Modification of polystyrene by reactive extrusion with peroxide and trimethylolpropane triacrylate

Polystyrene (PS) was modified by reactive extrusion with trimethylolpropane triacrylate (TMPTA) and dicumyl peroxide (DCP). The coupling reaction caused by TMPTA increased the molecular weight of PS, and this coupling reaction was enhanced in the presence of DCP at high TMPTA/DCP ratio. The rheological properties of the extrudate were examined. The impact strength of PS improved as the molecular weight increased by the coupling reaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1672–1679, 2004     

Surfactant-assisted removal of 2,4-dichlorophenol from soil by zero-valent Fe/Cu activated persulfate

The organic compounds contaminated soil substantially threatens the growth of plants and food safety. In this study, we synthesis zero-valent bimetallic Fe/Cu catalysts for the degradation of 2,4-dichlorophenol (DCP) in soils with persulfate (PS) in combination of organic surfactants and exploring the main environmental impact factors. The kinetic experiments show that the 5% (mass) dosage of Fe/Cu exhibits a higher degradation efficiency (86%) of DCP in soils, and the degradation efficiency of DCP increases with the increase of the initial PS concentration. Acidic conditions are favorable for the DCP degradation in soils. More importantly, the addition of Tween-80, and Triton-100 can obviously desorb DCP from the soil surface, which enhances the degradation efficiency of DCP in soils by Fe/Cu and PS reaction system. Furthermore, the Quenching experiments demonstrate that SO₄^-· and ·OH are the predominant radicals for the degradation of DCP during the Fe/Cu and PS reaction system as well as non-radical also exist. The findings of this work provide an effective method for remediating DCP from soils.     

Molecular structure evolution in peroxide-initiated crosslinking of an ethylene vinyl acetate copolymer and a metallocene polyolefin elastomer

A combination of molecular theories and chemical reaction kinetics was employed to study the molecular structure evolution in the ethylene vinyl acetate and dicumyl peroxide, EVA/DCP, and metallocene polyolefin elastomer, m-POE/DCP crosslinking systems. Premixed EVA/DCP and m-POE/DCP compounds were cured at different temperatures and their gel contents were then measured. The values of crosslinking efficiency were evaluated and were then applied in the theoretical prediction of molecular evolution in a crosslinking process. The molecular weight distributions, gel time, relationships among gel content, degree of conversion, crosslinking density and processing time can all be predicted effectively. Information involving molecular structure evolution provides insights to practical process synthesis and material design.     

Dynamic vulcanization of recycled milk pouches (LDPE–LLDPE) and EPDM blends using dicumyl peroxide

The viability of thermomechanical recycling of post‐consumer milk pouches (blend of low‐density polyethylene (LDPE) and linear low‐density polyethylene (LLDPE)) and its scope for suitable engineering applications were investigated. The effects of blending with ethylene‐propylene‐diene monomer (EPDM) rubber and subsequent curing using dicumyl peroxide (DCP) on the macromolecular structure and properties of recycled polyethylene (PE) blends were studied. The crosslinking efficiency of recycled PE/EPDM blends and possible thermooxidative degradation of recycled polymer upon peroxide curing was assessed using torque and gel content measurements along with infrared spectroscopic analysis. Both the torque and gel content of the blends varied with DCP crosslinking reactions and also were affected by oxidative degradation. In view of the electrical application area of this recycled blend material, the dielectric breakdown strength and volume resistivity were measured. The mechanical performance and thermal stability of recycled PE/EPDM blends improved with progressive crosslinking by DCP but deteriorated somewhat at higher DCP dose. Scanning electron microscopy showed good interface bonding between recycled polymer and dispersed EPDM phase in the cured blends compared to the non‐cured blends. Copyright © 2007 Society of Chemical Industry     

Exploring a novel cyclic monofunctional peroxide for curing of silicone rubber at elevated temperature

