硅烷接枝和交联工艺对天然橡胶性能的影响

以六接剂三甲氧基硅烷为接枝单体、过氧化苯甲酰为引发剂,采用熔炼加温水交联方法制备硅烷接枝天然橡胶(NR),研究引发剂和硅烷用量、接枝和交联工艺对硅烷接枝NR溶胀比的影响以及凝胶含量对硅烷接枝NR性能的影响。结果表明:硅烷接枝NR的溶胀比随着引发剂和硅烷用量增大、交联温度提高、交联时间延长和试样厚度增大而增大,随着混炼时间延长和混炼温度提高呈先减小后增大的趋势;随着凝胶含量的增大,硅烷接枝NR的邵尔A型硬度增大,热稳定性改善。     

硅烷接枝ABS树脂及其水解交联的研究

在Haake密炼机中进行硅烷和ABS树脂的接枝反应,接枝产物在沸水中进行水解交联。研究了硅烷种类和用量、引发剂种类和用量对接枝率和凝胶率的影响,同时考察了反应条件对凝胶率的影响。结果表明,在本研究范围内,对于ABS树脂,只有使用3－甲基丙烯酰氧基三甲氧基硅烷（VMMS）作为接枝单体和丙烯酰胺作为引发剂才能得到一定的凝胶率。接枝率随单体用量增加而增加,凝胶率则先升高后趋于一定值。接枝率和疑胶率还随引发剂用量的增加先迅速增加后趋于一定值。温度和转速较低时,对凝胶率没有明显影响,但温度和转速很高时,凝胶率有所下降。     

UHMWPE混炼接枝马来酸酐研究

讨论了超高相对分子质量聚乙烯(UHMWPE)混炼接枝马来酸酐(MAH)过程中，单体MAH用量、引发剂DCP用量、交联抑制剂己内酰胺(CAILA)用量、流动改性剂硬脂酸钙(CaSt2)用量及混炼温度、时间等工艺条件对UHMWPE接枝率和凝胶含量的影响。用红外光谱表征了接枝物的存在。并用滴定分析法和重量分析法测定了接枝物UHMWPE～g～MAH的接枝率和凝胶含量。实验表明，MAH用量为5份、DCP为0．15份、CALA为0．1份、CaSt2为1份时。混炼温度175∽180℃。混炼时间14min时，可得到接枝率0．75％、凝胶含量1．48%的UHMWPE接枝物。     

表面硅烷交联改性超高摩尔质量聚乙烯材料的制备及表征

采用紫外光辐照法在超高摩尔质量聚乙烯(UHMWPE)材料表面接枝乙烯基烷氧基硅烷,之后进行水解交联,制备了亲水性表面交联UHMWPE材料。研究了该材料制备条件的优化并对其凝胶含量、交联密度和亲水性进行表征。结果表明,引发剂、单体用量的适度增大和紫外辐照时间的适度延长可增加硅烷的接枝量,引发剂质量分数为5.0%、单体体积分数为20%,紫外辐照时间为0.5~1 h时,硅烷接枝效果相对最佳;接枝样品在聚乙二醇水溶液中回流交联,样品凝胶率和交联密度同时获得了大幅提高,可由未改性样品的51.62%和16.07 mol/m~3分别增大到88.00%和58.05 mol/m~3,接近于在二月桂酸二丁基锡催化下热水交联的状况;改性样品的亲水性明显提高,水接触角可由未改性样品的94.8°降到64.0°。     

硅烷接枝交联法制备发泡用高熔体粘度聚丙烯

以过氧化物为引发剂,不饱和硅烷为接枝单体,不饱和烃类为接枝助剂,并加入交联催化剂,通过反应型双螺杆挤出机一步实现共聚型聚丙烯的接枝和交联;制备出了可用于发泡的高熔体粘度聚丙烯。通过熔体质量流动速率(MFR)和凝胶含量的变化,研究试剂体系对接枝交联改性的作用。结果显示,改性后PP的MFR可降低至0．1 g／ 10min以下,凝胶含量可高达48％以上,体系中各组分都显著影响改性材料熔体的流动性和凝胶含量,缺一不可。随引发剂和硅烷单体含量的增加,体系熔体流动性逐渐降低,凝胶含量增加。而硅烷单体与接枝助剂的最佳量之比为1 :1。通过PP改性前后的力学性能和发泡性能对比研究表明,接枝和交联使改性后PP的耐热性、抗冲击性、拉伸性能均有所改善;而且用改性PP发泡可以获得泡孔均匀、细密,且具有独立泡孔的高质量泡沫塑料。     

