β-PP的结晶和熔融行为

通过差示扫描量热法(DSC)研究了冷却速率、加热速率以及等温结晶温度和时间等参数对一种市售β-PP形成β晶相对含量的影响。在非等温结晶过程中,较慢的冷却速率有利于β晶的生成和完善;在加热过程中,由于β晶不稳定引起的β-α转变会影响DSC测试结果:升温速率越低,β-α转变越显著,但升温速率过快又会影响DSC的分辨率。研究结果表明:利用10℃/min的升温速率进行β晶相对含量的测试和计算较合理;在等温结晶过程中,β-PP的最佳等温结晶温度是130℃。在该温度下进行等温结晶,只需5 min即可使β-PP的β晶相对含量高达90%,若继续提高等温结晶时间,可以进一步提高β晶相对含量。     

溶剂和结晶温度对尼龙12多晶型的影响

结晶温度和溶剂影响尼龙12晶型。将尼龙12溶于不同溶剂中，将其浇铸成膜并等温结晶，运用广角X射线衍射、差示扫描量热(DSC)法和傅里叶变换红外光谱研究了溶剂和结晶温度对尼龙12多晶型的影响。结果表明，以苯酚/甲酸(v/v=1/1)为溶剂时，室温结晶生成α晶；80℃及以上温度得到γ晶；40～70℃时，α晶与γ晶共存，但α晶含量随着结晶温度的升高而逐渐减少。以甲酸/二氯甲烷(v/v=1/1)为溶剂时，室温结晶得到α晶白色不透明粉末，60℃时却得到γ晶半透明薄膜。DSC结果表明，结晶温度越高，形成的α晶熔点越高，且部分α晶在升温过程中Brill转变为γ晶。尼龙12从甲酸/二氯甲烷溶液结晶所得α晶和γ晶的峰值熔融温度分别高于从苯酚/甲酸溶液所得样品的峰值熔融温度。     

液体冷却工艺对聚偏氟乙烯单丝结构及性能的影响

采用聚偏氟乙烯(PVDF)切片通过熔融纺丝制备PVDF单丝,根据PVDF切片的熔点确定纺丝温度范围,重点研究液体冷却工艺对PVDF初生丝结构与性能,以及PVDF单丝力学性能的影响。结果表明：PVDF切片的熔点为176℃,合适的纺丝温度为200～230℃;液体冷却温度为40～70℃条件下,PVDF初生丝形成的晶体结构一样,都是α晶型;液体冷却温度为50℃时PVDF结晶成核和晶体生长速率都较快,PVDF初生丝的结晶较完善,结晶度达55.7%,(100)晶面的晶粒尺寸为42 nm,有利于后道拉伸;随着液体冷却温度的升高,PVDF单丝的断裂强度呈先增后降的变化趋势,在喷丝头拉伸倍数为8、液体冷却温度为50℃时纺丝稳定性最好,PVDF单丝的断裂强度、断裂伸长率最高,分别为5.57 cN/dtex、35%。     

成核剂对聚丙烯力学性能与结晶行为的影响

研究了两种类型的成核剂对国产共聚聚丙烯的结晶形态以及拉伸强度、冲击强度的影响。结果表明:加入TMB-5型成核剂,聚丙烯的冲击强度有一定程度改善,w(TMB-5)为0.1%时,改性聚丙烯的缺口冲击强度达到最大;TMX-2型成核剂可改善聚丙烯的拉伸性能,但抗冲击性能降低较大;TMB-5型成核剂可显著地改变聚丙烯的结晶行为,诱导聚丙烯在结晶过程中主要形成β晶;TMX-2型成核剂可诱导聚丙烯在结晶过程中主要生成α晶,与纯PP相比,α晶的形成能力增强。     

