SMC中不饱和聚酯树脂增稠及贮存性能的研究

本文以甲苯二异氰酸酯（TDI）及其预聚物PU400、PU200为增稠剂对端羟基的不饱和聚酯进行增稠，通过树脂的粘度变化、螺线流动实验对这种新型增稠体系的增稠性能和片材的贮存稳定性进行了研究。并与以MgO为增稠剂的片材进行了对比研究，结果表明：（1）异氰酸酯预聚体的增稠性能优于异氰酸酯单体。（2）增稠剂PU400的质量百分数Wpu应该小于10％。在相同的－NCO浓度下，不饱和聚酯树脂的增稠速度随分子量的提高而加快；在273K下，不饱和聚酯树脂能在4天内完成增稠，在323K下，能在8小时内完成增稠。（3）聚酯片材贮存三个月后，由异氰酸酯增稠体系制备的片材的螺线长度，低于氧化镁增稠体系的下降幅度。     

SMC/BMC制备中树脂糊的粘度控制

本文研究了在SMC／BMC制作过程中分散剂氧化镁和二异氰酸酯化合物对树脂糊增稠特性的影响，通过树脂糊的粘度变化，考察新型增稠体系的增稠性能和片材的贮存稳定性。本研究对于改进SMC／BMC的成型压力、片材流动、制品质量、模塑料的贮存使用期有一定的指导意义。     

SMC制备中树脂糊的粘度控制

介绍ＳＭＣ制备中树脂糊粘度的影响因素，并通过对树脂糊增稠过程的分析，正确地对粘度加以控制，制备出高品质的ＳＭＣ片材。     

不饱和聚酯树脂增稠特性的研究

采用旋转流变仪研究了增稠剂的种类和用量、增稠温度以及填料种类等对不饱和聚酯树脂(uP)增稠体系粘度的影响,分别通过酸值滴定和红外分析等手段探讨了Mgo和MDI的增稠机理,结果表明,四种增稠剂的增稠速度不同,其中MgO最快;增加增稠剂的用量均可加快增稠速度,增稠速度也随增稠温度的增加而加快;填料的加入使得体系的粘度迅速增大.并且不同种类的填料对体系粘度的影响不同,与CaCO3相比,ATH使体系的粘度增加更多.因此工业生产中要综合考虑各方面因素,以获得合适的增稠工艺.     

不饱和聚酯树脂增稠特性和固化行为的研究

以氧化镁、氢氧化钙增稠不饱和聚酯(UP)树脂,通过测定树脂糊初期和后期的粘度及固化反应曲线,对影响增稠特性的几个重要因素和固化行为进行了研究。结果表明,氧化镁比氢氧化钙的增稠效果好,适宜用量为2~4份;增稠温度40℃较为适中;微量水促进初期增稠,但对最终粘度影响不明显;氧化镁与氢氧化钙复配增稠体系中,氢氧化钙能抑制初期增稠,而促进后期增稠;随增稠剂含量增加,增稠后树脂糊固化反应的峰顶温度升高,放热量减小;由不同升温速率的固化曲线可以确定凝胶温度、固化温度、后处理温度等工艺条件。     

分散相和分散介质对剪切增稠胶动态力学性能影响研究

研究了分散相和分散介质对剪切增稠胶动态力学性能的影响,为制备性能较好的剪切增稠胶提供理论依据。测试分析了用不同粘度的二甲基硅油制备剪切增稠胶的动态力学性能,其中由粘度为500 cst的二甲基硅油制备的剪切增稠胶剪切增稠效应和阻尼性能较优。测试分析了不同质量分数纳米二氧化硅制备的剪切增稠胶动态力学性能,分散相质量分数在一定的范围内,剪切增稠胶的剪切增稠效应和阻尼性能随纳米二氧化硅质量分数的增加而提高;但是纳米二氧化硅质量分数高于一定范围时,纳米二氧化硅质量分数的提高对剪切增稠胶的剪切增稠效应和阻尼性能有负影响。     

FRTP片材冲压成型技术的近况及市场预测

冲压成型工艺是利用FRTP片材为原科(坯料)加工制品的高速压模工艺,也是熔融流动成型工艺(a melt forming process)——熔融状片材投入模内,在高压下快速闭合上下模具,使物料充满模腔,最终制成制品。其坯料利用率为100％,系净模塑工艺(a net molding process)。分析一下当今FRTP工艺,可初步看出该冲压工艺较为先进,因而前景广阔。一、冲压系统冲压系统(见图1)的主要设备有片材加热炉冲压模具、冲压机和模温控制仪。     