The curing characteristics of silicone rubber (polydimethylsiloxane [PDMS]) in the presence of structurally different peroxides, namely dicumyl peroxide (DCP) and 3,3,5,7,7‐pentamethyl‐1,2,4‐trioxepane (PMTO), have been studied in details. At moderate temperature, DCP is more prominent for curing the silicone rubber but at high temperatures it suffers from low scorch safety. An inhibitor 2,2,6,6‐tetramethylpiperidinyloxyl (TEMPO) was added with DCP to stabilize the radicals in order to increase the scorch safety time. On the other hand, PMTO showed a prolonged scorch safety and better crosslinking efficiency rather than (DCP + TEMPO) mix at higher temperatures. PMTO‐crosslinked PDMS shows better crosslinking efficiency as indicated by a higher gel content and low swelling index value. Also the mechanical properties, thermal stability, and dynamic mechanical behavior of PMTO‐crosslinked PDMS are much superior than (DCP + TEMPO)‐crosslinked PDMS. Apart from thermoplastic vulcanizates (TPVs) made from PMTO‐crosslinked PDMS show better physicomechanical behavior compared to the TPVs made from (DCP + TEMPO)‐crosslinked PDMS. Moreover, DCP undergoes decomposition reactions at a higher temperature and forms acetophenone, which leads to an unpleasant smell in the final products whereas no such phenomenon is observed for PMTO. Therefore, PMTO turns out to be the suitable peroxide for crosslinking of PDMS at higher temperature. POLYM. ENG. SCI., 57:1073–1082, 2017. © 2016 Society of Plastics Engineers     

Effect of the various coupling agents on the mechanical and physical properties of thermoplastic‐bagasse fiber composites

Various types of bonding agents have been tried with blends of bagasse fibers and some thermoplastics such as low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC). These bonding agents are, namely, pentaerythritol tetracrylate (PETA), 1,6 hexandiol diacrylate (HDA), and dicumyl peroxide (DCP). In addition, a traditional coupling agents 3‐aminopropyltrimethoxy silane (AMPS) and di‐aminopropyltrimetoxy silane (DAMPS) were included for comparison. Electron beam (EB) irradiation is applied only for LDPE and HDPE at 40 and 10 kGy, respectively, before mixing with bagasse fibers. The data obtained reveal that incorporation of bonding agents remarkably increases the mechanical properties for all samples under investigation; the maximum improvement is observed in LDPE followed by HDPE, PP, PS, and PVC composites. Also, the physical properties enhanced but not at the same degree as mechanical properties. Among the tested bonding agents, it was found that PETA, DCP followed by DAMPS have highest efficiency in LDPE, whereas in case of HDPE, EB radiation was higher than PETA followed by DCP. PETA was superior in case of PS composites. Furthermore, PETA and HDA experienced higher efficiency than DAMPS and AMPS in case of PP and PVC composites. Comparison between the properties of thermoplastic composites and medium density fiberboard (MDF) reveals that most of the properties of thermoplastics composites are better than MDF. However, modulus of rupture of MDF was found to be slightly higher than thermoplastics except for PVC composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Evaluation of an improved epichlorohydrin synthesis from dichloropropanol using a microchemical system

Synthesizing epichlorohydrin (ECH) from dichloropropanol (DCP) is a complicated reaction due to the partial decomposition of ECH under harsh conditions. A microchemical system can provide a feasible platform for improving this process by conducting a separation once full conversion has been achieved. In this work, referring to a common DCP feed used in industry, the reaction performance of mixed DCP isomers with NaOH in the microchemical system on various time scales was investigated. The operating window for achieving high conver-sion and selectivity was on a time scale of seconds, while the side reactions normal y occurred on a time scale of minutes. Plenty of Cl?ions together with a high temperature were proved to be critical factors for ECH hydrolysis. A kinetic study of alkaline mediated ECH hydrolysis was performed and the requirements for an improved ECH synthesis were proposed by combining quantitative analysis using a simplified reaction model with experimen-tal results on the time scale of minutes. Compared with the conventional distillation process, this new strategy for ECH synthesis exploited microchemical system and decoupled the reaction and separation with potentials of higher productivity and better reliability in scaling up.     

