三氯异氰脲酸氯化改性天然橡胶硫化胶的研究

制备三氯异氰脲酸（TCCA）水性氯化溶液,用其对天然橡胶（NR）硫化胶进行表面氯化改性,研究氯化时间对表面改性效果的影响。结果表明：随着氯化时间的延长,NR硫化胶中的石蜡向表面的迁移量越小,NR硫化胶表面的Cl和N原子占比和NR硫化胶的剥离强度均先增大后减小,NR硫化胶表面的微裂纹增多及裂纹边缘更不平整;当氯化时间为6min时,NR硫化胶表面的Cl和N原子占比和NR硫化胶的剥离强度达到最大值。     

界面增强型PVDF/PET膜的制备及性能

通过对支撑材料进行表面改性处理和浸入凝胶法制备了界面增强型聚偏氟乙烯/聚对苯二甲酸乙二醇酯（PVDF/PET）超滤膜。用电导率在线测量法确定了硅烷偶联剂 3-氨丙基三乙氧基硅烷（KH550）水解液的制备条件,考察了改性处理条件对PVDF/PET膜的界面性能和力学性能的影响。通过180°剥离试验测试PVDF膜与支撑层间的剥离强度,用扫描电镜观察PET无纺布及PVDF膜破坏底面的微观形貌,用傅里叶红外光谱仪表征PET表面化学组成。结果表明,水解液中KH550用量较少时（≤3%）,处理时间延长,PVDF/PET间的剥离强度增大,水解液中KH550用量较多时（>3%）,处理时间延长,PVDF/PET间的剥离强度先增大后减小;PVDF/PET膜的拉伸强度随水解液中KH550用量的增加或处理时间的延长先增大后略减小。改性前后PVDF/PET膜的分离与透过性能对比表明,PET表面改性后,PVDF膜的牛血清白蛋白（BSA）截留率几乎不受影响,水通量略增。     

丙烯酰胺接枝聚丙烯多孔膜及其水解后的性能

采用丙烯酰胺接枝法对聚丙烯(PP)多孔膜表面进行亲水化改性,考察了硝酸浓度、接枝时间以及水解时间对膜结构和性能的影响。随硝酸浓度增加,接枝度先增后降,膜表面的水接触角先减小后增大;随接枝时间延长,接枝度先增加后几乎不变,水接触角先减小后趋于恒定;随水解时间延长,接枝度几乎不变,而水接触角先减小后趋于恒定。优选的亲水化改性条件下,PP多孔膜的接枝度为1 147μg/cm2,水接触角由124°降至47°。过膜压差为0.5MPa时,聚酰亚胺/PP纳滤复合膜的纯水通量和对1 g/L的Na2SO4溶液的截留率分别可达11.89 L/(m2·h)和92.86%。     

氟树脂-漆酚-三氯化铁复合涂膜表面的亲水改性

采用NaOH溶液对氟树脂/漆酚/三氯化铁复合涂膜的表面进行化学处理,考察了溶液浓度和浸泡时间对涂膜表面润湿性的影响,并通过扫描电镜观察处理前后涂膜表面的形貌变化,结果表明:接触角随浸泡时间的增加先减小后有所增大,最后趋于稳定;用不同浓度的碱液处理达到最小接触角的刻蚀时间不同;经NaOH溶液处理后的涂膜表面形成了不同程度的突起。     

化学处理对天然橡胶粘接性能的影响

通过TCCA/MEK溶剂型卤化法处理天然橡胶(NR),以解决其表面能低、粘接性能差的问题,并探讨了T型剥离强度确定最佳处理工艺.研究结果表明:T型剥离强度确定最佳处理工艺为,先将NR打磨,在室温下表面涂覆,w(TCCA)=15％(相对于TCCA/MEK溶液质量而言),且处理时间20min;用801强力胶粘接处理后的NR...     

