Degradation of natural rubber and deproteinized natural rubber (DPNR) at 70 °C and 150 °C for 24 hours was investigated. Natural rubber was degraded at 150 °C to produce blown viscous liquid, whereas pale yellow rubber was covered with black brittle rind after degradation of DPNR at 150 °C. FT-IR, ¹H-NMR and ¹³C-NMR measurements of degraded natural rubber revealed that the functional groups formed by the reaction with oxygen radical and hydroxyl radical were introduced into natural rubber. In contrast, trans-1,4-isoprene unit and vinyl group were formed by the degradation of DPNR, suggesting that the degradation of DPNR occurred in the absence of oxygen and water. The difference between degradation of natural rubber and DPNR was attributed to the existence of protein to provide oxygen and water.

Herein we investigate the molecular structures of EPDMs derived from different catalyst technologies and their effect on performance with automotive weather sealing profile extrusion as target application. Dow’s recent development of advanced molecular catalysts (AMC) enables new molecular design capabilities to surpass the performance of the previous generation of single site constrain geometry catalyst (CGC) EPDMs. New capabilities entail higher molecular weight, broader molecular weight distribution, more homogeneous long chain branching and higher diene content. All these polymer attributes were thought to be associated only with Ziegler-Natta (ZN) catalyzed EPDMs till now, however, a new EPDM (EPDM-AMC) is characterized by these attributes and has been specifically designed for fast dense extrusion processes. It’s molecular geometry anticipates high performance during processing (green strength, curing speed). As a final part the performance of EPDMs derived via three types of catalyst, namely AMC, CGC, and ZN are compared.

The influence of increase in both environmental temperature due to global warming and ozone concentration caused by ultraviolet on polymers has been worried. PP homopolymer without antioxidant was subjected to accelerated weathering test. Degradation rate of PP was synergistically increased by combination of degradation factor, i.e. light, heat, and water. The degradation rate reached 6 times or more, based on carbonyl index.

1. Unit cells of strain-induced crystals of NR, vulcanized NR, IR, vulcanized IR are the same because cis-1, 4-polyisoprene makes crystal units with exclusion of entanglements and network points. Unit cell of cis-1, 4-polyisoprene is composed of four chains with P2₁2₁2₁ symmetry.

2. Crystallites of NR, vulcanized NR, IR and vulcanized IR are cubic figure with the size of several nm being composed of around 100 chains. The sizes depend on temperature but do not increase with strain. The crystalline fraction increases with strain due to increase of the number of crystallites. Crystallites could be considered as a giant crosslink point, but many crosslink points are bound together at the upper and lower outside of crystallites. Therefore, crystallites do not increase necessarily the number of amorphous molecules which contribute to the elasticity of rubber.

3. WAXD patterns are affected by the size of crystallites, the orientation of crystallites and the completeness of crystal. We developed a simulation program to analyze the size, orientation and completeness of crystallites. The X-ray scattering peaks of NR and vulcanized NR are crescent figure, on the other hand the ones of IR and vulcanized IR are round. The differences are caused by the degree of orientation of crystallites, the crystallites of NR and vulcanized NR do not orient more than the ones of IR and vulcanized IR. The crystallites of NR and vulcanized NR are less degree of completeness of crystal than IR and vulcanized IR, although the stereo-regularity of NR is higher than the one of IR. Pseudo networks of NR and vulcanized NR may suppress a crystallizing process of strain-induced crystallization.

4. Higher order structure of crystallites such as the lamella structure is not observed well although NR show slight two points SAXS pattern only at 0 °C at strain 6.0. During stress relaxation after deformation, density fluctuation is observed due to orientation. It is not considered to be caused by strain-induced crystallization.