反应性挤出聚乙烯接枝低偶联马来酸酯

将低密度聚乙烯(LDPE)、过氧化二异丙苯(DCP)、低偶联马来酸酯(LCME)均匀混合后,在单螺杆挤出机中进行反应性挤出,得到聚乙烯接枝低偶联马来酸酯(PE-LCME)产品。红外光谱分析确证有部分LCME接枝到PE分子链上。示差扫描量热法(DSC)测定揭示了反应性挤出过程中化学反应的起始温度、峰温和终止温度,以及在静态下反应所需的时间。并且从不同升温速度的DSC曲线可以初步确定挤出温度及分布。反应性挤出得到PE—LCME的接枝率(G)随PE的型号、不同DCP的浓度而呈规律性变化。     

碳酸二甲酯做甲基化试剂合成2,6-二氯苯甲醚

采用碳酸二甲酯(DMC)代替传统的有毒有害试剂作甲基化试剂,以2,6-二氯苯酚(DCP)为原料,在固体碱与相转移催化剂(PTC)作用下,合成了2,6-二氯苯甲醚(DCA)。考察了PTC种类及用量、物料配比、反应时间、反应温度和碱性催化剂用量对反应的影响,得到最佳反应条件为:以聚乙二醇400(PEG-400)为PTC,x(PEG-400)=0.2%,n(DMC)∶n(DCP)∶n(K2CO3)=0.1∶0.05∶0.003,温度150℃,时间5h,在该条件下,DCA的收率为87.3%,DCP的转化率为100%。优化条件下的重复实验表明,该反应易于控制,重复性好。     

耦合透性化辅酶循环制备手性(R)-苯基乙醇

通过耦合透性化博伊丁假丝酵母(Candida boidinii,C.boidinii)加强了近平滑假丝酵母(Candida parapsilosis,C.parapsilosis)内羰基还原酶(Carbonyl reductase,CR)催化反应中的辅酶循环与反复利用,构建了有效的手性(R)-苯基乙醇透性化细胞耦合制备体系。实验结果如下:透性化的C.parapsilosis细胞底产物渗透效果增强,底物转化率由33.5%提升到43.8%;进一步外添加辅酶后,底物转化率由43.8%提高到了52.1%;耦合透性化C.boidinii细胞并同时外添加辅酶可大大增强辅酶循环效率,底物转化率可提高至71.8%。优化透性化细胞耦合体系反应条件,当以0.2 g近平滑假丝酵母(C.parapsilosis)为基准时,在C.parapsilosis与C.boidinii细胞质量比为1.5∶1,底物浓度为10 mmol/L,辅酶浓度为0.1 mmol/L时,底物转化率可达78.2%。离心法收集细胞进行多批次反应,当反应12批次时,耦合体系仍然保持有55%底物转化率,此时总的底物转化率达70.3%,产物经高效液相色谱测定为(R)-苯基乙醇,对映体过量值(e.e.值)达98.2%。     

过氧化二异丙苯催化分解反应工艺及动力学研究

针对在苯酚/丙酮生产工艺中二级分解反应过氧化二异丙苯转化率与α-甲基苯乙烯收率较低、α-甲基苯乙烯二聚体和枯基苯酚含量偏高的问题,利用高效液相色谱对反应物料进行分析,并研究过氧化二异丙苯的分解反应。通过单因素实验和正交实验方法,考察反应温度、丙酮加入量、反应时间和浓硫酸与反应原液配比等因素对过氧化二异丙苯分解反应的影响。结果表明,在反应温度50℃、丙酮加入量22.5 g、浓硫酸与反应原液质量比1∶333和反应时间80 min条件下,α-甲基苯乙烯收率最高,可达81.15%,并根据实验数据,建立了过氧化二异丙苯分解的动力学方程。     