氧化锌对硅烷交联聚乙烯的影响

利用叔丁基过氧化特戊酸酯作为引发剂,与氧化锌以及乙烯基三甲氧基硅烷以一定比例配合,制备了硅烷自交联聚乙烯。利用红外光谱表征了接枝产物,并确定了最佳配方和工艺。探讨了ZnO、引发剂的含量、加工温度对体系的接枝率、结晶度、凝胶含量以及力学性能的影响。结果表明:随着加工温度的升高,接枝率与凝胶含量均降低,结晶度增大,材料的力学性能则呈现先下降后上升的趋势;而随着ZnO和引发剂用量的增加,材料的接枝率和凝胶含量以及力学性能均呈先上升后下降的趋势;在温度为170℃,PV和ZnO含量为0.25份时,材料的结晶度最低,接枝率和凝胶含量最高,拉伸强度最高,为22.58 MPa。     

原材料对硅烷接枝交联高熔体强度聚丙烯流动性能影响的研究

采用不饱和硅烷为接枝单体,不饱和烯烃为共单体,在双螺杆挤出机上实现均聚型聚丙烯的接枝交联,制得了高熔体强度聚丙烯。实验通过熔体指数(MFR)和凝胶含量的变化研究原材料对改性PP的影响。结果显示,体系中的试剂均严重影响材料的熔体流动性能。在硅烷和共单体共存的条件下,材料的熔体流动性能随引发剂A含量的增加而下降。共单体起到稳定大分子自由基的作用,增加了硅烷的接枝效率和接枝速率,共单体与硅烷最佳摩尔比为1∶1。改性后材料的耐热性、力学性能等均有较大提高。     

乙烯-醋酸乙烯共聚物的硅烷交联及无卤阻燃研究

采用过氧化物为引发剂,用熔融法制备了硅烷交联EVA和无卤阻燃硅烷交联EVA.用红外方法(IR)和差示扫描量热法(DSC)对EVA的硅烷接枝反应进行了表征.研究了过氧化物含量对体系凝胶含量,相对接枝率和力学性能的影响,同时还研究了交联对体系阻燃性能的影响.DSC实验表明,硅烷A171比硅烷A151更容易接枝到EVA上.随DCP含量增加,体系的凝胶含量,相对接枝率,拉伸强度增加,而断裂仲长率降低.氧指数结果表明,交联以后可以适当提高氧指数值,改善阻燃性能.     

AIBN引发硅烷熔融接枝ABS及其水解交联的研究

研究了偶氮二异丁腈引发硅烷熔融接枝ＡＢＳ及其水解交联,发现只有使用３－甲基丙烯酰氧基三甲氧基硅烷作为接枝单体,才能实现接枝并得到一定的凝胶率。研究了硅烷、引发剂用量对接枝率和凝胶率的影响,同时考察了加工条件对凝胶率的影响。     

不饱和硅烷熔融挤出接枝聚乙烯

上海交通大学高分子材料研究所的王文杰等采用熔融挤出法对低密度聚乙烯（ＰＥ）进行硅烷接枝,然后在催化剂二丁基二月桂酸锡存在下进行水解交联,接枝单体为乙烯基三乙氧基硅烷（ＶＴＥＳ）,主要引发剂为过氧化二异丙苯。研究了改变ＶＴＥＳ用量、引发剂种类与用量、ＰＥ种类、接枝反应条件、加入添加剂对接枝产物的融体流动速率（ＭＦＲ）和交联样品的凝胶率的影响。结果发现,在ＶＴＥＳ用量较低时,用量增加能够提高凝胶率和ＭＦＲ;但质量分数超过２％后凝胶率基本不再随硅氧烷用量增加而上升,而ＭＦＲ有明显降低。引发剂用量增大有…     

硅烷交联聚氯乙烯的制备和性能

对由悬浮共聚合成的氯乙烯／乙烯基三乙氧基硅烷共聚树脂的水解交联行为和交联聚氯乙烯的性能进行了研究。结果发现，通过聚合过程添加pH调节剂可得到凝胶含量很低的氯乙烯／乙烯基三乙氧基硅烷共聚树脂；该类共聚树脂加工后有一定程度交联发生，凝胶含量随共聚树脂中乙烯基三乙氧基硅烷含量增加而增加；当加工样品在水中浸渍后凝胶含量又有较大幅度提高，说明水解交联的发生；交联后PVC高温力学性能和耐热变形性提高。     

Comparison in processability and mechanical and thermal properties of ethylene–octene copolymer crosslinked by different techniques

The crosslinking of metallocene ethylene–octene copolymer was investigated. The crosslinked polymers were prepared using two different techniques, i.e., peroxide crosslinking and silane–water crosslinking. In the former, the crosslinking reaction was conducted in a twin‐screw extruder, in the presence of dicumylperoxide. In the latter, the polymer was first grafted with vinyl trimethoxysilane in the extruder and subsequently crosslinked with water. The paper aims at investigation of the differences between these two techniques, in terms of processing and product mechanical and thermal properties. The results showed that the silane‐crosslinked polymers could be prepared with much higher gel contents than the peroxide‐crosslinked samples. The silane‐crosslinked polymers also retained the elastomeric characteristics of the pure polymer and showed remarkably higher extensibility, better thermal stability, and energy storage capacity. An explanation for the property differences between peroxide‐crosslinked and silane‐crosslinked polymers was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1179–1185, 2004     

