been investigated in order to obtain UL94-V2 rated PP at 3.2 mm thickness.

The results have demonstrated that 20 wt% of FGD is the optimal amount to be used together with 15 wt% MC and 3 wt% SolDP to get UL94-V2 PP material. The flame retardancy action of MC and SolDP can be, indeed, further strengthen by the presence of FGD filler, which is essential to guarantee the good fire reaction obtained. The results have also shown that the control of the dripping phenomena is essential and therefore a suitable plasticizer, acting also as flame retardant, shall be used in this system. The content of the plasticizer shall be optimized since, from one side, it favours dripping but, on the other side, it tends to decrease the heat stability of the polymeric matrix when used at high content (>5%). Finally, a synergy between this phosphate ester plasticizer and MC has also been revealed.

Flame retardant rubber composites have attracted a great attention during the past decades owing to their irreplaceable roles in complex industrial systems. Large amounts of efforts have been made to improve the flame retardant ability, developing high efficiency flame retardant systems which can reduce the release of heat, smoke and toxic gases while not deteriorate overall properties is becoming more and more important. This review briefly outlines the recent developments of flame retardant natural rubbers, silicon rubbers, some kinds of artificial rubbers and polyurethane elastomer composites, focuses on the design, development, mechanism and applications of advanced high-performance flame-retardant methods. Finally, outlooks the future tendency including more environmental-friendly strategies, higher flame-retardant efficiency and development of multifunctional flame-retardant rubber composites are proposed.

The study describes the hybridization of epoxy/flax-cotton (EP/FF) composites containing ammonium polyphosphate (APP) with micrometric expanded vermiculite (VMT) (1–10 wt%). The efficiency of hybridization of flame retarded epoxy/flax-cotton composites was assessed by performing static tensile and flexural strength evaluation, supplemented by impact strength measurements of the composites. Moreover, thermal and thermomechanical analyses (DMA, DSC, and TGA) were performed. Epoxy composites were subjected to flammability using a PCFC microcalorimeter and cone calorimeter measurement to assess the burning behavior of composites. The introduction of the low-cost plate-shaped filler resulted in several favorable thermal effects while deteriorating the structure of the composite. The addition of small amounts of vermiculite (1–2 wt%) into the matrix modified with APP enabled the reduction of heat release rate (HRR) and total heat release (THR) by 60% and 20%, respectively. The comprehensive structure-properties analysis determined the critical filler contents, yielding synergistic flame-retardant effects with a limited negative impact on the composites' performance.

Polyamides are essential thermoplastics whose current worldwide annual production exceeds 10 million tons. They are ubiquitous and easily ignitable polymeric materials that require addition of flame retardants to comply with fire safety requirements for various applications. Flame retardant additives can be incorporated into polymer matrix as fillers or at the molecular level, implying use of reactive additives. The latter approach is less developed, but usually offers several advantages over adding flame-retardant fillers: lower additive loading used to achieve specific level of fire performance, no flame-retardant migration with time, lower corrosiveness, better polymer stability etc. Rendering polyamides intrinsically flame retardant is therefore highly desirable. In this review we survey progress in inherently flame-resistant polyamides done over the period from 2004 to 2020. The polymers are grouped according to their chemical structures: aliphatic, semiaromatic and aromatic polyamides, polyamidoimides and hybrid siloxane-polyamides. Their monomer preparation, synthesis details, thermal properties and fire performance are discussed. The minimal inclusion criterion for this review was reported fire-resistance performance: either V-1/V-0 rating achieved in UL-94 burning tests or experimental or calculated LOI above 23%.

Melt flow ratio (MFR or I₂₁/I₂) was measured for dozens of polyethylene (PE) in the melt index (MI or I₂) range of 1–10 for various types of PE. I₂₁/I₂ for samples of linear low density polyethylene (LLD) polymerized by a Ziegler-Natta catalyst (ZN-LLD) lie near I₂₁/I₂ = 25, whereas those for specimens of metallocene linear low density polyethylene (m-LLD) scatter close to I₂₁/I₂ = 18. The plot of I₂₁/I₂ vs I₂ for LLD showed that I₂₁/I₂ is almost independent on molecular weight and short chain branching (SCB), but strongly dependent on molecular weight distribution (MWD). The broader MWD, the larger I₂₁/I_2. This rule basically holds for both low density polyethylene (LDPE) and high density polyethylene (HDPE). However, at a certain I₂ around 6 a discontinuous jump of I₂₁/I₂ for HDPE samples exits, where I₂₁/I₂ for samples of I₂ less than 6 lie near those of LDPE and I₂₁/I₂ for ones having I₂ bigger than 6 disperse close to those of ZN-LLD. In addition, bimodal PE or PE with long chain branching has a bigger I₂₁/I₂ in some case. Further, the relationship between the viscosity and melt index was discussed, indicating that I₂₁/I₂ as well as MWD is characteristic of all types of PE. Consequently, I₂₁/I₂ can be used as a convenient and efficient approach to identifying the type of PE.

The techniques for the detection and control of cyclic esterification (CE) in biodegradable polyesters are presented. It is pointed out that CE can be extracted by extraction or migration and then detected using GC-MS or LC-MS depending on their volatility, with LC-MS techniques being more commonly used due to the generally poor volatility of CE. CE was detected in several typical biodegradable polyesters such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS) and poly(butylene adipate-terephthalate) (PBAT) with repeating units less than 10; both the improvement of the polymerization process and the use of organic solvents to wash the biodegradable polyester particles can effectively reduce the content of CE, and the washing strategy is relatively more convenient and efficient.

To investigate the applicability of infrared thermography technique as a method for obtaining dynamic plastic deformation in polycarbonate, an infrared thermography experiment has been performed under four different loading rates. Three-point bending tests of polycarbonate have been conducted to evaluate thermal evolution obtained via infrared thermography in order to detect capabilities of plastic deformation. And photoelastic tests under the same experimental conditions were carried out to verify the reliable of experimental results of infrared thermography. The stability of the plastification region demonstrated the validity of infrared thermography as an approach for describing the dynamic plastic deformation when used on complex structures. Meanwhile, the conversion coefficient β of plastic work to heat at different loading rates have been investigated, and the results shown the β increases in 0.2–0.7 with plastic deformation. The photoelastic fringe patterns further verified the generation and propagation of plastification region. This research based on two basic tests, providing a useful suggestions for complex structure materials to evaluate the plastic deformation where middle wave infrared thermography was applied.