Effects of Malienated Ethylene Propylene Diene Monomer (EPDM) Rubber on Dynamic-Mechanical and Rheological Properties of Polyamide 66 (PA 66) Composites

Reactive blends of ethylene propylene diene monomer (EPDM) and polyamide (PA) 66 were prepared in the single screw and twin screw extruder using maleic anhydride as coupling agent and dicumyl peroxide (DCP) as initiator. The optimum concentration of DCP for grafting maleic anhydride on EPDM was determined. The grafting efficiency was determined by Fourier transform infrared (FTIR) spectroscopy, and (DMTA) tests were conducted to determine the damping, loss, and storage modulus of PA 66 composites. A capillary rheometer and parallel plate rheometer were employed to characterize the rheological properties at high and low shear rates. It was seen that the glass fibers are not long and continuous, and they act as fillers, therefore reducing the damping in the composite. No significant change was observed in the glass transition temperature of the blend as compared with the individual components, especially PA 66. In malienated EPDM blends with increasing EPDM from 10 to 15%, the height of glass transition temperature peak increases. Capillary rheometer tests show that for all samples the apparent viscosity decreases with increasing shear rate, which is a characteristic of a non-Newtonian pseudo plastic fluid. The viscosity ration of malienated EPDM and PA 66 shows a considerable difference between them and only at higher shear rates do the viscosities get closer.     

过氧化二异丙苯在聚乙烯切片中的热降解动力学

采用差示扫描量热法(DSC)研究了过氧化二异丙苯(DCP)在聚乙烯(PE)切片内部的热分解过程,结果表明,可以通过不同DCP含量样品的反应放出热焓与DCP含量的关系曲线呈很好的线性关系;应用Arrhenius方程描述了DCP在PE切片内部的热分解反应动力学,结果表明DCP的热分解反应可以按一级反应动力学进行,从而求得热降解过程的表观活化能和频率因子。     

Solar Dryer for Powder Drying

A natural circulation solar dryer for drying products in the form of powder has been developed. It is of modular design and aperture area of one module is 3.34 m². A new concept of moveable glazing has been introduced for ease in loading and unloading. Air entering the dryer moves in a zig-zag path as it flows over the product and under each tray before leaving from the top. There is a provision to dry the product under shade. Also, the dryer can be dismantled and stored in a room during off-season. The dryer was tested to dry Di-calcium phosphate (DCP) at Ludhiana (31°N). The average drying efficiency for a batch was found to be 54.0%. The cost of drying DCP using this solar dryer was 0.56 Rupees per kg of dried DCP as compared to 1.94 Rupees per kg of dried DCP for a wood-fueled industrial dryer. In comparison to a solar tunnel dryer for DCP drying, the initial investment per kilogram of the dried DCP, floor area per kilogram of wet DCP, and cost of drying per kilogram of dried DCP for this dryer was reduced by 7.1%, 67.2%, and 16.4% respectively.     

铝塑复合板用热熔胶的制备及性能研究

以过氧化二异丙苯(DCP)为引发剂、马来酸酐(MAH)为接枝改性单体和聚乙烯(PE)为主要原料,采用熔融挤出法制备了铝塑复合板用PE-g-MAH(聚乙烯接枝马来酸酐)基HMA(热熔胶),并着重探讨了DCP和MAH含量对PE-g-MAH的接枝效率和粘接性能等影响。结果表明:在试验范围内,PE-g-MAH的接枝效率(y)与DCP含量(x1)或MAH含量(x2)之间的关系符合y=28.03x1+1.49或y=0.73x2+10.65的线性关系;当w(DCP)=0.44%、w(MAH)=2%时,PE-g-MAH基HMA的粘接性能相对最好,其剪切强度(6.10 MPa)高于杜邦HMA(4.26 MPa),并且其接枝效率为12.91%。     

