The effect of cast film extrusion processing conditions, such as the chill-roll temperature, temperature of the melt, and line speed, on the structure of different isotactic polypropylene homo- and random copolymers has been investigated by means of Small- and Wide-Angle X-ray Scattering (SAXS and WAXS) and correlated to stiffness and haze. Stiffness and transparency have been found to be strongly dependent on the temperature of the chill-roll. Interestingly, line speed has been found to affect the total crystallinity when the chill-roll temperature is increased, while an overall minor effect of the melt temperature was found for all cast films. The polymer characteristics, defined by the catalyst nature and comonomer content, affect the final material performance, with the single-site catalyzed grades performing better in both mechanics and optics. Haze levels were found to correlate with the mesophase content rather than to α-crystallinity and to be dependent on the domain size for all grades. The remarkably low haze levels reached by the single-site grade with higher isotacticity can arise from high nucleation rate and orientational effects, which ultimately yield smaller and smoother scattering domains.

The crystallization kinetics of metallocene-catalyzed heterophasic isotactic polypropylene composed of a matrix of isotactic polypropylene (iPP) and rubbery particles made of random ethylene–propylene copolymers (EPC), often denoted as heterophasic iPP copolymers, was analyzed as a function of the cooling rate and supercooling in nonisothermal and isothermal crystallization experiments, respectively. Fast scanning chip calorimetry (FSC) allowed assessing crystallization at processing-relevant conditions, and variation of the content (0–39 wt %) and composition (0–35 wt % propylene counits) of the EPC particles revealed qualitatively new insight about mechanisms of heterogeneous crystal nucleation. For neat iPP homopolymer, the characteristic bimodal temperature dependence of the crystallization rate due to predominance of heterogeneous and homogeneous crystal nucleation at high and low temperatures, respectively, is reconfirmed. At high temperatures, in heterophasic iPP, the here studied ethylene-(C2)-rich EPC particles accelerate crystallization of the iPP-matrix, with the acceleration or nucleation efficacy correlating with the EPC-particle content. The crystallization time reduces by more than half in presence of 39 wt % EPC particles. An additional nucleating effect of the EPC particles on iPP-matrix crystallization is detected after their crystallization, suggesting that liquid/rubbery particles are less effective than solid/semicrystalline particles in affecting crystallization of the surrounding iPP-matrix. At low temperature, homogeneous crystal nucleation in the iPP-matrix outpaces all heterogeneous nucleation effects, and the matrix-crystallization rate is independent of the sample composition. The obtained results lead to the conclusion that the crystallization kinetics of iPP can be affected significantly by the content and composition of EPC particles, even towards superfast crystallizing iPP grades.

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates.

Polyethylene (PE) plastomers, single-site catalyst-based homogeneous linear low-density PEs (LLDPEs), combine low crystallinity, softness, and elasticity, making them ideal candidates for numerous applications such as hot-melt adhesives (HMA). As plastomers crystallize rather slowly, a number of possible low molecular weight polyolefin components were tested to accelerate solidification. An ideal modifier should accelerate solidification while maintaining transparency and softness of the base polymer. A Queo plastomer type was modified with different PE and PP waxes at concentrations of 5 to 25 wt.-%. Next to conventional calorimetry, a rheological technique was applied to study solidification. The resulting morphology was studied by atomic force microscopy, and the final compositions were investigated regarding their mechanical and optical performance. Accelerated solidification was observed in all cases, but a quite different course of structure formation could be concluded. PE waxes dissolve in the melt state, forming a lamellar network during cooling, whereas PP waxes form a heterogeneous blend in the melt for which the wax droplets solidify before the matrix. The particulate-type modification by the PP wax also affects stiffness less while retaining transparency better.

Concerns about the environmental and health impacts of plasticized poly (vinyl chloride) (PVC), from plasticizer loss to microplastic formation, have created a clear demand to find alternative packaging materials for medical and pharmaceutical use. As a possible polyolefin-based alternative, we blended polypropylene–ethylene copolymers with different ethylene content-controlled phase structures with styrene–ethylene/butylene–styrene block copolymer (SEBS), as modifier. SEBS is elastomeric and performs mechanically like a cross-linked rubber due to its unique microphase-separated morphology of hard spherical polystyrene (PS) domains dispersed in the soft elastomeric ethylene-butylene copolymer (EB) phase. Tests with injection-molded samples and cast films demonstrated promising combinations of flexibility, durability, and transparency—qualities essential for soft medical packaging like infusion pouches and blow–fill–seal bottles. For the desired level of flexibility (reflected by a flexural modulus of 150–250 MPa), blends with two random-heterophasic (RAHECO) copolymers achieved the lower limit with only 15–25 wt.-% SEBS, compared to the 37 wt.-% needed for a single-phase random copolymer (RACO). These blends also exhibited greater toughness and excellent transparency. In contrast, a standard impact copolymer (HECO), with its more crystalline matrix, required a higher modifier content of 45 wt.-% SEBS. Film morphology analysis indicated a gradual shift in disperse phase structure and orientation, leading to phase inversion at the highest SEBS content without negatively affecting transparency.

Concerns about the environmental and health impacts of plasticized PVC have created a clear demand to find alternative packaging materials for medical and pharmaceutical use. As polyolefin-based alternative, we blended polypropylene-ethylene copolymers of different, ethylene content-controlled, phase structure, with styrene-ethylene/butylene-styrene block copolymer (SEBS), as modifier, the latter being elastomeric and mechanically acting as cross-linked rubber due to a unique microphase separated morphology of hard spherical PS domains dispersed in the soft EB phase. Tests with injection-molded samples and cast films demonstrated promising combinations of flexibility, durability, and transparency—qualities essential for soft medical packaging like infusion pouches and blow-fill-seal bottles. For the desired level of flexibility (reflected by a flexural modulus of about 150 MPa), blends with two random-heterophasic (RAHECO) copolymers achieved this with only 15–25 wt.-% SEBS, compared to 37 wt.-% needed for a single-phase random copolymer (RACO); these blends also exhibited greater toughness. In contrast, a standard impact copolymer (HECO), with its more crystalline structure, required a higher modifier content of 45 wt.-% SEBS. Film morphology analysis indicated a gradual shift in disperse phase structure and orientation, leading to phase inversion at the highest SEBS content—without negatively affecting transparency.