冷却速率对β成核剂改性PP结晶行为的影响

利用差示扫描量热仪研究了冷却速率对β成核剂改性聚丙烯(PP)结晶行为的影响。冷却速率越慢,高温停留时间越长,则PP中β晶型含量越高,PP的冲击强度越高。冷却速率为5℃/min时,PP中β晶型质量分数达86.12%;冷却速率为20℃/min时,β晶型质量分数为72.04%;而当试样以极快速冷却时,β晶型含量为0。β晶型PP的结晶速率慢于α晶型PP,只有在较高的温度范围内等温结晶时,β晶型PP的结晶速率才快于α晶型PP。因此,一般加工工艺条件下β晶型含量较少。     

模具温度和冷却时间对α成核剂改性PP制品结晶行为与力学性能的影响

研究了不同模具温度和不同冷却时间对添加α成核剂聚丙烯(PP)结晶行为和力学性能的影响。采用差示扫描量热法(DSC)、偏光显微镜等进行测试。结果表明,较低模具温度(180℃)和较短冷却时间(1 h)成型的PP制品,其结晶温度较低,结晶速度较快,球晶细小均匀,导致其拉伸强度和韧性提高。     

卡马西平多晶型结晶工艺研究

通过生物显微镜、X射线粉末衍射(XRD)、马尔文粒度分析仪,差热分析(DSC)及在线聚焦反射测量仪(FBRM)和粒子成像测量仪(PVM)研究了在卡马西平结晶过程中各种操作参数对产品质量特别是晶型的影响,具体考察了溶剂、晶种、结晶方式、干燥、温度、搅拌速率及冷却速率对晶体产品质量的影响。结果表明,不同溶剂中缓慢结晶,高介电常数溶剂(如醇类)中得到卡马西平晶型Ⅲ,乙醇-水混合物中当乙醇摩尔分数低于40%时结晶产物为二水物,四氢呋喃中结晶得到晶型Ⅱ,其他溶剂得到产品为混合晶型;对于醇类溶剂,蒸发结晶一般得到卡马西平晶型Ⅱ,而缓慢冷却得晶型Ⅲ;以正丙醇为溶剂,加大量颗粒较小的晶种可以得到粒度较均一的产品;晶型Ⅱ产品由于特殊的结构,易于有结晶用溶剂包藏在晶体中,加热到约140℃溶剂逸出;温度是影响晶型的重要因素,在较高温度区间(90~76℃)结晶得晶型Ⅱ,而在低温度区间(52~20℃)得晶型Ⅲ;搅拌速率在较低的温度下对晶型没有影响,搅拌速率大可以避免晶体的聚集,形成较均匀的颗粒;3种降温速率结果显示,产品均为卡马西平晶型Ⅲ,但先慢后快的降温速率可以得到更均匀的颗粒晶体。     

乙烯基硅烷/苯乙烯接枝聚丙烯的结晶和力学性能

研究了乙烯基硅烷（VS）和苯乙烯（St）双单体接枝聚丙烯（PP-g-VS/St）的结晶性能和力学性能。结果表明,长支链的引入使PP-g-VS/St的结晶峰值温度和熔融峰值温度相对于线形等规聚丙烯（iPP）分别提高了10、2 ℃,且球晶得到了细化; PP-g-VS/St在10 ℃/min的降温速率下结晶产生的晶型为α晶型与少量γ晶型的混合物;在注塑条件下结晶产生的晶型为α晶型与β晶型的混合物; 利用莫志深法研究PP-g-VS/St的非等温结晶动力学过程发现,在结晶的早期和后期,长支链对PP-g-VS/St的结晶分别起到了加速成核和阻碍生长两种相反的作用;相对于iPP,PP-g-VS/St的拉伸强度、弯曲模量和冲击强度分别提高了29 %、40 %和453 %。     