Functionalization of styrene–butadiene–styrene (SBS) triblock copolymer with glycidyl methacrylate (GMA)

A styrene–butadiene–styrene triblock copolymer (SBS) was functionalized with glycidyl methacrylate (GMA). Grafting reactions were carried out in an internal mixer at 170°C, using dicumyl peroxide (DCP) as an initiator. The effect of three variables, % GMA, % DCP, and reaction time, on grafting were studied using a factorial design to analyze the experimental data. GMA was grafted onto SBS and its incorporation increased with the % GMA added. The factors levels studied indicated that was an optimum % DCP point about 0.1% w/w to achieve the best incorporation and conversion values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2074–2079, 2003     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improvements in morphology,mechanical and thermal properties of films produced by reactive blending of poly(lactic acid)/natural rubber latex with dicumyl peroxide

The effect of dicumyl peroxide (DCP) as a free-radical cross-linking agent on the morphology, thermal and mechanical properties, and gas permeation of blown films prepared by reactive blending of poly(lactic acid) (PLA) and natural rubber latex was investigated. In comparison to the blown films without DCP, SEM micrographs revealed that the amount of debonded rubber domains from the cryofractured surface reduced considerably. This was when DCP at 0.003 phr was incorporated and the free radicals from thermally decomposed DCP reacted with PLA and NR chains, generating PLA–NR copolymers and cross-linked NR as confirmed by FTIR spectra. These PLA–NR copolymers acted as compatibilizers, which increased the strength at the PLA/NR interfaces, leading to the improvement in tensile strength, elongation at break, tensile toughness, impact strength, and tear strength. Although DCP did not influence the cold crystallization of PLA, TGA thermograms showed that thermal stability slightly increased owing to the enhanced interfacial adhesion. However, the addition of DCP at 0.005 and 0.010 phr resulted in a high content of cross-linked NR gel, by consuming the free radicals instead in copolymer formation. Therefore, the compatibilization efficiency was significantly reduced and the mechanical properties of reactive PLA/NR blown films finally dropped. Also, this poor interfacial adhesion facilitated the microvoid formation at the polymer–rubber interface as a result of mechanical stretching upon the film blowing process, increasing the permeation of water vapor and oxygen molecules. According to our study, it can be summarized that to optimize the morphology, mechanical properties, and gas permeation property of the free radical-assisted reactive blends, it is of great concern to carefully balance reactive compatibilizer formation and gel formation by adjusting the DCP content.     

Preparation of poly(ethylene-co-dicyclopentadiene) copolymers and a study on their post-polymerization epoxidation

The copolymerization of ethylene with dicyclopentadiene (DCP) using the metallocene catalyst rac-dimethylsilylbis(indenyl)zirconium dichloride (Me₂Si(Ind)₂ZrCl₂) proceeds with high activity producing materials with DCP incorporations of 0.5–2.7 mol%. The residual olefin moiety of the DCP comonomer is still available for reaction following polymerization and was epoxidized using H₂O₂ and formic acid. This reaction was optimized and proceeds with good conversion and the resulting materials show increased physical properties compared to the untreated copolymers.     

过磷酸钙生产中添加肥料级磷酸氢钙的试验

德昌化工有限责任公司为了处理饲钙生产的副产品肥料级磷酸氢钙 ,在过磷酸钙生产中进行添加肥料级磷酸氢钙的试验。介绍试验过程及结果 :当肥钙 /磷矿的质量比为 15 / 85时 ,每吨过磷酸钙成本可降低 5 .2 6元 ,按年产 3万吨过磷酸钙计 ,年创经济效益 15 .78万元 ,年消化肥钙 (干基 ) 2 385吨 ,同时改善了过磷酸钙的物理性状 ,提高了转化率。