协合型增稠剂的流变性及其应用性能的研究

本文采用Brookfield RVT型旋转粘度计进行粘度测定,研究协合协增稠剂的流变性,将粘度数据进行计算机处理,回归出Casson方程,获得屈服值和无穷大剪切粘度,以描述增稠体系的遮盖力、稳定性、流平和流挂、沉降等性质,并对耐电解质性和后增稠进行了测试。本方法通过对粘度的测定,提供了一种对增稠剂的应用性能进行综合评价的途径。     

羟基乙酸对增稠体系粘度影响的研究

本文主要研究了70%羟基乙酸(AHA)对护肤产品配方常规4种增稠体系(黄原胶、羟乙基纤维素、U21以及TR-1)粘度的影响。实验数据表明:4种常规增稠体系在含有2%羟基乙酸护肤品配方体系中,都难以发挥增稠体系的作用。同时,本文也摸索并提出一种复配的增稠组合,本组合不仅能有效的增稠含有羟基乙酸体系的粘度,而且还能赋予产品水凝胶质地的感官特性。     

用试验方法确定SMC增稠性能

1.简介 SMC是一种含有经树脂浸渍的短切玻璃纤维的复合物。在SMC生产过程中,化学增稠是最主要的工艺过程之一。碱土金属氧化物和氢氧化物作为增稠剂加入到粘结剂配方中以提高其粘度。SMC化学增稠和固化过程需考虑的主要问题是:     

低压片状模塑料的研究

本文探讨了低坟模塑料的配方、性能及加工工艺。同片状模塑料比较表明，低压模塑料在成型压力，设备等方面具有明显的优势，不失为优秀的片状模塑料品种。     

Sheet molding compound resins from soybean oil: Thickening behavior and mechanical properties

Thermosetting resins for sheet molding compound (SMC) and bulk molding compound applications were synthesized from soybean oil. The SMC resins were prepared from maleated hydroxylated soybean oil (MHSO) and maleated acrylated epoxidized soybean oil (MAESO) with styrene. When thickened with divalent cations such as MgO, these resins exhibited a substantial rise in viscosity at room temperature because of complexation of MgO with the terminal acid groups on maleic anhydride. The resulting high viscosity sheet upon heating rapidly reduced its viscosity as the labile MgO‐acid groups thermally disassociated. The flexural strength σ and moduli E of these polymers varied from 61 to 87 MPa and from 1.6 to 2.4 GPa, respectively and the tensile strength and moduli varied from 27 to 44 MPa and from 1.6 to 2.5 GPa, respectively. The mechanical and fracture properties of these polymers were related to the amount of functional groups f, on the fatty acid backbone, and followed the Rigidity Percolation and Twinkling Fractal Theories, σ ～ [Eν]^1/2, where ν ～ [f ? 1]. The fracture energy G_IC decreased significantly with increasing crosslink density, as G_IC ～ ν^?2 and the plastic zone r_p decreased as r_p ～ ν^?3. The new bio‐based resins possessed mechanical and thermal properties comparable with petroleum‐based unsaturated polyesters. POLYM. ENG. SCI., 47:1469–1479, 2007. © 2007 Society of Plastics Engineers     

Air entrapment in sheet molding compounds (SMC)

Entrapped air can commonly lead to large delaminations in thick walled sheet molding compound (SMC) products. In this work different sources of air entrapment in SMC are investigated. The critical process is shown to be the impregnation of the fibers. If no surface active additives are used, large volumes of air may be entrapped in this process, unless the viscosity of the compound is very low. In this situation of poor wetting, the viscosity of the compound during fiber impregnation will critically determine the interlaminar, tensile strength of the product. However, if surface active additives are used, the air escapes entrapment even at relatively high viscosities. The lowering of the viscosity, which is a side effect of the additives, has practically no importance under these conditions of good wetting. Large numbers of small air bubbles are also entrapped during the mixing of the components, but it is shown that these bubbles have very little effect on the mechanical properties of the finished part.     

Effect of two stage pressure molding on surface quality of sheet molding compounds

The goal of this work was to investigate the effect of two stage pressure molding on the compression molding of a sheet molding compound (SMC). It has been shown in previous studies that a rapid drop in pressure during SMC curing significantly reduced severity of sink marks. This study concentrated on a method of predicting the optimum time during curing to release pressure by examining material behavior through process data from in-mold sersors. A simple control scheme was them applied for automatic pressure release at the optimum time corresponding with the peak of the material expansion and the onset of the reaction exotherm.     