蛋氨酸皂化液冷冻除碱过程研究

对蛋氨酸皂化液的冷却结晶除碱过程进行了研究,系统考察了冷却终温、降温速率、晶种添加量等结晶参数对冷却结晶产品十水碳酸钠的纯度以及碳酸钠脱除率的影响。实验结果表明:随着冷却终温的升高,碳酸钠的脱除率逐渐降低,十水碳酸钠的纯度先增加然后几乎保持不变;随着降温速率的增大,十水碳酸钠的纯度逐渐降低,碳酸钠的脱除率变化不大;随着十水碳酸钠晶种添加量的增加,十水碳酸钠的纯度先增加后降低,碳酸钠的脱除率几乎不变。优化工艺条件:降温速率为0.05 ℃/min,晶种添加量为7.5%（以生成结晶产品的质量为基准）,冷冻终温为-10 ℃。在优化工艺条件下制备的十水碳酸钠的纯度为96.41%,皂化液的碳酸钠脱除率为81.2%。     

ABS-g-MAH在PA 6/ABS合金中的应用

采用固相接枝的方法制备了马来酸酐(MAH)接枝丙烯腈-丁二烯-苯乙烯三元共聚物(ABS)(ABS-g-MAH),并以ABS-g-MAH为相容剂,制备了聚酰胺6(PA 6)/ABS合金.ABS-g-MAH能有效改善合金的相容性,提高合金的力学性能,当w(ABS-g-MAH)为10%时.合金的冲击强度与未添加相容剂的合金相比提高了30%左右,其拉伸强度、弯曲强度也显著提高.PA 6中加人ABS和ABS-g-MAH影响了其结晶形态,球晶显著减少,并出现了大量的片晶.PA 6的α松弛温度为70℃左右,而加入ABS和ABS-g-MAH后α松弛温度为115℃左右,并且出现明显的β松弛,γ松弛温度也从-50℃降到-70℃左右.     

WAXD and FTIR spectroscopy studies on phase behavior of syndiotactic polystyrene/1,1,2,2-tetrachloroethane complexes

Crystal polymorphism, conformation, and transformation of syndiotactic polystyrene (sPS) thin films cast from 1,1,2,2-tetrachloroethane were investigated via wide angle X-ray diffraction, transmission electron microscopy, electron diffraction, differential scanning calorimetry, and Fourier-transform infrared spectroscopy (FT-IR). The solvent-induced crystallization of sPS yielded an ordered crystalline γ-form packed with a helical conformation of lower degrees of perfection. The 1,1,2,2-tetrachloroethane solvent was unique in that, instead of forming a meso crystalline δ-form (which is a polymer-solvent complex) for most other solvents, it could induce sPS to develop a crystalline γ-form. The unique behavior was attributed to the discrepancies in the location of solvent molecules after solvent casting. As evidenced by FT-IR characterization, the solvent molecules within the polymer-solvent complex were identified being mainly trapped in the non-crystalline/amorphous phase. The solvent-induced crystalline γ-form exhibited a crystalline morphology having small crystal aggregates with an average size less than 100 nm. Upon heating, the crystalline γ-form gradually grew into much perfect packing, and finally went through a γ→α′ transformation at temperature of 200 °C.     

Effects of crystallization temperature on the polymorphic behavior of syndiotactic polystyrene

The influence of crystallization temperature on formation of the α- and β-form crystals of syndiotactic polystyrene (sPS) was investigated by X-ray diffraction and non-isothermal differential scanning calorimetry analysis. For sPS samples without any thermal history, the crystallization temperature must be the intrinsic factor controlling the formation the α and β-form crystals. Being crystallized at different cooling rate from the melt, sPS forms the β-form crystal until the temperature cooled down to about 230 °C, and α-form crystal can only be obtained when the temperature was below about 230 °C.     