硝酸对HTA炭纤维表面形貌和力学性能的影响

为了提高炭纤维（CF）的表面性能和拉伸强度，用浓度为65％的HNO3对HTA炭纤维的表面进行不同时间的氧化处理。采用SEM观察炭纤维表面形貌的变化，用BET吸附研究比表面积和平均孔径的变化，并进行力学性能检测。结果表明：随着炭纤维表面氧化时间的延长，由于氧化刻蚀的不断加剧，炭纤维表面先粗糙后光滑，比表面积先增大后减小，拉伸强度先增大后减小，最后增加。当硝酸处理时间为15min时，炭纤维的表面性能和拉伸强度最好。     

HF/H_2SO_4溶液腐蚀时间对玻璃表面结构及其性能的影响

以HF/H2SO4混合水溶液作为复合腐蚀剂,利用金相显微镜、原子力显微镜、接触角测量仪、紫外可见分光光度计、电子万能试验机、维氏硬度计等测试手段,研究腐蚀时间对钠钙硅酸盐玻璃表面结构以及润湿性、光学和力学性能的影响。随着腐蚀时间延长,腐蚀速率逐渐降低,表面腐蚀坑尺寸先减小后增大,腐蚀坑分布均匀性先提高后降低;接触角逐渐增大并趋于稳定值;抗弯强度先增大后减小,断裂韧度变化不明显。腐蚀20 min时腐蚀深度41μm,腐蚀坑均匀细小,表面粗糙度Ra达到最低值5.8 nm,表面接触角和抗弯强度达到最大值,分别为71°和174 MPa。     

超高分子量聚乙烯纤维液相氧化改性及其橡胶基复合材料制备

为了增强超高分子量聚乙烯(UHMWPE)纤维与橡胶基体之间的界面粘结强度,采用高锰酸钾溶液对UHMWPE纤维进行表面处理,并将处理后的纤维加入到天然橡胶中制备短切UHMWPE纤维/橡胶复合材料。结果表明,高锰酸钾溶液处理可有效增加纤维表面粗糙度及表面含氧官能团含量,最佳改性工艺条件是:按照m(高锰酸钾)∶m(浓硝酸)=1∶30配置高锰酸钾溶液,在室温下将UHMWPE纤维放入上述溶液中处理1 min。与纯橡胶样品相比,在m(UHMWPE纤维)∶m(天然橡胶)=0~6∶100范围内,随着处理后短纤维质量分数的增加,复合材料的硬度不断增大,最大增加量达到94%;复合材料的撕裂强度先增大后减小,在m(UHMWPE纤维)∶m(天然橡胶)=4∶100时达到最大值,最大增加量达到43%。     

表面处理对NR粘合性能的影响

研究机械打磨、硫酸处理和次氯酸钠处理3种表面处理方法对NR粘合性能的影响.结果表明:经过硫酸适当处理后,NR硫化胶与水的表面接触角明显减小,表面润湿性改善,牯合性能显著提高;硫酸处理NR硫化胶的粘合性能优于机械打磨和次氯酸钠处理的NR硫化胶.     

紫外光诱导接枝甲基丙烯酸甲酯对预硫化天然胶乳胶膜的表面改性

在紫外光辐照下,通过光敏剂二苯甲酮的引发作用,使甲基丙烯酸甲酯(MMA)单体接枝共聚到预硫化天然胶乳胶膜表面,并采用傅立叶变换红外光谱-衰减全反射技术(FTIR-ATR),扫描电子显微镜(SEM)及表面接触角测试仪对表面接枝改性后的预硫化胶膜样品进行了表征.FTIR-ATR谱图清楚地表明,MMA单体已被接到硫化橡胶的分子链上;SEM显微照片显示,接枝改性后的样品表面因龟裂导致粗糙化而使其形态发生改变;表面水接触角的测试值随紫外光辐照时间的延长而降低,辐照15min的样品,其接触角测试值为62°,比未处理样品的96°降低了34°.这表明在实验条件下,MMA单体可以较为容易地接枝到天然橡胶分子链上,有效地改善了预硫化天然胶乳胶膜表面的亲水性能.     

