高固体分羟基丙烯酸树脂的合成

以过氧化二苯甲酰（BPO）／过氧化二异丙苯（DCP）（质量比为2：3）为复合引发剂，二甲苯为溶剂，选用适量含羟基单体和分子量调节剂，以减缓树脂合成聚合反应中的自动加速现象，合成了分子量为3000-4000，多分散性指数d〈2的高固体分羟基丙烯酸树脂．该树脂与缩二脲多异氰酸酯（HDI）的配漆实验证明，所得漆膜鲜映性好、丰满度高、色泽好、雾影值低、综合性能较好．     

Bulk Free Radical Polymerization of Methyl Methacrylate and Vinyl Acetate: A Comparative Study

The model and methodology for estimating diffusion‐controlled rate coefficients for the methyl methacrylate (MMA) polymerization system is extended to the vinyl acetate (VAc) case. Comparison of the kinetic behavior and termination rate coefficients (k_t) of both monomers suggests that at low conversions the termination reaction is controlled by the chemical step, whereas at moderate and high conversions it is controlled by the diffusive step which in turn is determined by the segmental diffusion of the long radicals and not by the center of mass diffusion of short radicals. It is found that, for most of the conversion range, diffusion coefficient for VAc is lower than the one for MMA notwithstanding that k_tVAc > k_tMMA. An explanation of this apparent inconsistency on the base of the model results and in terms of segmental mobility is proposed.

     

Kinetic studies on the n-alkyl acrylate polymerization

Kinetic studies on the polymerization of n-butyl acrylate and n-octadecyl acrylate in toluene at 70°C with benzoyl peroxide as initiator are reported. High monomer orders of 1.55 and 1.75 were obtained for n-butyl and n-octadecyl acrylates, respectively. Though the initiator order in butyl acrylate polymerization was 0.5, the octadecyl acrylate polymerization showed less than square root initiator order. The activation energy for the polymerization of both the acrylates was determined. Autoacceleration was found even at low conversions. The autoacceleration was influenced by both monomer and initiator concentration. Molecular weight data was presented in support of the gel effect. © 1992 John Wiley & Sons, Inc.     

TMDSC and Dynamic Rheometry,Gelation, Vitrification and Autoacceleration in the Cure of an Unsaturated Polyester Resin

The free radical cross-linking copolymerization of an unsaturated polyester resin with styrene is studied in isothermal conditions using temperature modulated differential scanning calorimetry (TMDSC) and dynamic rheometry. The dynamic rheometry measurements show that gelation occurs at a conversion below 5%, while TMDSC measurements show that an important autoacceleration starts near 60% conversion, giving rise to a maximum cure rate closely before the (partial) vitrification of the system near 80%. This indicates that the autoacceleration is not due to the sharp increase in bulk viscosity at gelation, but rather to a change in molecular mobilities at higher conversion.This revised version was published online in November 2005 with corrections to the Cover Date.     

Characteristic Events in Free Radical Polymerization of Lower n-alkyl Methacrylates

It is well known that the free radical bulk polymerization of lower n-alkyl methacrylates is characterized by autoacceleration after definite conversions of the monomers. The conversion vs.time curves of polymerization have a typical 'S' shape. There are several characteristic points in these curves: the onset of autoacceleration (point M), the maximum in the polymerization rate (point S) and the end of the polymerization (point K). We have observed points P and R (maximum and minimum of autoacceleration) as inflection points in the derived polymerization rate vs. time curve. In this work, the free radical bulk polymerizations of methyl, ethyl and butyl methacrylates were investigated by differential scanning calorimetry. The effects of the polymerization temperature and the alkyl group length in the esters on the monomer conversions at the points M, P, S, R and K were studied. By regression analysis of the experimental results, relations were developed with which it is possible to predict the positions of the characteristic points, depending on the polymerization temperature and the alkyl group length. This revised version was published online in July 2006 with corrections to the Cover Date.     

A novel photoinimer for the polymerization of acrylates and methacrylates

A new class of multifunctional photoinitiating system based on 3‐(acryloyloxy)‐2‐hydroxypropyl methacrylate (AHM), N,N,N′‐trimethylethylenediamine (TMED) and 3‐benzoylbenzoyl chloride present in the same molecule has been synthesized and characterized by ¹H and ¹³C NMR spectroscopy. This self‐contained photoinitiator‐monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacrylates. Both rate of polymerization and percentage conversion increased with increase in initiator concentration. An increment in rate of polymerization observed when the benzophenone moiety was directly attached to the parent molecule (obtained from the Michael addition reaction between AHM and TMED) appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo‐activated system involving benzophenone and a hydrogen atom source from an electron‐rich tertiary amine. For the three initiating systems investigated, lowering the initiator concentration plays an important role; i.e., the polymerization rate for the chemically linked system was about two times faster than the mixed initiating system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5661–5670, 2005     

Autoacceleration and inhibition: Free volume. Epoxy-amine kinetics

The epoxy-diamine cure process was studied. We found that the mechanism can be described in three steps: (i) initiation up to 20–25% of conversion. (ii) autoacceleration and (iii) inhibition. It has been observed that after the initiation there is a clear autoacceleration effect which has been explained in terms of free volume, considerations: the volume occupied by the products of reaction diminishes the available volume increasing the “local concentration” of the reactants and therefore the rate of reaction. The reaction was followed by FTIR (near infrared) as the main technique. We used a purified epoxy resin as well as phenyl glycidyl ether cured with m-xylenediamine. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1001–1016, 1998