再循环对密度极限破裂的影响

用简化的再循环模型和破裂模型,研究了边缘发生的电离与电荷交换的能量损失与密度极限破裂的关系,得到HL 1M装置的临界破裂密度nc≤1.6×1020m-3。     

Pd/CaCO3 in liquid poly(ethylene glycol) (PEG): an easy and efficient recycle system for partial reduction of alkynes to cis-olefins under a hydrogen atmosphere

Lindlar’s catalyst (Pd/CaCO₃) in PEG (400) has been found to be the most reusable reaction medium for selective reduction of alkynes to cis-olefins. The catalyst and PEG were recycled five times without loss of activity.     

The viscoelastic behavior of melts of virgin and recycled polycarbonate reinforced with short glass fibers

Three series of shear oscillatory tests are performed on polycarbonate melts reinforced with short glass fibers at the temperatures T₁=250 and T₂=290 °C. The content of glass fibers ranges from 0 to 20 wt.%. In the first series, virgin polycarbonate is used, in the other series, dynamic tests are performed on recycled polymer, whereas in the third series, a mixture of virgin with recycled polycarbonates is employed. Constitutive equations are derived for the viscoelastic behavior of a polymer melt at isothermal deformations with small strains. A polymer is treated as an equivalent transient network of strands that rearrange at random times as they are agitated by thermal fluctuations. The time-dependent response of a network is determined by four adjustable parameters that are found by fitting the experimental data. Excellent agreement is demonstrated between the observations and the results of numerical simulation. The study focuses on the effects of temperature and filler content on the material constants in the stress–strain relations.     

Flexible waste management under uncertainty

In this paper, we use stochastic dynamic programming to model the choice of a municipality which has to design an optimal waste management program under uncertainty about the price of recyclables in the secondary market. The municipality can, by undertaking an irreversible investment, adopt a flexible program which integrates the existing landfill strategy with recycling, keeping the option to switch back to landfilling, if profitable. We determine the optimal share of waste to be recycled and the optimal timing for the investment in such a flexible program. We find that adopting a flexible program rather than a non-flexible one, the municipality: (i) invests in recycling capacity under circumstances where it would not do so otherwise; (ii) invests earlier; and (iii) benefits from a higher expected net present value.     

Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc.     

Studies on the recycling of glycolyzed nylon 66 using novel chain extenders

Nylon 66 (NY66) polymer based products widely used in automotive applications undergo deterioration in their mechanical properties when repeatedly exposed to ethylene glycol (EG) solution. In this study, recycling of glycolyzed NY66 (g-NY66) samples was carried out through melt-compounding with novel isocyanate based chain extenders namely hexamethylene 1,6-dicarbamoyl dicaprolactam (HDC) and tolylene 2,4-dicarbamoyl dicaprolactam (TDC). The recycling efficiency of HDC and TDC on g-NY66 was compared with two commercially available chain extenders 1,1-carbonyl biscaprolactam (CBC) and 1,3-phenylene bis(2-oxazoline) (PBO), and the resultant changes in molecular weight, melt flow, and crystallization behavior in the modified NY66 samples were confirmed from intrinsic viscosity, rheology, and differential scanning calorimetry measurements, respectively. The active ingredients (isocyanate and ?-caprolactam) liberated from HDC and TDC during the melt-compounding process reacted efficiently with the end groups of g-NY66 (-OH and -NH₂) resulting in improved molecular weight compared to g-NY66 and the results are reported in detail.     

HL—1装置边缘参量的光谱学研究

用光谱学方法测量了HL-1托卡马克等离子体中性氢原子密度n_0的时空分布,氢原子流入通量Г_0。粒子约束时间τ_p及再循环系数R等,测得n_0约为10~9—10~(11)cm~(-3),Г_0为10~(15)—10~(16)cm~(-2)·s~(-1),τ_p为几毫秒到几十毫秒,R≈0.8。根据多次放电实验数据得到了有关的定标关系。实验表明,孔栏半径的大小对氢原子流入通量及粒子约束时间都有显著影响。孔栏在粒子再循环方面起主要作用。     

Utilization of 2-alkenoic acids for biosynthesis of medium-chain-length polyhydroxyalkanoates in metabolically engineered Escherichia coli to construct a novel chemical recycling system

This study describes the biosynthesis and thermal degradation of medium-chain-length polyhydroxyalkanoate (PHA), focusing on 2-alkenoic acids as a recyclable carbon source. Using metabolically engineered Escherichia coli, PHA consisting of 3-hydroxydecanoate (3HD) was synthesized from 2-decenoic acid. Solvent cast film of poly(3HD) [P(3HD)] was transparent and showed thermal property similar to that of polycaprolactone. In addition, the use of various 2-alkenoic acids (C6-C12) resulted in production of PHAs with over 95 mol% of the corresponding single monomer units. The pyrolysis product of P(3HD) was dominantly 2-decenoic acid used for the P(3HD) biosynthesis. This demonstrates the feasibility of PHA recycling via 2-alkenoic acids, which act as pyrolysis products and raw materials for PHA biosynthesis.     

Tertiary recycling of commingled polymer waste over commercial FCC equilibrium catalysts for producing hydrocarbons

A mixture of post-consumer polymer waste (PE/PP/PS) was pyrolysed over cracking catalysts using a fluidising reaction system similar to the FCC process operating isothermally at ambient pressure. Greater product selectivity was observed with a commercial FCC equilibrium catalyst (FCC-E1) with about 53 wt% olefin products in the C₃-C₆ range. Experiments carried out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A kinetic model based on a lumping reaction scheme for the observed products and catalyst coking behaviours has been investigated. The model gave a good representation of experiment results. This model provides the benefits of lumping product selectivity, in each reaction step, in relation to the performance of the catalyst used and particle size selected as well as the effect of operation conditions, such as rate of fluidising gas and reaction temperature. It is demonstrated that under appropriate reaction temperatures and suitable catalysts can have the ability to control both the product yield and product distribution from polymer degradation, and can potentially lead to a cheaper process with more valuable products.