Weak boundary layers on vulcanized styrene–butadiene rubber treated with sulfuric acid

A synthetic vulcanized styrene-butadiene rubber (R2) was used in this study. The presence of paraffin wax and zinc stearate in the rubber composition prevented the adhesion of R2 rubber to solvent-based polyester-urethane adhesive. To increase the adhesion properties of R2 rubber, a surface treatment with sulfuric acid (cyclization) was applied, and the length of the immersion in sulfuric acid and the time between the immersion time and the neutralization were varied. The treated R2 rubber surfaces were characterized using ATR-IR spectroscopy, contact angle measurements (water, ethanediol), and scanning electron microscopy (SEM). The mechanical properties of the treated rubber were obtained from stress-strain experiments. The joint strength was obtained from the T-peel test on treated R2 rubber/polyurethane adhesive joints. Due to the penetration of the sulfuric acid into the R2 rubber bulk, the mechanical properties decreased. The treatment with sulfuric acid produced several chemical modifications on the rubber surface: sulfonation of the butadiene and the creation of C C and C O bonds. Furthermore, the surface treatment of the R2 rubber with sulfuric acid removes paraffin wax from the rubber surface, which had a beneficial effect on adhesion to the polyurethane adhesive. To remove the wax layer, the surface was wiped with petroleum ether solvent after treating the R2 rubber with sulfuric acid. However, in some experiments a progressive migration of wax from the R2 rubber bulk to the surface with time happened. The migration of wax was prevented by increasing the immersion time in H₂SO₄ by more than 5 min.     

UV-Ozone Surface Treatment of SBS Rubbers Containing Fillers: Influence of the Filler Nature on the Extent of Surface Modification and Adhesion

SBS rubbers containing different loadings of calcium carbonate and/or silica fillers were surface treated with UV-ozone to improve their adhesion to polyurethane adhesive. The surface modifications produced on the treated filled SBS rubbers have been analyzed by contact angle measurements, ATR-IR spectroscopy, XPS and SEM. The adhesion properties have been evaluated by T-peel strength tests on treated filled SBS rubber/polyurethane adhesive/leather joints. The UV-ozone treatment improved the wettability of all rubber surfaces, and chemical (oxidation) and morphological modifications (roughness, ablation, surface melting) were produced. The increase in the time of UV-ozone treatment to 30 min led to surface cleaning (removal of silicon-based moieties) due to ablation and/or melting of rubber layers and also incorporation of more oxidized moieties was produced. Although chemical modifications were produced earlier in an unfilled rubber for short time of treatment with UV-ozone, they were more noticeable in filled rubbers for extended length of treatment, mainly for S6S and S6T rubbers containing silica filler. The oxidation process seemed to be inhibited for S6C and S6T rubbers (containing calcium carbonate filler). On the other hand, the S6S rubber containing silica filler and the lowest filler loading showed the higher extent of modification as a consequence of the UV-ozone treatment. The UV-ozone increased the joint strength in all joints, more noticeably in the rubbers containing silica filler, in agreement with the greater extents of chemical and morphological modifications produced by the treatment in these rubbers. Finally, the nature and content of fillers determined the extent of surface modification and adhesion of SBS rubber treated with UV-ozone.     

Chlorination of SBS rubbers with different styrene contents using trichloro-isocyanuric acid

In order to improve their adhesion to polyurethane adhesives, three unvulcanized block styrene-butadiene-styrene (SBS) rubbers with styrene contents between 33% and 55% were surface-treated with solutions of 2 wt% trichloro-isocyanuric acid (TCI) in ethyl acetate. The joint strength was estimated using T-peel tests and the failed surfaces were analyzed to assess the locus of failure. The failed surfaces were analyzed using ATR-IR spectroscopy, contact angle measurements, XPS, and SEM. An unexpected trend in the joint strength was obtained because the locus of failure depended on both the styrene content and the mechanical properties of each SBS rubber. A mixed mode of failure was obtained in joints produced with S 1 rubber (33 wt% styrene content), whereas failure in the chlorinated layer was observed with S3 rubber (55 wt% styrene content); cohesive failure in the adhesive was found for the joints produced with S2 rubber (44 wt% styrene content).     