Thermal analysis, X-ray and electron diffraction studies on crystalline phase transitions in solvent-treated poly(hexamethylene terephthalate)

The crystal polymorphism, transformation, and morphologies in chloroform solvent-cast poly(hexamethylene terephthalate) (PHT) were examined by using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and temperature in situ transmission electron microscopy (TEM). Solvent-induced crystallization of PHT at room temperature yielded an initial crystal of γ-form, as confirmed by WAXD. Upon DSC scanning, the original γ-form in PHT exhibited three endothermic peaks, whose origins and association were carefully analyzed. The first peak, much smaller than the other two, is in the temperature range of ca. 100-120 °C. It was found that the solvent-induced γ-form was transformed to β-form at 125 °C via a solid-to-solid transformation mechanism. In addition, WAXD showed that γ- and β-forms co-existed in the temperature range of 100-125 °C. These mixed crystal forms were further identified using TEM, and the selected-area electron diffraction (ED) patterns revealed that both γ- and β-form crystals co-existed and were packed within the same spherulite. Solid-solid transformation from the solvent-induced γ-form to β-form in PHT upon heat scanning was presented with evidence and discussed.     

等规聚丙烯与液晶成核剂的共混改性研究

以单丙烯酸酯液晶单体（RLC）为成核剂,通过共混反应法对等规聚丙烯（iPP）进行改性,制备含β晶型的聚丙烯产品（β-iPP）。首先介绍了β-iPP的制备工艺,然后通过偏光显微镜、广角X射线衍射对纯iPP、iPP/RLC共混物的球晶结构进行了分析;最后通过X射线衍射、差示扫描量热分析等测试方法研究共混物的结晶结构、结晶行为和热性能。结果表明,液晶成核剂RLC能够诱导iPP生成β晶型;制备β-iPP的最佳工艺条件是RLC含量为0.5 %（质量分数,下同）,结晶温度为110 ℃;β晶型相比于α晶型处于热力学亚稳态,在升温过程中,会发生β晶向α晶的转变,但较高的升温速率会抑制这一转变。     

Compared structure and morphology of nylon-12 and 10-polyurethane lamellar crystals

A comparative study of the structure and morphology of nylon-12 and 10-polyurethane (10-PUR) lamellar crystals, was carried out. Lamellar crystals were obtained by isothermal crystallization from diluted solution. Electron diffraction of lamellae combined with WAXS data recorded from crystal sediments indicated that nylon-12 crystallized in either α-form or γ-form according to the solvent chosen for crystallization. The α-form was the crystal modification predominant in doubly oriented films of nylon-12 prepared by epitaxial crystallization. On the contrary, 10-PUR invariably crystallized in α-form regardless crystallization conditions. The α-form of nylon-12 and 10-PUR shared the same crystal structure with hydrogen-bonded sheets made of antiparallel chains and stacked with progressive shifting along both b and c directions. Lamellar crystals of nylon-12 in γ-form and 10-PUR in α-form displayed similar morphological features but only the former appeared to be sensitive to temperature. Upon heating the nylon-12 crystals near to melting, the real-time WAXS analysis evidenced the occurrence of a partial γ-to-α crystal transition, and in situ AFM observations revealed the appearing of more or less regular ridges on the crystal surface. None of these changes were observed in 10-PUR crystals when subjected to similar treatment.     

Isothermal crystallization of isotactic polypropylene blended with low molecular weight atactic polypropylene. Part I. Thermal properties and morphology development

The thermal properties and morphology development of isotactic polypropylene (iPP) homopolymer and blended with low molecules weigh atactic polypropylene (aPP) at different isothermal crystallization temperature were studied with differential scanning calorimeter and wide-angle X-ray scattering. The results of DSC show that aPP is local miscible with iPP in the amorphous region and presented a phase transition temperature at T_c=120 °C. However, below this transition temperature, imperfect α-form crystal were obtained and leading to two endotherms. While, above this transition temperature, more perfect α- and γ-form crystals were formed which only a single endotherm was observed. In addition, the results of WAXD indicate that the contents of the γ-form of iPP remarkably depend both on the aPP content and isothermal crystallization temperature. Pure iPP crystallized was characterized by the appearance of α- and γ-forms coexisting. Moreover, the highest intensity of second peak, i.e. the (0 0 8) of γ-form coexisting with (0 4 0) of α-form, and crystallinity were obtained for blended with 20% of aPP, the γ-form content almost disappeared for iPP/aPP blended with 50% aPP content. Therefore, detailed analysis of the WAXD patterns indicates that at small amount aPP lead to increasing the crystallinity of iPP blend, at larger amount aPP, while decreases crystallinity of iPP blends with increasing aPP content. On the other hand, the normalized crystallinity of iPP molecules increases with increasing aPP content. These results describe that the diluent aPP molecular promotes growth rate of iPP because the diluent aPP molecular increases the mobility of iPP and reduces the entanglement between iPP molecules during crystallization.     