环氧片状模塑料在模压过程中的纤维分布

纤维的流动分布对环氧片状模塑料(ESMC)制品的各项性能有十分重要的影响。以纤维含量作为性能指标,对原材料组分、片材黏度、铺层方式、模压工艺参数等因素与纤维流动分布的关系进行系统研究。研究结果表明,当玻璃纤维含量为24%、长度为24 mm、填料粒径为45μm、片材黏度为5×103Pa·s、铺料面积为60%、压机闭模速度为1 mm/s时,ESMC模压制品纤维分布的均匀性较好。     

Estimation of viscosity functions for thermosets from spiral mold filling

It is typically difficult to measure viscosity of a fast polymerizing molding compound using a rheometer. So, spiral mold filling experimental data were used to obtain viscosity functions of a silica filled epoxy–novolac molding compound. The functions could describe the effect of temperature and conversion on viscosity change during cure. With the flow rate data obtained from the mold filling experiments, parameters of the viscosity functions were determined through regression of a simulation model developed in this study. The reaction kinetic equation considering an autocatalytic reaction mechanism was used for the molding compound in the simulation model. The viscosity function of the molding compound determined from the rheometer data and the reaction kinetic data measured at a relatively slow reacting condition was compared with simulation results. The viscosity function determined through nonlinear regression of the spiral mold filling simulation model showed a good correlation with the viscosity function obtained from the rheometric study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 873–884, 2001     

Viscosity characterization of highly filled photopolymerizable liquid encapsulants for microelectronic devices

In this paper the viscosity of novel photopolymerizable liquid encapsulants (PLEs) for microelectronic devices was characterized as a function of the particle size distribution of the fused silica filler. Microelectronic devices are typically encapsulated using a transfer molding process in which the molding compound flows over the leadframe and wire bonds as it fills the mold. The molding compound should have a low viscosity to minimize problems such as: (1) incomplete mold filling; (2) lead frame movement during cavity filling; and (3) displacement of the wires that connect the die with the leadframe (wire sweep). We have developed a photopolymerizable liquid encapsulant using an epoxy novolac‐based vinyl ester resin that may alleviate these problems. In this contribution, we have investigated the blending of two different particle size distributions of fused silica to tailor the viscosity of PLEs for microelectronic applications. We have characterized the viscosity of highly filled PLEs containing 70.0, 72.0, and 74.0 wt% silica, and found that a blend of particle size distributions with a particle size ratio of 3.13 resulted in the best viscosity reduction. In addition, the PLE viscosity decreased slightly with increasing concentration of a silane coupling agent. The resulting PLEs exhibit low viscosities at ambient temperature while maintaining desirable material properties for microelectronic applications.     

环氧树脂/碳纤维复合材料模压制品表面质量影响因素分析

通过正交试验研究了模压温度、模压压力、保压时间、合模速度对环氧树脂/碳纤维片状模塑料模压成型制品表面质量的影响,通过方差分析,表明各因素对表面粗糙度影响程度的主次顺序为：模压温度T>保压时间t>模压压力P>合模速度v。通过邓肯法多重比较进一步探讨了各影响因素中不同水平之间平均值的差异性,并绘制了各因素所对应的表面粗糙度实测平均值关系图。发现随着模压温度的增加,制品表面粗糙度先缓慢后急剧增大;保压时间与模压压力对表面粗糙度的影响作用相反;随着合模速度的增大,表面粗糙度不会发生明显的变化。获得最佳工艺参数为：模压温度T=130℃、模压压力P=600 kN、保压时间t=720 s、合模速度v=15 mm/s。通过模压成型实验验证：在最佳工艺参数下,表面粗糙度相对于正交实验结果中的最小值减小了19.3%,有效提高了模压成型制品表面质量。     

发泡塑料板的生产及应用

介绍了用美国Hettinga公司的低压注塑技术和设备生产发泡塑料板 (CD板 )和塑料托盘的情况 ,着重介绍了CD板的性能及应用     

Application of factorial design to SMC viscosity build-up

Summary The thickening behavior of SMC varies with formulation and operating conditions. During the SMC compounding process, alkaline oxides such as MgO, Mg(OH)₂, CaO, Ca(OH)₂ are added to the formulation to yield the viscosity build-up from a flowable paste to a semi-solid sheet. The thickening curve of SMC can be divided into three stages: 1. The initial thickening period for the wetting process, 2. The middle thickening rate period for viscosity increasing, 3. The final viscosity period for the molding process. By means of factorial design with an appropriate objective set-up, one is able to define the influence of each factor on thickening curves. Combined with the experimental work on some individual factors, the maturation control system can be further understood and the proper thickening rates can be obtained.