硅烷交联聚烯烃弹性体的改性研究

通过硅烷交联方法对聚烯烃弹性体（POE）进行了改性研究；重点研究了交联时间、过氧化物引发剂（ISK2P）和乙烯基一三甲氧基硅烷用量对交联POE的凝胶率、拉伸强度和断裂伸长率的影响，借助红外光谱、热失重等手段对硅烷交联POE进行了表征。结果表明，交联时间、硅烷和ISK2P引发剂用量对POE的交联改性起着很大作用，当交联时间在6h，硅烷用量在1．2％（质量），ISK2P用量在0．1％-0．15％时，POE交联效果较佳，凝胶率比较理想，拉伸强度达到了最大28．4MPa，且热稳定性得到了显著提高。     

Effect of peroxide crosslinking on thermal and mechanical properties of poly(ε‐caprolactone)

Poly(ε‐caprolactone) (PCL), a saturated polyester, derived from ring‐opening polymerization of ε‐caprolactone, was chemically crosslinked with various amounts of benzoyl peroxide (BPO) by a two‐step method by first evenly dispersing the BPO into the PCL matrix and then crosslinking at elevated temperature. The gel fraction increased with an increase in BPO content. The modified Charlesby–Pinner equation was used to calculate the ratio of chain scission and crosslinking. The results showed that both scission and crosslinking occurred, and that crosslinking predominated over scission. The number‐average molecular weight between the crosslinks determined by the rubber elasticity theory using the hot set test showed a decrease with increasing BPO content. The melting temperature and crystallinity decreased with an increase in BPO content, and the crystallization temperature increased after crosslinking. Dynamic mechanical analysis results showed a decrease in the glass transition temperature as a result of chemical crosslinking of PCL. This was explained by the observed reduction in crystallinity and the increase in free volume due to restrictions in chain packing. Moreover, Young's modulus and elongation at break generally decreased with an increase in BPO content, but the tensile strength first increased with BPO content up to 1.0 wt%, reached a maximum, and then decreased. Copyright © 2007 Society of Chemical Industry     

硅烷交联聚乙烯电缆料抗预交联添加剂的研究

研究了抑制硅烷交联聚乙烯电缆料预交联反应的方法。测试不同储存时间下的硅烷接枝聚乙烯的熔体流动速率和硅烷交联聚乙烯电缆料在挤出机中停留不同时间后挤出物的表面状况、凝胶含量等。实验结果表明,抗预交联添加剂SRA能有效地抑制硅烷接枝聚乙烯在储存和挤出加工过程中的预交联反应,提高硅烷交联聚乙烯电缆料的挤出加工性。     

An investigation of water crosslinking reactions of silane‐grafted LDPE

Factors—including time, temperature, morphology, and thickness of sample, the extent of silane grafting, and water concentration—that affect the rate and degree of water crosslinking reactions of the silane‐grafted LDPE are investigated. The gel content of the water‐crosslinked sample increases with increasing time, temperature, and water concentration, but with decreasing content of the crystalline component in the sample and thickness of the sample. The relationship between the gel content and the crosslinking time is dependent on thickness and morphology of the sample, and the extent of silane grafting in the sample. The crosslinking rates and the resultant gel content are inversely proportional to the content of crystalline component of the sample, suggesting that the crosslinking reactions occur mainly in the amorphous domain of the sample. For those samples with high resultant gel contents, the crystallizations of the samples are significantly enhanced by crosslinking when the gel contents are higher than about 40%, leading to a dual relationship between the gel contents of the samples and the crosslinking times. For low temperatures, the rate‐determining step of the crosslinking reactions is the diffusion of water, rather than the hydrolysis and the subsequent condensation reactions of the silyl trimethoxy groups. For high temperatures and high extents of silane grafting in the samples, however, the chemical reactions dominate the crosslinking process. The overall activation energy of the crosslinking reactions is dependent on thickness of the sample. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 186–196, 2001     

Role of silane crosslinking on the properties of melt blended metallocene polyethylene‐g‐silane/clay nanocomposites at various clay contents