Compatibilization of natural rubber–polyolefin thermoplastic elastomeric blends by phase modification

Natural rubber–polyolefin (70/30) blends have been studied by incorporation of modified rubber and plastic phases with a view to make the heterogeneous phases compatible. The modified rubbers used were epoxidized natural rubber (ENR) and sulfonated ethylene–propylene diene rubber (S-EPDM) at a level of 20 parts. Other rubbers such as chlorinated polyethylene (CPE) and ethylene propylene diene rubbers (EPDM) were also used at a level of 20 parts in the natural rubber–polyethylene (NR/PE) systems. The plastic phase was chemically modified with maleic anhydride (MA) in presence of benzoyl peroxide (BPO) and used at a concentration of 10% of PE, i.e., PEm. The tensile properties such as the modulus, elongation at break, tensile strength, and hysteresis were studied. NR/ENR/PEm/PE shows the greatest improvement in tensile strength (45% over control NR/PE). NR/S-EPDM/PEm/PE also shows similar improvement, although the hysteresis loss decreases. The change in these properties could be related to the adhesive strength. This was found to be improved by the incorporation of modified rubber and modified plastic phases. The best adhesion values have been obtained with NR/ENR/PEm/PE and NR/S-EPDM/PEm/PE. Thus, a correlation between tensile and adhesive strength was obtained for all the systems. The increase in adhesive strength is due to chemical reactions between the various phases. Probable chemical reactions have been suggested. Morphological observations show that the phases are interpenetrating, and this is consistent with the increased tensile strength. The natural rubber–polypropylene (NR/PP) systems do not offer good strength properties with the modified PP and modified rubbers. The adhesive strength also decreases with the incorporation of the modified system. The hysteresis properties show some improvement.     

Adhesive tack and green strength of EPDM rubber

Measurement of tack of EPDM (ethylene-propylenediene terpolymer) rubber with natural rubber (NR) of four different molecular weights, styrene-butadiene rubber (SBR), butadiene rubber (BR), bromobutyl rubber (BIIR), and polychloroprene rubber (CR) was done over a range of rates of testing, contact times, and temperatures of contact. The effect of different additives, namely carbon black, phenol-formaldehyde resin, coumarone-indene resin, and methyl methacrylate is also reported. Green strength of all the rubbers was measured. Tack strength increases with increase in contact time for all the rubbers. Adhesive tack between EPDM and low-molecular-weight NR is much higher than that between EPDM and NR of high molecular weight. Tack strength of EPDM with BIIR is the highest among the tack values obtained for synthetic rubbers. The adhesive tack between EPDM and natural/ synthetic rubber passes through a maximum when plotted against temperature of contact. It increases with testing rate. All these phenomena could be explained in terms of interdiffusion of rubber chains under different conditions and solubility parameter of two contacting rubbers. It was observed that tack strength varies with (contact time)^1/2 and (rate)^1/2 in accordance with the reptation theory. Phenol-formaldehyde resin (PF) or coumarone-indene (CI) resin in EPDM improves the tack strength quite significantly. The resin in the NR phase does not have a marked effect. The presence of carbon black decreases adhesive tack strength between EPDM and NR. The surface of EPDM, however, becomes smoother with the addition of the additives. Peel tests and commercial tack tests give similar results in the tack strength between EPDM/NR and EPDM/SBR.     

Surface Characterization of Vulcanized Rubber Treated with Sulfuric Acid and its Adhesion to Polyurethane Adhesive

Modifications produced on a vulcanized styrene -butadiene rubber surface by treatment with sulfuric acid were studied and several experimental variables were considered.

The treatment of R1 rubber with sulfuric acid produced a noticeable decrease in contact angle which was mainly ascribed to an increase in surface energy due to the formation of sulfonic acid moieties and C=O bonds, and the removal of zinc stearate. The rubber surface swelled and became brittle as a result of the treatment, and when flexed microcracks were created. A rubber surface layer modification was produced with a consequent decrease in tensile strength and elongation-at-break values. The treatment enhanced the T-peel strength of R1 rubber/polyurethane adhesive joints and the locus of failure was cohesive in the rubber.