Synthesis and characterization of novel random copolymers based on PBN: Influence of thiodiethylene naphthalate co-units on its polymorphic behaviour

Poly(butylene/thiodiethylene naphthalate) copolymers (PBN-PTDEN) were synthesized in bulk according to the usual polycondensation procedure and examined by NMR, GPC, TGA, DSC and XRD techniques. At room temperature they appeared as semicrystalline materials; the copolymerization caused a lowering in the T_g value, a decrement of T_m and of the crystallization rate. Pure α- or β′-form was obtained at low and high TDEN unit content, respectively; crystalline form transition never occurred in the solid state, analogously to PBN. After cooling from the melt, the pure α-form was always evidenced in PBN-PTDEN10, whereas the pure β′ crystal phase develops in the copolymers containing 30 and 40 mol% TDEN units, independently on the cooling rate. In the case of PBN-PTDEN20 a pure α- or β′-form was obtained at low and high cooling rate, respectively.     

热处理工艺对纳米γ-氧化铝粉体性能的影响及优化

以异丙醇铝水解得到的水合氧化铝为原料,利用正交实验考察了焙烧条件(焙烧终点温度、升温速率、终点温度保温时间、277℃保温时间和590℃保温时间)对γ-氧化铝粉体性能的影响。结果表明:焙烧终点温度和升温速率对γ-氧化铝粉体性能的影响显著,终点温度主要影响氧化铝的结晶度、晶粒大小以及比表面积;升温速率则主要影响晶粒大小和粉体的团聚粒径。终点温度越高、升温速率越慢,晶体的晶粒越大,晶体发育趋于完整,比表面积下降,粉体的团聚现象得到明显改善。最佳工艺条件:焙烧终点温度为850℃,终点温度保温时间为30 min,升温速率为3℃/min,277℃和590℃均不保温。     

Effects of crystallization conditions on sedimentation in canola oil

The effects of various factors on sediment formation in canola oil were studied. The crystallization temperature of sediment varied with cooling rate, whereas the melting temperature depended on heating rate as well as the cooling rate during sediment formation. The final crystal size depended on cooling rate. The crystal habit of sediment was generally rod-like but could change to a round and leaf-like shape at low cooling rates (<0.5°C/min). Crystal nucleation occurred in the initial stage of crystallization, while crystal growth was observed during the whole crystallization process, decreasing as cooling proceeded. Crystal growth rate of the sediment was proportional to the crystal surface area Lecithin did not affect the phase transition temperatures of sediment, but retarded crystal growth.     

快速热处理对电子辐照直拉硅中氧沉淀的影响

对n型[111]晶向直拉硅样品进行电子辐照,然后分别在不同温度和降温速率下快速热处理(rapid thermal process,RTP),再在1100℃下进行常规一步退火。研究了RTP温度和降温速率对硅样品内氧沉淀的变化及样品表面清洁区形成的影响。结果表明:经过RTP再经高温一步退火后,硅晶体内形成了密度较高的氧化诱生层错以及完整的位错环,样品表面形成了一定宽度的清洁区;清洁区的宽度随RTP温度及降温速率的升高而变窄。当RTP温度达到1280℃时,样品中的层错和位错环明显减少,此时当RTP降温速率增加至150℃/s时,大部分层错消失,样品中出现了大量的点状腐蚀坑。