A study to investigate matrix properties and their interaction with loaded nanoclay was designed under controlled clay dispersion. Metallocene polyethylene grafted vinyltriethoxy silane (mPE‐g‐silane) was served as the matrix, with or without silane crosslinking (grafting and post crosslinking with catalyst versus only grafting without catalyst), to assess the strength of commercial organoclay (20A)‐filled nanocomposites prepared via a melt mixing. According to X‐ray diffraction and transmission electron microscopy analyses, all nanocomposites achieved similar dispersion degrees at specific clay contents mainly due to the silane interaction with the dispersed clay via hydrogen bonding and/or chemical bonding. Chemical bonding of grafted silane with clay was inferred based on the slightly higher crosslinking degree with increasing clay content for crosslinked cases. For uncrosslinked cases, the crosslinking degree was virtually zero regardless of clay content. The dynamic mechanical properties revealed enhanced interaction between mPE‐g‐silane and clay with increasing clay content based on the increased glass transition temperatures. Young's modulus of nanocomposites with crosslinked cases showed higher values in comparison with uncrosslinked cases at a specific clay content, indicating the significance of matrix crosslinking effect and the effective interfacial interaction between silane and clay especially at higher clay content. To the authors' best knowledge, this is the first study which generally maintains similar clay dispersions through the effect of uncrosslinking (only grafting) and crosslinking (grafting and post crosslinking), and then probes the effect of matrix properties and interfacial interactions at the large deformation state (tensile test) and small deformation state (cutting test). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Performance evaluation of silane crosslinking of metallocene‐based polyethylene–octene elastomer

Vinyl trimethoxysilane (VTMS) was grafted onto metallocene‐based polyethylene–octene elastomer (POE) using a free‐radical reaction of VTMS and dicumyl peroxide as an initiator, and then the grafted POE was crosslinked in the presence of water. The effects of VTMS concentration on crystallization behavior, mechanical properties, and thermal properties of POE before and after crosslinking were studied in this article. Multiple melting behaviors were found for POE after silane crosslinking by using DSC measurement. Degree of crystallization of silane‐crosslinked POE decreases from 18.0 to 14.3%, with increase of VTMS from 0 to 2.0 phr. Tensile strength of silane‐crosslinked POE reaches a maximum of 28.4 MPa when concentration of VTMS is 1.5 phr, while elongation at break is 487%. TG shows that the temperature of 10% weight loss for pure POE is 405°C, while for crosslinked POE with addition of 2.0 phr VTMS the value comes to 452°C, indicating that crosslinking significantly help improve the thermal stability of POE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5057–5061, 2006     

Thermal and mechanical properties of silane‐grafted water crosslinked polyethylene

The effects of linear low density polyethylene (LLDPE) grafting with vinyltrimethoxysilane by different types and contents of peroxide were studied. When grafting silane onto LLDPE, with 0.10 phr of Dicumyl peroxide (DCP) or 0.05 phr content of 2,5‐Dimethyl‐2,5‐di (tert‐butyl‐peroxy)‐hexane (DHBP), it was found that the grafting effect was improved; however, as Di(2‐tert‐butylperoxypropyl ‐(2))‐benzene (DIPP) or excess DHBP was used, LLDPE was supposed to cause self‐crosslinking, which reduced the grafting effect of silane and was invalid in the processing of extrusion. In this study, vinyl trimethoxysilane (VTMS) was grafted onto various polyethylenes (HDPE, LLDPE, and LDPE) using DCP as an initiator in a twin screw extruder. The grafted polyethylenes were able to crosslink utilizing water as the crosslinking agent. The effects of varied crosslinking time on the mechanical properties of the crosslinked polyethylenes were studied. It was found that the HDPE and LLDPE were apt to crosslink during the grafting process and thus decreased the grafting ratio. Multiple melting behavior was observed for crosslinked LDPE and LLDPE. Mechanical and thermal properties of the crosslinked PE are much better than that of uncrosslinked PE. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2383–2391, 2005     

Preparation of pH‐responsive crosslinked materials from natural rubber and poly(4‐vinylpyridine)

Stimuli‐responsive elastomers are smart materials for sensing applications. Natural rubber (NR) is a renewable elastomer with excellent elasticity and fatigue resistance. In this work, a straightforward method for the preparation of pH‐responsive crosslinked materials from NR and poly(4‐vinylpyridine) (P4VP) via free radical crosslinking reaction using benzoyl peroxide (BPO) as an initiator is described. The effects of P4VP and BPO concentrations, reaction time and reaction temperature on immobilization percentage were investigated. It was found that the immobilization percentage reached 90% when using a P4VP concentration of 150 phr and a BPO concentration of 10 phr for 24 h at 90 °C. The pH responsiveness of the crosslinked materials was studied via water swelling, water contact angle and dye release measurements. Unlike unmodified rubber, the P4VP‐crosslinked NR was found to be pH‐responsive in acidic solution. Indigo carmine adsorption studies showed the Langmuir isotherm suggesting monolayer coverage of dye on the rubber surface. The dye could also be released upon increasing the pH of solution above 4. Based on these results, the introduction of pH responsiveness to NR will lead to novel responsive rubber‐based materials that can be used in biomedical and sensing applications. © 2016 Society of Chemical Industry