The optimum immersion time in H₂SO₄ solution was less than 1 min., and the reaction time in air was not found to be critical; the neutralization with ammonium hydroxide and the high concentration of the sulfuric acid (95 wt%) were essential to produce adequate effectiveness of the treatment.     

Halogenation of styrene-butadiene rubber to improve its adhesion to polyurethanes

Halogenation of styrene-butadiene rubbers has been carried out using solutions containing different amounts (0.1-5 wt%) of trichloroisocyanuric acid in butan-2-one. The treated rubber surface showed increased peel strength in joints made with polyurethane adhesive. The effects of chlorination on the rubber surface were studied using scanning electron microscopy, contact angle measurements, and infrared spectroscopy. It was shown that cracks appear in the rubber surface after halogenation, a factor which favours adhesion; the larger the amount of trichloroisocyanuric acid used, the larger the number of cracks. On the other hand, chlorination of the carbon double bond (butadiene) and the formation of carboxylic acid groups seem to be the most important chemical changes in the chlorinated rubber surfaces. Chlorination increases the surface energy of the rubber, although this increase is a function of the rubber composition. In fact, for a simple rubber formulation, the polar component of the surface energy increases for the highest concentrations of chlorine on the rubber surface; but for rubber with a more complicated formulation, the same value of surface energy after chlorination was obtained, independently of the amount of trichloroisocyanuric acid added. A good correlation was found between the contact angle measurements, the infrared spectra, and the peel strength values.     

Surface Characterization of Vulcanized Rubber Treated with Sulfuric Acid and its Adhesion to Polyurethane Adhesive

Modifications produced on a vulcanized styrene –butadiene rubber surface by treatment with sulfuric acid were studied and several experimental variables were considered.

The treatment of R1 rubber with sulfuric acid produced a noticeable decrease in contact angle which was mainly ascribed to an increase in surface energy due to the formation of sulfonic acid moieties and C?O bonds, and the removal of zinc stearate. The rubber surface swelled and became brittle as a result of the treatment, and when flexed microcracks were created. A rubber surface layer modification was produced with a consequent decrease in tensile strength and elongation-at-break values. The treatment enhanced the T-peel strength of R1 rubber/polyurethane adhesive joints and the locus of failure was cohesive in the rubber.

The optimum immersion time in H₂SO₄ solution was less than 1 min., and the reaction time in air was not found to be critical; the neutralization with ammonium hydroxide and the high concentration of the sulfuric acid (95 wt%) were essential to produce adequate effectiveness of the treatment.     

Adhesion properties of pressure-sensitive adhesives prepared from SMR 10/ENR 25, SMR 10/ENR 50, and ENR 25/ENR 50 blends

The adhesion properties, i.e. viscosity, tack, and peel strength of pressure-sensitive adhesives prepared from natural rubber/epoxidized natural rubber blends were investigated using coumarone-indene resin and toluene as the tackifier and solvent respectively. One grade of natural rubber (SMR 10) and two grades of epoxidized natural rubbers (ENR 25 and ENR 50) were used to prepare the rubber blends with blend ratio ranging from 0 to 100%. Coumarone-indene resin content was fixed at 40 parts per hundred parts of rubber (phr) in the adhesive formulation. The viscosity of adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength was determined using a Lloyd Adhesion Tester operating at 30 cm/min. Results show that the viscosity of the adhesive passes through a minimum value at 20% blend ratio. For loop tack and peel strength, it indicates a maximum at 60% blend ratio for SMR 10/ENR 25 and SMR 10/ENR 50 systems. However, for ENR 25/ENR 50 blend, maximum value is observed at 80% blend ratio. SMR 10/ENR 25 blend consistently exhibits the best adhesion property in this study, an observation which is attributed to the optimum compatibility between rubbers and wettability of adhesive on the substrate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008